Kaya

Hello,

I recently picked up a 91 firebird that was a 305, but now has a(I think) TBI truck motor in it. I am diagnosing a stumble/hesitation issue I am having and am looking for a little input. Heres a little backstory.....

I bought it and wasnt told much other than it had a 5.7l in it. Compression checked out, and I dont seem to recall and hesistation or stumbling when I drove it or was looking over it.

On my way home, the CEL came on, pointing to the EGR. Sure enough, the vacuum line was disconnected and plugged. Upon plugging it in, it ran terrible. Real similar to the issues Im currently having with the brand new EGR, probably a little worse.

Naturally I assume the valve was sticking, or ripped. I ordered a new valve and installed it only to have similar issues with it. There is no vacuum at idle, and the CEL doesnt stay on, or turn on until the PCM triggers it @ cruising speeds.

I started to have a feeling that it was a "350" which was actually a 305.....

So I start digging. I now realize there are a number of valves depending on which SBC you have. 17087185 is what was on the car when I bought it, and I expected to see the valve clogged or the diaphragm ripped, but it appears just fine. I see that this valve is for 88-95 TBI trucks.

Block casting numbers are there, but just about impossible to make out for me, so I cant see which block I have to cross reference much of anything. I can make out the GM 5.7LG, and am now pretty sure the motor is in fact a 5.7 from a truck, and I am unsure about whether the valve itself is, or even can be causing the issues.

I did a tune-up, and replaced the CTS, rebuilt/cleaned the TBI, check for vac leaks, and calibrated the TPS. I need to check fuel pressure, but Im kind of at a loss.

Any ideas?

Kaya

Turns out it was the wrong EGR. I had a port valve and needed a neg pressure valve.

Hope this helps someone sometime!