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1991 - - Champagne Gold – 156K - $5000.00
Price reduced
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Pete -
I used them for racing only, no curb rash, but there are some very minor scratches. They will fit 88-96.
Thanks for the interest.
Subman

Matatk -
I bought it a long time ago, but I think I got it from MidAmerica
Let me know
Thanks
Subman

Priorities have had to change, so I am selling the following items:
2 - V710 295/40/17 with 6 runs on them - 175.00 ea. SOLD
Koni Sports Shocks - front and rear - 65.00 ea
32MM front sway bar solid VB and B with poly bushings - 75.00 SOLD
Adj. fuel Pressure regulator - 30.00 SOLD
J55 calipers, brackets, rotors and pins with 2 sets pads - 300.00
4 GS wheels 9.5 x 17 black w/silver edge (AFS) - 300.00 SOLD
I will pack them up, buyer will be responsible for shipping costs.
Thanks for looking
Subman

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Do you know what happened this week back in 1850, 158 years ago?


California became a state.
The State had no electricity.
The State had no money.
Almost everyone spoke Spanish.
There were gunfights in the streets.

So basically, it was just like California today;


except back then the Women had real breasts and the men didn't hold hands.

I just installed #7 in 3 years. All AZ, all under LT warranty. After the 3rd one, a couple of years ago, I decided to find out what was up. There are 2 areas that are 90% the cause of mine that failed:
1 - the biggest culprit is the bearings. If you hold a new alt up to your ear and rotate the shaft back and forth, you can hear the bearings click. When I opened them up, they are a little over 1/2 ball bearing short. The large gap between the balls becomes even more of a challenge when they get as hot as these do from just compartment heat. I made them give me new, in the package, Timpkin bearings. And those had no problems and the alt lasted 3 years.
2 - number 2 is the regulator. I am pretty sure they get a bunch of bad regulators, don't QC 'em, ship the alt's and wait to see if Joe Consumer bitches a bunch when they return them. My #5 alt would over-volt to 19 volts, intermittently. I had to wait until it over-volted, rush to AZ so somebody there could look at it. #6 alt would under-volt to 7 volts, again, intermittently. This time I got a little smarter, I took pict's with the phone. #7 seems to be doing ok.
I did write to the AZ home office to let them know of my displeasure (a gentlemans version), but have yet to hear back from them. It don't take too many trips to replace parts to find a different supplier. I'm already there.
Subman

I decided to start the failed smog test fix(es) on my 91 with some Seafoam, swap plugs and a new O2 sensor. After the Seaform, pulled the plugs and went to my stash of #5's, some with less than 1K, all with less and 3K, to check 'em out and maybe save myself $40.00. I had never noticed any differences before, but after looking pretty close, I had 6 plugs with a small tip on the end of the electrode. Found some other differences as well (see the photo).
So the question is, did Delco make a couple versions of the #5, or did AZ pick up some bootlegged stuff. Not that it's gonna make much difference at this point, but it'd be kinda interesting to find out.

Subman

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What size injectors, is the motor totally stock, has there been a tune done on it?
I am working from memory here, but I believe the pink tops are 22# with FPR at 43#. Other than that, bone stock without a tune.
I do have a guy around the corner in case...
If it fails 1 more time, . . . .

I would try a delco 02 and see if BLM's change
Since they aren't that expensive, that can be done when I change the cat

I'm still unclear, why the questions when you know the Cat is bad.
I'm just trying to keep from throwing good money after bad.
doesn't that year have 4 O2 sensors?? Two behind the Cats?? If the Cats where bad, wouldn't this throw off the readings from the O2 sensors that are expecting a Cat that is in working order.
Nope. 91 is the last of the L98's. It has 1-O2 sensor (left side just after the exhaust manifold)

Thanks
Subman

Vacuum leak? How does it idle? Any loping?
I have not found a vacuum leak, but that doesn't eliminate the possibility. The idle stays steady and there isn't in loping. I am gonna try blowing smoke into the intake, hopfully this weekend, to make sure

do you have any of the EASE reports saved? If so, posting one would be good.
Not a single report saved. Tried more than once, just couldn't get it done.

