Some background on the car is necessary. It's a 1987 IROC, with a Jasper 350. Started life with an LB9. Automatic. 140k on the body.

It stalls when coming to a stop. The car also seems to hesitate after it heats up a bit. Main problem, when at WOT, towards the top of the RPM range, the car loses all pull, the SES light comes on, and it dogs around until I shut it off and start it again. It then runs with less than usual power, until I shut it off and let it sit for a while. I disconnected the knock sensor in the block and installed another one and let it hang there. It still set off a Code 43.

The car also runs hot, between 220* and 240*, and never any lower. Even cruising on the highway it barely dips below 220*.


The bottom end is brand new
TPS is set at .54v, tested and climbs steady to 4.07v
New IAC
New 22lb Bosch III injectors
New Southbay AFPR set at 48psi
New cap and rotor
Base timing at 8* BTDC
No vacuum leaks
Small exhaust leak at passenger side heat riser

I do hear the fuel in the tank boiling after about 30 minutes of driving if that is a contributing factor to some of these issues.

I have no idea what kind of computer is in the car. It might still have the 305 PROM. It did have an AEM computer rigged into the factory one when I got it.

I really have no clue as to why the car is running like it is. Even when it's running at it's best (which is a very short period of time), it is as slow as my Trans Am. The cars have the same drive train, excluding the motor. I'm inclined to believe the 350 would outperform my peanut cammed 305, but that is not the case, and it drives me nuts. It can't be the way it is.


Any help is greatly appreciated.

 

Sounds almost exactly like when I had my knock sensor plug switched with my fan switch plug ... According to my 91' firebird's wiring, dark blue is the knock sensor, green w/ white is fan switch. Single wire connectors.

 

http://chevythunder.com/maf_esc_module_code_43.htm
You might want to post the letters on the memcal in your ecm for identification.
The wrong calibration tune will make your car a dog, I have no idea what your amen thing is
But you might want to address that and toss it to the side. The ecm should be a 1227165.

 

Do you know where I could get a L98 memcal? Even if it is right, god knows if it's been modified at all.

 

I can reprogram it if its not correct and do have tpi maf memcals as well.

 

The forced knock test is failing. There is also the knock filter which may be an issue. Running too high of an octane will also cause this test to fail.

The ECM adds spark advance, trying to force knock as a test of the ESC system.

RBob.

 

I know almost nothing about how these cars work as far as electronics go. Why is it testing the ESC? I run 93 octane in the car, is that an issue?

 

Do you sell them on their own? It's my everyday car, so to take the memcal out and have it down for however long would be a problem.

 

I do have the memcals so you wouldn't have the down time. I wouldn't want to sell you something until you identify the broadcast code on your memcal. you should address the code 43 bye force knock the ecm is advancing the timing to force a knock and test to make sure the knock sensor 100k iirc and esc is working properly to protect your engine bye retarding the timing. I'm curious what the aem thing is that is attached to your ecm.

 

So wait, I just noticed that your said your fuel was boiling? That's going to have to be fixed ... Also did you make sure your wires are correct? It's free.

 

The ECM is testing the ESC system because GM ECMs are good at testing the various sensors. Other manufactures didn't do this as well. GM's OBD-I (on board diagnostics, version 1), was the template for OBD-II which all manufacturers needed to implement.

Using 93 octane may be the issue. Having the base timing lower then 6* BTDC can also cause a no-knock situation. Personally, I hate this test. The first time I ran into it was many years ago after doing an EFI retro fit on an old school hot rod.

I laid into the throttle, suddenly there was an unusual burst of power (a bunch of SA was being added), and a ton of knocking. I quickly backed out of the throttle and went: huh, what was that?

Log file showed what was up. Disabled that code right quick. Later removed it entirely. I even wrote patches for the '7747 ECM and '8746 ECM to bypass it. Didn't do any patches for the '7165 ECM though.

RBob.

 

I finally had a chance to look at it today, Number on the brown and blue chip is 35006 8647. It has a re-manufactured ECM in it.

 

your memcal should have some letters on it

 

ABUN
8517

 

Abun is a 305 calibration

 

I'm not surprised. What can I do about it?

 

Send me a pm, I'm not sure if this is your dd but I have a few choices to help assit you? I can reprogram your or I can sell you a memcal.