RMC_SS_LDO

>Repost from CamaroZ28.com<

Evening all,

I have been chasing what seems to be a ghost for some time now (7 months so far). Here's the deal, all of which has been worked under waranty so far:

Took the car in b/c it was idling rough and seemed to be getting crappy mileage. At the time, I only really noticed it idled bad and seemed to stumble/bog down as I slowed to a stop; almost SEEMED like the tranny was not dis-engaging bogging the engine down at the time. Thought it may have been a slug of crappy gas and it set a SES code P0300. I was traveling then and it was only occasional so I ensured I was getting descent gas and took it in when I got home. Dealer couldn't find anything and cleared the code.

Same symptoms came back, so back to the dealer it went. The dealer said they did a fuel injector cleaning (no idea WTF they actually did) and called it good..... no joy.

Drove the car and the problem was not fixed and became much worse quickly. Less than a week of getting it back, it would even stall out at slow speeds (parking lot manuvering) and set a SES code (P0430). Back to the shop and they replaced BOTH catalytic converters (nothing with the O2 sensors).

Picked up the car June 30th and initially seemed to run much better. We went for a short road trip on the 4th (few hundred miles round-trip) and the car seemed to run fine (on the interstate) until we got into stop-go traffic. Same crap again; rough idling and now noticed that when it is happening, it still runs like crap even if I put it in neutral (so much for the tranny idea). Set a pair of new SES codes (P0174 and P0300) and was blowing black smoke at idle. Got back on the interstate and it was running descent again, but when I got back into low speed stuff in traffic, running like crap again. Even though the code indicates a lean condition, it "smells" like it is running rich as hell.

The only common tie I can find and how I have figured out how to re-create it is to get the engine up to normal temp, stop the car, leave it in gear and set the E-brake (i.e. you're stuck in traffic). Within a 5-10 minutes the idle drops to <400 and starts running like crap. Shut the car down and restart (with no cool-down) and it will run ok for a few minutes and it starts acting up again.

The common tie seems to be running low RPM and getting hot.... seems almost like vapor lock in an older car- never seen or heard of it in an LSx. The car is bone-stock and I must admit it I'm fairly ignorant about working on it. Runs fine on initial start (before it gets really hot). It also seems to have lost a lot of power in normal driving after it has warmed up.

Right now, it's back at the dealership. They are working it under waranty since it came in for the issue while under waranty (which expired the beginning of June). They seem to be trying to figure it out, but they don't seem too sharp- on guy in the service dept that was walking by asked "damn, what cam you runnin?!" the car was shaking so bad!

Sorry for the long post, but it seems like the folks here have run into just about everything already. I really don't want to go on a wild-goose chase hunting for this. Other than what the dealer has done, I haven't done anything other than ensure fresh premium gas and looked for any obvious loose connections under the hood or any obvious heat sources near a fuel line. This is becoming very frustrating and I get the feeling this is not going to be resolved any time soon....

Thanks in advance!

Allen

ArcticZ28

iTrader: (14)

I know it sounds retarded, but have you checked your plugs?

Jon87transam

iTrader: (1)

could the fuel pump be heating up, causing a low pressure situation, making car run bad?. i had a 93 formula do something like this once. cold startup-good pressure, run longer-low pressure...just a thought

RMC_SS_LDO

Well, the saga continues...

They initially replaced the right-side fwd O2 sensor. Thinking it was licked, I picked up the car and drove it for a day and the idle was much improved. Then the problem shifted a bit.

Driving at steady speed (abt 55 MPH) the car started sputtering and had another flashing SES light. Slowed and it set a steady light/code. It went directly to the dealership while it was running crappy.

Running rough and blowing black smoke (again), I didn't get what code was set (guessing it was another P0300). The service guy scanned the car and said injector 6 was stuck open. They are replacing the injector tomorrow and I'm hoping this is the root cause, but at this point I'm not holding out hope that it will be fully resolved.

I may be off base, but this seems to make sense to me thinking about it backwards. Stuck injector causes a rich condition... fouling the cats. The failed fwd O2 sensor compounded the problem, making the ECU think the engine is running lean so it dumps even more fuel to compensate making it run even more rich and helping clobber the cats.

I was wondering about the stuck injector thing.... but I am far from a tech so in this case I am at the mercy of the dealership.

I really don't want to meddle in the service depts procedures, but they are just as sick of seeing this car as I am of having it there. I have not been in there ranting and raving over this (eventhough it has been a royal PITA) since I know that troubleshooting an intermittent problem is tough to do- the service manager and the lead tech have been bending over backwards to try to make it right, and everything has been done under warranty. I still intend to do a full seafoam on the car and change the plugs/filters.