What are you running for an 02 sensor?
Bosch O2 sensor. Changed June/July 07

Most of the time, it will run like a scalded dog. There has been a few occasions it just didn't "feel" right.
I have reset the IAC and the TPS (this one isn't supposed to adjust and doesn't much) Double checked the timing (6*)all good.

Thanks for the replys

Subman

Last Saturday my 91 failed the CA smog test for the 3rd time. It was 2 yrs ago that a dead short wiped out the ECM and the CCM and a 1 ½ years ago I had the last test, and had some EGR issues. A new heat tube gasket finally resolved that. But in the interim I replaced a blown radiator, heater core, trans, and a bunch of other stuff.
The specs on the car are – 91, auto, L-98, base model, bone stock save the 50MotorSports pinktop injectors (7 years in and no challenges), front sway bar and shocks.
I took the car to a local (reputable) muffler shop to have the cat checked. I have had this done before, but it was always a “pressure” test. They used a simple heat sensor and found the inlet was 354* and the outlet was 251* indicating a bad cat. This cat is about 6 years old and has about 30k miles on it.
I made the trip to see Andy with all the emission reports and his thoughts are these. .
The cat should not have gone south at this point unless something triggered its demise.
If I was running very fuel rich, makes sense. But it doesn’t seem to be.
The next item would be the smog pump. That was replaced (new, not rebuilt) in October along with both the check valves.
Then there is AIR control valves. I think this could be a real possibility.
Replacing the cat is a given, so, before I start throwing money at the car, I thought I would post on Guru and let y’all take a shot at coming up with a quick, easy and CHEAP ways to test any and all things that could/would toast the cat so it doesn’t happen again.

Here is the 6/2/07smog numbers:
15 mph – fail
HC(ppm)-max-112 / mine-136; CO(%) max-0.72 / mine-0.32; NO(ppm)778 / mine-981
25 mph – pass
HC(ppm)-max-86 / mine-86; CO(%) max-0.60 / mine-0.06; NO(ppm)717 / mine-555

Here is the 6/16/07 smog numbers after some Seafoam and changing the plugs
15 mph – fail
HC(ppm)-max-112 / mine-156; CO(%) max-0.72 / mine-0.75; NO(ppm)778 / mine-1665
25 mph – fail
HC(ppm)-max-86 / mine-139; CO(%) max-0.60 / mine-0.50; NO(ppm)717 / mine-1355

Here is the latest smog numbers with new plugs, valve seals in (Nov/Dec) dist cap, rotor, ign. module and a pickup coil (late Oct):
15 mph – fail
HC(ppm)-max-112 / mine-156; CO(%) max-0.72 / mine-0.39; NO(ppm)778 / mine-1159
25 mph – fail
HC(ppm)-max-86 / mine-116; CO(%) max-0.60 / mine-0.07; NO(ppm)717 / mine-822

Andy will probably chime in with some more info and ideas, but don’t let that dissuade anyone from puttin’ in their $0.02.
As always, my thanks in advance to the brain trust here at Guru

Subman

The hubs are the same ones that were on the car. There were new in June. Strange thing is that I hit the plate with the left side of the car.
And the right speed sensor goes berzerk? Go figure.
There are times when I think you may be right - this Gold Vette is somehow jinxed.
But - - when it running right, it's just fun to drive.
Talk soon -
Subman

A month or two ago, I developed a smoking engine on start up - then it went away after running a minute or so. After I posed the question here about replacing the seals in the car, I decided to go for it (the right tools made this job easy) and while I had it that far apart, replace the intake gaskets to finally rid myself of the never ending end seal oil leak.
What amazed me was there are NO end seals, just black RTV.
I have built a s--tload of small block Chevys way back when and they all had end seals. So I decided to make my own. Pep Boys gasket material + the black RTV = no leaks, at least none I've been able to detect. The gaskets took about 10 or so minutes to make and was worth every minute.
Moral of this story - if you're gonna go deep into the top end, make the gaskets. You'll be glad you did.
Good Luck
Subman

