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| lunytnz | Running rich and hunting for idle | ||
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Guru Newb
 
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I noticed my 87 was hunting for idle (between 500-700 RPM). It's worse with no load and smooths out pretty well under load (such as A/C on). I replaced the IAC, but the hunting for idle remains. And, since then, I've gotten a Code 45 (Rich Exhaust) a few times. The car seems to run fine, other than at idle.
According to the FSM, a code 45 is set when it's in closed loop and the O2 sensor records a high (> 0.7 V) reading for more than 50 seconds. The FSM lists lots of potential causes. I just got set up with a bluetooth ALDL adapter and I'm using ALDLdroid on my phone to log data. What I found is that it's not staying in closed loop very long. It went into closed loop a few minutes after cold start, but then went back into open loop 20 seconds later. For the first 10 mins, it was in open loop most of the time, switching to closed loop about 5-6 times for only about 10 seconds each time. Finally, about 20 minutes into the trip, it stayed in closed loop for about 2 minutes (while I was cruising on the freeway). The O2 was typically between 400 and 600 mV. It got as high as 850 when I was on the freeway. Cross-counts reset about 20 times during the trip, but were stable when it was running rich for a period of time, (seems to make sense, to me). BLMs were typically between 108 and 124, but hit 128 and 130 at times, while I was on the freeway (about 15 mins). From what little I know, it's supposed to stay in closed loop once it warms up. Is that right? Does it seem like the O2 sensor is working correctly? What else should I be looking at? On another trip, it started out in open loop for about 4 minutes, running lean with BLM = 118, O2 between 350-450, no cross-counts. Then O2 started climbing to 700 and it went into closed loop. O2 was in the 750-850 range while I was cruising on the freeway. When I got stuck in stop-n-go traffic, the O2 came back down to 4-500 range and it went back into open loop with BLM 108 most of the time. It toggled in-n-out of closed loop a few times. It looks like once I took my foot off the throttle for 10 seconds, it goes back to open loop. Any other ideas of what might likely be causing it to run rich? It also seems to be an intermittent problem because there are days that it idles smooth and seems to run normal. Any help would be MUCH appreciated! |
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Posted on: 2014/9/4 3:43
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| Woodstock | Re: Running rich and hunting for idle | ||
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The mV should be in the 50-950mV range, and the cross counts a lot higher.
Sounds very much like a lazy O2 sensor. Replace it and the idle situation should be gone. |
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Posted on: 2014/9/4 10:41
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| Schrade | Re: Running rich and hunting for idle | ||
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Elite Guru
 
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Loping idle can be a vacuum leak. Try this:
Quote: FIRST (fully warmed up motor); block the gas pedal, or block the throttle linkage. YOU HAVE TO DO THIS TO GET A STEADY IDLE , around 1,250 rpms, or a little higher. If you don't, you can fish starting fluid, a propane hose, or WD40, or Krylon, or hair spray, or pee, anything, until you need a sweater in Hades, but if the motor is lopin' idle already from a vacuum leak, you ain't gonna' find any leak, unless it's so big that Little Jack Horner can stick his thumb in it and pull out a pineapple NOPE. |
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Posted on: 2014/9/4 13:32
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| lunytnz | Re: Running rich and hunting for idle | ||
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Quote:
I was considering throwing an O2 sensor at the problem, but wanted to get some data first. So, the O2 values look normal, but the cross counts mean it's spending too much time either lean or rich, right? Does 'lazy' mean it's just taking too long to sense, and report, the changes? If you were to replace it, would you choose a wide-band sensor? Or a stock one? And, if stock, a Bosch or an AC/Delco? Thanks much! |
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Posted on: 2014/9/4 15:24
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| Matatk | Re: Running rich and hunting for idle | ||
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A non heated 02 sensor has about a 30,000 mile change interval and costs around $35. Not really "throwing parts" at it if you change it.
You will not use a wide band, that is used for tuning and not for everyday driving. Bosch, ac delco, or NGK are fine for replacements. Question - do you have long tube headers? Matthew |
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Posted on: 2014/9/4 15:47
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| lunytnz | Re: Running rich and hunting for idle | ||
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Quote:
No, I have stock headers. Thanks for the info! I will get a new O2, then... I just wish it wasn't such a bitch to get at :-) |
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Posted on: 2014/9/4 16:45
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| j3studio | Re: Running rich and hunting for idle | ||
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Quote: lunytnz wrote: Wow! I didn't know or think to check if they made such things ... |
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Posted on: 2014/9/4 17:52
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| bogus | Re: Running rich and hunting for idle | ||
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I'm with John on this... I didn't know there was one for ODBI.
