Ford Fiesta (1995 - 1999) - 1999 1.4 erratic high speed idle

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Fri 3 Oct 2008 18:28
1999 1.4 erratic high speed idle - rich1608
Hi,

I wonder if you would be kind enough to give me some advice regarding the TPS on my 1999 Fiesta Zetec 1.4. A few weeks ago the car started suffering from eratic high idle speed (approx. 1500 rpm) when coasting in neutral and which stayed high until I came to a complete stop. I found the over-revving thread which you contributed to, checked my PSP switch and found a broken wire. Fixed that, reset ecu and hey presto problem solved... or is it?

The idle speed when stationary is now spot on at around 875 rpm however it still increases very slightly to around 1000 rpm or fractionally over when coasting out of gear. Is this normal for my car or could the TPS also be at fault? I measured the TPS wiper voltage with key on & engine off, it was 0.980 volts. This was with the TPS tightened against the screws anti-clockwise to give the lowest voltage. I took the TPS off and it dropped right down to 0.549 volts. You mentioned 0.8 volts as being the threshold for the ecu and mine is significantly above that, do you think I should fit a new TPS or drill out the bushes on the existing one to get the voltage down to 0.7 volts? On the other hand the problem has almost disappeared and I can easily live with the way it behaves now.

Many thanks

Rich

slt

Edited by Pugugly on 03/10/2008 at 18:40

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Fri 3 Oct 2008 22:38
1999 1.4 erratic high speed idle - Number_Cruncher
Is this normal for my car


Yes, idle speed increasing when coasting is fine. Coasting, on these engines isn't saving fuel - you're missing out on the benefits of overrun fuel cut off.

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Fri 3 Oct 2008 23:33
1999 1.4 erratic high speed idle - rich1608
Yes idle speed increasing when coasting is fine. Coasting on these engines isn't saving fuel - you're missing out on the benefits of overrun fuel cut off.


I haven't heard of overrun fuel cut-off before, does this mean that no fuel is injected during overrun? Also what are the other benefits of this?
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Sat 25 Oct 2008 12:46
1999 1.4 erratic high speed idle - hrvoje dagelic
"it still increases very slightly to around 1000 rpm"

Mine also sometimes goes a little higher and takes a little time to stabilize low; guess it's normal.


The TPS should be 0.7V; but I had over-revving even with 0.7 because the voltage fluctuates a little and can go around 0.05V up; I would put it to 0.6 - 0.65. (I written 0.4 in that other thread; but it was in fact 0.6 because my instrument had a problem)
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