teebee1994 wrote:
No the engine was not hot......are you thinking that the higher temps might make a difference on the ohms readings I am getting?

Maybe since it is running better, maybe I need to take it out and drive it some and let the computer re-learn. Maybe?

biggrizzly wrote:
Weav,

Did you replace knock sensors? I replaced mine when I rebuilt the top end, and wound up ordering the wrong knock sensors from a part no. I found on CF.
Although the sensors are essentially the same, they are different impedence values for OBD1 and OBDII. When I had the 96 knock sensors installed I was getting all kinds of knock values and retarded timing below 1000 rpm on my data logs.

Just a thought
Don

BrianCunningham wrote:
Have you checked the coil and the ignition module?

How about the harness itself?

The connectors been known to go bad.

Weavsvet wrote:
Also, when the A/C is on the car idles fine. A lot faster but smooth. Normal idle is around 550 rpm. It's around 800 rpm or better with the A/C on. I do not have a Tech I so I'll have to get it to my mechanic to check out the ASR/throttle adjustment. Without the A/C on it has a nasty lope at idle after it warms up good. FP is good. 39 @ idle and goes to 48 or so on acceleration. Holds it's own after shutdown.

Blade_1 wrote:
Quote:

Weavsvet wrote:
Also, when the A/C is on the car idles fine. A lot faster but smooth. Normal idle is around 550 rpm. It's around 800 rpm or better with the A/C on. I do not have a Tech I so I'll have to get it to my mechanic to check out the ASR/throttle adjustment. Without the A/C on it has a nasty lope at idle after it warms up good. FP is good. 39 @ idle and goes to 48 or so on acceleration. Holds it's own after shutdown.

Lopin' idle is an air issue; gotta' be a vacuum leak somewhere.

Block the TB linkage, brick on pedal, anything to get a steady idle (DON'T rely on A/C for this steady idle, for this test!), then start sprayin' startin' fluid EVERYWHERE, a little at a time, to find where it's gettin' sucked in, and causin' a brief rev increase.

Vac leak will make a engine lope idle - 20 year old lawn mower, or a new car on the lot...

Weavsvet wrote:
I tried the starting fluid as Blade suggested.

I got a little rev from around the IAC. It seemed to be erratic though. It may have been getting in around the intake boot on the TB. I snugged all that up but no difference. If there is another leak I can't find it! Does the IAC have a gasket? I replaced it a while back but I don't remember one being supplied with the new one.

biggrizzly wrote:
Tom,

I agree they seem like a quality item. I have about 500 miles on mine now and so far so good. I did re-apply red Locktite on the rotor screw to make sure it would not come off, and I installed the O-ring with the Opti off the car so I was absolutely sure it was seated correctly before installing the cap.

Calm wrote:
Quote:

biggrizzly wrote:
Tom,

I agree they seem like a quality item. I have about 500 miles on mine now and so far so good. I did re-apply red Locktite on the rotor screw to make sure it would not come off, and I installed the O-ring with the Opti off the car so I was absolutely sure it was seated correctly before installing the cap.

Sadly, I did NOT use locktite on my MSD. Rotor blew off within a month!

Pcolt94 wrote:
Most bad opti's do not throw a code. That’s because a code an only be set by what the PCM monitors. Hundred of items can be defective but only a hand full of signals are interrogated or monitored for radical changes. The opti's low resolution signal is monitored but the high voltage and cap functions are not. So if a rotor or cap is causing weak spark or cross spark in the ignition, the engine can have a wide variety of symptoms but no codes.

The low and high resolution pulses from the optical pickup are the very reliable and cause the least amount of problems. Bad bearings can cause problems but not usually on a 2 year old unit.

I was going to suggest pulling the fuel pump assembly and checking the sock and tank for debris and water but since you are replacing the opti lets hope that that takes care of it.

teebee1994 wrote:
OK, I've tried to find the cause and fix this issue, but it's getting to me now. Here's the Cliff Notes version.

After a long week long trip (3000 miles) I started to have a miss at idle only in drive (auto). sometimes when it misses it shakes the whole car, sometimes it just slightly noticeable. Only when in gear and only at idle. If I rev up just past idle 800-900 RPM stumble goes away. (mades me think IAC, but why only under load?)

Here's what I have done/checked:

#1 no SES light and have checked, No codes set either in History or Current.

#2 I have changed Fuel Filter, opti, plugs, wires, WP, Injectors all within the last 6k miles

#3 Cleaned TB and MAF within the last 8K.

#4 Removed and cleaned IAC and EGR.

After performing these things I thought the miss was gone, but on the next outing it came back. All the way down she runs pretty good, maybe a touch warmer than usual (200-205). I get about 140 miles from home and going through a town the little miss at idle in gear starts again (not bad but I can feel it). I get back in to head home, the little miss is back. No biggie when I have to stop I just kick it in neutral, then once I get it going again she's alright, but as I get further down the road the worse she runs rough, pinging, bucking at times. And when all this is going on the temps start to climb (up to 230). Once I get it up to cruising speed she kind of smooths out, but don't step on the gas (as in passing) as it starts pinging and bucking and the temps start up again. Once I get in to a cruise mode the temps will come down some (215 -220). I have made it home (170 miles) and she is running like cr@p.
(indicating lean condition...yes?)

