Bouncing Idle that won't go away

[Dukenukemx]

It's starting to annoy me that my 90 3.1 Retta Gt has a bouncing idle. I've changed the gaskets in the past and a few vacuum lines here and there, but it still happens. The only thing I haven't tried is changing this sensor that's on the air box, which is now on my cone air intake. The other day I was charging my AC system and started the engine without this sensor connected. The idle would race to 2k rpm without stopping. Nothing but disconnecting the battery would restore the engine to normal idle. Similar thing happened with a vacuum leaked that broke open near the cruise control pump and even though I had repair the leak the rpm was stuck high unless I disconnect the battery.

If anyone could give me suggestions on where to look I would be grateful. Also what is that sensor in the air box? I know it's not a mass airflow sensor, but I think it's for the air temperature? I know I've tried looking for it in the past but it was either extremely hard to find or expensive to replace.

[1988GTU]

make sure the hose for the pcv isnt cracked/torn. It can be found going to the under side of the uim.


it goes on the port in that pic.

This is the hose:

[Money pit Beretta]

Oh man I hate that thing. Mine broke in half when putting a new PCV valve in. Lets just say I was lucky that the parts store was open and had the gaskets and hose. Almost missed work on Monday.

That sensor is the inlet air temperature. Are you sure you do not have a thottle position sensor problem? When they go bad the idle sits at 2k.

[Dukenukemx]

I've changed the PCV and the tube to it. The TPS was changed maybe 5+ years ago with standard. I've tried other Ebay brands but they broke within 2 weeks and ended up going back to this stardard TPS. Any brand TPS anyone can recommend?

Also, is the inlet air temperature sensor important?

[ifixalot]

My daughter had a 90 GT that stayed at a high idle. It turned out to be corrosion on the
ECM pins and connector due to the firewall leak on the passenger side.
The IAC has two wires that open it and two that close it. It would open but not close
because of the corrosion. So check out the connector and pins with the battery disconnected.

[Dukenukemx]

My daughter had a 90 GT that stayed at a high idle. It turned out to be corrosion on the
ECM pins and connector due to the firewall leak on the passenger side.
The IAC has two wires that open it and two that close it. It would open but not close
because of the corrosion. So check out the connector and pins with the battery disconnected.

Did that like a year ago cause I replaced the ECM. Connectors were fine and even threw in some dielectric grease for good measure. But the problem existed long before that.

I guess I should look into a replacement TPS?

[Dukenukemx]

Think I found the problem. There was a vacuum line that ran under the coolant tank to I think the charcoal canister? I couldn't keep it in there so I used a spring clamp to hold it on.

[Money pit Beretta]

That is great, I sure didn't want to start with my vapor cainster crap again. Always seem to fall back on that. Oops.......better check my lines to that!

[Dukenukemx]

Just to remind people, my car hasn't ran better. Can't believe it was that vacuum line the whole time.

[Money pit Beretta]

It's the last thing you check or even think about that is the problem. Sure seems that way.

[Ramborogers44]

i used to have a sunbird with that motor make sure that the vaccuum line under the pletum is not bending i had that problem it will cause a stumble because of air and mine also sounded like a whistle on the track before i found the problem, if that dosen't fix it try the map sensor