However, do avoid Bosch... they are junk. NTK, NGK, Denso or Delco. |
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Posted on: 2014/9/4 20:37
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| lunytnz | Re: Running rich and hunting for idle | ||
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Quote:
There are actually a couple of choices out there that I found. The one I bought is made by Red Devil River (http://www.reddevilriver.com/ALDL_Bluetooth.php). The one drawback is that it requires 12V power, so you either have to add a connector to pin G of the ALDL plug or you have to connect a USB cable from the adapter to a computer or lighter socket. |
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Posted on: 2014/9/5 2:59
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| Schrade | Re: Running rich and hunting for idle | ||
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Maybe get the tune diagnostic BEFORE putting in a new O2.
Rich burn might foul the O2 element. It WILL foul cats... |
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Posted on: 2014/9/5 14:02
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| lunytnz | Re: Running rich and hunting for idle | ||
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Quote:
That's *exactly* what I was hoping to do, Schrade. But, I'm not able to figure out, so far, what the cause might be. I have heard that the O2, itself, might be the cause. The part that has me most confused is that I'm getting the 45 code (running rich), but the MPG on the dash (which I believe is based on pulse width) is high, indicating that the engine is running lean. But, *actual* (calculated) MPG is lower than normal. I'm also wondering about the Evap Emissions system... I think it may be pumping air into the exhaust full time, but can't figure out how that would cause a rich condition. Any help will be most appreciated! |
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Posted on: 2014/9/5 14:10
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| Matatk | Re: Running rich and hunting for idle | ||
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I doubt the air pump is running constantly. Change the sensor, clean and reset the IAC and base idle, and go from there. The next thing I would check is plugs and wires.
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Posted on: 2014/9/5 14:38
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| bogus | Re: Running rich and hunting for idle | ||
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Quote:
what comes first? chicken or the egg? A bad O2 most certainly can and will cause this... it's the logical place to start. Setting the IAC... meh, it might help with the idle, but I would be more inclined to clean up the throttle body first. If it's all coked up, well, all bets are off. Whatever you do, do NOT oil the IAC. It can be cleaned, just don't oil it. Evap emissions? Well, the air pump technically runs all the time, but it will, if anything, lean out the mix, not richen it... sure, the injectors will compensate to a degree... The valves could be out of sorts, it's easy enough to test. Pull off hoses, feel for air. Also check the exhaust check valves... they can be sticky and cause all sorts of secondary issues. And not throw a code. These valves are on the air pump lines near the manifolds, Round things that are inline with the rubber lines... 2" round, silver or black... 1" long... line in, line out. They open with the higher air pressure hits them, but if they are jammed open... A little too much air, computer adjusts, now running a bit fat... |
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Posted on: 2014/9/5 17:48
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| Matatk | Re: Running rich and hunting for idle | ||
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Andy, I personally think any time you clean the IAC you should reset the idle as well. I also agree with cleaning the TB passages.
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Posted on: 2014/9/7 19:58
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| istter1 | Re: Running rich and hunting for idle | ||
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Quote:
Neat toy |
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Posted on: 2014/9/7 23:37
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| Schrade | Re: Running rich and hunting for idle | ||
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Quote:
I'VE heard that O2 itself CANNOT be a cause. AND I've read it too. See my 2 margin notes in the first column, below... ON A WELL TUNED MILL, THE O2 DOES LITTLE MORE THAN GO ALONG FOR THE RIDE. Ray Bohacz put it in print. Schrade ain't gonna' argue with Ray, because Schrade AGREES.  If you have a 45 DTC, there is a diagnostic flow chart in FSM which will lead to the solution - PERIOD. If you want the rest of the TPI article, which applies to LB9, L98, LT1, LT4, LT5, and perhaps others, PM me. Or I can post it (think I did here already; Matt?) EDIT: I've re-read this TPI article MANY MANY times, since getting it in vette mag in 11/00. EVERY TIME I READ IT, SOMETHING COMES TO A GREATER UNDERSTANDING, THAT I DIDN'T GET BEFORE. See notes, underlines, superscripts, etc., ... DOES YOUR MOTOR LOPE RHYTHMICALLY AT IDLE??? 2 edit: Never mind; I see by your title, that it does. Did you do the leak test, 100% as described above in post 3? Because if you DO have a vac leak, as I strongly suspect, and you do not find it, you will NEVER EVER get the tune correct. A 50 year old lawn mower, and a 2015 new car will not run correctly with a leaking intake component gasket - hoses, gaskets, etc., ... Attach file:  tpi3.jpg (468.28 KB) |
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Posted on: 2014/9/9 1:00
Edited by Schrade on 2014/9/9 1:22:56 Edited by Schrade on 2014/9/9 1:29:41 |
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| j3studio | Re: Running rich and hunting for idle | ||
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Thanks for posting that article!
