Misfire?????

[rajinder_1]

Guys,
I have been through all sorts now and can not cure a misfire on my SL320. I have had the following done:
2 x new cats From German and sweedish
1 x new coil pack
1 x Mas sensor swapped
2 x new leads
1 x new injector

all on cylinder 6 which seems to be the root cause of it closing the whole bank down ie cylinders 4, 5 and 6.

even my mechanic is scratching his head with disbelief. They have ruled out the ECU as if the faults are wiped from the car it runs fine for around 5-10 mins then it starts to misfire again.
Apparantly if the ECU had gone it would misfire all the time.

Any suggestions welcomed

Raj

 

[mstar]

hmmm... dude which garages have you been to? i am from the west midlands (oldbury), near eurocarparts/gsf parts

 

[rajinder_1]

Mstar
Im in coventry so i use GM services on lythals lane who are a independent specialist.

Raj

 

[124coupe]

Raj, can you describe the misfire in detail including how it starts after the few mins of clean running?

Also, once is starts, does it then occur after a subsequent cold start?

Is it present at all revs?

 

[rajinder_1]

Steve
The misfire is there when hot or cold. The car once the faults removed runs fine and changes gear ok. You will then feel it holding back before it starts to go lumpy ( revs dont jump ) but the car slows down and need more accelaration to get it moving. The more you drive the harder you need to push it.
Once the misfire starts then it is ther at all revs, it also seems to kick in either after a certain time period or when i put my foot down (well it feels like that).

Raj

 

[124coupe]

Raj, if the car runs fine after an ECU reset but then fails after a while and STAYS in the failing state then it sounds like a sensor is out of spec somewhere, causing the ECU adaption to try to compensate.

What codes show now? (I assume you have had them read again since the injector swap).

Was the CAT that failed on the same side as the misfire/injector issues?

 

[rajinder_1]

Yes steve the cat was on the same side (left) the codes that read are the P0300 P0306, P0305 and P0304 which all say that the cylinders are misfiring, but initially we found it to be cylinder 6 then the whole bank shuts down.

 

[124coupe]

Looking at the specs for this engine, the only thing I can see that you haven't yet attacked is the tendency for cr@p and/or water in the fuel to affect the cyls you have a problem with more than the ones you don't (if that makes sense). Something to do with flow around the fuel rail dropping crud like a river does when it bends!

Worth unscrewing and see what comes out?

 

[rajinder_1]

Steve was the Fuel, we just had a sample taken out and found sludge in it from the last fill up at BP!!!!

 

[124coupe]

Glad you're sorted - got to be worth seeing if others were hit as well - maybe a Small Claims action for your costs?

Was the muck held back by the filter or small enough to make it to the injectors?

 

[rajinder_1]

It disperses when shaken but then gathers in the bottle we took sample in, its remarkable, but this fuel was taken from the pipe going into the injectors!!!!

 

[124coupe]

I would suggest a good look at the contents of the fuel filter as it should really have held that back - probably full of bigger bits!

That kind of fine "sand" will have done the injectors no good at all...

 

[rajinder_1]

will give it a load of injector cleaner as well to try and clean them out