Teddy952

While driving to work today in the magnificent Massachusetts weather (45 deg and rain) my idle got stuck at 2000 rpm. I could rev her up but would come back down to 2K no lower.

After driving for a bit the idle finally fell to just below 1k. Drove a bit more and she shot up to 2k again. By the time I made it to work the idle was normal.

Any places that I should start to troubleshoot? ICV? TPS?

thanks
89 951

Melchior

Sounds like the Idle Control (Speed) Valve. I took mine out and cleaned it before. Fixed the problem. On the 951's, the valve is impossible to remove without first removing the intake manifold: sucks. First try disconnecting the bosch-type connector from it and see if the idle comes down. To clean the valve without removing it, try taking a long straw and sticking it up the air tube as far as it will reach. Then spray some WD-40 or some kind of penetrating fluid into the valve. Then start the car and rev the engine several times to move the valve gate. If that doesn't work, then you may have to remove it. Usually the valve's electrical side doesn't go bad. When I cleaned my valve, there was a lot of crud coated in it that was making the valve gate stick.
One note, K&n air filters tend to make these valves crud-up faster than normal due to their higher bypass. Preventative maintenance for this is to keep the filter cleaned and well-oiled to trap the dirt.

Teddy952

I though that may be it (ICV). Most of the time my idle is right on 1K. I know it should be around 950. Im going to get the vacuum kit from Lindsey and replace all lines as well as delete the ICV and Cycling Valve?? I think thats what you call it.

Good tip on keeping the filter as clean as possible. I have a MAF 3 kit installed and the cone filter looks a little dirty. If I delete the ICV will anything that bypassed filter get into the intake????
Or do you just plug the holes on both ends??

TED

Jeremy Himsel

A faulty or unplugged TPS will also have the same effect. When it does it, pull the hose from the intercooler pipe to ISV and put your finger over the holes. If it doesn't idle down, check the TPS to make sure it clicks when you crack the throttle.

Dave E

My TPS was bad and it WAS clicking, I ended up going through the procedure in the manual to diagnose the problem. I had an intermitent variation of the voltage at the closed position which caused the idle to fluctuate at random, but usually up to around 1700-2000 RPM, so the click test won't tell you much if the switch is worn out.

hosrom_951

I also suspect the Throttle Position Sensor, since you revved it up, it went to normal (under 1k, it should be somewhat of 840+ - 50) but sound like the TPS is getting stuck.

Danno

Also note that the tach is off my about 200rpm. The correct idle speed of 840 +/- 50 will show up as 1040 +/-50rpm.

Teddy952

hosrom_951:
When I blipped the throttle the RPM came back to rest at 2k and stayed there. Do you still think its the TPS??

Driving today to work the idle was at 950 and while I was at a red light the idle slowly rose to 1500 - 1800. It stayed there for a brief moment and then slowly came back down to 950. This all happend at the light and I did not touch the throttle.

Danno:
What should I be reading on the tach for a correct idle? Near 700??

Thanks for the help everyone!

brad-cam

I had exactly the same problem last month, and though the TPS was "clicking", it was the problem. Replaced it and everything is perfect now.

GWTurboS

Teddy,

I had the exact same problem as you. At a traffic signal, my idle speed would rise to 2000 rpm and would stay there. Occasionally a blip of the throttle would bring it down, but most of the time it did not. I followed the factory manual and used an Ohmeter on the DME plug to test the throttle position switch. TPS checked out okay.

I ordered a new ISV and intake manifold gaskets from Pelican and spent a weekend changing the ISV and cleaning up under the manifold at the same time (removed the cycling valve.) That also gave me a chance to inspect all the vacuum hoses and replace some of the clamps on them with new radiator style clamps.

To conclude this long and boring explanation, the problem is gone now. The old ISV didn't look too bad, but it doesn't take much crud to clog them up.

Good luck!

Greg W.

Teddy952

Interesting....

Im going to do the whole vaccum line replacement procedure soon. Ill check the TPS then, unless things get worse.

About the ISV being clogged.....It seems that the reason why the ISV got clogged was because of crud getting into it from the MAF connection. If I delete the ISV won't crap just get sucked into the intake manifold if it by passes the filter??

TED