Ford Fiesta (1989 - 1995) - 94 1.3 HCS CFI Idle Problems - Overrevving/Underre

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Sun 3 Aug 2008 19:01
94 1.3 HCS CFI Idle Problems - Overrevving/Underre - stubes
Hi,

I'm having a problem with my Mk3.5 fiesta. Periodically when i'm driving it will start revving between 2-3000 between gear changes with my foot off the pedal. Sometimes I will notice it accelerating from low speed also with my foot off the pedal. When I come to a stop in neutral it will hold these revs, sometimes 'pulsing' between 2-3000 for a few seconds (occasionally longer, has done it for up to 10-20sec to me before) before dropping back to idle.

In addition sometimes it will display a similar problem except with underrevving, where the engine barely revs over 500. Gear changing becomes jerky and i'll find it slowing down to a crawl without any power due to the low revs, and again when coming to a stop it will recover to 8-900rpm after a few seconds (but occasionally longer!).

When starting the engine sometimes it will start and go straight to 500 revs as if there is no choke and then usually stalls if i give it no power.

When I first got the car about 6 months ago displayed both issues usually at least once or twice every trip, but then after a few long motorway runs seemed to go away until I changed my oil and set the tappets. Again problem went away until last week when i replaced the oil pressure sensor. Both times i'd removed the air filter and had a poke around so i'm thinking this is due to me disturbing some dodgy sensors or wiring??

Thanks,
Stu
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Sun 3 Aug 2008 23:17
94 1.3 HCS CFI Idle Problems - Overrevving/Underre - Rattle
Check the throttle position sensor and also the throttle cable is not stuck. The TPS seems to cause a lot of problems with those fuel injected HCS engines.

Also check the idle control valve is clean.
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Mon 4 Aug 2008 01:20
94 1.3 HCS CFI Idle Problems - Overrevving/Underre - stubes
Rattle, as far as i'm aware the throttle cable isn't stuck, when pressing/releasing the pedal and looking at the linkages all seems to move back easily with no hesitation.
I don't think I have an idle control valve - I believe idle is controlled directly from the engine managment via a motor that connects to the throttle plate.
The TPS is something I was wondering about - it and its wiring look ok to me but I wouldnt know how to check its functioning? do I need to use a multimeter?
Stu
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Sun 3 Aug 2008 23:38
94 1.3 HCS CFI Idle Problems - Overrevving/Underre - Screwloose
Stu

What make of CFi throttle body is on this one?
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Mon 4 Aug 2008 01:31
94 1.3 HCS CFI Idle Problems - Overrevving/Underre - stubes
The throttle body is a weber type. (I didn't know there was more than one type for CFi?)
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Mon 4 Aug 2008 13:44
94 1.3 HCS CFI Idle Problems - Overrevving/Underre - Screwloose

There are three; on that one, check the idle control actuator.
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