joes90gt

Guys, I could use some help here.... 90 GT, runs great with no issues. I've already changed plugs, cap, rotor, etc. since I bought the car 2 months ago...just making it mine.

The problem I have occurs only when it's a cold start (sat overnight). It will run rough and act like it's missing but if I lightly tap the gas, the problem will go away. One the car has ran for a little while this won't occur again for the rest of the day.
The throttle body looks relatively clean inside. I also checked the TPS and it reads .998......looks good there. I also checked the vacuum at idle and its a smooth 20.

Any idea or suggestions on what I should look for next? I would suspect a vacuum leak, but the car runs to damn good otherwise. Just an issue during cold start up.

PRO50SC

Is there any noticeable black smoke from the t-pipes. You could have a leaking injector or even a faulty ect sensor causing the condition.

joes90gt

I haven't noticed any black smoke from tailpipes. Plugs are burning clean, car runs great. Just cold starts crappy.
Is there a cold start solenoid that I could be missing? I know early chevy TPI engines had them.
I'm stumped on what to check. Granted it only occurs once daily, but that's enough!

PRO50SC

No extra valves. It's done thru the injectors. The ect can def cause the condition though. Might wanna look into that. Have you tried cleaning the IAC, t/b and the mass air?

joes90gt

I haven't cleaned anything (yet). I didn't even think about the mass air sensor - Good point!
The TB I'm sure could use a good cleaning, even if it looks OK.

Not to sounds like a total dumbass, but what is IAC?

PRO50SC

Idle air controller on the side of the t/b. 2 bolts, 1 plug to remove

LesteR723

and it runs fine if you like go to the store and pick up something and come back out and start it? Yeah mine is doing the exact same thing. I cleaned out my IAC/Mass air and TB and it still does it. Nobody on here had anything to say about it after that... so good luck with it... and PLEASE let me know if you find the problem!

SICNINETYCOUPE

ECT or Bap or ACT check em or change em let us know

mjr46

how 'bout before slappin parts go about this in the proper way by running a KOER test and checking for codes and go from there, vaccum leaks will also cause your issue

5.0stanger

I had that same problem for a long, come to find out I had my fuel pressure too low for the cold starts. 38 is the minimum from what I found. I had an AFPR on, thought it was messed up, put the stocker on, all problems went away. Went out and got another AFPR, set it up at the original fuel pressure that the old one was set to, problems came back (hard cold starting) SO I bumped up my fuel pressure up and it got better.....so check your fuel pressure.