Hopefully someone can help. I just bought a 1989 IROC with the 5.7l TPI eng in it. Here is my problem: The car idles and runs great until you push the accelerator pedal past 1/3 of the way down, after that the car acts like the fuel is being cut off (like it is in some kind of valet mode or something). I have checked and adjusted the TPS, checked fuel pressure, the fuel pump and filter, distributer cap,plugs and wires have also been changed. Please Help!!!!!

 

Hmmm, do the rpm's keep raising even if it's sputtering? Or does it act more like a rev limiter. Does it do it only when hot, only when cold, both?
I'd put money on a faulty MAF, or maybe the previous owner swapped in an SD set-up and it has a MAP.
Does it do it when in park? 1st gear? 2nd? 3rd and 4th? Is it worse going up hills?

 

Thanks for responding, The RPMs go up smoothly unless you romp on it, it does it hot or cold, it has done it in park but not always. It also does it in all gears and no it is not worse going uphill. How do you check the MAF? Ive found voltage readings but dont know what pins to read it on.

 

An SD set-up is the computer system used from '90 to '92. It utilizes a MAP sensor (mounted on the plenum, by the distributor) instead of a MAF sensor. To check a MAF sensor, you need some sort of datalogging program to read the airflow as the car runs. If it goes up/down smoothly, then the MAF is fine. If you don't have this, I can only recommend swapping the MAF for another one. If it doesn't fix the problem, then just return it and get your money back. It definitely sounds like MAF issue considering: the vehicle only does it when it's under load (or mostly only does it when it's under load).

If the MAF doesn't fix anything, I'd check your ign system.

 

Check this out: I unplugged the MAF and it solved the cutout/surging problem but of course did not idle smooth and wanted to die. I purchased a new/remanufacturd MAF and installed it and now it threw a code 33 (MAF sensor, it has not put out this or any code at all prior) and does not idle well but it also does not cut out or surge. I think I may have gotten a faulty MAF. This is frustrating.

 

Yeah, it's not uncommon to have to run through two or three MAF sensors before you get one that works. If you can find a delco, you're set. That, or just buy a cheapo (but working) unit, and read up on MAF to MAP swaps in these message boards.

 

Did you guys figure out if replacing the maf sensor solve code 33?

 

Have you changed the fuel filter?

 

I do believe I changed it a couple months back I recently replaced the fuel pump and the filter seemed to be fine I still have code 33 it starts up fine but when i drive down the street it starts acting up its almost as if it wants to shut off

 

It did solve it, also, when trying to troubleshoot the problem, I unplugged the sensor and the car ran smooth, but of course did not have as much power. Hope this helps.