Random revs at idle (when cold)
Discussion
Hi guys, another one which has me stumped. The car (Chimaera 400, 1999) has always started fine. However, a couple of times now, when it has been a bit cooler, the car has started with the revs sitting at about 1,500 but this is not settling. I then drive off, car warms but if I idle again the revs pick-up to maybe 1,600 but then drop to 1,100 then back up and down... It makes me look really impatient when I get to a junction!
If I stop the engine and restart the problem clears instantly... any thoughts? It sounds like one of those usual TVR things but not too sure how to resolve this one. It's in for a service next week so I can advise the gararge on what needs tweaking I suppose.
Thanks again for any help, Rus
p.s. I realise this may well be on here somewhere but a search failed to find it for me.
If I stop the engine and restart the problem clears instantly... any thoughts? It sounds like one of those usual TVR things but not too sure how to resolve this one. It's in for a service next week so I can advise the gararge on what needs tweaking I suppose.
Thanks again for any help, Rus
p.s. I realise this may well be on here somewhere but a search failed to find it for me.
Ok, thought this was job done. Stepper cleaned and the high / low rev issue at start-up has gone. But I have a new one now.
Start the car when it's cold and as soon as a dab the throttle the revs drop right down and it almost stalls, off the throttle and the engine catches and stays alive. It was like driving with no idle... Sort of like the car would keep the engine at 1,400 (cold) but as soon as I showed I was there (throttle dab) it decided to hand the idle control to me! Manually keeping the car alive is clearly fine when moving and once warmer (1+ mile) it seems almost fine but tricky when manoeuvring our of a car parking space...
Any thoughts?
Rus
Start the car when it's cold and as soon as a dab the throttle the revs drop right down and it almost stalls, off the throttle and the engine catches and stays alive. It was like driving with no idle... Sort of like the car would keep the engine at 1,400 (cold) but as soon as I showed I was there (throttle dab) it decided to hand the idle control to me! Manually keeping the car alive is clearly fine when moving and once warmer (1+ mile) it seems almost fine but tricky when manoeuvring our of a car parking space...
Any thoughts?
Rus
I have a similar issue with my 4.0 Chim, but I have learned that it is best to let it idle for about 30 secs to 60 secs or so depending on how cold it is, then it goes fine. If I try to bring up the revs immediately after starting, it nearly stalls. It only does this when it is cold outside though, in the summer there is no problem so I guess it must be something to do with the fueling as has been suggested.
If everything is working as it should, it will tend to overfuel for about the first 20 seconds of running as the orgional Range Rover fuel map dumps in excess fuel, but you can clearly hear and smell this, like the engine is on choke. After this time the lambda probes start to work, so the mixture gets corrected, and you should hear a noticable change in engine note, at which point the car should drive reasonably well. If you have dead or slow responding lambda probes, it wont be able to correct as it should, but you cant really tell unless you put a test meter on the lambda outputs, as the ECU will run quite happily without them working as it warms up. If you had an air leak its possible its running lean to start with, and then being corrected as the probes get hot but I've not experianced it dieing due to overfuelling I must admit.
Mine runs like a total hound when its cold, revs all over the place until it gets warm.
Someone on here suggested a 2 minute warm up after you start it with absolutely no throttle input to let the EFI sort itself out - seems to help mine settle itselft, albeit not a perfect fix.
It also got me shouted at by a neighbour for making "a ghastly noise with your ghastly car". To which I took umbridge as the noise of a V8 isn't ghastly and neither is my beloved Chim.
Someone on here suggested a 2 minute warm up after you start it with absolutely no throttle input to let the EFI sort itself out - seems to help mine settle itselft, albeit not a perfect fix.
It also got me shouted at by a neighbour for making "a ghastly noise with your ghastly car". To which I took umbridge as the noise of a V8 isn't ghastly and neither is my beloved Chim.
Green is good said:
I have a similar issue with my 4.0 Chim, but I have learned that it is best to let it idle for about 30 secs to 60 secs or so depending on how cold it is, then it goes fine. If I try to bring up the revs immediately after starting, it nearly stalls. It only does this when it is cold outside though, in the summer there is no problem so I guess it must be something to do with the fueling as has been suggested.
+1Milky400 said:
Green is good said:
I have a similar issue with my 4.0 Chim, but I have learned that it is best to let it idle for about 30 secs to 60 secs or so depending on how cold it is, then it goes fine. If I try to bring up the revs immediately after starting, it nearly stalls. It only does this when it is cold outside though, in the summer there is no problem so I guess it must be something to do with the fueling as has been suggested.
+1Apart from starting from cold the old girl is running fine (famous last words!)
John
domV8 said:
Rossco2010 said:
It also got me shouted at by a neighbour for making "a ghastly noise with your ghastly car"...
Anyone who uses the word "ghastly" should be shot for bringing England into disrepute with their appalling middle-class vocabulary.You have my permission.
jr6yam said:
domV8 said:
Rossco2010 said:
It also got me shouted at by a neighbour for making "a ghastly noise with your ghastly car"...
Anyone who uses the word "ghastly" should be shot for bringing England into disrepute with their appalling middle-class vocabulary.You have my permission.
Hi all,
I get the high-rev thing regularly with mine and you're right it is a tad embarrassing. Mine starts up and goes to a normal high-idle for cold starts but then after I pull away and take the revs up higher, the idle speed can go up to around 1600 or even 1800rpm. As it's a daily driver, I have found a couple of tricks that seem to resolve the problem.
1. To avoid the problem in the first place: when you pull away, for the first few gear changes down, lift off the throttle completely before touching the clutch. Not sure why this works and it may just be peculiar to my car. Maybe the vacuum transfered from the engine pulls the stepper motor back in and stops the high idle or it just makes the ECU think differently about what to set the idle at.
2. If the high revs do start, the most effective method of stopping it - bring car to a complete stop and wait, no need to turn engine off. Traffic lights are good for this. It has to be a complete stop, if you keep rolling even a bit the ECU doesn't do anything. When it sees the complete stop, it starts to adjust the idle speed back to normal.
Cheers, Matt
I get the high-rev thing regularly with mine and you're right it is a tad embarrassing. Mine starts up and goes to a normal high-idle for cold starts but then after I pull away and take the revs up higher, the idle speed can go up to around 1600 or even 1800rpm. As it's a daily driver, I have found a couple of tricks that seem to resolve the problem.
1. To avoid the problem in the first place: when you pull away, for the first few gear changes down, lift off the throttle completely before touching the clutch. Not sure why this works and it may just be peculiar to my car. Maybe the vacuum transfered from the engine pulls the stepper motor back in and stops the high idle or it just makes the ECU think differently about what to set the idle at.
2. If the high revs do start, the most effective method of stopping it - bring car to a complete stop and wait, no need to turn engine off. Traffic lights are good for this. It has to be a complete stop, if you keep rolling even a bit the ECU doesn't do anything. When it sees the complete stop, it starts to adjust the idle speed back to normal.
Cheers, Matt
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