high idle

[stb616]

It seems like about 60% of the time my Disco is idling at about 1500rpms. Sometimes it will drop where it should be.

I plan on doing a seafoam treatment and cleaning the TB and IAC. Anything else to try or check on why it's idling so high?

[Spike555]

Vacuum leak.

[stb616]

Replaced small vac lines...no change
Seafoamed just for fun....no change
Did carb cleaner spay down on all vac connections....no change
unhooked IAC wires....no change
unhooked, then caped IAC air inlet....idles where it should

Two questions- 1) is there anyway to test that a signal is actually getting to the IAC? 2) What is the GM IAC part that I want to get?

Are the screws/bolts that hold the IAC on an allen/hex wrench? I couldn't see them.

[Spike555]

Remove the IACV, plug it in, have a friend turn ignition on/off and see if the plunger moves at all.
It is a Jeep 4.0 IACV that is a direct fit, I think a GM 4.3 works as well but dont know for sure.
It sounds like your IACV is stuck open and letting in to much air.
If you have not removed and cleaned it yet start there, also clean the port it mounts into.
I dont remember what type of screws hold the IACV on, make sure its that you remove and not the TPS, the TPS is the closest to the throttle mouth.

[stb616]

Well it's all set...at least for now. I've got most of the vac lines replaced and put in a new IAC after I cleaned up the port a bit. It seems to be running good as of right now.

Thanks for the input...again.


FYI- On a 95 D1 I used a IAC from a 1989 Chevy S-10 w/ a 4.3L V6 application...it's a perfect match. The jeep version is not correct for my 95....it bolts on where mine needs to actually thread into the port.

[stb616]

I spoke too soon.

On start up it starts, runs, and idles normal.

It drives fine but once I come to a stop the idle is back up and when put back in park it settles in at about 1200rpms. If I shut it off and then restart it, it idles where it should...around 800rpms.

What's next? This is an OBD1....does it have an adaptive memory?

[PTSchram]

'95s do not have adaptive capabilities.

I'd be looking for vacuum leaks.

[stb616]

Originally Posted by PTSchram

'95s do not have adaptive capabilities.

I'd be looking for vacuum leaks.

Good. I didn't think so. Thanks for the clarification.

[stb616]

How do I check for other vacuum leaks? I've replaced everything I can see. Any help would be appreciated....I can do a lot of stuff but this isn't something I have much experience with.

[Spike555]

With the engine running and idling to high take a can of brake cleaner without the straw and spray around the intake and all vacuum lines.
If the engine speed changes then pay special attention to that area.
When you spray around the leak it will suck the brake cleaner into the engine and lower the engine speed for a second or two.
The intake plenum is a common leak spot, it someone had it off and did not put it back on correctly or the gasket is just worn out it will leak, usually at the back.