chris3385

I have a 89 Mustang I bought last summer, not really sure what modifications are done to it because the owner didn't email me a list like he was supposed to do. Anyhow I know it has an aftermarket cam, edelbrock heads, and all boltons. I got the car, the car had a intake gasket leak from the day a bought it, found out after it started sucking out into the exhaust. Then after I fixed that I had a really bad idle surge. I have just recently replaced the intake gasket, tps sensor and map sensor. And did the idle reset procedure. The surge got a bit better after this but is still there.

Now when you start the car when it's cold, it starts up and surges between 500rpm and 1100rpm. But after about a minute it calms down and idles perfect at 750rpms. Then if you give it a shot of gas, it jumps up and surges for about ten seconds when it comes back down and it fine again. I know there's a whole checklist, and I've tried everything. I'm just wondering if it's a IAC Motor issue, I believe it has a aftermarket fuel pump because it's loud when it's running, and also an aftermarket fuel pressure regulator, doesn't look adjustable like an Aeromotive one but it's red on the top. I've heard of people having surging problems with too much fuel pressure.

But if anyone has had any problems like this please let me know what your problem was.

Thanks,
Chris

nacanitihs

try cleaning the IAC with some carb cleaner and a q-tip also get some electrical contact cleaner and clean your maf sensor

lx5.0

you still have a vac leak mine would do the same thing when i installed my gt40 upper and lower intake it would surge teh same way u describe it, get a vac check gauge and check it