Engine revs to 2000 rpm in park at start-up

[57chevyragtop]

1993 Park Ave, 3.8, automatic,110kmiles..distant friend describes as follows. When starting in park the engine revs to 2000 rpm, foot on the brake, when dropping into reverse or drive the engine is sluggish. Does not happen all the time but more often recently. I did tune up plugs/wires one year ago. check engine light comes on then goes after a short drive. then may not happen again for several days. found no similar posts in search of this forum. I don't think there is place in the small town they live to get codes if set.

[HotZ28]

Wow, 5000 rpm would require a lot of air, like the TB stuck, or large vacuum leak! How long does it rev 5000 rpm? The rev limiter should kick in at 4500 rpm when in park, or neutral.

[57chevyragtop]

Big oops here, I apologize for the errant post. The revs are 2000 NOT 5000...regardless of MY error He is going to clean the trottlebody and check for vacuum leak(s) He reminded me also that I didn't do the throttlebody and maf on this particular vehicle but did on the other 3 he owns. Thanks for the kick in the head Hot Z28....

[HotZ28]

Title changed to reflect "2000 RPM" rather than 5000. While cleaning things, be sure to remove & clean the idle air control seat & pintle. In addition, check the TPS voltage through the full range. .45v @ closed throttle & 4.0 -4.5v @ WOT. (This is on the Blue wire)

[57chevyragtop]

Update: 1993 not 96..Man, I screwed this up! he checked the throttlebody and it was clean and working freely but did find plugin not plugged into the air filter box, I think this is the air temp sensor, or early MAF.... plugged that in and is running smoother now. Thinking this was not re-attached when getting oil change at one of those oil change outfits. I will post if this is not the cure. will know for sure when temps drop to 30 or below... Man I'm getting old....

[HotZ28]

Originally Posted by 57chevyragtop

Update: I think this is the air temp sensor, or early MAF.... plugged that in and is running smoother now. Thinking this was not re-attached when getting oil change at one of those oil change outfits. I will post if this is not the cure. will know for sure when temps drop to 30 or below... Man I'm getting old....

This is a very common problem at "Quick Lubes"; they simply do not have the expertise on hand to even know what an AIR sensor is, much less, where it is located. They pretend to check the air filter, hoping they can show it is dirty and charge the customer 200% markup for replacing the filter. Nine times out of ten, they can not install the filter or connect the air box correctly.
BTW, you are not "old" yet!

[57chevyragtop]

Thanks for the "not old comment". question: Stopped by the library and looked up what that connection is called...listed as the "IAT" but no translation given in manual and I could not find in internet search...I am thinking "intake air temp" sensor...is this correct? I remember seeing a list some time ago of automotive acronyms but don't recall where. Would be helpful on this site perhaps. Dave~

[HotZ28]

Yes, you are correct, the acronym for the "Intake Air Temerature" sensor is; (IAT) Click Here for a good list of automotive acronyms. BTW, what is the status of the high idle?