High Idle

[DR1947]

My 97 SL2 suddenly started idling at about 1300 RPM. The throttle body has been cleaned and seem ok. I have some luck lowering the idle by forcing the throttle linkage toward the idle screw. The butterfly valve and the butter fly shaft seem ok as well. The idle screw had never been tampered with. any suggestions are appreciated.

[Mork]

Check for vacuum leak or EGR valve problem if so equipped.

[DR1947]

Mrok thanks for the reply. I was thinking the EGR would cause rough Idle not a fast idle. The Idle is smooth but to high. No other symptoms. No pings knock or error codes. I was thinking a bad fuel pressure regulator and high fuel pressur at idle would cause this or a defective coolant sensor.

[drjag]

Originally Posted by Mork

Check for vacuum leak or EGR valve problem if so equipped.

Item 134 (Idle Air Control) has other discussions on the high idle problem. drjag

[emailer33]

where can i see this Item 134?

[sierrap615]

top four causes of high idle in saturns (in order)
1. ECT cracked(only applys to older nylon ECTs)
2. EGR clogged(even more likey on 91-94s)
3. drity IAC (very small piston shaped solenoid, controlled by PCM, allows air to bypass throddle body plate during idle.)
4. bad driving habits(mainly with a manual trans, remember there is a stop idle speed and a rolling idle speed)


i've never heard of the IAC being called "item 134"

[drjag]

There is another source of the problem - a leaking intake manifold gasket! My reference to '134' was not what I thought it was - ignore it. However, search for 'idle air control valve' title and read Lucas1's comment.

I just came out from my garage after putting on a new intake manifold gasket (a moderate amount of work for the unskilled), and the car runs great. Idle, when fully warm, in now 700 rpm, about 600-700 in drive.
The old intake manifold had been sucked in a little at the #1 intake port (passenger side of engine). There are 8 studs that are obvious, but one bolt behind the power steering pump. When I finally discovered this bolt and went to loosen it, it was barely tight - that's where the gasket problem was. The gasket wasn't ripped, just buckled enough to leak in air. If the idle changes when you spray carb or throttle body cleaner around the intake manifold gasket, then you know the problem is with the gasket or the o-rings at the injectors. I hope this helps. drjag

Originally Posted by sierrap615

top four causes of high idle in saturns (in order)
1. ECT cracked(only applys to older nylon ECTs)
2. EGR clogged(even more likey on 91-94s)
3. drity IAC (very small piston shaped solenoid, controlled by PCM, allows air to bypass throddle body plate during idle.)
4. bad driving habits(mainly with a manual trans, remember there is a stop idle speed and a rolling idle speed)


i've never heard of the IAC being called "item 134"