misfire emergency

T

Tirion

Well-Known Forum User
Hey,

I have a misfire problem which is spiralling out of monetary control. Two weeks ago i drove to scotland, and my Z started misfiring intermittently. I could hover @ 3000rpm and it would be ok, so i got home ok.

so, i changed the leads, spark plugs.... no improvement. the problem was still intermittent. i could drive for a bit, and then it would start misfiring. or sometimes it would misfire from cold.

so i changed the fuel filter and put in some fuel cleaner. i thought there was an improvement, but alas no.

then i looked at the distributor cap and the little springy nob thing was missing. problem solved i thought! so i replaced the cap and rotor, but no improvement. also, since sunday the misfiring is pretty much consistant, tho i havn't really done much driving.

i got my timing belt done, as it needed doing anyway. then i went down to the garage and asked if they could find the misfire fault. no such luck. they thought it might be a sticking valve, so they added some more fuel cleaner or something. no improvement really.

they suggested i go to an engine tuner guy. i personally think it's something electrical because of its initial intermittent nature. other people have suggested compression, the power transistor thing, coil... ad infinatum. :/

any thoughts before i sell a kidney for someone to troubleshoot it?

neill
 
I would check the coil next, as you've changed the likely things already also maybe injector wiring so try to check injector connectors if you can get the car put on an exhaust analyser to check the co (emmision) output while it missfires that will give you an indication of wheather it is an electrical( no spark) /mechanical (burnt valve type) missfire, as if it's electrical your Hydrocarbons count will be way over 1200 ppm ( parts per Million) as if there's no spark at one cylinder then the injected fuel will not have been burnt and so emmisions will be high. if the injector is not working then it will missfire but there won't be unburnt fuel coming out from the exhaust so emmisions won't change too much.. also does it now smoke more when missfiring?
Hope this give some help I used to track these kind of faults for a living they sometime s skrew your head up for days always fixed them in the end though....

Nick..
 
I have the exactly the same problem at the mo with my 240, best option mate.
Call in Hometune. They are probably the biggest franchise bunch about, smaller guys havnt always got the right stuff.
I have hometune coming on Monday, and I know he will sort it out, they also do servicing, so thats worth bearing in mind. These units and set ups are not rocket science, (well they are for me actually), so they should be able to nail the problem before you have to donate anymore body parts to ebay.
Don.
 
Snap. Got it on my Cavalier. Though it is intermittant. I have found if you start mine and let it run for a minute then give it a bit of gas at first it cures the problem. I have been led to believe that it is a dodgy injector or sticky valves. I have completely flushed the system with engine cleaner but the problem is still there, so my conclusion is dodgy injector. Now all I have to do is track which one. Good luck.
 
thanks for the replies, it's always encouraging to know i'm not alone :) i'm taking it to a local engine tuner on monday, and i'll go through some of this stuff with him.
thanks,

neill
 
Zbirdy said:
Call in Hometune. They are probably the biggest franchise bunch about, smaller guys havnt always got the right stuff.
I have hometune coming on Monday, and I know he will sort it out, they also do servicing, so thats worth bearing in mind.
Click to expand...
How much do they charge?

Si
 
Coil / power transistor will show as ignition fault code on ECU self test (see "Articles" section for details). This may throw up other codes which will shed light on the problem, but if all clear then follow the conventional routes. Other suggestions will require more direct testing (compression, fuel pressure). Also, ensure new plug leads are all connected to the right terminals and absolutely clear of all metal objects. Check the coil lead support too - this often flops over onto a metal pipe when the engine is warm. the ignition spark is a powerful one and will arc to any metal object, even through the lead covering.
 
thanks mr F i'll try running the codes tomorrow. i think my old man has a compression tester too, i'll have a go with that.
there was a 'zapping sound' coming from the off-side cylinders, but we thought that might be the solenoids, and it didn't totally coincide with the misfiring.
 
Your "zapping" sounds like a spark arcing to me - try running the car with the bonnet up when it gets dark tonight. You may find a mini fireworks display will pinpoint your problem!
 
the engine tuner said electrically there is no problem. he reckons on a stuck valve. said to try some more fuel additive... can anyone reccomend a really good brand?
 
I put STP engine cleaner into my cavalier. Didn't cure the problem but it did radically reduce it though. I think there must have been plenty of muck in the engine in the first place which just increased the problem. My local garage advised me to put the entire bottle into the tank (about double the amount of normal to give a good flush) which I sort of did. In fact I put more than that in or rather a bottle of the stuff in just over half a tank and ran it to almost empty. Did the job quite nicely and no hassles.
 
STP Injector Cleaner works well in respect of cleaning injectors, but it probably wouldn't free a sticky valve.
 
I was curious about this and did a search on Zcar.com to see if there was any info on it, turns out it's a common problem which is hard to pinpoint.

The advice they gave is as Mike suggests with starting the car at night and seeing if you get an ARC from the Dizzy, someone also suggested that replacing the crank angle sensor did the trick.
 
Hi


My car did a similar thing recently and after an evening of checking the obvious i checked under the rubber boot of each injector lead and found a wire had broken inside one of them. Sometimes the car would have trouble idling and at full throttle it would splutter quite badly. Once the lead was repaired the car was fine. It's worrying that one wire can cause so much trouble in a car as full of wiring as the Z31:eek:
 
hey,

i ran the ECU codes and got,
11,12,21,23,31
so crank angle sensor, AFM, ignition signal, idle switch signal, and load signal circuit (tho i have no Aircon)

to quote aliens,
"It's reading right man,"
"Then you aint reading /IT/ right."

so many errors... bad wiring, ECU?

also, on Mr F.'s right up he mentions battery voltage... i changed the battery last year and installed a good but not quite correct spec battery. i don't think it should be causing any problems but i've studied enough electronics to be superstitous over anything :/

neill
 
i checked it out but there were no obvious arcs... i thought i saw something near number 2 cylinder a couple of times but i think it was just a trick of the dark, i dunno. i'll try again tonight.
 
Tirion, are you sure your not running my car.
Ive had an identical prob, until I called out the Hometuine guy.
Si, he charged me 47.00 for a tune, and it was £70 odd for plugs points and tune, plus he sorted out the carb.

Right tirion. He found that one of my su carb cylider pot thingys was sticking, so he freed this up with some wd40, and showed me how to do it myself, looks simple.
He then replaced the plugs, points, did the tune up and hey presto. NOT SO BAD. but, BUT BUT, he said my valves were caked up with cadburys dairy milk i think, cant remember, but they are caked up.
So, heres the reccommendation.
add REDEX, every fill up, not just for 3 months, use it all the time. it will clear them and keep them clear. But use it by the dosage, dont overdo it. also with a large philips scredriver, loosen off the distributor and give it a turn on the markings . Trial and error, and run it for a 1/2 mile and see. If no better try a little further adj, and test again. Your not doing any harm apparently, so fiddle about with the setting until it runs nicely. Ive dine this and it is 99% better.
Don.
 
thanks for the tips, i'll give some of this a try.

i should also point out that in a sense it's not really a misfire... it's like all cylinders are momentarily cutting out. it doesn't just sputter the whole car 'shudders', and revs fluctuate allot.
 
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