First thing this AM, I cleared the code 21. drove it 20 feet and code came back. Pulled the plug from the right sensor, disconnected the sensor harness from the pair that goes to the ECBM. Disconnected the sensor harness from the ABS harness and disconnected the ECBM from anything.
ALL the sensor wires are clean, no breaks.
Following Caseys suggestion from another post, I swapped the hubs, backed out of the driveway, and a familiar growl sound eminated from the well behind me. No code ! Drove around the block, hit the brakes a couple of times. Stopped the engine and restarted, NO CODE!
I have no idea what fixed it, the swap, re-connecting all the wiring, or what. But I know I didn't have to chase an elusive short.
BTW - it's good to be back here again. It's been a while
Talk to you soon,
Subman

Car is a 91 auto. Driving to an appointment Wednesday, I had to travel on a road construction zone with the steel plates covering trenches. I hit one that didn't have a asphalt ramp at about 35-40 that jarred the car like I'd been hit from the bottom. And the Service ABS light came on (no I wasn't on the brakes when I hit the plate) and stayed on. I pulled over, shut off the engine, restarted and no light. I didn't remember hearing the ABS growl in the morning so I finally check the codes tonight. Code 21 - right front sensor.
I have pulled the wires and the connection to the ECBM and re-seated them, can't find any broken wires or bad connections. I replaced the ABS pump and ECBM earlier this year and (finally) got rid of 90% of the mushy brakes. I have an old hub that I check continuity from pin to pin at the speed sensor - 1.017 k resistance. Is that about correct?
I did find 1 thread on the Forum with the same challenge and I will take Caseys advice from it and swap hubs tomorrow, but if the code stays on the right, are there any tried and true ways to chase this "short" down. The FSM has a brn/wh wire from the right sensor to the ECBM. It doesn't show it changing color, so if can find both ends of the wires, I check continuity from wheel to ABS, it should show a problem, if there is one, correct?
God, I would rather wire a complete house or have root canal than deal with electrical problems in a car. So any help out there is appreciated.
TIA
Subman

It's been a while since I posted, which is a good thing! In '07 it seemed like I was here everyday trying to figure out the wiring in my 91!.
A quick note re: TQL. I had the trans rebuilt last Dec and it worked real well until a month ago. Then it didn't want to get in TQL at it's usual 42 MPH. I called the trans guy and he wanted to keep the car for a few days. Since its a daily driver, I needed to find another way to work, so I let it go for a week. On the way home from work, by chance, my left foot slid onder the brake pedal and lifted it ever so slightly. And the TQL kicked in! I checked the 2 switches that are activated by the pedal, the light switch worked fine, the other was at max adjustment, kinda loose and would not depress fully. The pedal bushing was worn (only 146k on the clock) which allowed the pedal to wobble and made contact even worse. Until I have the time to tear the dash apart again, a 1/8" piece of adhesive foam tape did the job. Shifts like it's supposed to.
The moral of the story is sometimes dumb luck can save you a ton of $.
Another challenge cropped up, but that's another thread.
Good Luck
Subman

I fought code 32 on my 91 L98 for over a year. I checked the valve, had a member send me a solinoid (since no one makes them anymore), ECM vacuum lines, electrical, and finally discovered the problem by accident (isn't that how it usually goes)
The heat tube from exhaust to intake manifold gasket at the manifold had blown out the side. When the valve opened, it was sucking to much "fresh" air and tripped the sensors . . "check engine" light. Replaced the gasket and no more code 32.
That's not to say it the challenge your having, but $3.00 worth of gaskets and 15 minutes isn't throwing money at it, (consider it a maintainence thing) and it just might work!

Good Luck
Subman

What does new seals accomplish if the valve guides are worn?
Good question CC. This is one of those times when you hope that the Gods have smiled down on you. However, with everything that I had to replace or rebuild last year, it's iffy.

Thanks to all who replied. The Guru kinda reminds me of the other place 4 or 5 years ago.
Good folks with, normally, good advice.

