Intermittent idling fault.

[handyman]

Our high mileage 1.8! petrol Xantia estate has decided to start playing silly buggers, just when its MOT is due soon.

Idle speed sometimes goes into overdrive at between 1500-1800 rpm, instead of its normal sub 900 rpm. Engine runs OK with acceptable fuel economy so I do not think it is overfuelling. I've pulled out the ADI unit and given that a clean, not the tidiest looking as there was a fair bit of grunge in it and the throttle valve assembly.

I have thought along the lines of trying a spray-in inlet tract cleaner, like Wynns or similar, just to eliminate oil & grunge contamination as the source of the problem, before I get out the Lexia and see what that does.

Any recommendations for these cleaners for petrol engines? Anybody used them with success? My local factors, all three of them, were totally unaware that these products existed.

H

[citronut]

have you removed and cleaned the idle stepper motor,

i have discoverd you can clean these with carb cleaner, as long as you give them a shot of duck oil afterwards,

as i managed to resusitate one on a pug 206 that was playing up after a good blasting with carb cleaner,

they obviously dont work if they are running all dried out,


regards malcolm

[handyman]

Hi Malc, you say idle stepper motor, I say ADI unit, we are talking about the same thing!

Yes, that was the first component that sprang to mind. Taken off and cleaned with electrical switch cleaner, which is better as it not only cleans, it lubricates.

I am wondering if something like one of the vacuum or bypass tubes has got partially blocked, hence using a cleaner to remove the gunk.

I used to use a bit of TQF to clean out carburettors in older cars and that always worked a treat but did initially generate clouds of smoke from cleared deposits. Not sure I'd want to do that on an engine with a cat.

I do regularly use a fuel additive to help keep the injection jets clean. That contains benzine as a cleaning component, which is quite harmful.

H

[citronut]

i dont know what does ADI stand for ,

a freind of mine used to be the mechanic at a citroen service agent i used to work at,

he is a bike fanatic who used to pour TOTAL T (CMATIC blood) down the carb's on cars in the workshop for a similar reason, with a similar result like a very sweet smelling P supper fog filled the workshop,


regards malcolm

[DickieG]

Check the manifold pressure sensor and vacuum pipe running to it as a build up of crud there can cause these symptoms.

[handyman]

Thanks for that pointer Dickie, I'll check it out tomorrow.

Handyman

[handyman]

Before dismantling anything, I have pumped a can of Wynn's Petrol Injection Cleaner down the big hole.

What a difference this has made to the cars performance! Better accleration and response, improved fuel economy, engine running more smoothly.

And the tickover is back to where it should be.

Handyman