Sticky-open throttle
 

Guys,

Any ideas (e.g. an over-active WUR) for anything other than the accelerator pedal / cables / levers sticking which could cause the tick-over RPM to be as high as 1,200RPM (instead of 900RPM)?

When it happens (even from cold - though not especially), if I reach down and pull the throttle pedal back, there's no play and no change in the RPM. (Only way to bring them down again is to blip the throttle a few times and drive.)


Car has always done this to me (in the early days, I thought the carpets were getting stuck around the pedal), but it seems to be getting more and more pronounced.

If "blipping" the throttle brings the rpms back down, then it still points to something sticky in either the throttle cable or the linkage at athe throttle body, or the throttle body plate maybe gummed up and sticking in the body?
There's a stiff wire (call it a "rod") that goes from a pivot point attached to the tranny(IIRC) and runs up through a gap in the firewall to the engine. If that rod is bent and perhaps rubbing on something, that could be your issue (sorry for the poor description).

Outside of those reasons, how well is your AAR working? Does it do this: High idle when stone cold, idle drops in a couple minutes when warming up, high idle for a short period when starting back up after shutting down hot? Blipping the throttle, though, won't have an impact on the AAR. It will either admit the correct amount of air or it won't, and your idle will either be high or it won't if it's faulty.

There should be "certain" amount of play when pulling the throtle pedal back... if there is no play, something is too tight somewhere between the pedal and the firewall as mark said above.

Thanks, guys.

I hadn't driven the car in 8 months - but the problem was really pronounced.

It's such a stupid problem which should be easy to remedy. (This makes it all the more annoying!) But when you're prone to leaning a car through the corners, an unwanted extra 300RPM can be a bit dangerous!

If it's a mechanical thing the throttle linkage rod could be rubbing on something in the center tunnel too. If it isn't rubbing on something from the transaxle on back through the engine tin and on to the bellcrank and throttle body a mirror and flashlight looking forward from the shift coupler might be of help to see.
There's also a hole in the front of the tunnel behind the center tunnel the mirror may fit into.
Could be an adventure looking around under the car and getting to know it better.
Use jackstands before getting under there.

Latest trouble this morning is the car refusing to start - the battery isn't charging. (Put the 'main beams' on last night, and the radio would switch off!)

Wonder if the extra 300rpm is due to a dodgy alternator?.. *Sigh*

Losing patience here :(

I think I have the answer - it's none of the things suggested.

I'll take a picture, but it's the part which has a pipe down from the right side of the Intercooler.

My local specialist identified this part as the problem (he's seen it in other old 930s), but he doesn't necessarily have the skills to take this thing apart and recondition it himself. (Have a suspicion that, after 30-odd years, the bimetalic strips inside will be failing.)
http://i371.photobucket.com/albums/o...3072011735.jpg

Todd informs me that this is known as the 'Auxiliary Air Regulator'

Fixed! (Or at least I think it is. :))

Thanks a lot, Todd - have to see if the fuel consumption improves any now - it was the AAR (and not the cable / linkage catching on anything).

I tried to point you there back on June 15, but I think we were all getting hung up on throttle linkages getting "hung up". Glad you got her sorted out.

Outside of those reasons, how well is your AAR working? Does it do this: High idle when stone cold, idle drops in a couple minutes when warming up, high idle for a short period when starting back up after shutting down hot? Blipping the throttle, though, won't have an impact on the AAR. It will either admit the correct amount of air or it won't, and your idle will either be high or it won't if it's faulty.