Subman

91 L98 with Auto trans - 142,000 on the clock.
Notice some smoke when starting after over night parking about a month or so ago. A necessary pickup coil replacment (the car just quit) gave me the reason and time to pull a compression test. 218-220#'s on 1,2,3,5,6,8. 212#'s on 4 and 208#'s on 7. All dry, and after running SeaFoam through it a week before. It is now smoking on start up after sitting for 3 or 4 hours and occasionally if I am sitting in traffic. I installed 2 separate switches to turn on the fans so I don't typically let the car get any hotter than 200* and never let the fans come on by them selves.
So all of this leads me to believe that I could use some new seals. I have seen a pneumatic insert to keep the valves in place while you remove the keepers and springs to replace the seals. After replacing every thing, release the air pressure and move on to the next cylinder.
Since I have never used one of these tools, I'm just looking for tips and tricks on using one, or reasons for NOT using one. I have always pulled the heads, sent 'em for machine work, and reinstalled complete. I could do that now, but would rather not as it's a daily driver and I don't have the time to dick around with it.
So - If any one has experience doing this with the heads still on the car, I'd appreciate hearing from you!
T.I.A.
Subman

Slow in fast out - LOOK AHEAD
If you are looking ahead far enough, the turn you are coming up on is already plotted, both position and speed, the exit is set by the position and speed of the entry (slow in). The exit of the turn should place you in the correct position for the next element (fast out). All of this input should takes place prior to the previous turn or element.
Drive the course in your mind over and over and over until you know where the turns, straights, slalom and key cones are. If you go to a new town and try to find the market, you end up puttin' along not sure where to go. In a familiar town, you drive right to the market, know where the lights and driveways are.
Drive the first run at about 7/10ths. Then re-run the drive in your mind to see where you can push you and the car to limits. Try different things during the day, change one section at a time. If you time improves, it was right, if you slow down, you did it wrong. Seat time will you better, but ONLY if you push your own envelope.
I run my 91 auto in AS with Kuhmo V710's. However, the basic alignment is about the same as when running street tires. All shims out on the fronts should give you -.9* to -1.25* camber. Caster is not an issue. Toe out should be 1/4" to 3/8" total. If your pushing a ton, increase toe out a little at a time. The rear on mine likes a lot of negative camber so I run -1.75* to -2.25*, depending on the course layout. You could probably start with -1.75* and see how the car feels as well as check the temps across the tires as soon as you can get over after the finish. The temps should be pretty close to even from the outside to inside.
The last thing on my list now is to get all the S2000's out of AS. They been kickin my butt for a while.
Remember that autocross is a lot like sex. If there is no squealing, your not pushing hard enough!
Subman

I just spent 30 or so minutes responding to both Casey and Jeff and lost a really long post somehow. Guess the Gods were telling me something.
The replacment ABS and ECBM were supposed to be out of a '90, but I don't think so. But that's another chapter.
I re-installed the original ECBM and pump with bleed valves in all ports. I attached the incoming rear line and bled at the pump. Solid pedal. Then attached the rear outgoing line and bled at the calipers, L/R first, then R/R. Solid pedal. The pedal did not waiver. Stayed solid, never moved after putting pressure.
Attached the incoming front line and bled at the pump L/f first, then R/F. Solid pedal. Attached the L/F line to caliper and bled at the caliper. Not as solid as the rears. Same with the R/F.
I kept getting micro bubbles in the left front and found the speed bleeder threads were sloppy when the valve was slightly open. Replaced the valves. Still not solid and kinda mushy.
Pulled the calipers and checked the piston seals without taking the calipers apart and found no moisture.
I pulled the SS brakes lines and put on the rubber ones. bled and pinched off the rubber line. Much better pedal, almost as solid as the rears only. Re-installed the SS lines with new crush washers and still had a pretty good pedal. Oh - for JOY. . . NOT. Started the engine and applied the brakes and the pedal ended up 1 1/4 to 1 1/2 inches from the floor and mushy. Bled again with the engine running, slight pressure, short strokes. Got a slightly better pedal. Put on the tires, heated up the pads like a break-in, cool off a little then panic stopped. ABS active light, left front lock up then released. Cool slightly and tried it again with basically the same results.
I am really at a loss here. The ABS should not let the wheels lock up - ever.
Now - - back to the ABS - ECBM or pump.
I appreciate the responses and the help
Subman