Is there anything I might suggest for them to check while they have it? I would like them to check the fuel pressure and the MAF(I haven't had the car since posting this to check it for myself), but what else would make sence based on the problems. Not to say they will do it, but based on the long-running issues, I think they are willing to try more to get rid of me .

Thanks

DWillTA

iTrader: (3)

It sounds more like a O2 or MAF issue. The rich smell with a lean code is explained like this. The O2 gives an inaccurate lean condition even though the mixture is good. The computer knows only what the O2 is telling it so it opens the injectors longer to richen the mixture. This is now to much fuel and you burn out a cat and bellow black smoke.

I would disable the MAF and monitor the O2's while the problem is occuring.

Also the reason it runs fine when cold is because the O2's are a nonfactor. Open Loop operation. Just my guess.

Dave

DWillTA

iTrader: (3)

Not sure of the power the dealership has over the computer, but you could have them force open loop at all times and see if it is a closed loop O2 problem. I know this can be done with aftermarket scanning software like EFILive and HPTuners.

Might see if you can find someone local to help you out with that.

Dave

RMC_SS_LDO

Well, got the car back.... for about an hour

Replaced injector 6 and its spark plug (fouled badly) and confirmed fuel rail pressure running about 56 psi. After delivery, it initially seemed to run fine. The tech and the service manager test-drove it and said it ran fine.

Again, after it was fully warmed up and when in stop-and-go driving, same symptoms. At a stop the car still idles rough and RPMs dip to <500 and at slow speed/partial throttle it stumbles.

Drove it directly back to the shop and put it on a scanner, showing cyl 6 misfiring. No codes were set, in fact I got back to the shop and had it scanned even before the SES light started flashing to indicate the mis-fire.

After talking to the service tech, I'm not sure what's next but looking at replacing the coil pack (and plug wire) for cyl 6- atleast it is staying consistant to one cylinder. I can't figure out anything else (other than coil/wire) that would be causing this with one cylinder but if its a coil/wire I can't figure out why it would only seem to happen after the car is warmed up. Worth a shot anyway...

Dave, you mentined this looking like a closed-loop issue and that seems to fit the sequence of events, but why would it only seem to affect one cylinder (#6)? I'm not questioning your logic, just trying to tie it all together to narrow the search.

Hell, am I missing the forest 'cause I'm staring at all of the damn trees?! I did not ask about their ability to force the system to open loop- we didn't get that far, but I am trying to work with the shop on this. They seem stumped and willing to listen to suggestions- I'm not pissed at the shop; they've actually been pretty great all things considered.

The search continues..... If they have the car much longer, they're making a few payments!

Allen

3.4camaro

iTrader: (1)

i had similar symptoms on my camaro. the wiring on the cam position sensor came out of the isulation and contacted on the engine block, causing sputtering and stuff. have them check all the wiring.

RMC_SS_LDO

New coil, no joy

As the svc manager was pulling the car around, started running like crap again.

Put it on a scanner and cyl 6 still mis-firing. We forced the car to open loop (briefly) and it smoothed out some, but the scanner they use will only allow a the system to be shifted to open-loop briefly and it would not shift to a diagnostic screen to monitor mis-fires.

We also noted that all of the bank 2 cylinders are mis-firing as well, with nbr 6 the worst. All other bank 2 cyls miss, but much less by comparison. The car runs very rich and the system (per the scanner) is attempting to lean it out, but it's not actually adjusting (still blowing black smoke and smells very rich). O2 sensors are switching and apear to be working fine .

The MAF was suggested, but this only apears to be affecting bank 2. Fuel rail pressure is fine (poor pressure would affect both sides, but grasping at straws here).

Still at the shop, and no end in sight. They are still trying to figure it out and they are actually listening to suggestions (since they are stumped too).

RMC_SS_LDO

MAF is good, O2 sensors (all 4) are shifting and reading good (both on bank 2 have been replaced as well). As for the temp sensor, I think it's reading fine- seemed to remember seeing it incrementing up while monitoring it on the scanner but I'll check again. Not sure how the system would shift to closed loop if the temp sensor was bad.... and not sure how a failed temp sensor could affect only bank 2. Are the signals for temp sent seperatly to bank 1 and 2?

Thinking about this, does anyone have an LS1 wiring diagram (PDF link maybe) that shows all of the ignition and control circuits? It seems like this could be a bad ground or sensor somewhere on bank 2, but I don't have any documentation to start with.