I take fuel pressure readings and find 41-42# at idle maybe dipping below 40 at times. Drops below 40 at times when I rev the engine. So I think that the FP is about to Cr@p out, I order a new FP (GM) and filter. Install them and in the process of changing the filter I find that my #8 spark plug is just finger tight (no-one to blame for that except my self). Thinking that I found the miss issue I tighten up the plug. Also after changing the FP and filter, Fuel pressure readings are just like before.

So I decided to scan the computer. My first data scan is below.
Trouble Codes
43 Electronic Spark Control failure
Pending Codes

1 Desired Idle 600.00 RPM
2 Engine RPM 550.00 RPM
3 Coolant Temp 194.90 °F
4 Oil Temp 142.20 °F
5 Manifold Air Tmp 92.30 °F
6 A/C Pressure 156.00 PSI
7 MAP Sensor 2.23 Volts
8 Throttle Sensor 0.58 Volts
9 Throttle Angle 0.00 %
10 Battery Voltage 12.4 Volts
11 Barometric Press 4.35 Volts
12 Left O2 Sensor 1007.00 mVolts
13 Right O2 Sensor 906.00 mVolts
14 Block Learn Cell 16.00
15 Left Block Learn value 140.00
16 Right Block Learn value 153.00
17 Left Integrator value 128.00
18 Right Integrator value 128.00
19 Left Inj Pulse 6.60 mS
20 Injector Pulse 7.20 mS
21 Mass Air Flow 8.00 gr/sec
22 CCP Duty Cycle 0.00 %
23 Idle Air Mtr Pos 53.00 steps
24 Learned Idle Pos 34.00 steps
25 Spark Advance 14.00 °
26 Knock Retard 7.00 °
27 Knock Sensor 22.00
28 EGR Duty Cycle 0.00 %


So I get the FSM out and follow the flow chart and find the left Knock sensor is way out of range, so I replace it. Still no love.

Next data scan:

Trouble Codes
43 Electronic Spark Control failure
Pending Codes

Operational Data
1 Desired Idle 712.00 RPM
2 Engine RPM 650.00 RPM
3 Coolant Temp 150.30 °F
4 Oil Temp 92.30 °F
5 Manifold Air Tmp 86.90 °F
6 A/C Pressure 139.00 PSI
7 MAP Sensor 1.70 Volts
8 Throttle Sensor 0.58 Volts
9 Throttle Angle 0.00 %
10 Battery Voltage 13.60 Volts
11 Barometric Press 4.35 Volts
12 Left O2 Sensor 1003.00 mVolts
13 Right O2 Sensor 862.00 mVolts
14 Block Learn Cell 16.00
15 Left Block Learn value 140.00
16 Right Block Learn value 153.00
17 Left Integrator value 128.00
18 Right Integrator value 128.00
19 Left Inj Pulse 5.80 mS
20 Injector Pulse 6.30 mS
21 Mass Air Flow 8.00 gr/sec
22 CCP Duty Cycle 0.00 %
23 Idle Air Mtr Pos 51.00 steps
24 Learned Idle Pos 34.00 steps
25 Spark Advance 20.00 °
26 Knock Retard 1.00 °
27 Knock Sensor 22.00
28 EGR Duty Cycle 0.00 %

I am then told to check all the connections for the ignition system (Opti, coil, etc) and to check all the vaccum lines. Which I do and I actually replace some of the vacuum lines out. It runs better, doesn't miss quite so bad, but still not right.

Here is the last data scan I did. I did this one with the engine revved a little (about 1700 rpm)

Desired Idle (RPM) 675 675 675 675
Engine RPM (RPM) 1775 1775 1775 1775
Coolant Temp (°F) 192.2 192.2 192.2 192.2
Oil Temp (°F) 155.7 155.7 155.7 155.7
Manifold Air Tmp (°F) 90.9 90.9 90.9 90.9
A/C Pressure (PSI) 75 75 77 77
MAP Sensor (Volts) 0.82 0.8 0.84 0.8
Throttle Sensor (Volts) 0.72 0.7 0.72 0.72
Throttle Angle (%) 3 3 3 3
Battery Voltage (Volts) 13.7 13.7 13.6 13.6
Barometric Press (Volts) 4.33 4.33 4.33 4.33
Left O2 Sensor (mVolts) 950 893 893 897
Right O2 Sensor (mVolts) 206 418 224 79
Block Learn Cell 17 17 17 17
Left Block Learn value 129 129 129 129
Right Block Learn value 129 129 129 129 Left
Integrator value 128 128 128 128
Right Integrator value 138 133 137 134
Left Inj Pulse (mS) 3 3 3 3
Injector Pulse (mS) 3.2 3.1 3.2 3.1
Mass Air Flow (gr/sec) 13 13 13 13
CCP Duty Cycle (%) 0 0 0 0
Idle Air Mtr Pos (steps) 24 24 24 24
Learned Idle Pos (steps) 21 21 21 21
Spark Advance (°) 36 36 37 36
Knock Retard (°) 0 0 0 0
Knock Sensor 182 182 182 182
EGR Duty Cycle (%) 0 0 0 0

The things that seem to stand out I highlighted. The readings are 1/2 second intervals.

