high idle

[Jarek5_7]

I have high idle , around 1100 or little more rpm.

on datamaster desired idle is 650. recently I changed plenum gaskets, injectors, coils, spark plugs and wires because there was a problem with ingnition, miss etc. now the only problem left is high idle.
(oh maybe not the only but most annoying)

I`ve read that tps v should be from 0.54 to 6v
mine at idle are around 0.24v

other thing is how to check iac?
datamaster shows that iac is 0 on idle , whem I rev a little it goes to 30 and them falls to 0, with it rpm falls but now as low as I wanted it to be.

is the a way to check iac? or to calibrate it?

[XfireZ51]

The fact that the IAC count is 0 at idle suggests that there is bypass air
present. Does idle drop to 700 or so if you stab the pedal?
Did you move TPS? With scantool in place, move throttle from closed to open and back
Does it feel smooth? Do volts seem to hang or move in a abrupt or choppy manner?

[Jarek5_7]

the idle dont drop even below 1000.

I dodnt move tps. volts from tps move smoothly.

what do You mean by bypass air present?

is 0 the middle position for IAC? is the middle position for iac the required position to maitain idle (650) rpm?

by bypass air present you meant the air bypass by half opened aic?

[Demps]

First thing I would check (since you just performed work) is the hose under the throttle body. You can see the "L" shaped fitting pointed aft from the driver's side under the TPS-->get a small flashlight and mirror. If not attached, you will have a high idle. Sometimes you can attach it without removing the plenum again. The rubber hose has a compression-type clamp on it.

Also, the TPS is adjustable and should read correctly.

Ted

[Jarek5_7]

It had high idle before the work I did. I think I know about which hose you r talking about, I think its in place, but I`ll check it again.

so what v should tps at idle have? 0.54?

[XfireZ51]

Jarek,

0 steps for IAC means it's completely closed. Outside air is getting in some other way. Throttle plates may be opened too far or there's an air leak.
Loosen TPS and set it to .5v with scantool connected. You'll do that with
ignition on, motor off.

[tpepmeie]

Originally Posted by Demps

First thing I would check (since you just performed work) is the hose under the throttle body. You can see the "L" shaped fitting pointed aft from the driver's side under the TPS-->get a small flashlight and mirror. If not attached, you will have a high idle. Sometimes you can attach it without removing the plenum again. The rubber hose has a compression-type clamp on it.

Also, the TPS is adjustable and should read correctly.

Ted

I'm with Ted... the canister purge hose under the front driver side of the plenum is likely disconnected, which will cause the massive air leak = high idle. That was the first troubleshooting I did on my '91 back in 1999.

[XfireZ51]

Originally Posted by tpepmeie

I'm with Ted... the canister purge hose under the front driver side of the plenum is likely disconnected, which will cause the massive air leak = high idle. That was the first troubleshooting I did on my '91 back in 1999.

He mentioned that it had a high idle even before he did the plenum removal.
So whatever is causing high idle hasn't been affected.
Surprising he 's not getting code for LO TPS V.

[WB9MCW]

Originally Posted by tpepmeie

I'm with Ted... the canister purge hose under the front driver side of the plenum is likely disconnected, which will cause the massive air leak = high idle. That was the first troubleshooting I did on my '91 back in 1999.

This was an early post in the thread that was telling you of this common problem

Originally Posted by Jarek5_7

I`ve read that tps v should be from 0.54 to 6v
mine at idle are around 0.24v

Correctly set your TPS, and I think you will find the high idle will go away.