Another challenge with my 91, automatic (Bogus thinks the car is jinxed) Long story short-Mushy brakes for some time. I have done the search thing both here and at the other place and I think I have tried most every "reasonable" suggestion. New J55 upgrade (Nov, 07), SS lines, new (last week)booster & MC, adjust the booster rod (.75 MM gap), bias spring, pads (2 or 3 times). Pedal feels soft and travels almost to the floor. But, hard on the brakes locks up right front, then releases, lockup left front, releases (not a pulse, a hard lock up with a skid). Bought what is supposed to be a 90 ABS pump and BCM, arrived on Friday, race on Sat., so I did not get the chance to install. Autocross, 6th run, tap brakes, left lockup, release, then ABS light, drive on to hard left u-turn, hard brakes, both fronts lockup, slide through a bunch of cones. Put the car on the trailer. Replaced the BCM, but got Service ABS. Checked pins from ABS harness to BCM - different config. So on to replace the entire mess. However the incoming harness connectors don't match the '90' connections. I was under the impression that the ABS units (both pump and BCM) were the same from 89-91. I have taken a bunch of photos of the differences between the 2 units and will send them to all who ask. Hopefully, one of you gurus has "THE" answer to all of us that drive our Vettes with spongy brakes. Making an assumption that I will probably have to re-install the original pump, I did try 1 thing that seemed to "get the air out" of the ABS pump. With the pump on the bench, I put caliper bleed valves in both the incoming and out going ports. Attached bleed hoses to both the front out going ports and into a jar. On the incoming port, I then attached a bleeder hose to the "vacuum" side of a MiteyVac canister top, a hose on the inside nipple about 1/4" short of the bottom of the canister and a long hose on the top side of the nipple. Filled the canister with new brake fluid and turned the canister upside down, placed it higher than the ABS pump and the bleeder jar, opened all three bleed valves (1 incoming and 2 outgoing) for the front, applied a little "lung" air pressure into the long hose and pushed the air out of the pump until I saw brake fluid and then let it gravity bleed for a while. Closed all 3 valves and did the rear side. I figure if I have to replace the existing pump, by keeping the out going ports closed when I put in the line from the master cylinder, the pump should not loose to much fluid. Then attach the bleed hoses again and bleed the pump 1 more time before installing the lines to the calipers. Then do another bleeding at the calipers. I have until Wednesday night, Thursday night at the latest, to figure this out. I am suppose to run a Nationial Prosolo event on Saturday and I would REALLY like to be able to stop the car. Thanks in advance. Subman.

A few months ago, I kinda hijacked a thread re: a code 32, not passing smog. etc. Mentioning the vacuum solenoid was all but impossible to get, dan0617 send me one he had removed. Thanks, Dan. After I installed it, no change :{
So Dan's is still up for sale.
However, after putting in another booster and M/C this week, I started the car and heard an unusual noise, like an exhaust leak from the right side. A quick look with a flashlight found the challenge - the gasket between the intake manifold and the heat tube from the exhaust had blown out on both sides. It took a while finding the time to fix it and tomorrow we will find out for sure, but, for now, all is well.
Subman

Unfortunately, this is the 4th booster I have put in my 91. The 1st one I bought from Chevy. It split in 13 months. The second, from AutoZone. It lasted 3 weeks. The replacement has lasted 1 1/2 years, but it's a lifetime warranty. I was pleasently surprised when I swapped out the last booster to find AutoZone had, apparently, switched suppliers.
The new booster has a metal casing, the pushrods seems more solid and is generally tougher. You might try AZone and take a look at the booster your local store has. For my $0.02, I would NOT recommend going to the stealership. The part is WAY more expensive and without any warranty
Now, if I can get the brakes to stop the car, I would be happier than h-ll. I have one of those Vettes that has the mushy brakes and have not been able to find why - yet.
I hope it helps
Good Luck
Subman

