After searching through many posts I've come up with lot's of solutions to these problems but I still can't be certain. So, from the beginning...
A few weeks ago the timeing belt went. My Dad and I got the engine apart and found 3 of the valves bent so my Dad decided to replace all of them anyway. When we came to refit the head and all other parts removed the weather was awful - lots of heavy rain. He stopped when the weather was bad but needless to say the engine bay got fairly wet. When it was all back together the car ran almost perfect - it seemed a little bit rough or like it was hunting for air or misfiring (not sure what exactly is causing it). So this is the rough running part of my thread - it does it all the time not just when idleing.
I read through the Haynes manual looking for what could be the cause and searched the internet. I checked all the electrical connections which seemed OK. Having had this problem on a Ford Escort a couple of years ago I thought it could be the idle control valve playing up. So I decided to unplug it and start the engine. It idled way too high so I thought great this must be the cause and plugged it back in only to find it was still idleing too high! I got a new idle control valve which didn't fix it but then found instructions to reset it and that fixed the problem (although the engine was still running rough).
Since then the problem of idleing too fast has come back. Turning the ignition off then restarting the engine will sometimes fix it. Disconnecting the battery for 10 minutes to reset the ECU also fixes it, but the problem always returns. Also, I removed the coolant/engine temp. sensor and cleaned that off which fixed it temporarily. When turning the ignition off, it idles normally on restart until the throttle is pressed. When reseting the ECU it last for 5-10 minutes of driving before idleing too high.
I took it to Renault to get a diagnostic check - no faults on the ECU but cos it was idleing high they disconnected the battery to reset it and that fixed it. Of course by the time I got home it was idleing too high again!
Sorry for such a long description of the problem but hopefully somebody can spot the problem in there! I need to know:
1. What keeps making it idle too high? (Which only started after I unplugged the idle control valve electrical connector)
2. What is making the engine run rough?
Thanks in advance,
Alun
{edited to make use of drop down menus that weren't originally here when first posted}
Edited by Dynamic Dave on 29/12/2008 at 18:25
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Sorry I forgot to add... It's a P-reg (1997), and It's the D-type engine (D7F I think), 1159cc
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Strangely the high idle fixed itself yesterday (for how long i don't know).
It's still running a bit rough though.
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I've finally fixed a very similar problem to this with my daughter's Clio ('92, type E 1.2 engine). I tried several things, including:
Checking all of the throttle body electrical connections to the ECU
Swapping the throttle body with another from a previously dead Clio
Checking the engine coolant temperature sensor & wiring
Re-setting the valve clearances
Changing the plugs
Cleaning the dist. cap & rotor arm
Swappnig the lambda sensor
Or course it was (as ever) the last thing you look at. In this case it was an air leak into the inlet manifold from a damaged gasket (grrr - who ever refits a broken gasket...). Amazing that an air leak could cause rough idling, poor emissions readings yet the car performed fine when driven. New gasket and it feels like a new car!
The way I found it was to liberally spray WD40 round the inlet manifold to engine joint, and found that doing so caused the engine to run more smoothly as the WD blocked the air leak.
Posting just in case it might help someone else diagnosing this kind of thing.
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Just check the throttle cable is not too tight first. Also redo the tappets and leave them slightly loose, tight tappets on these engines make them run like a badgers .........
Check also all the vacuum pipes from the throttle body especially the servo hose.
Interestingly you mention the coolant temp sensor, a failing sensor would not neccessarily generate a fault code but could keep telling the ECU the engine is cold which would raise the engine speed and slightly over fuel the engine.
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