Missfire

[stevolution2010]

Right, I've gapped all the spark plugs to 0.7. I've also run a compression test on each cylinder. They came out at 11bar which I think is good.

One thing I did notice is that the bottom of the spark plus (around the screw thread) were pretty coked up and they've only been on a week. Could this be telling me something?

I've got my usual trek up to the north east tomorrow so that should tell me if gapping the plugs to 0.7 has worked.

Thanks for all the help so far.

what were the gaps before u re-gapped them could be why it has black on the plugs

or its running to rich?

 

[markd77]

what were the gaps before u re-gapped them could be why it has black on the plugs

or its running to rich?

Gaps were around 0.5/0.55.

 

[stevolution2010]

Gaps were around 0.5/0.55.

thats normal then,altho you are running slightly more horse power so go with the 0.7 and see how u go

let us know your findings mate

 

[sponners]

Is the intermittent missfire when cruising or going flat out?

I'd leave the plugs at .55 - .6mm (more power, smaller the gap)

strange why unplugging the one lead and putting it back on would cure it briefly.......that would suggest to me that the fault is with the pack/leads somewhere.

really black plugs would suggest overfueling.......lambda sensor maybe?

also the cam sensor can lead to intermittent missfires.

compression test would be a good idea also.



.....so basically could be a number of things to go through till you get to the bottom of it.

 

[markd77]

Is the intermittent missfire when cruising or going flat out?

I'd leave the plugs at .55 - .6mm (more power, smaller the gap)

strange why unplugging the one lead and putting it back on would cure it briefly.......that would suggest to me that the fault is with the pack/leads somewhere.

really black plugs would suggest overfueling.......lambda sensor maybe?

also the cam sensor can lead to intermittent missfires.

compression test would be a good idea also.



.....so basically could be a number of things to go through till you get to the bottom of it.

I'm going to see how it runs with the plugs at 0.7. If it still runs rough I'll put them back to 0.55.

Missfire happens both when cruising and flat out. It's like the engine just stops and picks up again.

Anyone know how I can check the lambda sensor?

I have done the compression test and got 11bar on all 4 cylinders. Suggests no problems there.

 

[markd77]

thats normal then,altho you are running slightly more horse power so go with the 0.7 and see how u go

let us know your findings mate

I'll keep you posted. Thanks for the help so far.

 

[sponners]

plug gap is only really an issue whilst on boost (more boost, smaller gap needed to stop it 'blowing out' )

if the car is the same driving steady and full throttle then its unlikey to be the lambda.

have you tried checking the resistance on the coilpacks (testing across second and third pin) should be 1k+ohms

 

[B6lee]

correct, ive just dropped mine down to 0.55 cos i had a slight missfire when on full chat

 

[markd77]

plug gap is only really an issue whilst on boost (more boost, smaller gap needed to stop it 'blowing out' )

if the car is the same driving steady and full throttle then its unlikey to be the lambda.

have you tried checking the resistance on the coilpacks (testing across second and third pin) should be 1k+ohms

Fit brand new coil packs only a week ago along with plugs and leads.

 

[sponners]

Fit brand new coil packs only a week ago along with plugs and leads.

cam sensor checked?

 

[markd77]

cam sensor checked?

Not changed the cam sensor yet. Is it worth trying this next?

 

[sponners]

Not changed the cam sensor yet. Is it worth trying this next?

have you got a mate with a evo so you can just borrow it to try? (I dont want to say yeah go out and buy one when yours might be fine)

 

[B6lee]

wouldnt a cam sensor fault put the engine light on ???

 

[sponners]

no mate, they only seem to throw a cel when they're really fooked.

 

[markd77]

Right, drove 100 miles to work this morning and not a sniff of the original problem. Will see how things go this week.

 

[markd77]

Well, it ran without a problem for 4 days then this morning started missing again. Next stop Evotune.

 

[markd77]

Jamie at evotune had the car for a couple of days. Found that it was running lean. Fitted a walbro fuel pump and tweaked the map, car now running the best it has ever been. Looks like the problem is fixed.

The moral of this story, take the car to an expert.

 

[stevolution2010]

Jamie at evotune had the car for a couple of days. Found that it was running lean. Fitted a walbro fuel pump and tweaked the map, car now running the best it has ever been. Looks like the problem is fixed.

The moral of this story, take the car to an expert.

thats great news mate

 

[sponners]

Jamie at evotune had the car for a couple of days. Found that it was running lean. Fitted a walbro fuel pump and tweaked the map, car now running the best it has ever been. Looks like the problem is fixed.

The moral of this story, take the car to an expert.

glad its sorted mate.


did Jamie say exactly what the issue was? why it was a intermittent fault?

 

[markd77]

glad its sorted mate.


did Jamie say exactly what the issue was? why it was a intermittent fault?

I am not sure there was one issue exactly, think it was a combination. He did explain it to me but it was over my head.