91hatchgt

Hey all, I have a 91' GT and I was wondering. I did the exhaust on it, headers, H-pipe no cats, and the flowmaster system. Sometimes when I am driving, I will go to slow down, and when I press in the clutch, the RPM's stay @ 2000. If I shut off the ignition, and restart it, it will go back to normal idle of 650 - 700 .. Has anyone ever had this problem? It only started after I did my exhaust. I thought it was a vacuum leak, so I replaced a lot of vacuum lines. It stopped it for about a week, and just started again the other day. HELP, it's annoying...

88GT40

I have the same type of annoying problem, i have replace my iac and tested my throttle position sensor and they are good so today i checked for vscuum leaks with carb cleaner i fond that my upper to lower intake is leaking but all my vacuum lines aren't. so try some carb cleaner at all hose ends and throttle body and upper to lower intake to see if its the vacuum or not.

Dan89lx

a blown upper to lower intake gasket causes all kinds of strange sh*t. When mine was blown, my car would jerk and rev weird too. Like 88GT40 said, check for vaccum leaks.

91hatchgt

Ok, it couldn't be exhaust leaks right? hmm, why would the up/low intake gskts blow all of a sudden? I have also noticed a HUGE drop in gas mileage. I used to get like 210miles to the tank, now I get like 140... Does that mean anything? I will check though..

Thanks for the responses so far. I will keep looking. BTW, you know that connecter on the passenger side of the engine bay that connects 4? vacuum lines, I broke one of the plastic (why?) vacuum lines, so I replaced them with rubber vacuum lines, but the one that goes behind the intake I have no idea where it goes. I broke it, but then tried to fix it with a little piece of rummer vacuum line over the break in the plastic line. Should I just rip it all off and redue the whole thing? Could this still be the source of the vacuum leak. But it is pretty tight, and I don't know how it would leak.

ALSO: If it is a vacuum leak, why does it go away when I restart the car? I just think that if it was a vacuum leak, it would leak all the time, and cause the problem all the time? Can someone explaine why it goes away when I restart the car?

91hatchgt

And how do you check for vacuum leaks with carb cleaner?

bobby

prolly a vaccum leak for sure..............

Dan89lx

you didnt mess up the oxygen sensors while you were messing with the exhaust did you? is it possible that you could have pulled one of the wires loose or something like that? just a thought, oxygen sensor problems cause some strange sh*t sometimes

91hatchgt

I don't think so, I took them completely out from under the car while I was doing it so that I didnt have to worry about it. But now that you mention it I will check to make sure they are okay... Can anyone answer how to check for leaks with carb cleaner?

Dan89lx

check for leaks by spraying it around the vaccum lines and where the upper and lower meet with the engine running. If you see any bubbles or anything like that then you know you have a leak. Good Luck

Dan89lx

the carb cleaner helps you see the air leaking out, its the same principle as putting soapy water on a tire to find a leak