An emissions control system for dummies book might me helpful too , since this now SEEMS to be isolated to a closed loop issue. I am looking for descriptions of what is happening in closed loop and how the 2 banks are actually controlled.

Thanks for all of the suggestions. It still amazes me just how much info is out here from you folks.

Allen

2001WS6Vert

You might ask the dealer if they are a member of IATN (international Automotive Technician's Network). If they are they could post a live help request and you will get very imformed responses via e-mail from professional mechanics. I own an auto repair shop and probably couldn't exist without it nowadays. If they are not a member you could have them write a concise detailed story about the car and I could post it. It takes a couple days to get all responses.

Pro Stock John

iTrader: (34)

Bad coolant temp sensor in head? If those are unplugged or broken, the car will run like total crap since the pcm will freak out at the reading.

RMC_SS_LDO

Got word back today that GM has suggested replacing the ECM.

My ignorance of how the entire system works prevents me from understanding how this will fix the problem, since it seems to be isolated to one bank (nbr 2).

If they can't get this figured out soon, I'm seriously thinking of trading the car .

Update on Tuesday.... unless they make an awesome deal on something new...

DrkPhx

iTrader: (15)

This is what I'm thinking also.

RMC - What are the exact codes you are seeing?

RMC_SS_LDO

Monday, I'll see if the scanner they are using shows the head temps or atleast the status of the sensors. For clairification- the ECM take readings from both heads (if I understand correctly)? Forgive my ignorance, I have NOTHING that shows what signals the ECM takes or how it actually functions (still looking for some good documentation).

Thats part of the problem now, the codes have been cleaned up but there is an obvious misfire at low rpm (haven't scanned at higher rpm but still getting crappy mileage).

At this point, I don't think we're letting it run long enough to set a code. The mis-fire at idle is pronounced enough to feel before we get the "flashing" SES for a mis-fire. When it is on a scanner (again, after shifting to closed loop) it shows all bank 2 cyls misfiring with nbr 6 missing the worst for some reason.

The guy at the shop tried to explain that the ground/return path for control voltages is via the ECM which is why they (GM) are replacing it- thinking something with the return line in closed loop is faulty. That seems logical, but I have nothing in the way of documentation to refute it or offer a more logical cause.

I am not an expert on how the damn thing should run on the hwy since we came from Hawaii and this is the first time we have been on a "real" highway, but I would think 16-18 MPG is low as hell for this car (was getting better than that in town before in stop-and-go).

After the ECM replacement, I'll see what changes. As I said, I have no documentation to chase the sensors to start with. I had a Haynes (I think) manual but it seemed to be pretty much useless so I ****-canned it about a year ago. I'm still looking for some good documentation on the sensors and electrical system on this car to figure this (and anything else) out. Yes, the dealer service department is working on it, but they have had it off-and-on for three months now and have really made no headway with it as far as the root cause is concerned so it is time to take over. I'm getting damn sick of making payments for the car to sit at the service department.

I love this car, but it is really pissing me off at this point.

We actually went at drove a Buick Lucerne CXS today thinking about getting rid of the Camaro and its problems. Gladly, it wasn't that impressive since most of the trade-in motivation was from frustration (looked at a 300 STR8 as well.... dayum but a bit pricy!).

Please keep the suggestions coming, the folks at the dealership are still taking my suggestions and are motivated to get this car out of their hair!

Allen

RMC_SS_LDO

Got the car back this afternoon.....

Well, it may actually be fixed!!

Apparently, they replaced the PCM with new including a "new revised configuration". I wasn't aware there was a revised config from GM for the LS1 and I doubt anyone here would care since most have tuned it anyway.

Still, anyone else hear of this revision?!

So far I tried everything to re-create the symptoms including maxing out the AC and electrical system and holding the car in gear at idle. Scanned the car and NO misfires on either bank, so it looks good so far! Runs VERY smooth now (better than when we bought it new it seems) and is much stronger. Hell, punched it on a straight deserted hwy this afternoon and passed 125 before I realized it!

I fear that since the entire PCM was replaced I'll never know just what the specific cause was (assuming it is fixed for good) and this will not help anyone else with similar problems.

Still, it is really amazing the volume of information here and thanks for the suggestions. I have learned a great deal about the workings of the car thanks to all of you.

Thanks!

Shoulder Shaker

iTrader: (36)

Good to hear that you got your car back and it is really good to see dealerships stick with it until they got the problem fixed. That's great customer service.