Hi all,

Need a little help troubleshooting this one.

Problem: high idle in park only, once warm. Not experiencing this issue in neutral. I've searched and seen mixed responses for problems with park & neutral idle, but not just park.

Any thoughts? Throttle body, idle air control valve?

Thanks

 

I will be honest in that I don't know what would be magic about "park" versus "neutral" that would be causing the RPM to rise. However, a high idle can be a vacuum leak.

 

what year 240? there's at least 3 different fuel injection systems used on the 240 in its 25+ years of production

 

It's a 1990 DL w/ EGR (if that makes a difference).

Also, it now happens in P and N -- but only intermittently. For instance, when I drive the car harder it will idle higher. I will check for vacuum leaks.

 

Cleaning the IACV will help if it hasn't been done before. I had the same issue when I first bought my LH 2.4 244.

 

Thanks for the suggestion. I cleaned the IACV; no luck. Searched for more vaccum leaks and still nothing visible.

I did, however, confirm and isolate the issue... when driving it hard, then putting it into P or N, the idle is high (sometimes, very high).
When driving it easy, the idle is normal, or close to normal.

My guess is replace the IACV?

 

How high is "high"?

 

Unknown, no tachometer. I'd guess it to be double what it should be.

I just noticed a lovely oil leak has increased coming from the front of the engine, near the timing belt. Not sure if that's related to high idle (if it could have an impact on a vacuum leak).

 

is the oil leak from the top or bottom of the front? if the top, its probably the valve cover gasket, if the bottom, its more likely the camshaft seal.

neither should effect idle speed. air leaks are the #1 cause, things like a hairline crack in the hoses to the IACV. That or the throttle position switch that senses the throttle is at idle. or the throttle body not actually closing completely.

 

Hi Pierce. Oil leak is on the front passenger side of the block; looks like its dripping down on to the front of the exhaust manifold. Valve cover gasket?

Update on the idle: when I turn the car off for a few minutes and then restart it, the idle goes back to normal.

 

yeah, probably the valve cover gasket then. you can get a UV dye you add to the oil, drive it a short distance, then inspect it with a ultraviolet light in a dark place, you should see exactly where the oil is seeping from