Missfire missery

[artfailier]

[&o]Hello all, here is a puzzle. My 3.6 C2 has had a recuring problem. A missfire on the same cylinder after a good roasting . This first occured about 8 months ago after a good hard run( clear of the clogged south east traffic!)The car was fine until I stopped at the traffic lights and it went all lumpy and the engine light flashed. Off to OPC who fiddled around for a couple of hours and said it was fine and reset the computer .It was showing a multiple missfire but other error codes for cylinder 6. So 2000 miles went by and no problem. Then after another spirited run same again when stopping for the lights . So off to Parr this time ,yes cylinder 6 so they replaced the coil pack as there was some signs of perishing on two coils. Another 2000 ish and the same again. Back it went and the replaced some spark plugs but it didn't fix it .Played around with a bunch of terminal -no that didn't work and yes it was Cylinder 6. Cleared the computer down played with the chip ecu settings -no joy so fiddled some more and it worked but they don't have a clue why or how. Another 1000 miles and after a short burst ,same again and I think it may just be CYLINDER BL***** 6. Help please They are all bemused and I don' like the sound of a flat 5

 

[Richard_Hamilton]

A faulty coil pack or spark plug would be the obvious choice, but you have eliminated those possibilities. The only thing I can suggest is checking the wiring between the coil pack and the ECU, and the earth wire to the coil pack. If there aren't any problems with the wiring, then maybe there is a fault with the ECU itself.

 

[Rodney Naghar]

A faulty injector may be the cause.

My CEL light came on a while back and the engine became slightly lumpy. My OPC diagnosed this as a faulty injector, replaced it, and the problem has now gone.

 

[Richard_Hamilton]

You could be right Rodney, but I think an injector failure would show up as a different fault code on a diagnostic test.

 

[artfailier]

Thanks Rodney and Richard, any ideas are helpful as it is getting boring and costly to keep going back with a fault they can't find and don't know how they fixed it!! [8|] Has any one else come across this problem? A mechanic friend has suggested the idea of a piece of muck getting into the tappet bucket but I can't quite see how that may be . Any more thoughts ?

 

[delboy]

Had a similar problem with mine, and did the usual (coil pack, spark plugs).

Light came on whilst I was in an OPC having a battery swap out. Very nice guy there diagnosed it as an O2 sensor, and plan to do this when it's next booked in.

 

[Richard_Hamilton]

Tony - I don't suppose you have the error codes? If you have them it would help a lot.

 

[Rodney Naghar]

You could be right Rodney, but I think an injector failure would show up as a different fault code on a diagnostic test.

You're probably right Richard, but as you know in my case it wasn't that simple. They first thought it was the tappets (so replaced all of them) then they thought it was the coil packs (so replaced most of those), then they were certain it was a faulty injector, which was the final remedy which worked.

I sometimes wonder about the effectiveness of these diagnostic systems. In 3 times that they have been called on to source problems in my cars, they have always failed to do so correctly, and it usually ends up being a costly process of trial and error.[:-]

 

[SNDa]

There's no substitute for a mechanic who know his / her stuff inside out and uses the diagnostics as a guide.

 

[Diesel130]

ORIGINAL: SNDa

There's no substitute for a mechanic who know his / her stuff inside out and uses the diagnostics as a guide.

Agree totally, so if you don't have an OPC warrantee (which I assume you don't) then why not take it to a specialist who knows their stuff about engines, such as Baz Hartech ?

 

[Richard_Hamilton]

Parr are one of the most respected independents in the country, and they really should know their stuff. I'm a bit surprised they are scratching their heads.

 

[artfailier]

Many thanks again for all these thoughts guys .Parr went into the system and did a full diagnostic. I haven't got the error codes but they said there was one for a multiple missfire but it always comes back to No 6 cyl.The injector is a good point but the Co2 ( if that what you mean't Derek) sensor is another good idea, does it have one for each cylinder?
It does give us something to aim at !!

 

[Richard_Hamilton]

I don't think it would be an O2 sensor, as it would affect the whole bank.

 

[SNDa]

Just to be clear: I wasn't commenting on Parr specifically as I have no experience of my own with them. The comment was more related to diagnostic systems.

 

[Richard_Hamilton]

Sorry Sanjib I didn't word my post very well. I wasn't criticising your comment and I agree with you that it all depends on how the diagnostic results are interpreted, which needs someone with a lot of experience. I think Diesel had missed the fact that Tony had taken it to an indy.

 

[Diesel130]

ORIGINAL: Richard Hamilton

.... I think Diesel had missed the fact that Tony had taken it to an indy.

Yep, missed that. Where are Parr out of interest ?

 

[Richard_Hamilton]

Crawley, W Sussex - http://www.parr-uk.co.uk/