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Posted on: 2014/9/9 2:06
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| Matatk | Re: Running rich and hunting for idle | ||
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Sorry but that article is crap. It contradicts itself between your first note and the caption under the oxygen sensor picture. It is also dead wrong about the oil pressure switch turning off the fuel pump.
Furthermore, I have personal experience with my 89 that the O2 sensor will affect idle. Ask Axel about my datalogs along with tuning to correct it. I have also worked on other vehicles where lazy O2 sensors (as shown on real time scanners) were the culprits of running problems. |
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Posted on: 2014/9/9 3:33
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| Schrade | Re: Running rich and hunting for idle | ||
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I don't know what else to tell him Matt.
Others have argued against that very point, when I posted the article - the fuel pump cut-off, from no O/P signal. I don't know - I never tried to test with cutting off the signal... I can post the rest of the article, and whatever is wrong, show it. I'm ALL ABOUT learning. No one has ever actually showed what's wrong. You might be right, but ya' gotta' show it. All bets are off, on my notes, to be clear. And no one knows all - not even the guy paid for print. |
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Posted on: 2014/9/9 4:14
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| lunytnz | Re: Running rich and hunting for idle | ||
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Thanks for posting the article. I rarely find anything that is flawless, but can usually find something worthwhile in most everything I read.
Since Matatk pointed out the caption under the pic of the O2 sensor, that brings up a significant possibility... just a couple of years ago, I had the head gaskets replaced because of a coolant leak. I just got the AC Delco O2 sensor tonight, so I'll be curious to see if the old one has a white coating. From the data I've collected, it appears the code is intermittent and the airflow seems commensurate with throttle position and engine speed (so the MAF doesn't *appear* to be the culprit). The FSM chart for Code 45 points you at the Diagnostic Aids. Unfortunately, for me, I'm lacking the equipment to get very far. I can check the fuel pressure (and when I did it a year ago, it was fine), but I don't have an injector tester to do an injector balance test. So, I hope to find time to get the O2 replaced in the next few days and also to check the fuel pressure again. Thanks for all the info and the help! |
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Posted on: 2014/9/9 7:20
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| captmike13 | Re: Running rich and hunting for idle | ||
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I had a "lazy" O2 sensor once and it took a mechanic to find it using a diagnostic scope. The O2 sensor should be changing lighting fast. It did cause my car to fail emissions and run like crap. I don't remember if it caused an idle issue though.
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Posted on: 2014/9/9 10:14
Edited by captmike13 on 2014/9/9 11:01:01 |
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Mike| Woodstock | Re: Running rich and hunting for idle | ||
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Of the probably 15-20 dead or lazy O2 sensors in various Vettes and F-bodies I replaced, close to none had visible signs.
Maybe my first post wasn't clear. The O2 sensor should at all times be in the 50-950mV range and switching fast back and forth across the 450mV cross count threshold. Only during warm up, at WOT and during fuel cut off it will be linear and not add to the cross counts. Idle was always most affected, when the O2 sensor was on it's way out. I am still pretty certain, replacing the O2 will cure the condition. We'll find out soon, I guess. |
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Posted on: 2014/9/9 10:56
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| lunytnz | Re: Running rich and hunting for idle | ||
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Surprise Surprise! I put the new O2 sensor in Friday and the initial data didn't look good. I collected more data today on the drive to, and from, work (30 mins). The O2 is spending ALL it's time between 950 and 1,000 mV!! So, it's running rich ALL the time and I have virtually NO cross-counts.
The old O2 sensor was pretty coked up with black soot. My O2 sensor is installed on the drivers side, right after the manifold connects to the exhaust pipes. The Evap system feeds in waaay downstream, well after the cats, so I suspect that is less likely the issue. Tonight, when I pulled in the garage, I swear I could hear a misfire, so I'm going to look into checking the injectors and plugs, starting with 1, 3, 5 and 7. |
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Posted on: 2014/9/16 5:26
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| lunytnz | Re: Running rich and hunting for idle | ||
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I finally checked the resistance on the injectors... after figuring out how to release the plugs (push inward, toward the plenum, on the u-clip and pull up on the wires at the same time) a pretty consistent 17.6-17.7 ohms each.
I checked the fuel pressure... 42 PSI on prime, running at 40. Holds pressure for a few minutes, but was at 20 PSI after 15 minutes and 10-15 PSI after 30 mins. I pulled a couple of plugs (#5 and #7) and found both to be pretty fouled with black soot. I cleaned 'em up because I didn't have any replacements on hand. Wondering what this points to next... |
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Posted on: 2014/9/16 6:55
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| Matatk | Re: Running rich and hunting for idle | ||
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How is your cap/rotor?
