Misfire

Mr S

Member
Messages
275
So, after thinking the car was running sweet and well, on the trip down to Dover, it developed a slight misfire on cylinder 7&8, this was after 30 minutes of being in the car, at pretty much constant speed, though it wasnt all the time, just occasionally you would feel it. Stopped off at a services for 10 minutes and when it started, it came up with ‘slow down’ and blinking CEL light showing all of Bank 2 misfiring. Reset the codes but it came back pretty much straight away. Then after a while of driving it all disappeared and normal service was resumed. I have also had hot start issues occasionally also. Car would crank but not fire, then after turning the ignition off and on again, it would eventually fire with a tickle of throttle.

Want to get it booked in for an SD3 somewhere when i return, but any suggestions as to possible cause? Unplugged the MAF and running seemed lumpier. I replaced the front 2 oxygen sensors, but not the rear 2. Is it possible these are causing an issue. One of the faults was something like swapped banks.

Seems fine at high RPM, its just low/medium its doing it. Could it be crank sensor or something?

Any suggestions welcomed
 

Mr S

Member
Messages
275
Would also add that i replaced the coils for cylinder 7&8 a few days ago after similar issues, and these appeared to have fixed it on the long run home from Essex, but now its back.
 

Spartacus

Member
Messages
2,798
It would nt be a coil pack as its on two cylinders . I'm no expert but I would check the fuel supply to bank 2 . I know after nearly runnning mine out of fuel that that bank starves of fuel first.
 

GeoffCapes

Centenary Club
Messages
9,826
Do you have white residue on your exhaust tips?

Sounds suspiciously like failing cats (if you still have them).
 

Swedish Paul

Member
Messages
616
All cylinders on 1 bank? I had this, the variator had locked in the open position. Felt better at 6000rpm and rubbish below 4000. The machine felt he could move the camshaft. Cracked it full open with pliers and the blockage went.
 

Mr S

Member
Messages
275
I had a full tank, so not sure why it would be starved of fuel? Could it be injector rail or injectors?

So had it again on the run from Spa to Nurburg, but generally felt good, and certainly better above 3/4k. Gave some beans on the back roads into town, and it felt epic, not to mention the noise.
 

Mr S

Member
Messages
275
Love a squirter!

Il give the fuel rails a test today.
Also, would head gasket be a possibility?
 

Mr S

Member
Messages
275
So i stripped 3 plugs out the engine earlier, after a very smokey, and loud cold start. All 3 plugs, 6/7/8 had oil on them. Also, i noticed that the channel the leads sit in had a small pool of oil, and a sensor plug was soaked in it. Cleaned it all up and GT85’d the contacts etc. No idea why iv got oil on the plugs, one suggestion was that the valve stem seals need sorting, which is why i only seem to have the misfire when cruising. However open to suggestions and thoughts.
 

Attachments

Gp79

Member
Messages
1,025
Might be worth a cylinder pressure test if not done already, just to rule out anything more serious.