Warm Idle is to darned fast!

[mike65]

Okay its not that much too fast but instead of 800 ish its 900+ reaching 1000 on a hot "stuck in traffic" engine. The idle valve is as far in as it will go. Now I presume the only job of the threaded valve is too cut the ammount of air passing across, so is the problem a leak elsewhere letting air into the system?

Any ideas?

Mike.

 

[Hal Fisher]

Do a search on the "fast idle" problem. You'll find your problems probably either you idle speed control valve (not what you have been turning) or the idle speed controller.

Hal

 

[mike65]

Cheers, I'm hoping its a vacume leak myself!

Mike.

 

[Hal Fisher]

Well if its a hose than ok. Otherwise the simple replacement of one of 3 parts is far less expensive than reseating one of the manifolds. The chances of it being a manifold is very slim anyway. I'd start doing the tests and finding the problem right away. Its simplier than you think and fixing it right away will reduce the stress on you torque converter, another very expensive part to have replaced.

Hal

 

[mike65]

You mention the idle speed control valve and the idle speed controller where are these found? I may know them by a different name (or I may not). :?

edit.> I relised what the speed controler is I think - the micro switch, yes?

Mike.

 

[talbir]

If you had a vacuum leak, your idle would shoot upto 110 rpm or so, cold and hot.

I would suggest it is your idle air valve - it's is closing but not fully, so idle drops to where it should do when temp is low, but as temp rises, idle rises to 800rpm.

Try cleaning idle air valve our with carb cleaner, however this rarely solves the problem. The slide gate is solenoid operated and usually replacement is the best solution. Try fitting a known working one from another car before buying.

 

[mike65]

Idle air valve, thats also called the aux air device is'nt it? At the back of the engine...

Mike.

 

[Hal Fisher]

Thats their names. Do a search on these and you'll find all you need to know about locations, troubleshooting, and replacement.

Hal

 

[NDavies4]

Presume you have a "Deceleration throttle micro-switch" like mine which sits at the end of the throttle linkage. With the accelerator pedal up the top arm of the throttle linkage rests on the little button switch and needs to depress it sufficiently for it to 'click'. Have you checked/discounted this?

I only mention it as I had a similar high idle problem last week (1500 RPM in 'P' when engine's at working temp) after getting the car back from the garage - was having the crankshaft position sensor replaced. As the mechanic duly went on holiday I did a bit of reading up to try to fix the problem myself. From some other posts I read about the significance of this little switch, and sure enough my linkage had somehow been altered so the switch no longer clicked. All I had to do was turn a little black plastic adjustment screw on the linkage a half turn, which slackened off the cable sufficiently for the spring to pull the arm more forcefully onto the switch. Immediately the switch clicked the idle revs dropped to 600'ish!

Might not be the solution for you but just thought I'd throw it in in case other readers are suffering due to something so trivial.

 

[mike65]

Thanks for tjhe suggestion that postion looks fine to me and I hear a sharp click when pressure is lifted off the wheel.

Mike.

 

[teky]

"Deceleration throttle micro-switch" is simply a fuel cut off switch your problem is idle bypass valve and needs cleaning out

 

[mike65]

Teky I read that on a thread at mercedesshop, so I'll look to do that his week.

Mike.