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View Full Version : C20XE, intermittent misfire...?



Spudly
03-03-13, 07:55 PM
Right ive found an odd problem on my nova, went over to scunny yesterday and was enjoying the backroad blast on the way there, engine was fine till i got almost to Robs!

Going round a roundabout in third, doing about 35 mph, i put my foot down and it lost all power and the rev counter dropped for a second, then it came back and carried on fine, if youve ever experienced hard cornering with an xe that doesnt have an injection tank/swirl pot, with quarter of a tank or less, it cuts out due to fuel starvation, this was exactly the same and was what i first thought it was, till i realised it has a full tank!

Carried on about quarter of a mile and put my foot down and bang, violent misfire/cut out!

Got to robs and it seemed fine, put it in his garden overnight and when i fired it up today, misfire when rev'd and actually cut out on tickover a couple of times.

When i left to go home it was missing badly when revved and it was a struggle to set off, once moving if i feed the revs in really slowly, it will drive and accelerate fine, it seemed to get a little better once it warmed up and by the time i got home it was revving far better, and i got it almost all the way to the limiter in third by gradually putting the revs in!

Try putting my foot down quickly and it still misses and obviously cuts in power, try putting my foot down hard and its a violent misfire and the rev counter drops almost to zero before springing back up to where it was when it stops missing!

Ive tried a second known working fuel relay and its the same, ive checked my wiring to my pump, my wiring to the fuel cutoff switch, the plugs are fine and are gen gm ones with only about 3000 miles on them, there dont appear to be any air leaks and my donut pipe is almost new, the airbox has no cracks or leaks, but im thinking the problem has to be electrical, and i dont know if the eml is on as its not connected :roll:

Im thinking it might be coilpack at fault, its never been changed from when the engine was in my cav, nor have the leads as ive just not gotten round to it yet, and i wouldve tried a coil pack from either Rob's or Hendrix' novas, but theyre both on dizzy so dont have them lol

Any suggestions/ideas peeps?

MK999
03-03-13, 10:03 PM
Definitely spark related as that's why your rev counter died, I'd be looking at coilpack first if plugs/leads are reasonably new.

Spudly
03-03-13, 10:48 PM
Plugs are recent, coiplack and leads havent been replaced in my ownership, theyre unknown mileage as they were on the engine in the cavalier when i first bought it, i was hoping an opinion of pack and leads would come up as thats seconded my first guess :d

maddogdaz666
04-03-13, 10:17 AM
I'd say it's the plug leads, I'd be fairly sure it's them with how you describe the problem.

Spudly
06-03-13, 06:38 PM
Now running and revving on all four happily, was the leads, thankfully, cheapest option :d



Sooooo happy again lol

maddogdaz666
06-03-13, 07:07 PM
Was that a thank you? :D

Spudly
06-03-13, 07:12 PM
Go see yer rep message wench :p

maddogdaz666
06-03-13, 08:16 PM
Yay rep!!!!

I would rep you but u called me names :(

joff-turbo-nova
06-03-13, 09:13 PM
I see you managed to use your work discount at last !

Joff

Spudly
06-03-13, 09:19 PM
Ive not paid for them yet Joff, as there was a choice of three for some reason, tried one before and they were too short (thats why ive never replaced them) so got these, ill have to pay for them when i return one set tomorrow, £14 :d

Cheers for your offer of a set to try though Joff, wouldve come to yours if i couldve got the use of my dads car lol

joff-turbo-nova
06-03-13, 10:23 PM
wouldve come to yours if i couldve got the use of my dads car lol

And petrol ...... :eek::eek::eek::eek:

Spudly
07-03-13, 11:27 AM
Really not happy now, got almost all the way to work and the misfire has returned!
I've got GM twin electrode plugs in it at the mo, I've been told at work that they're crap and they will be at fault, has anyone else heard this?

meritlover
07-03-13, 12:00 PM
im surprised the rev counter died due to HT leads as the output from the coil is isolated from the RPM trigger.

i would be tempted to investigate the crank sensor or ecu to coil wiring.

does it always happen at the same RPM, is it under load or just random?

ML

joff-turbo-nova
07-03-13, 12:31 PM
Spud,

When I was running a dizzyless XE I had similar rough running problems.

Turns out a little bit of water was getting in round the main wiring grommet on the bulkhead and then getting into the main ECU plug and causing slight corrosion on the pins which created the rough running.

I just got a bit of wet&dry and cleaned off the pins and resealed the grommet and it sorted it - worth a try if now't else !

Joff

Spudly
07-03-13, 06:21 PM
Set of NGK plugs fitted now and it 'seems' fine, drives and accelerates as it should, with no misfire at all, looked a right plum after saying i didnt believe the gm plugs would be at fault and that theyre not crap, and oh, they were at fault it 'seems' :eek:


It seems smoother than it was before, and im happy again, but im still really pissed off with it although i dont know why....:cry:

maddogdaz666
07-03-13, 07:47 PM
Go knock the granny out of it and I'm sure you'll be happier :)

Spudly
07-03-13, 07:55 PM
Ive given it a few good squirts and had it running/driving/sat in traffic for about an hour as i did an errand on the way home from work tonight!

Still feel really pissed off/down heartened with it for some reason!