All, I need some advise.

The other day I noticed my '88 GT (V6) had a high idle (2500rpm). I started by replacing the IAC (A buddy gave me a new one), and all of the soft vacuum hoses. After looking closer, I found the broken EGR Tube (broken @ the plenum.

I spent most of the day today installing a new EGR Tube. While I was at it, I installed the steel vacuum lines, too. I cleaned the throttle body & the plenum really well.

I got everything assembled, and started her up. Now the idle is at 3,000 rpm! What should I check!?

Now, while inspecting everything with the plenum off, I noticed something weird. The rear valve cover has a hole for a tube coming from the air intake (before the throttle body). The gasket that holds the tube in-place was old & broken. I need a new one (what do you call that & where can I get it??). For now, I detached the tube. Could this be the source of my high idle?

Everyone's input is greatly appreciated. Thank you!!

------------------
Scott & Traci
'88 GT

Perhaps I didn't use enough RV Sealant when I put the plenum back on????

quote Originally posted by NASAReeves: I got everything assembled, and started her up. Now the idle is at 3,000 rpm! What should I check!?

The rear valve cover has a hole for a tube
coming from the air intake (before the throttle body). The gasket that holds the tube in-place was old & broken.

do you mean the rubber grommet that is in the valve cover?

you can get the grommets at advance auto.
are you sure you didnt miss a vacume line?
how about the vac line that connects under the top plenum? also lots of time the metal line that goes into the bottom of the throttle body comes lose during installation of the throttle body Its hard to see so double check that.

Perhaps I didn't use enough RV Sealant when I put the plenum back on????

I dont think thats your problem I never use that stuff on the manifold (i just use felpro gaskets) and ive never had a problem (ive got 3 fieros and had the manifolds off lots) sounds like its time to double check all the vac lines.

good luck

I fixed it!! I took a piece of vacuum hose & used it to listen around all potential air leaks. I heard air by the IAC Valve and around a few of the rubber ends.

First, I replaced two of the vacuum hose rubber ends (both elbows...one to the EGR, and one to the plenum). Then, I removed the IAC, only to find that there was a new gasket, and an old gasket. Pretty good reason for an air leak, eh? The old one was caked on pretty good, so I used some valve gasket remover. That normally works great, but this gasket was on good. I wound up getting out the dremel tool, and lightly sanding the old gasket off in-between coats of gasket remover. That worked well. Then, I used some of the copper gasket to ensure that the new seal would take well. It might be tough if I ever take the IAC out again, though.

While fiddling around the IAC, I noticed the end of a (~1/4") pipe staring me in the face. At first I was frustrated, because I thought I might have to take the manifold off (again) to see where this came from & where it went to. But...After looking all around, I found that the Throttle Body (on the bottom) has spots for not only the two small vacuum hoses...but also for this larger pipe, which must be guided in there before mounting the TB back to the plenum. I unmounted the TB, guided the pipe in the hole (to the right of the IAC), and remounted the TB to the plenum.

Reconnected the battery...cranked her up, and presto...the idle is no longer 2500-3000 RPM. I'm now down to 1500RPM cold, and 900-1000RPM warm . Thanks everybody for all the help!

------------------
Scott & Traci
'88 GT

GREAT!!!

im glad you got it
that big line on the bottom of the throttle body has given me troble before too.

Glad that you got it all done and the problem(s) worked out!

- Stan