Cascade Crew

[dlp]

My 87 IROC developed a bad over fuelling problem last night as soon as it went into closed loop. It runs so rich that you smell fuel burning in the cat, black smoke billows from the exhaust and it has to be revved to 4500 rpm plus to keep it running. After a couple minutes of this and revving the crap out of it the over fuelling stops.

I have checked the fuel pressure, TPS voltage, coolant temp, and basicly every reading you can with a scanner while it is running rich. Everything looks normal except for the injector reading. Stock at idle the scanner reads 1.2 ms, when it's over fuelling they are 12.2 or higher, throttle position has no effect on the reading.

I unplugged the MAF while it was overfueling and it didnt make a difference. Through all of this not one code has been set in the computer.

Anyone have an idea whats wrong?

[aaron_sK]

Might be injectors leaking down. That probably wouldn't throw a code. Wierd that it would stop once it warms up though.

[Raiden]

Maybe try and burn another chip. I had a chip go bad on me. Every time I put a new bin in one particular chip, my car would not run right. I also noticed my speedometer would not work. I threw it away after multiple occurrences of this happening. Just a though as it sounds like you have checked all other avenues of the problem.

[dlp]

Thanks for the advise fellas, this is what I have done so far without fixing the problem.
Replaced the computer tonight with a reman unit from Schucks. Still over fueling. It cleared up after a couple minutes of running like crap. I thought maybe there was so much fuel on the plugs it had to burn it off. Wrong. Just as it reached closed loop it died. Tried to start it but the over fueling was back. The scanner was not able to monitor after it died.

So, I am now looking for the stock chip. The current chip was burned by Ed Wright 9 years ago. I realy dont think a sensor is causing this condition becuase the over fuelling has happened while in open loop. I may be wrong but the 02 sensor should not influence the computer until it reaches closed loop? I havent checked it yet becuase of this thinking.

Still hasnt set a code.

HHHEEEEEELLPP!!!

[fiveoformula]

hows the EGR? functioning properly?

[Xophertony]

from what you posted in the other thread i would recommend a stock chip as soon as possible. those after market one-tune-runs-all chips are usually worse then stock.

diagnose from there.

[dlp]

That is the next thing I am going to try.

I've never heard of a chip go bad though? I can understand if it just came out of a box, this one has been in the car for 8 years.

[dlp]

I used to know were my stock chip was. Two moves later it's gone

Anyone have a stock chip for a 87 / 88 MAF car I can borrow?

Another futile attempt at a WAG failed. I unhooked the MSD box and MSD coil, reinstalled the stock coil with the same results.

[blue89]

i have an extra ecm and stock chip but its for a V6, sorry man.

[Xophertony]

i did not realize you had had it so long. i did not thing the chip had "gone bad", i thought it was just a crap tune.

i know Paul has my stock tune saved on his PC. he could probably email it to you. do you have the ability to burn chips?

[dlp]

I dont have the knowledge or equipment to burn my own chips. It's on my laundry list of things I would like to learn how to do though.

[dlp]

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 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 elimenation of the 9th injector.

Anyhow, thanks for the input fellas.

Xophertony, you win the brownie button, it was the chip!

[dlp]

Belated update, problem not fixed. The over fueling isnt as bad with the stock chip, but the dumping of fuel into the intake is still happining.

So far I have done the following -

Replaced the injectors with the stockers
Replaced the computer with a remanufactured unit.
Put the stock chip back in it.
Shook the computer / harness while it was acting up with all possible combinations of stock chip / used comp / new comp / perf chip.
Clamped jumper cables to the block / frame / neg side of battery, computer to make sure all were grounded.
Un hooked the MSD ignition and coil, swapped coil for stocker.
Checked fuel pressure, no drop.
Removed FPR regulator, inspected, no tears, spring works.
Replaced 02 sensor.
Plugged in scanner and watched the readdings as the problem is occurring, the only thing that looks out of wack is the injector pulse rate. It is maxed out, throttle angle doesnt matter. Keep in mind there are no codes. The temp sensor readdings looked correct, no minus numbers.I unplugged the TPS while it was running, then the MAF, no codes, no change in the condition.

The only money I have spent so far was for the new 02 sensor. The rest of the stuff I borrowed or returned.

I am now thinking that the MSD ignition module that came with the pro billet ditributor may be bad. I used to have a complete stock distr but I loaned it to my bro and now it's missing the ign module. I dont want to through money at this thing, any ideas what the problem could be????


Any ideas?????

[83Z28BlackBetty]

I'm just as lost as you are on this.

But as long as you are "un-upgrading" your car, let me know what performance parts you are going to replace with the stock ones next! Maybe you should swap out the heads for my stock heads

~JAKE

[blue89]

What are your BLM's at? If you have a massive air leak could this be a symptom?

Is your base timing set correctly? You should check your base and then what the engine runs at normally.

At this point, I would start looking at your valvetrain. Is your cat clogged? Sounds like the ecm knows what it's doing, it's just being confused by something.

Don't give up yet. It's always something simple.

*I edited cause I answered my own questions by reading your post*

[Dewey316]

MAF right? How do the maf readings look coresponding to pulse-rate? Have you tried a different MAF?

[blue89]

If he's unplugged it then it will base PW off of throttle position right? He's unplugged it and it made no difference.

[dlp]

Thanks for the input fellas, trust me, I am more stumped then anyone.

To adress some of the posts -

First and formost, the speed parts will be reinstalled when the problem is found

I cant see how a plugged cat would cuase a random sever fuel enrichment problem? It has a Random Technology Cat that is toast now. It was glowing red several times. Now the exhaust sticks and sets off the alarm in my furnace ( in the garage) when the car is started, didnt do this before. I do know that gasoline makes it through the cat, if the cars runs for 5 minutes while this problem is occuring, gas will come out of the tail pipes.

If the valve trane was the issue it would not be an intermitten problem.

I have not tride another MAF, if I remember correctly the readings looked normal. I did try tapping on it, no change. I unplugged it and didnt get a code, weird.

If I remember correctly, the BLM reading was around 110 while the over fuelling was occuring.

I havent checked base timing, but this is an intermitten problem.

[chevymad]

If the pieces of cat intermittantly plug the exhaust pipe by turning sideways inside it could cause problems. When the exhaust is plugged manifold vacuum drops, making the ecm think it needs to add more fuel.

[dlp]

Thanks for the explanation. I guess it could be a possibilaty, but it only has about 4K miles on it. When the problem first arose, the car was warm and I was driving down the street at 50 MPH. If the cat was plugged it would stay plugged, the problem comes and goes, it is not static.