874ME

iTrader: (1)

I am not sure if this is the correct board, please delete if not. My 87 IROC started over fuelling so bad it would barlely run tonight. It billowed black smoke and would only stay running if the rpm's were around 5k. Unfortunetly I was 5 minutes away from home. I parked it and checked all of the sensor connections I could reach. After a half hour, I started it up and drove it around a parking lot running like crap and killing mosquitos. It cleared up and ran fine after 1 minute. I drove it home and parked it in the garage. Twenty minutes later I started it up and it was running pig rich and blowing large amounts of black smoke out of the exhuast again. I plugged the scanner in and noticed the injector pulse rates didnt change with throttle input. The readding was 12.2 ms.

I have an SLP TRAM intake and LS1 injectors. This combo has 5K miles on it, never had this problem before.

What can cuase this?

874ME

iTrader: (1)

Update, I yanked the side tanks of the T-RAM and checked Ohms of injectors. Also pulled the FPR hose and no ssign of gas.They were all within 13.20 - 13.60 I put it back together and started it. Same crap, really rich. I drove it around the block with one foot on the brake and the other on the gas and it cleared up within 100 yards. It seems to run fine above 4500 rpm even if it wont idle. Three blocks later it started the over fuelling again. I pulled it into the drive, revved it, burned out, then it cleared up again.

When it over fuels the readings on the scanner dont change, 12.?? mS.

Any help would be apreciated.

RBob

iTrader: (1)

Sounds like the ECM went belly-up. Can try it with the MAF unplugged, see if that makes a difference. Also check the TPS, when reading high it can cause strange things to happen.

RBob.

874ME

iTrader: (1)

Thanks for the responce.

I have tried unpluging the MAF while it is running rich, it didnt have an effect. The odd thing is that the check engine light didnt come on with the MAF unplugged and it didnt set a code.

I will check the TPS voltage next.

Is there a procedure for testing the ecm?

RBob

iTrader: (1)

As crazy as it sounds, the "tap test" is the best for the '165 ECMs. With the engine idling, tap on the ECM. If the engine changes how it runs with tapping on the ECM, the ECM is bad.

This is a common problem with the '165's. Not sure why, just that over the years this is an issue: intermittent connections within the ECM. Heard it was a soldering problem.

I would also wiggle the ECM to harness connectors. They too can have issues.

RBob.

874ME

iTrader: (1)

I am more than willing to hit with a hammer right now

Any particular spot to tap on?
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Another thing I noticed after driving it again today is that it runs OK in open loop. The problems start after closed loop begins. The coolant temp looked normal as did the MAP and tps while it was running pig rich. I am using a scanner to monitor readings while driving.

The only thing that looks out of wack is the injector readings. I dont know alot about block learn and integrator though.

874ME

iTrader: (1)

Update,

Installed a remanufactured computer, reinstalled the 9year old Ed Wright chip and........ran like crap. The car was cold, open loop. After a couple minutes of steady 3500+ rpm it cleared and ran OK. When the coolant hit 190, it died. Started it up and the over fueling was back. My scanner would not monitor after it died, display said " vehicle not responding".
When I first started it and it ran like crap I reached over and shook the harness with no change.

I am stumped. Could it be the chip? Bad injector causing the other three on the same harness to stay open? If it's an injector, why would the scanner show the computer calling for 12.??mS at idle?

Any advise is apreciated.

RBob

iTrader: (1)

Could be a bad chip. As you are thinking a bad injector won't cause the ECM to report (and apparently use) a high injector pulse width. Other then poking and prodding everything in the EFI harness, check the harness grounds on the engine block (back of pass side cylinder head?), and the coolant temperature sensor.

RBob.

874ME

iTrader: (1)

Thanks for the advise, our local board guru's are also suggesting it's the chip. In your experience have you ever seen one go bad? I've had the chip in the car for 10k miles and 8 years without issues.

I will check the grounds while I try to find the stock chip or borrow one. When I put the new engine in I used loctite on all of the ground studs and lock nuts on the other ends.

It may have been a waste of time, but I un hooked the MSD box and coil and re connected the stock coil. Same condition, way rich.

874ME

iTrader: (1)

A dim bulb flashed tonight as I was heading towards the garage, wife close behind bitching about me not going to dinner with her mom. "Ahhaa", the automotive electrical junk box! Thats were the stock chip is! Yep, it was in the electrical box o crap and it fixed the over fueling problem. I have never heard of a chip go bad, but I guess they do.

Havent driven it yet but now I remember why I HAD to have a custom chip. The freindly warm glow of the check engine light presented itself after a couple of swats to the throttle, code 33 MAF to high, the fans didnt come on till 220 degrees, and the elimination of the 9th injector.

Anyhow, thanks for the input fellas.

874ME

iTrader: (1)

Grrrrrrrrr, problem not solved.

The stock chip seams to aleviate the severity of the problem but it is still happening.

I swapped out the the LS1 injectors for a set of 24lb 87 covette stockers and installed a new 02 sensor tonight with the same results. While the upper intake was off I looked at the injector harness, seemed fine and also cleaned the MAP sensor. I also checked the adjustable FPR, no rips in the rubber. I started it and the same over rich condition existed. The scanner said engine load was 255, no matter what the throttle position. The car was parked the whole time, never in gear let alone under a load.

My question is, what can make the computer max out the injectors and make the car run pig rich? It doesnt matter weather or not it is in closed loop, it is an intermittant problem. Some times it runs fine.

Please help, this thing is driving me crazy.

shingadaddy

Man I feel for ya. Only thing I see in the threads that bothers me is u said when you unplug the MAF sensor, the SES light did not come on. This sounds like maybe a clue. The light may not come on unless the condition is present for a time period. Since your problem seems intermittent, just maybe when you unplugged it when it was running bad and made no difference, the connection from the MAF may have been already broken somewhere. Causing the overfueling problem. The connection may RECONNECT at times and this probably resets the timer that triggers the light. Follow me? In other words the ECM might be almost ready to light the light and for an instant the MAF reconnects and resets the timer. And your condition clears up. I think I'd be running down that MAF and or O2 sensor wire and maybe even wire around them. Or unplug for a good time period and see if your SES light comes on after a time period. Mine is a 91 and has no MAF so I am poking in the dark somewhat but would like to help ya! Please let us know what you find and good luck. I say MAF and O2 because both play into the fuel mixture picture I believe.

874ME

iTrader: (1)

shing, thanks for the reply.

I havent had time to dig deeper yet, but I will continue to up date the post.

My gut feeling is that it is an electrical problem. Bad ground, bad connection etc. Anyone have a recomendation for good shop manuel? It would have to include electrical schematics and voltage for every wire?