'97 Fiesta 1.25 38500 miles developed a slightly lumpy tickover over the last few weeks. I'm sure most people wouldn't notice.
Worst when cold, barely, if at all, noticeable when warm.
Symptomatic perhaps of a partial "miss" e.g if some of HT tracking to earth?
As it's nearly due for plugs, I thought I'd stick some new ones in, followed by some new leads if this doen't help. (Ford ones)
Strangely enough, the car performs perfectly otherwise - accelerating and cruising without missing a beat!
Also, for the last 5 years, I've been running the car on Costco Chevron fully synth oil , changed every 3000 up until a few months ago when I thought I'd give the Ford stuff a try...
Any clues??
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do the revs seem to oscillate?
i have a 86,000 mile 1.25 and when cold and running all the electrics the car does seem to hunt slightly - it's almost as if the idle control system is having trouble compensating for the load. however when warm there is no problem at all.
the only sensors to have gone on my car are the MAF and the Lambda probe (this i'm not even certain of, but changed it anyhow). the maf sensor gave some interesting faults - rough idle and dodgy fueling when accelerating hard (open loop fueling), which resulted in 'flat spots'.
dunno if that helps or confuses....
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Hi Fiesta Man,
Thanks for your feedback - Interesting to hear of your problems as it's a good indication of what's going to go wrong on mine!
I have heard that a faulty lambda probe can cause the idle to oscillate slowly and that a faulty MAF sensor can cause problems with flat spots but this isn't really my problem (yet!!)
In answer to your question - the idle speed doesn't oscillate but when the engine appears to "miss" you can see the idle speed servo attempting to compensate for the blip.
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Check out the HT leads and coil pack. I had a misfire on my previous 1.25 1998 Fiesta. Main dealer found a faulty coil pack and one of the HT leads. They run on such voltage and weak CO mixture that any breakdown in the spark supply causes a misfire.
Mine was fine at idle, when you tried to pull away it complained.
Shame - when running it was smooth as silk. My father has a year 2000 facelift model and I am sure they altered the induction side of things as it does not run as well as earlier models. Suspect Euro emission regs for that.
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the 99my and onwards to the best of my knowledge doesn't have a maf sensor, or at least it's very well hidden. having been in a variety of fiestas i'd agree the later models are rougher, and despite the book times being the same the later models feel notably slower both in throttle response and in out-right pace... hmm a 1.25 fiesta and pace mentioned in the same sentence - bit of an oxymoron that one!
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An acquaintance had the coil pack partially fail on her 99 1.25, but the symptoms it gave were much more noticeable than the problems you've reported. It was also a very discrete change from working fine to continually miss-firing. Ditto a friend with a mondeo (same coil pack to my knowledge).
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