What Can Cause A Misfire?

[aido]

OK guys my car is still misfiring as seen by Mike the other night, think it's misfiring anyway, not sure what else it could be!

Basically under WOT conditions occasionally the car loses all power before kicking back in, feels like I've hit the red line.

Spark plugs have just been changed thanks to Gord but the problem is still there (but I am getting much better MPG cheers fella :D)

What else can cause this problem?

Dodgy fuel pump? Anything else?

Just trying to work up a check list so I can get an idea - no CEL's yet so haven't taken it to the dealer....

Thanks in advance

[Mr Singh]

o2 sensor?

[chips229]

Shame that when you had the plugs out and changed someone didnt check to see if it was always the same plug missing.If the car uses coil packs then it could be one of them

[BAGGY]

If you know which cylinder is missing try changing that coil pack to another cylinder if then that cylinder starts to misfire you know its the coil pack if it stays with the original cylinder then get a compression check :)

[waddy]

Assume you've got a piggy back chip with the S/C? - could it be faulty?

It could be something else that is controlled electronically?

It could just be witchcraft?

[Gord]

Been to lexus stockport today re-Eng/Man/Light coming on :duh: needs 1 new coil pack

[RoadRash]

Misfiring can happen when you run too lean air/fuel mixture.

[SpOcK]

Misfiring can happen when you run too lean air/fuel mixture. 

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I'm currently having a misfire problem, and because of that I've tried to find out what causes it. Engine/cylinder misfires when it does not have enough compression for the air/fuel mixture to ignite. Causes can be at least the following (among others):

1) faulty spark plug

2) spark plug too loose (cpmpression "escapes" through the threads)

3) spark plug too tight (ALWAYS use torque wrench(?), 17Nm)

4) leaking valve (crust on valve, doesn't close properly)

5) jammed or crusted piston ring

6) damaged piston (due knoking)

7) faulty coil pack

8) faulty ecu

I suggest that you take compression test, as someone suggested. Compression should be ~12bar/cylinder if everything is in order. Mine cyl 1 had only 2 bar, so it's pretty f%¤d up... :tsktsk:

But whatta heck, now it's time to put in some forged internals, and then... more BOOOOOOST!!!

[ColinBarber]

o2 sensor?

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shouldn't be because at WOT the ECU should be in open-loop.

[RoadRash]

o2 sensor?

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shouldn't be because at WOT the ECU should be in open-loop.

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Can you explain what open-loop mode and closed-loop mode means??

I often heard about it, but never found a good explanation.

[javadude]

I asked the same the other week. The answers on this thread: Loopy stuff

[aido]

Thanks for the comments guys, I'll get a compression test done to see what that says as I've tried another set of spark plugs and still getting the problem...

This may be a silly question but where do I get a compression test done - is it the sort of thing that the dealer can do?

[Mr Morse]

Thanks for the comments guys, I'll get a compression test done to see what that says as I've tried another set of spark plugs and still getting the problem...

This may be a silly question but where do I get a compression test done - is it the sort of thing that the dealer can do?

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It's something that any run-of-the-mill garage can do mate, only takes a few mins.

[Lex-aholic]

Just a shot in the dark, but it wouldn't happen to be the gap on your spark plugs being out ?

[aido]

Just a shot in the dark, but it wouldn't happen to be the gap on your spark plugs being out ?

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No idea buddy, I'm going to get in touch with some garages now so they can check that for me - in fact feck it I'll call Lex Sheffield as I need them to check out my front bumper anyway :D

Fingers crossed eh :D

[aido]

Sorted, booked in tomorrow at 2 :)

They've said it could be coilpacks too - we're going to roadtest it and then they'll get it in the workshop!

Who knows, I may have a fully working car without anything broken soon :D

Where and what are the coilpacks?

[Mr Morse]

Where and what are the coilpacks?

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The little black boxes that sit on top of the plugs :D

[Gord]

About £17 each :D

[aido]

Mega, thanks fellas :D

Maybe I knackered one when I jet washed the engine

If they're 17 quid it's probably worth replacing all of them on a high miler right?

Better safe than sorry and all that?

[Mr Morse]

How old are you plugs Aido, if you are replacing them go for the IK22's which are recommended for forced air motors. Would be worth replacing all the coil packs and plugs in one go mate.

[aido]

They're pretty new Mike, they came out of Gord's car when he had the HKS plugs fitted, we were testing them to see if the problem came back which it has...

I'm going to order some IK22's off eBay mate from the USA, in fact i'll do that now :D

I have to admit that with these plugs the MPG has gone through the roof - I've never seen the needle that high before, where it was sitting at 20 it now sits at 30 or 40 a lot of the time - saying that it does drop nicely when I boot it, well happy with that ADL clutch :D

[Mr Morse]

They're pretty new Mike, they came out of Gord's car when he had the HKS plugs fitted, we were testing them to see if the problem came back which it has...

I'm going to order some IK22's off eBay mate from the USA, in fact i'll do that now :D

I have to admit that with these plugs the MPG has gone through the roof - I've never seen the needle that high before, where it was sitting at 20 it now sits at 30 or 40 a lot of the time - saying that it does drop nicely when I boot it, well happy with that ADL clutch :D

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This is where I got mine from:

Performance Parts

[aido]

Thanks mate :)

[Gord]

Up-date mate coilpack not £17 more like £80 :o lexus stockport say not going to change mine under warranty coz of the supercharger ringing lexus GB to see if can sort it out :o

[aido]

Up-date mate coilpack not £17 more like £80  :o lexus stockport say not going to change mine under warranty coz of the supercharger  ringing lexus GB to see if can sort it out  :o

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That's knackers pal, the SC doesn't affect the coil packs at all - Chris had his engine work done under warranty when that went - GB should swing them, it's all official parts after all!