874ME

iTrader: (1)

My 87 IROC developed an over fueling problem tonight that is intermitent. It ran fine for about 5 minutes, then ran so friggin rich the only way to keep it running was to hold the rpms at 5K plus. I pulled over at a parts store to check it out. The car was warm, fans on when this happened. I checked the following-

unplugged the MAF and started, no codes.
checked the electrical plugs on - MAF, TPS, injectors, all connected.checked fuses, all good.
After a half hour, I drove it around the parking lot while it struggled to run, billowing black smoke, then it cleared up. I drove it home, 3 miles. It ran fine. I pulled it out of the garage 20 minutes later and was over fueling again. I plugged in the scanner, the the readding that jumped out was the injector pulse rate being pegged at 12.2 ms.

What can cuase this? I looked at the wiring harness for the injectors and didnt see anything pinched. I dont understand why unplugging the MAF didnt through a code. I have a SLP T-RAM on the car with LS1 injectors.

Any help will be appreciated.

Pontiacdaddy

see next post

Pontiacdaddy

check the coolant temp sensor data on the scan tool while it is running rich and make sure it is not reading like negative 80 degrees or something like that. if so suspect a bad coolant temp sensor or connection at the sensor or wiring

874ME

iTrader: (1)

The temp readings are within normal range. I am using a scan tool while driving. All of the readings look correct except for the injector pulse, normal at idle is 1.2, while over fueling they stay 12.2 or higher.

doc

How long was the engine running good with the items you have above?

Also, you most have bought a special injector connector to run the LS1 injectors.

874ME

iTrader: (1)

The only thing I have changed since 2000 was installing the LS1 injectors about 4 years ago.

I did not use a special connector. The factory harness plugged right into the LS1 injectors.

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 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 swatts 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.

Case closed???

874ME

iTrader: (1)

Problem not solved. Over the last several months I have replaced or removed the following -

Installed a new computer, alternated stock chip with after market chip that has been in the car for years. No change.

Unhooked all of the MSD ignition products except for pro billet distributor, reinstalled the OE stuff and a new ignition module. No change.

Installed a new 02 sensor, replaced the LS1 injectors with a trusted set of 24lb injectors, checked the ohms on all of them while hot. No change.

Removed the alternator, no change.

The problem tends to occur more often right after the computer goes into closed loop. Some times it occurs at start up or within seconds of start up though. This may have something to do with heat soak from the last time it was run?

The MAF is ported / gutted and the custom EPROM was made with this in mind. The stock EPROM used to through a code for excess MAF flow or something like that right after the car was started. With the custom chip, the computer has never set a code for this.
Could the MAF be bad and the custom chip be overiding the code that would normally be set? When the stock chip is installed the code comes up instantly.

Something is telling the computer to call for max injector pulse and ignore the TPS and 02 sensor and I cant figure it out.

Any suggestions will be greatly apreciated.

doc

1) Is the ECM going into closed loop mode?

2) Have you tried a new MAF sensor? Mine went bad a few weeks ago, which caused the engine to run very very rich. Please stop calling this condition "over fuel"....never heard of that!

3) With your scanner, see what the ECM is "seeing" from the MAF at idle and what the engine load is. When my MAF was bad, the engine load was very high, as well as, the MAF output. The ECM was commending very long injector pulse widths, and therefore, a very rich engine. The engine was so rich that it would barely run. I thought that I had at least two bad cylinders.

874ME

iTrader: (1)

Thanks for the reply doc.
To say that the car was running rich would not do justice to how rich it is actually running. If it runs for more than a couple of minutes while running "rich" the cat glows red and raw gas drips from the exhuast. The POR 15 melted off of the subframe connector on the passenger side and the header gaskets are toast now to.

The problem seems to happen more freuqently when it warms up, then is shut down. At restart it will always run rich, clears with a couple of swats to the throttle. From a cold start, it usually runs OK considering it was shut down running pig rich. It warms up, goes into closed loop for awhile then bang, extreme rich condition.

I just installed new relays for the MAF power and MAF burnoff, then started it up. It ran OK for a half hour in the driveway. Shut it off, hooked up a vacumn gauge then restarted. Pig rich on restart and wouldnt clear up with revving the engine. Still trying to get the smoke out of the garage so the furnace alarm will shut off.

So, yes it goes into closed loop, and yes engine load always goes to 255 when this happens. The MAF reading looks out of wack also, about 150ish when the rich condition happens, no matter what the TPS position is. The 02 reading is alway rich also. Does the computer overide the MAF, TPS, 02 and temp input and really wholey on the MAF at WOT?


Must be a bad MAF?

874ME

iTrader: (1)

Installed a remanufactured MAF tonight and the " rich" condition seems to be gone.

Lesson learned - remember that the Ed Wright chip took care of the code for excess air at ported MAF. They must have aliminated the ability of the computer to set a code for a MAF problem in the chip. When I swapped back to the factory chip I got the expected code for excess air at the MAF.

Hope the replacement MAF solves the problem.

doc

Hope you are back on the road again. As I said above, I had a very similar issue. I first suspected the injectors, tested then but they all checked out even though they are 12 years old or older. I decided that since I removed the SuperRam in order to get the injectors out that I would install the Holley Stealth Ram and new 30#/hr Ford injectors. I was on the verge of running out of fuel with the 24s. Got it all installed and still had the rich condition. It was so rich that the engine would barely run. Finally, deduced that the MAF was bad and was steadily outputting high air flow values, even sitting in the garage. Replaced the MAF and no more super rich problem.

BTW: I also had to kill the 33 error code as you mentioned above. I did this a long time ago.