Fast Idle After Tune Up

[crow1]

My 94 just had a major tune up (plugs, wires, cap, rotor button, throttle body cleaning, etc). Now it has fast idle issue (1100-1200 rpm). Oddly I can tap on the egr valve and it will drop to 650rpm and continue there until car is turned off. Fire it back up and the fast idle will start all over.

It would seem that this would be a sticking idle speed control valve but why would tapping on the egr valve get it to run? Can a defective egr effect idle spped?

question:

do I replace (or can it be cleaned) the egr valve?

Or is it the idle speed control that needs replacing?

both are not cheap parts...hate to buy t he wrong one.

thanks in advanve for any help.

[Lexls]

Was the throttle body fully cleaned, meaning did you take the thottle body off?

I'm not sure about the EGR valve, my guess is that it's not that. What I think you need to do is adjust your TPS. From the tune-up things have changed, especially the thottle body, part of the tune-up is adjusting the idle speed. This should help ya: http://www.lexls.com/tps.html

You can try making adjustments on the TPS before buying any new parts. Let us know if it works out.

[crow1]

Was the throttle body fully cleaned, meaning did you take the thottle body off?

I'm not sure about the EGR valve, my guess is that it's not that.  What I think you need to do is adjust your TPS.  From the tune-up things have changed, especially the thottle body, part of the tune-up is adjusting the idle speed.  This should help ya: http://www.lexls.com/tps.html 

You can try making adjustments on the TPS before buying any new parts.  Let us know if it works out.

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thanks Lexls,

You have a nice site!!!

The photos of the model LS 400 on the site are different than mine. The egr valve on my 94 has no filter. It has two by pass water lines connected to it as well. I took it apart and cleaned it however. There was a great deal of carbon on the plunger.

It did not help the problem. It still idles high until I tap the valve body a few times. And as before, it sometimes idles correctly at start up.

Question: Do you still think it is the TPS that needs adjusting?

thanks again.

[Lexls]

Hmmmm, it sounds like you're going to have to do a little more trial and error. I'm a little confused...are you tapping the throttle body? If you are the TPS is connected to it. Yours may look slightly different than mine if your LS has TRAC, then it would have two sensors connected to the throttle body. If tapping this does something the TPS may have been damaged when the throttle body was cleaned.

[crow1]

Hmmmm, it sounds like you're going to have to do a little more trial and error.  I'm a little confused...are you tapping the throttle body?  If you are the TPS is connected to it.  Yours may look slightly different than mine if your LS has TRAC, then it would have two sensors connected to the throttle body.  If tapping this does something the TPS may have been damaged when the throttle body was cleaned.

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No, I am tapping the egr valve. the valve on at least the 94 is different from the site. I took it apart and cleaned it but that did not help. There is a plunger inside that moves up and down. I assume the carbon buildup has made the plunger unable to ride completely inside the egr It still runs fast idle unless tapped on. I have ordered a new one and hope this will take care of the problem.

thanks

[crow1]

The new egr valve and adjusting the TPS after installation and warm up...runs smooth as silk...rpm level at 650...finally fixed

thanks for the help.

[Lexls]

Great to hear it's back to normal :)