Strange idle problem
Discussion
First some details: 4 litre, Supercharged, 14CUX replaced by Full Megasquirt (fuel and spark), Wideband Lambda, no AFM.
Until today, the car was holding a high(ish) idle, around 1200 RPM, for a few seconds whilst stationary then it would drop to around 800 RPM.
Today I experienced some strange behaviour.
When coming to a stop, the idle was hanging higher - more like 2000 RPM, and was taking a long time to drop at all. When it did drop, it was dropping to around 1300 RPM or so.
On a couple of occasions, the initial idle was around 2000 then it INCREASED to 3000.
Another couple of times, it never dropped below 3000.
The only way I could find to stop the engine "racing", was to brake towards a stop in gear, then declutch just before the engine died, by which time the revs were down to below 1000 .
When going along if you take your foot off the throttle pedal completely, the car very rarely drops revs to below 2000, unless the brake is applied.
Again a couple of times today, in that situation the revs "stuck" at 3000.
Any ideas?
Thanks,
Simon
Until today, the car was holding a high(ish) idle, around 1200 RPM, for a few seconds whilst stationary then it would drop to around 800 RPM.
Today I experienced some strange behaviour.
When coming to a stop, the idle was hanging higher - more like 2000 RPM, and was taking a long time to drop at all. When it did drop, it was dropping to around 1300 RPM or so.
On a couple of occasions, the initial idle was around 2000 then it INCREASED to 3000.
Another couple of times, it never dropped below 3000.
The only way I could find to stop the engine "racing", was to brake towards a stop in gear, then declutch just before the engine died, by which time the revs were down to below 1000 .
When going along if you take your foot off the throttle pedal completely, the car very rarely drops revs to below 2000, unless the brake is applied.
Again a couple of times today, in that situation the revs "stuck" at 3000.
Any ideas?
Thanks,
Simon
sgrimshaw said:
First some details: 4 litre, Supercharged, 14CUX replaced by Full Megasquirt (fuel and spark), Wideband Lambda, no AFM.
Until today, the car was holding a high(ish) idle, around 1200 RPM, for a few seconds whilst stationary then it would drop to around 800 RPM.
Today I experienced some strange behaviour.
When coming to a stop, the idle was hanging higher - more like 2000 RPM, and was taking a long time to drop at all. When it did drop, it was dropping to around 1300 RPM or so.
On a couple of occasions, the initial idle was around 2000 then it INCREASED to 3000.
Another couple of times, it never dropped below 3000.
The only way I could find to stop the engine "racing", was to brake towards a stop in gear, then declutch just before the engine died, by which time the revs were down to below 1000 .
When going along if you take your foot off the throttle pedal completely, the car very rarely drops revs to below 2000, unless the brake is applied.
Again a couple of times today, in that situation the revs "stuck" at 3000.
Any ideas?
Thanks,
Simon
Mines behaving in exactly the same way coupled with some shocking fuel economy. Be interested to see if anyone else has experienced and solved this.Until today, the car was holding a high(ish) idle, around 1200 RPM, for a few seconds whilst stationary then it would drop to around 800 RPM.
Today I experienced some strange behaviour.
When coming to a stop, the idle was hanging higher - more like 2000 RPM, and was taking a long time to drop at all. When it did drop, it was dropping to around 1300 RPM or so.
On a couple of occasions, the initial idle was around 2000 then it INCREASED to 3000.
Another couple of times, it never dropped below 3000.
The only way I could find to stop the engine "racing", was to brake towards a stop in gear, then declutch just before the engine died, by which time the revs were down to below 1000 .
When going along if you take your foot off the throttle pedal completely, the car very rarely drops revs to below 2000, unless the brake is applied.
Again a couple of times today, in that situation the revs "stuck" at 3000.
Any ideas?
Thanks,
Simon
Sounds fairly similar to the problem I had for months and months.....
The engine would idle high when the car was moving (ie you dip the clutch) and remain high for a few seconds when you stop, before returning to around 800-1000
Anyway, this is by far the least technical answer you'll recieve, but when TVR Power looked at it they found that the wires that go from the various sensors in the engine to the ECU (presumnably) were all gunked up with "green stuff" at a point they were all taped/sealed together, upon cleaning the gunk out and resealing the wires back togther it all went back to normal.
I'd guess the result was the at ECU was getting odd readings and then telling the engine to do odd stuff...for the record my car used to stall a lot due to this...
Hope that helps...
The engine would idle high when the car was moving (ie you dip the clutch) and remain high for a few seconds when you stop, before returning to around 800-1000
Anyway, this is by far the least technical answer you'll recieve, but when TVR Power looked at it they found that the wires that go from the various sensors in the engine to the ECU (presumnably) were all gunked up with "green stuff" at a point they were all taped/sealed together, upon cleaning the gunk out and resealing the wires back togther it all went back to normal.
I'd guess the result was the at ECU was getting odd readings and then telling the engine to do odd stuff...for the record my car used to stall a lot due to this...
Hope that helps...
Mine did the same thing - the idle would missbehave intermittently. After much searching, poking about and cleaning connections and censors frustration took over and I took the stepper motor out and cremated it.
After blocking off the bypass hose, the idle is manually set with the bleed valve, and have not looked back in a couple of thousand miles.
The only downside is that carefull cold starting is required, to make sure that it does not stall once the engine has fired.
It may be me, but the performance has become much more consistant like this, and power delivery is smoother.
Andy
After blocking off the bypass hose, the idle is manually set with the bleed valve, and have not looked back in a couple of thousand miles.
The only downside is that carefull cold starting is required, to make sure that it does not stall once the engine has fired.
It may be me, but the performance has become much more consistant like this, and power delivery is smoother.
Andy
Gassing Station | Chimaera | Top of Page | What's New | My Stuff