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Offline trevauk

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Lumpy idle when warm
« on: August 28, 2008, 14:26:46 »
Hi All

I have a problem with my 1988 RRC 3.5 Efi auto that I can't solve.

When the car is started from cold it idles perfectly.

The problem starts when the car reaches normal temperature.

When I slow down to 10 mph or pull up at a junction the revs go really lumpy on me. It seems to go from 0 revs to 250 revs, up and down, sounds really rough and if I do not add revs myself the car stalls. It does start again first time (never fails), but as long as it is warm this situation does not go away. The car still drives fine with all the power and I have not noticed the fuel consumtion going down any quicker.

I have checked all the hoses and pipes for splits and checked the plugs but all is fine there.

Can anyone be of assistance and point me in the right direction.

Many thanks

Treva.
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Offline andyb

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Re: Lumpy idle when warm
« Reply #1 on: August 28, 2008, 15:02:02 »
My first thought is to clean out the idle air valve.
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Offline trevauk

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Re: Lumpy idle when warm
« Reply #2 on: August 28, 2008, 15:20:37 »
Where is the Idle Air valve?

I can't find it listed in the Haynes I have.
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Offline andyb

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Re: Lumpy idle when warm
« Reply #3 on: August 28, 2008, 15:33:58 »
Sorry it might be called by-pass air valve. IIRC is it control by a stepper motor. They should be in your manual :)
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Offline trevauk

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Re: Lumpy idle when warm
« Reply #4 on: August 28, 2008, 15:36:51 »
Yes - by pass air valve.

Right I will have a look and get it cleaned and then try a run out to check.

Thanks Andy
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Offline Rossko

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Re: Lumpy idle when warm
« Reply #5 on: August 31, 2008, 22:53:55 »
Quote from: trevauk on August 28, 2008, 15:36:51
Yes - by pass air valve.

Isn't this a flapper-type EFi, with no stepper motor?   Hunting at idle sounds like it may be going rich, could be a whole number of reasons.  Start with some basic checks - coolant temp sensor, dribbling ninth injector, pressure regulator vacuum pipe, etc.

cheers, Ross K
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Offline trevauk

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Re: Lumpy idle when warm
« Reply #6 on: September 01, 2008, 20:41:29 »
Cheers Ross

Hopefully we will get no rain here tomorrow and I can check these out.

One thing extra I did notice today. I pulled up after a good run, put it in neutral and the engine went lumpy on the revs. I gave it a bit of throttle and then came off it and the revs went back to normal. They stayed there until I put it back in drive. The minute it went back in drive it the revs went down to virtually 0, spent about 15 secs going up to 50 or so and back again and then stalled!!!

Treva.
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Offline andyb

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Re: Lumpy idle when warm
« Reply #7 on: September 02, 2008, 10:45:57 »
@Ross. You maybe right. There are some 3.5 on hot wire, but '88 is a bit early.  :oops:
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