ikillu

Hey guys. So I have a constant surge in my 91 350 tpi car. So far I have replaced the EGR, IAC and TPS cleaned out the TB and now I am stumped. The strange thing is it used to do it only when the car was in gear. I swapped the tps and cleaned the iac (before new iac) and then it switched and the surge started when the car was in park. I have also since changed the cold start sensor as well but the problem remains. I dont know if its related but there is a big surge as well when i turn on the air conditioning and seems to make it chug worse. Sometimes it runs fine with no issues. Also i think it seems to be worse when it warms up but that may just be me. Also I get a check engine light from time to time. Wondering if maybe someone can give me some direction before I have to resort to taking the damn thing to GM. Anyways thanks for your time.

NathanLewis

I don't wanna go shooting false answers, but possible guess is alternator? My car would chug when I turned the ac on, ran the radio, headlights, and it the lights would dim, idle would bounce down like it was straining, but Ever since I upgraded my alternator to a 250 amp, I have had none of those problems whatsoever.

z28romance

GM Check Engine light Codes without a Scan Tool

here are the instructions to pull your trouble codes. this might help to piont you in the right direction.

rdhanded2

iTrader: (3)

https://www.thirdgen.org/forums/tech...idle-dies.html

Here is my thread about the issue.

HisDivineShadow

I'm having the same type of issues as well, thread is a few posts down. Currently I will change the EGR valve, if that does not work I am guessing EGR solenoid.

89BadRS

I have a 91 RS TBI that the PO supposedly pulled the 305 out of and dropped in a 350 but put all the 305's stuff back on....heads,intake,TBI......everything. After I changed the plugs about three weeks ago I started having surging problems.....at a idle it surges between 1000 rpm and then drops down to 250 rpm just like it is going to stall. Then when I am driving it when ever I put my clutch in to roll up to a stop it surges up and down then stalls out. It is running really rich as well. What was said above about the alternator is peckular because I remember the PO telling me that the one on the car isn't stock that he had to upgrade it to a higher amp. When you have the lights on they dim with the dropping of the rpm. IDK what the heck it is but I'm pulling my hair out.

torque_is_good

do not chase your tail

you have to eliminate the basics


the first thing that I would do is remove/inspect all of the spark plugs that you put in (did you do them yourself?) one may be gapped incorrectly or have a cracked insulator, check them good. With the shorty headers on your car that's only a 30 minute job

once you verify that, if they are good, next up is your timing.

if that shows as good then spray starter fluid around vacuum hoses and the intake manifold to check for leaks

I'll assume that it does this even with the air cleaner off of the engine?

does it only do it when the engine is warm?

89BadRS

I did put the plugs in and I put new wires on the other day and when I did that I pulled all my plugs and checked all the gaps. It does it no matter if the air cleaner is on or off and if it is warm or cold. I checked the alternator and it is fine.

3.4 grape

iTrader: (1)

How old are your o2 sensors? It may be time for a new set. Could be the reason your running so rich.

bigjcfiredog

I have the exact same issue well had the same issue. My issue was that the PO did infact put in a used truck 350 which uses a different EGR. From what I understand, the truck computer and the car computer request the EGR differently so they work the opposite of one another. My PO only put the tbi and sensors back on the 350. Once I put in the correct caprice computer and injectors and ESC it cleared up all my issues except the surging, which was corrected by disconnecting the EGR until we get our new engine rebuilt when I will get a new one for my Vortec head intake.
Try the disconnect and plug the egr and drive, see if it still acts up. This will throw a code but if the issue clears up you have found your cause. This issue can also be because of a bad CTS which is right by your thermostat. You can unplug it and go for a drive, it makes the computer think it is cold outside and if it runs it could be sending the wrong signal to the computer and causing it to run rich. And it could be the O2 but I am against changing parts without working to find the culprit first.

These are just my thoughts, put into rambling text.
John

89BadRS

I appreciate all the help that I have been getting....Well I dont know the last time that the O2 was changed and I already unpluged the CTS and took it out and even changed it.....I already changed the IAC, fuel filter, fuel pressure regulater....unplugged the egr and even took it off and cleaned it and the ports making sure that it moves freely...IDK what the heck is going on.