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[Clouseau]

Ok. Moving on from the intermittent stalling and fluctuating idle I have now cleaned all breathers, Idle valve, throttle body, inlet manifold, cleared breather jet, removed cam cover, de-gunked and replaced everything with new gaskets. The original fault was probably caused by the 3" split in the air intake duct between the air flow meter and the throttle body!  That's taped up pending arrival of a replacement duct (£20).

However.

Engine started immediately and is running smoothly. Only problem is that it is idling now at about 1000 rpm when it was previously about 750?  When in park after a few seconds it does settle down again to this figure, but when in drive and stopping at junctions etc it is staying around 1000. I have checked that there is sufficient slack in the accelerator cable and the throttle valve is returning to its idle stop.

Any ideas?

(2000 Ecotec X20 XEV)

[Clouseau]

Ok. Tried paper clip test and getting:

0, 1, 2, 0 (repeated).  Indicates throttle speed sensor error?

This seems to offer the right sort of explanation in that the throttle butterfly is closed yet the engine thinks its running at about 1100 rpm.  This is not good for driving - using brakes heavily to stop and it just wants to keep on running at speed without natural engine braking.

Do the sensor units mounted onto the throttle body fail?  There was nothing wrong with this before the strip and clean - could I have damaged it with carb clean / wd40? Seems there are plenty of them out there (BOSCH 0280 122 001) - does anyone have a spare knocking about?

[Abiton]

I doubt if the throttle position sensor itself has failed, but the connector and loom wiring to it may well need checking.  Would have been disturbed during the work you've done.

I may well have a good spare, if they didn't change between '95 and 2000, and they're the same on manual/auto models.  I'll see if I can find it in the morning for you. 
Internally they seem very robust and well designed, to my eye.  Hence my suggestion that the problem is more likely to be between the TPS and the ECU, rather than the TPS itself.

[Clouseau]

Cheers Abiton - I think the Bosch TPS is pretty universal so should be the same.  If it makes no difference I can post it back to you.

Does anyone happen to know the specific voltage range for the signal on the TPS? It's going to be around 0.5-4.5v but it would be handy to know the actual spec.  I'm going to test the signal voltage later to see that the TPS is working, although it may be that the lower range is no longer accurate

[amba]

Had a similar issue with mine about 18 months ago.

Fault code gave TPS so like a fool I went a got a replacement.When I removed the plug to replace it I found the inside was corroded and had a mass of green verdigree over the terminals.

Trip to local breakers and cut off the plug and abit of wire from one they had in peices.Soldered the wires back together with the donor plug on...all worked fine as hasn,t had a further problem since...I took the TPS back for a full refund.

Might be similar problem as mine.

[Clouseau]

Ok, bumped again ...

I have tried a different TPS (thanks Abiton) but still have the same issue.

In Park or Neutral the revs drop to 1000 when you take your foot off the pedal and then slowly drop further to 750 after about 10 seconds. In 'drive' this takes much longer, hence the problems I am having just driving the thing!

I have again stripped, checked and reassembled the air-in components including the ICAV but cannot find anything untoward.  All wiring and plugs are fine.

Still showing 0500 and 0120 fault codes but as I don't have a reader I have to wait for these to clear in time.

Anyone got any suggestions?

[Abiton]

I'm thinking the 0500 might be the answer here.

Pretty sure the ECU keeps the minimum revs higher when the vehicle's moving than when it isn't.  So if it doesn't know, maybe it defaults to assuming it is moving.

Trouble is, I don't know how the vehicle speed could be reported wrongly. ABS ECU fault ? :-/

[Clouseau]

Pete

The 0500 only appeared after I ran the engine without the TPS connected (it idled at around 2000 rpm). I'm sure this will clear now that it is reconnected

[Abiton]

Ah, I see.  That's probably good news.

How sure are you that your patched intake duct is no longer leaking?

[Clouseau]

Pretty sure, but I'm picking up the new one tomorrow so will rule that out then...

[Darth Loo-knee]

Sounds abit like an air leak to me mate :-?

[Clouseau]

Ok. New air duct fitted. Battery disconnected for a couple of hours then reconnected to see if this makes any difference to the ECU settings.

High idle still there.  :-(

Getting cheesed off now.