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28th February 2020, 08:08 | #1 |
This is my second home
75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007
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Lumpy idle v6
I have got a lumpy idle caused by the front right cylinder not coming to the party on my V6 (Cylinder 5) mainly during idle.
The spark plug fires, the injector injects, and compression is fine. (11.5 Bar on cylinder 5 and cylinder 3 for comparison) I have replaced the spark plug and also swapped the injector just for safety, but the problem sort of remains. The engine runs well at higher speeds, which is evident when the spark plug lead is removed. I will put some injector cleaner in the tank and drive a bit with the new injector (which came off my spare engine and has been sitting for a couple of years. I have triggered it and sprayed brake cleaner through it. It gives a fine mist under pressure) The engine light comes at times and is currently on. No code reader, yet. Anyone seen anything similar?
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28th February 2020, 08:49 | #2 |
I really should get out more.......
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First thing that comes to mind is a damp IMG even though you coat them with paint, any evidence on no.5's spark plug, although with your reputation I would guess you've already checked.
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28th February 2020, 08:57 | #3 |
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Funny. I haven't even thought of that! To be honest.
But there is no loss of water, and the spark plug seems to covered in petrol, not water. When we did compression test there was no water ejected, so I doubt it could be that. But I will check. Good thinking.!
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28th February 2020, 09:37 | #4 |
I really should get out more.......
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Leaking cam cover gasket contaminating the plug with oil
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She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide. |
28th February 2020, 14:32 | #5 |
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No, no oil at all on the plugs.
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28th February 2020, 18:26 | #6 |
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If it's got leads,they are known to break down (early mk 1's)
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28th February 2020, 19:22 | #7 |
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No, there is spark at all times!
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28th February 2020, 22:28 | #8 |
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Could be the plug breaking down under compression. No slight cracks in the coil when you had the plug out to check for spark?
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29th February 2020, 05:53 | #9 | |
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Quote:
So to recapitulate: Compression is good. Spark plug is good. Spark fires at all times (checked by pulling plug lead at different revs). Cylinder fires at higher revs (also checked by pulling plug lead at different revs). The injector has been swapped (which didn't seem to make a big difference). So by elimination, the idea of water getting into the cylinder fits the bill, except there is no evidence for that. Which leaves the possibility that the injection control can be faulty. Is it possible for the control to one cylinder to be out of spec? Either too long or too short delivery, or wrong timing???? But only at idle. That is about the only logical option I can see left. The only other option is that the swapped injector has a fault as the original must then also have had. The only way to make sure is to also swap the injectors like the spark plugs and see if the fault follows the injector or not. That is possible, but I guess unlikely.
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29th February 2020, 09:06 | #10 |
Posted a thing or two
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its a long shot but maybe an o2 sensor?
had somthing similar when i bought a dud new o2 sensor. try unplugging the front o2 sensor, plug is next to the aircon pipe near fire wall so easy to test The car will still run fine but this will make the car revert to a default fuel map . may be worth a shot!! |
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