Hi

This car has a misfire at about 1300-1500 rpm even without load. In park and holding the throttle open will get it to miss.

The car has been to the main agents and another garage where they have replaced the crank sensor, the plugs and leads, the air flow meter and the injectors have been removed and tested.

I have checked with the Pico scope and WPS500:-
Exhaust waveforms, even though the miss appears mainly on cylinder No.1 all the other cylinders do miss.
Running compression test, this was ok.
Coil drivers, both volts and current
High tension.
Injector driver, both volts and current.
Clean throttle body and checked TPS
O2 sensors. Front O2 is a broad band sensor and switches ok, even during miss, and the rear stays nearly static as it should.
Charging system.
Breathers and PCVs
Clamped carbon canister.
MAF sensor [even though it is new]
Fuel pressure and flow.
Live data on VAG-COM

If you hold the idle speed up to about 1300rpm you can feel the miss and see it on the WPS waveform, however, if you put a load on, say the A/C the miss smooths out, not totally but a great improvement.

Not sure where to go now, and am going grey by the second.

Sorry for the long winded post, but if anyone has any suggestions I would appreciate and help.

Regards

Simon

just a thought is the valve timing correct pete

hi when you say injectors have been removed and tested OK i wondered if you had tested the injectors in situ referencing signal against current trace.
it also might be helpful for you to check the emissions
as well as a cam to crank trace to confirm valve timing
hope this helps
martin

Evening Simon,

Martin touched on this: What are the 4 gas readings showing when you have the misfire? I am assuming natural and fast idle readings are ok. The results may well guide you down the correct diagnostic route.

Regards

Pete M

A quick look at the misfire counters and STFT may help?

Regards Mark

Hi guys

Many thanks for your replies.

I have taken a camshaft sensor and crank trace, however, I have not got a good one to compare it with. I did check it with the WPS500 running compression and all looks well.

I don't have access to a 4 gas at this time.

Fuel trims appear ok. Not sure what block the missfire count is on. Can you advise?

Garage tried a new coil pack even though I had tested it,it made no difference.

I re tested the missfire with the WPS500 in the exhaust just to confirm the missfire IS on No.1.

Regards

Simon

if the miss is definatly no1 then to confirm not injector swap injector with no2/3 and see if fault moves
i seem to recal cam issues or valve sticking issues with some of these may be worth having a look

Hi

Many thanks for you help. I have added some JPGs of traces that might help.

I can post them as PSDATA if required.

The injector trace appears to trigger correctly


Taken from No.1 cylinder



Regards

Simon

hi i had one of these that tested fine with all traces was giving me loads of grief. until i bit the bullet and swapped the injector over to another cylinder and yes the fault did move with the change i could only think the injector was suffering a mechanical fail
hth matin

Hi Martin

I am following the same thought. Have asked the garage to do just that when the car comes back in this week. I will then re check what cylinder is missing.

Many thanks

Simon