I have a 1985 Volvo 240 that seems to have developed a problem while sitting for about a month or two without being driven.

When I start the car the idle speed almost instantly revs up to twice (or more) of what it should be. If I tap the accelerator the rpm's drop down to normal but then start ramping up almost immediately.

When I drive the car, the idle seems to stay at the correct position for much longer (on a flat stretch, with the car in gear) but will then suddenly, and for no apparent reason, start to idle faster again.

Apart from the idle problem there seems to be no other problem with engine or fuel delivery. No sputtering, no lack of power, no hesitation, missing etc.....It seems to run normally.


Since I can't drive the car for any distance, I can't determine if the speed ramps with the accelerator in any other position . I get the feeling that it wouldn't - I'm pretty sure that the problem only happens at idle.

I should mention that while the car was sitting, I did take the fuel pump relay out and swap it with my other 240. The other car was having a vapor lock problem that I later pinned down to a faulty fuel pump (the in-tank pump). I put the relay back (actually swapped them around several times.) The original relay is back and both relays seem to work the same in both cars - This doesn't seem to be related, but I thought that I should mention it.

I would greatly appreciate any help with this. I really need the car back and any suggestions are welcome.

Thank you in advance for any reply.

 

Sounds like throttle position sensor to me. Have u messed with it? Loosen the 2 screws and position it where it click right whent the throttle is moved. May b time for a new on though

 

It would be good to check the idle air valve, it could be getting stuck....

 

Yup...might also be one of the hoses to the iac has failed. To check the iac, just clamp off one the iac hoses while it's at high idle...the idle should drop immediately. I once drove months with a set of hose clamp pliers clamped just right on an iac hose!!

 

Thank you for the quick replies bigdaddyrdpjr, morrisamazon53 and swiftjustice44 .


I'll be checking on all of these things this afternoon. I really appreciate the help. The manuals that I was reading didn't seem to be getting me anywhere. If you don't know where to look they'll take you nowhere fast.


Thanks again!

 

An update:

I loosened the Idle position sensor and it seems to click properly (I didn't have time to ohm it out.) I'm not sure about it yet.

I clamped the one hose to the IAC (This was one part that I couldn't seem to identify or locate over the past month as I read about the fuel control system. I finally found it tonight (underneath just about every other part of the fuel system). I clamped one of the hoses almost completely off. This brought the speed down to normal.

Now I realize that I know even less about the system than I thought....Did I isolate the problem to the IAC or did I just mask the problem? Would clamping a working IAC hose completely shut the engine off?

I wish that I had more time to work on the car tonight. Not enough time in a day.......


Thanks again.

 

replace the iac valve, its bad. Like swift said he ran with pliers on one for awhile!