Did you check the wires for arcing or cracks? Did you ohm them? |
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Posted on: 2014/9/16 16:11
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| Matatk | Re: Running rich and hunting for idle | ||
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You should unhook the battery to reset the ecm. It may have fuel table adjustments based on the old/bad O2 sensor.
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Posted on: 2014/9/16 16:13
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| Schrade | Re: Running rich and hunting for idle | ||
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The Black on the O2's, and the plugs is fuel - from a rich burn. And it's fouling your cats...
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Posted on: 2014/9/17 2:25
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| lunytnz | Re: Running rich and hunting for idle | ||
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Quote:
I didn't pull the cap, but it (and the rotor) was replaced just 2 years ago. I moved some of the plug wires a bit, just in case, but no difference. I just checked for vacuum leaks by spraying carb cleaner around the intake and every vacuum hose I could find. No surges in engine speed. I suspect, since both 5 and 7 were equally fouled, that the rest are fouled, too. I'm sort of at a loss at this point... A few years ago, when the car failed emissions (high Hydrocarbons (of 450; limit 220)) at idle, a shop said a component of the A.I.R. system wasn't working right (the diverter or switching valve, I think), but also said a replacement part was not available. Even though it failed emissions, at idle, it idled and ran fine. So, if the valve isn't working right and there IS air to the ports in closed loop, that means it's potentially injecting air into the exhaust, right? How would air injected into the exhaust cause a high hydrocarbon reading at idle? |
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Posted on: 2014/9/17 5:50
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| Woodstock | Re: Running rich and hunting for idle | ||
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Pull off the O2 sensor, or rather disconnect it. Let it run and see if it runs better without it. If it does, the new O2 is toast right out of the box or the ECM is doing BS.
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Posted on: 2014/9/17 12:08
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| Matatk | Re: Running rich and hunting for idle | ||
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Are visual emissions required in your state? You could try capping off the air lines at the exhaust manifolds.
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Posted on: 2014/9/17 14:21
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| lunytnz | Re: Running rich and hunting for idle | ||
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It turns out I don't have to go through emissions anymore (exempt after 25 years old, I think), so I can definitely try capping off the AIR lines. What is the easiest way to 'disable' the AIR system? It seems those tubes run in, and around, everywhere!
If I reset the ECM (disconnect battery), that might force it to 'learn' from scratch, but it shouldn't effect the O2 sensor reading, right? And the O2 indicates it's running extremely rich. |
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Posted on: 2014/9/17 19:31
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| Matatk | Re: Running rich and hunting for idle | ||
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Remove all the solenoids under the throttle body, remove the hoses from the manifolds to the box, disconnect and tuck back wiring connections. You can either leave the pump as is, break the internal fins off with a chisel or screwdriver and reinstall, ot get a delete kit. Don't forget to cap off the manifolds.
As far as the reset, it wouldn't change the sensor values, but if it is running super rich from before it might reset those values. Worth a shot and it is free.... |
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Posted on: 2014/9/17 20:10
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| lunytnz | Re: Running rich and hunting for idle | ||
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Quote:
Thanks for the info! What is best to use to cap off the manifolds? Is is a typical size cap you can buy? Or do you just use duct tape? Sorry for the delay... I've been out of town for a week and need to get back to figuring this out |
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Posted on: 2014/9/30 6:02
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| Matatk | Re: Running rich and hunting for idle | ||
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If you want it to look nice, you use brass caps. I was cheap and used standard pipe caps. I don't recall the size off hand but believe it's 3/4"
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Posted on: 2014/9/30 11:29
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| lunytnz | Re: Running rich and hunting for idle | ||
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So, what happens if you remove the hoses to the manifolds and DON'T cap them off? That would mean some air would be drawn into the exhaust, right?
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Posted on: 2014/10/4 14:13
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| Matatk | Re: Running rich and hunting for idle | ||
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Possibly drawn in, more likely pushed out in to your engine bay.
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Posted on: 2014/10/4 14:21
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| lunytnz | Re: Running rich and hunting for idle | ||
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I disconnected both of the solenoids (for diverter and switching valves, I think; hoping they would close, by default, when disconnected), but it made no difference in the high O2 readings and it running rich all the time.
I tried disconnecting the MAF, too. But, it also didn't seem to make a difference in O2 readings. It *could* be a rich, or leaking injector, but since 2 spark plugs looked the same, I suspect more a whole system problem. From looking, again, at the list of possible causes in the FSM, it could also be the ECM. I wonder about the EGR valve... could THAT be the cause? |
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Posted on: 2014/10/9 6:07
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| Schrade | Re: Running rich and hunting for idle | ||
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If the pintle on the EGR valve is fouled, it will act like a vac leak, and lope idle.
It could also vary INJ pulsewith incorrectly, since ECM thinks throttle / TPS is increasing. |
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Posted on: 2014/10/9 13:53
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