Hi all,
After a long period of searching I found that the cold start chugging problem is related to the ECU. When I removed the plug, cleaned it up and replaced it then the chugging disappeared. However now it returns at random intervals. Maybe the next day - or maybe in two or three days. I just stop the car remove the plug and replace it and the engine works fine.
When I removed the ECU the n/s corner was broken off and not attached to the back plate it shares with the ABSCU I re-attached it at another point. As far as I understand it the ECU needs to be earthed, but all of the CU's are isolated in their plastic box which is floating free because the wing locating nub is broken off and the bolt on the bottom has been missing since I bought the car.
I suspect that the ECU has developed an intermittent fault due to the impact it must have received when the corner broke off. Does anyone have any ideas about the possible nature of this failure?? I have a spare ECU but dont want to fit it in case the problem is not due to the earthing but something else in the engine management that might re-occur in the replacement.
Thanks '[8)]' '[8)]'
ECU question on V6??
Moderator: RichardW
Hi,
I swapped the ECUs' and the fault has now appeared on this one so it doesn't seem that my theory about the knock affecting was correct. Next I will try attaching an earth lead to the back plate and see if that makes any difference. Then put the swapped out ECU into the SEI and see if the fault disappears, which will indicate whether it is an engine problem i.e must be the lambda sensor which is the only remaining component not checked.
I swapped the ECUs' and the fault has now appeared on this one so it doesn't seem that my theory about the knock affecting was correct. Next I will try attaching an earth lead to the back plate and see if that makes any difference. Then put the swapped out ECU into the SEI and see if the fault disappears, which will indicate whether it is an engine problem i.e must be the lambda sensor which is the only remaining component not checked.
Sounds like what is happening is that the ECU is learning the engine settings again after you disconnect it. It will take a little time to do this and during this time it will use default settings.
An old AX of mine used to jerk when you lifted off due to a throttle solenoid problem. When I disconnected the battery and reconnected it it would be fine for a couple of small journeys whilst the ECU was learning again. Obviously it just started jerking again after a while.
Your problem could be any sensor or actuator but ECU failure is rare and unlikely.
An old AX of mine used to jerk when you lifted off due to a throttle solenoid problem. When I disconnected the battery and reconnected it it would be fine for a couple of small journeys whilst the ECU was learning again. Obviously it just started jerking again after a while.
Your problem could be any sensor or actuator but ECU failure is rare and unlikely.
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Stuart McB
- Posts: 1635
- Joined: 03 Oct 2003, 00:50
- Location: United Kingdom
- My Cars:
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Yep ECU's have to learn the vehicles set parameters after you disconnect it. This results in a sort of rough running and no power. If memory serves me right you have to keep the revs up at about 3k for about 10 mins. This way the ECU 'learns' the engine preformance and the vehicle then gets the benefit of the ECU programme back.
Thanks guys,
I have put the old ecu back in since it seems to start better with that one. Also I rigged up an earth wire from one of the bolts on the ecu back plate to the earth braid on the bonnet arm in case it's not earthing properly. I will run it for a while and see if the problem returns. Thing is the rough running doesn't return for quite some time. I can do a journey of 28 miles leave it for day and return 28 miles then after not using it for a couple of days it will start/run badly again. I think the head job it had before I bought it has something to do with it, and engine sounds a bit ticky would the anti knock sensors come in to play in this case? The thing is though that this only occurs on starting from cold and until the engine is up to temp, but the engine must be stopped and restarted before it goes away??
I have put the old ecu back in since it seems to start better with that one. Also I rigged up an earth wire from one of the bolts on the ecu back plate to the earth braid on the bonnet arm in case it's not earthing properly. I will run it for a while and see if the problem returns. Thing is the rough running doesn't return for quite some time. I can do a journey of 28 miles leave it for day and return 28 miles then after not using it for a couple of days it will start/run badly again. I think the head job it had before I bought it has something to do with it, and engine sounds a bit ticky would the anti knock sensors come in to play in this case? The thing is though that this only occurs on starting from cold and until the engine is up to temp, but the engine must be stopped and restarted before it goes away??