Car backfires and hesitates when cold

[94GTStang]

I've already done a lot of searches already trying to find an answer, but no luck.

I have a 94GT with 120K miles on it with no internal work done like a cam or heads. All stock other than the Trickflow intake.

When I start it up from a cold start, it runs fine until I put a load on it. The car will backfire and hesitate real bad until it warms up or gets into the higher RPM's. After it has been driven around for a while, it runs perfectly.

I've replaced the spark plugs, cap/rotor, and checked all vacuum lines. Also the timing is set at 10 degrees. The idle has been reset and I cleaned the IAC.

What could this be? Bad IAC? ECT? EGR?

 

[94GTStang]

Well, just in case anyone else has this problem, it was a dried up vacuum hose underneath the upper intake. Problem solved!

 

[toyman]

The idle has been reset

Since the idle is controlled by the PCM attempting to adjust the idle can create problems. Did you play with the adjusting screw and/or the TB air bleed? Have you cleaned the MAF sensor? Have you checked for any fault codes? If not you are likely to be throwing parts on in the hope of hitting the correct one. Not that we all haven't done this at one time or another

Just read that you solved the problem.

 

[94GTStang]

It's all good. Thanks for the reply. It still has a bit of a flat spot/ hesitation when it's cold and I give it some gas. I'll try bumping up the timing tonight and see if that fixes it. Right now it's at 10*...