I am still getting the code 43 after it goes into closed loop.

teebee1994 wrote:
Well, I have my fingers crossed when I say this but, my saga has ended. I got the Vette back today after a long time fighting the issue. It was the opti. Actually the cap and rotor were toast. Don't ask me why, but it is obvious when you look at the inside of the cap that this was my issue. Less than 6000 miles on this genuine GM AC/Delco optispark. I did replace this with an MSD unit, I could have probably gotten by with a new cap and rotor, but I decided that if I was in this far, I wasn't going to take any chances and just replaced the entire unit. Notice the inside of the cap here.
[IMG]http://img.photobucket.com/albums/v281/toms94/Maintenence/Optispark-Bad002.jpg[/IMG]

So if anyone needs a 6000 mile optispark (that needs a new rotor and cap) drop me a message, maybe I can recoup some of the cost of the MSD unit.

The mechanic also believes that he found the source of my oil leak as well. He said it appeared to have been leaking around the shaft that drives the opti. Seal was good, the shaft was about 15 thousandths smaller than the MSD units shaft. After driving it for about 45 minutes I put it on the lift and checked it and it is dry as can be under there.

Thanks for all who posted with ideas and suggestions.

Blade_1 wrote:
Sounds great.

Now, I'd be interested in seeing scans, SAME TEMPS, and the effects on all data of the new opti...

teebee1994 wrote:

I'll see if I can get the scan this weekend.

Pcolt94 wrote:
I had your typical opti problems. Got bad when at operating temperature, coughed bucked on acceleration and sometime the idle wonder break up and hunt. After I check all under the hood and found basically nothing but knew it was miss-firing (of course no codes) . I even changed the coil, and EGR valve which was actually bad. But in the end when I replaced the opti all problems were fixed and it ran normal.

Pulled the entire old opti apart to inspect it all. Did not see any bearing wobble and the cap looked great with no carbon tracking visible or any other kind of problem that I could see visually for the original opti with about 75,000 miles on it. Never really determined exactly what was bad in it but I assume something was wrong with the cap or rotor. A littlie bit of rust on the inside on the rotating disk and that was about it.

teebee1994 wrote:
Sorry guys, I've been very busy with things and I was gone all last week, so I haven't even started the Vette up in three weeks. So I have not run a scan. When i do I'll post the numbers.

Pcolt94 wrote:
Blade_1 - You got my attention and got me thinking about what you said in regard to pulse width. I remembered that mine were half of what teebee posted. Then I looked at the fuel trim and they look out of range. My engine is all stock and thought perhaps my numbers which I think are good might be of some help for comparison for a possible clue or direction.

I just base lined all the engine data this week. I did it with key on, open loop and closed loop. I have only posed closed loop because the file copies poorly.

Item Closed Loop
RPM desired 622
RPM 625
Engine Coolant Temp 198
Air intake temp 147
MAP 37
BARO 104
Throttle Position 0.64
Throttle Angle 0
BNK 1 HOS 1S 100-800
Loop Status closed
BNK 2 HOS 2S 100-800
Loop Status closed
Eng Speed 630
BNK 2 HOS 2S 71
ST Fuel TR BNK 1 130
LT Fuel TR BNK 1 131
ST Fuel TR BNK 2 124
LT Fuel TR BNK 2 125
Fuel Trim Cell 16
Fuel Trim Enable yes
Spark Advance 20
Mass Air Flow 6.5 g/sec
Knock Retard 0
Knock Signal no
Lo Res Signal 23
Hi Res Signal yes
INJ Pulse Width Bank 1 3.4 ms
INJ Pulse Width Bank 2 3.3 ms
Idle Air Control 28
Leaned IAC 31
EGR Duty Cycle 6
Ststem Voltage 13.5
Air Control off
Fuel Evap Purge 0%
Knock Sensors OK
Engin Oil Temp 194
Injector Fault no
TCS/AIR Active no
Fan 1 2 1 off 2 off
Engine Coolant Temp 196
A/C Request no
A/C clutch no
A/C Status off
A/C comp pressure 93
TCC Brake Switch closed
TCC Solonoid off
Trans Range SW -
Park/Netural -
Cruse control off
MPH 0
1-2 Shift Sol on
2-3 Shift Sol on
Pass Key enabled
Time From Start 4 minutes

7 MAP Sensor 2.23 Volts (= about 50 kPa)
8 Throttle Sensor 0.58 Volts
9 Throttle Angle 0.00 %
10 Battery Voltage 12.4 Volts
11 Barometric Press 4.35 Volts (= about just < 90 kPa)

7 MAP Sensor 1.70 Volts (= about 40 kPa)
8 Throttle Sensor 0.58 Volts
9 Throttle Angle 0.00 %
10 Battery Voltage 13.60 Volts
11 Barometric Press 4.35 Volts (= about just < 090 kPa)