I have a very well cared for 1.4S on a 'S' reg, with 67000 miles, and lots of servicing.

On Saturday night I left it on idle for half an hour while I was elsewhere (don't ask). On return, it wasn't idling properly. It's hunting, but the revs don't rise, they fall away, then return to normal, in a cycle. This problem is now only intermittant at traffic lights etc.

Also now during partial acceleration the engine frequently can be felt to skip a beat. But only under partial acceleration, full acceleration is fine. It did this all the way home from Fort William yesterday, as that's were I left it idling; thats 120 miles from home so a considerable drive.

Mpg is fine. No actual misfiring. So the questions are:

a) Can the idle control valve affect the car under acceleration, as well as idle?

b) What are the odds the low oil pressure at idle has goosed the engines top end (the cam visible under the filler cap looks fine).

c) Any chance it's another problem with the engine management system?

What would you do next if you were an able home mechanic?

Thanks

Jeff

P.S. Engine temp fine, no warning lights on.

a) idle speed control valve could not affect the engine under acceleration. it will be closed when accelerating, unless it is faulty, that is a possibility, but a fualty ISCV usually causes poor acceleration throughout the rev range.

b) the engine should be able to idle for as long as you leave it with no damage. the oil circulation and cooling system on a modern car are more than adequate to allow on the spot idle for as long as neccessary. the 1.4 suffers from poor oil curculation so it could be possible that the engine overheated.

c) thats like asking if there is a god. who knows?


as an able home mechanic i'm sure you noted the temperature on the gauge when you returned to the car. what was it? i've got the feeling that leaving the car at idle for so long has caused it to overheat. that could be caused by a problem with the cooling system (check it) or the oil circulation. either way the likely damage will be a headgasket failure, constant overheating, coolant loss etc etc. if you're getting no head gasket failure symptoms then its probably not a case of overheating damage. but i'd check that out first, it wouldn't be the first time i've seen a car cook itself at idle.

Hello Jug, part of the reason I'm posting this is that I've been through a lot of the steps you can think of with no further clues provided.

The temp guage was normal when I returned to the car. The cooling fan wasn't running, but I heard it running last week (I'm going to double check it's correct operation later).

There are no signs oil/water has mixed; no oil in the expansion bottle and no emulsion under the filler cap. All the engine fluids are fine.

"thats like asking if there is a god. who knows?"

It's only an engine management system! I'm an electronic engineer so they don't scare me, just want to find out if anyone has had a similar problem; power of the net and all that. The only problem with management systems is that without getting Fiat to carry out a diagnosis I need an ECU plug adapter, oscillioscope and the raw data to work out whats going on......and I've only got the data at hand. Off to have a look at the workshop manual for clues on fuel control.......in case the engine isn't cooked.

And now this evening the injector light kept coming on. The engine is still skipping a beat under partial acceleration, the idle is still weird.

No pearls of wisdom anyone?

Think I'll be going to the garage for a diagnostic.

the poor idle definately makes it worth while cleaning the ISCV out with some petrol.

but i get the feeling its a sensor fault, so a diagnostics is probably the best bet.

Problem appears to be solved; cleaned idle actuator, reset ecu, checked leads and plugs, took car for an Italian tune up (thrash). Thanks for your help!

italian tune up