1st test - when you apply the brake, do you hear a hissing sound? If yes - new booster.
2nd test - With the engine off, apply the brake 3 or 4 time. The brake pedal should get higher with each pump. If no - new booster.
3rd test - After test #2, do not remove your foot from the pedal. Start the engine. The pedal should drop slightly and return to normal position. - If not new booster.
4th test - disconnect the vacuum line from the booster port. Plug all other openings. Attach a vacuum pump and apply 10 - 15 inches of vacuum. It should hold this vacuum for a minimum of 3-5 minutes. If not - new booster.
When you replace the booster (I just did this, again, yesterday), you will find it easier to get to the bolts under the dash if you remove the entire seat and drop the steering column. Remember to remove the air bag fuse and disconnect the battery before you drop the column. When you replace the nuts, use a couple of really long extentions, a swivel and a short socket with a little "sticky" grease inside the socket. The grease will help you keep your sanity by keeping the nut in place. There really is a place under the dash of C-4's that hides dropped nuts and bolts - once there, you'll never find 'em
Good luck
Subman

FWIW - RO water will search out and pull minerals from where ever it can find them - copper, tin, lead, brass, iron are the most readily available in any water system other than PVC. I only know this because I had to replace the entire copper water line(s) to 2 new multi million dollar printing presses with PVC. The copper connections (solder) were the first to go, a little bit at a time, then - wham - major water leak on the roof.
Filtered water from the fridge or Home Depot cartridge type would probably work just fine, but R.O. will f/u the entire cooling system.
My $0.02 -
Good Luck
Subman

Almost a year ago, my 91 did the same thing. I did some research on the other forum, posed a few questions, followed most advice (specfically Bogus, CFI, Casey and a few others) and found I had a 12 volt to ground challenge - dead short. After a month of weekends and nights, testing as I went, I found the wire to the starter solenoid wire along with the knock sensor and temp sensor wires bared to the bell housing behind the right head. The real down side is that it took out the ECM and the CCM.
Check to see of you have excess drain on the battery. If so, start pulling fuses until the drain goes away. The start with that circuit looking for anything out of the ordinary.
BUT, before you do anything, find a copy of the FSM electrical book (the 91 is a red cover - I think the 90 is as well) Without it, you might as well send the car to a good electrical shop - Just my $0.02
Good Luck
Subman

Last November, the guy that makes the diecutting dies for me found out I run AX in my '91 and wanted to try it in 1 of his cars. He showed up at a practice in a screaming yellow Porsche 939 turbo. Kickazz car but as an AX car, the turbo kicks in way to early.
Yesterday, he delivered a die and ask if I would drive his other car to check it out, seemed to be running rich.
Out to the parking lot - and there is a replica 427 Cobra - 550+ HP and you could eat off any part of the car.
The guy tossed me the keys and off we go. I drove it around a couple of blocks, jumped on once or twice, plenty of power, but it lacks that "push you back in the seat" power. It's running really rich so that sitting at a light it loads up. To get to take off ya gotta rev up the engine a couple of times to clean it out. Even running bad, what a rush to drive.
I found out this guy has these 2 incredible toys and hasn't a clue what to do with them. He loves the cars but is kinda afraid to really drive them and has no ability to work on 'em.
So, as soon as my kids get their stuff outta my garage (mid-March), the Cobra comes to visit me.
Subman

So, did you get a new or used solenoid? Are you running your car with the SES light on? What was your fix?

Still searching for the part. Since the SES doesn't come on during the drive to work, I cleared the code and drive on. Hopefully, some mom & pop a/p store has one sitting on a shelf collection dust somewhere.
Good Luck
Subman

When the engine is keyed on, the ECU goes through a POST. That test will check for a problem with the switch. If the SES fires with a EGR code, then you know WHY the code has fired. If it happens at start up, it's the switch, if it happens after a drive, then it's the valve.

I can only speak from my expereince, so here's what's up with the above.
The SES light would come on after 4-5 minutes of driving at somewhat consistent speed (freeway driving). After clearing the code, driving back and forth the 7 minutes to the office, no SES. Back on the freeway, 4-5 minutes, SES. Having gone through the FSM tests and then some, I found the EGR valve was good (held vacuum for longer than required), the vacuum lines held required vaccum, checked the 2 electrical wires to the EGR vacuum solenoid all the way back to the ECM, finally re-read all the instructions again and found the solenoid did not preform as it was supposed to.
Now the down side is - - find a EGR vacuum solenoid - I have spent hours with the local a/p stores and their warehouses - there is another post regarding this - Standard is still up in the air if they are going to manufacture again, B/W is out of stock on the part number, as is Blue Streak and AC - J&D, if they have a used one, is "somewhere around $125.00".
All that said, re-read the FSM and all the test proceedures before throwing $ and time only to find the valve was ok and it's the ECM or the solenoid or a broken wire that's the culprit.
Good luck
Subman

