Hi folks. I'm new here, but grateful to see so much troubleshooting going on. Been super helpful so far.

My 87 240 dl has been having a recurring idle issue over the past 4-6 months or so. It runs fine for an extended amount of time, and then every so often (at least once per time I drive it, and in increasing frequency over the past 2 months) it will idle really high when in park and/or rev really high when in gear. Sometimes dropping into neutral will drop the idle to normal, but most recently this doesn't seem to affect it. Most recently the idle is super high, as if the gas pedal was pushed all the way down. I'm a total newb, but have the will, and sometimes, patience to try and learn what's happening under the hood.

I searched the forums pretty extensively and found people with similar issues, but mixed results. So far I've done the following--I think correctly. Also my this model appears to not have the LED that signals codes, as far as I know, haven't seen it.

-Tested MAF--unplugged, tested resistance according to haynes manual, ran engine with MAF unplugged, idle ran more erratically than when plugged in.
-tested TPS for resistance according to manual. Seemed fine. Throttle clicks as I've read it is supposed to.

Not sure where to look next or if I'm even getting anywhere. Any suggestions or guidance?

Thanks

 

First eliminate possible mechanical causes such as the linkage/pedal binding--it sounds like the most likely cause. Then look for air leaks in the intake manifold/gasket as that may cause surges. Check and clean the Idle Valve, the one under the intake manifold.
Your car has no "code box". A surge like the "pedal is all the way down" is dangerous... should not be happening...

 

I had an 87 wagon with the same problem and ended up being an intake hose unplugged....check all your hoses and clean flame trap...

like you I checked for everything and did not find a thing.....
I had replace both fuel pumps and relay and trans flush fill and cyl head gasket kit and when putting all back together missed a hose and had my idle just like yours,...........
check the plugs if they are loose....another problem on my wagon that caused idle problems...

 

Thanks for the feedback folks. I fixed the problem with new spark plugs and cleaning the flame trap. Funny how simple things are sometimes...