Good old fashioned misfire

fubar andy

Moderator & N/W Rep
Staff member
Took the car out this afternoon. After driving it around for a little bit and giving it some stick, I turned the boost up to 1bar and immediately had a misfire from 4k onwards all the way to the redline.

Restored boost back to 0.65bar and still had misfire issues.

Back in the garage, took out the plugs and checked them (dry and no black fouling)
Also cleaned up the leads connections to the dizzy and plugs.

Back out on the road and the same issues, fine on standard boost, then up it to 1 bar and misfires from 4k.
Once returned boost to standard, it still misfiring so retuned home.

To note, my turbo is on the way out and oil IS passing oil via the seals and into the intercooler/engine, I doubt that it making any issues to it firing as the plugs still look clean.

I'm running BCR8ES's at present and aftermarket leads. Dizzy is reasonably new (3-4k on it) and only started to fail once the boost was turned up!

Any ideas?
 

PobodY

Moderators
Staff member
plug gaps, old fuel?,fuel filter.
Gaps would be my guess too. - Last time mine was on the rolling road that was the cause of my low power (although I couldn't tell it was misfiring).

I think I'd just installed the BCR8ES' out of the box, and the problem was that the spark wasn't strong enough when the revs built.
 

Fast Guy

Moderators
Staff member
Ignition amp? Oil getting into the inlet can mix with the fuel and lower the octane/det threshold from what I heard a while back.
 

fubar andy

Moderator & N/W Rep
Staff member
gap down to .6mm and see if the fault goes.....could be coil or ign amplifier as well ya see.
I'll whip them out tomoz and gap them to .6 and see what happens


the problem was that the spark wasn't strong enough when the revs built.
It seems similar to what I have, once the revs his a certain point and the boot comes in, it then turns into a gaylord sounding Impreza a loss of power and I look/sound like a bellend!


Oil getting into the inlet can mix with the fuel and lower the octane/det threshold from what I heard a while back.
I'm not too sure if its that, but I certainly have oil getting into the intercooler and inlet and I do think that my oil has a distinct smell of petrol!
 

red reading

Active Member
oil will get contaminated if you have a misfire, and you would need to have a lot of oil to make the car miss getting in the engine
 

vss irvine

Well-Known Member
another thing to look at if its not the ign side is the fuel pump or pump wiring.

few people have come across this lately.
 

fubar andy

Moderator & N/W Rep
Staff member
Another question, how likely are the ign leads to break down/last for as they've been on the car for about 7-10 years?

I'll have a look at the fuel pump wiring today also...
 

PobodY

Moderators
Staff member
I've found it's hard to tell with leads. - You can tell the obvious things like if the insulation is damaged, or the end fitting are loose.

I guess you can check the resistance on them all and see if it's the same when you correct for length.
 

KieranEG6

Member
Any results with this?

Iv just started mine an it seems to have very similar symptoms. Idled fine but turns into an impreza as soon as you try for any boost on the road. But tootls round fine off boost.
 

campbellju

Moderators
Staff member
That cross sound like an ignition issue. Follow Dan's advice on gapping plugs first. Quick and free.

@andy, hadn't spotted this thread. Drive over to mine sometime and we can swap everything over on the ignition system to prove it or rule it out.
 

fubar andy

Moderator & N/W Rep
Staff member
I changed the leads, dizzy and rotor and it went away.

I guess it was the rotor and dizzy and they looked like they'd e seen better days.

Check inside the cap and rotor for furring up and burn marks on the rotor (this is what mine had, but it was 20+ years old!)

Jim - Car is still off the road and my turbo has been sent back because OD sent a 200SX inlet which didn't match the GTiR intercooler pipe!

However I'll give you a shout when it's back on the road and we'll have to arrange a meet up!
 
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