Klaus - Thanks (I think) for the info and update. I found 2 independant auto parts stores that SAY they can get it on Monday. Hopefully, between those 2 and Chris May, somebody has something. BTW, I have been trying to get this car smogged since May. It failed twice because for N0x (this solenoid has probably been the cause) and since then every time I have the time to get it to the test station, something else broke. The SES light doesn't get a chance to activate since the drive to work is surface streets and I have not taken a non-stop and go ride on the freeway in a year.
Subman

UPDATE - Started from the beginning this morning on all the tests and found I had neglected to turn the key on when checking the vacuum test through the solenoid.
Vacuum dropped. Tested the ECM and it did what it was supposed to. . . . diagnoses – EGR vacuum solenoid is toast. Now the challenge is finding one. I checked AZ, Kragens, NAPA, Pep Boys, local Chevy dealer, local independents and J&D Corvette to try to pick one up today. Prices ranged from 55.00 – 125.00. And nobody has one in stock - I think that it’s Borg-Warner that no longer makes the part.
I can feel the Corvette tax coming. I don’t mind a bit of taxing, but when I don’t even get kissed - - -
Subman

This is gonna sound real weird but, jack up the back and pull on the tires N/S & E/W. I had the same "noises" in my 89. After 3 months on and off at the dealer, I found the problem when I rotated the tires and doing the above. The "C" clip that holds the spline in the differential was gone, allowing the half shaft to move outward on right turns. Fortunately it was still under warranty.
Good luck
Subman

Kinda strange, but the FSM sheets I have must be for an earlier model(s). It keeps referring to the EGR temp switch, which to 91 doesn’t have.
I also have a sheet I copied from the “other” forum that refers to placing a diode between the temp switch and the grey wire to the EGR solenoid.
So I went to the “other book” (Haynes) -

“#20 - Ignition on, engine off, ground ALDL, apply 10” vacuum to the manifold side of the EGR solenoid. If it holds, proceed to #24
#24 – Unground ALDL and vacuum should drop
#25 – If no drop in vacuum, disconnect the solenoid harness. If vacuum drops, repair short to ground in circuit 435. If no short, ECM is faulty NOTE:Before replacing the ECM check the resistance of each ECM controlled relay and solenoid . . . . . . . . Replace any relay or solenoid that has 20 ohms or less resistance
If there is no drop in vacuum, replace the EGR solenoid.

At that point it was late and I stopped trying to figure it out. However, copying the above, I noticed there is an additional test involving vacuum, starting the engine, run at 1500 rpm in park, then in drive, test lights etc.
I’ll try that tomorrow. If that passes muster, I’m back to a faulty ECM, I think.
Will post findings as soon as I can figure out what I’m supposed to find.
Subman

It’s been a really bad year for my ’91. Dead short wiped out ECM & CCM. Removed every wire in the car before finding the bare wires behind the right head (against the bellhousing). Then found the new GM CCM was bad. Side tank of the radiator cracked (on course during AX run), new upper ball joints went bad, heater core blew a seam, auto trans went south just before Christmas. Dec 29, heading out of town for 29th anniversary and New Years, 5 minutes up the freeway and I get a SES. Checked the codes when we got home - 1.= H72; 4.= C32. EGR fault.
I checked the diaphragm (holds vacuum), replaced the tube from the solenoid to the valve, checked ohms on the solenoid (28.4 - anything over 20.0 is supposed to be ok), the 91 doesn't have a EGR temp sensor (which eliminates one potential problem), test light to solenoid harness and - whoops - a challenge. According to the book - ground test light, probe each wire with the key on, engine off, test light should light up on each wire. The pink wire lights up (from the fuse box) the grey one doesn't (from the ECM). The wire from ECM grey connector to EGR solenoid is good. Indicating the ECM is not working??? Or did I read it all wrong. Should the grey wire only light up when in closed loop?
Any help trying to understand all this would be appreciated.
T. I. A.
Subman