[Mk2] [Turbo] HELP, Misfire on full boost...turned boost right down and its fine again?!

[Jonnie1987]

My 1990 mk2 Rev 1 turbo has developed a misfire on full boost and WOT. It was running 0.8 bar through the Gizzmo IBC. I turned the boost down to 0.6 and the mis has gone away.


Ive recently replaced all the ignition components apart from the coil. The plugs suggest perfect running conditions but could be the wrong grade. Im running the forge atmospheric bov if this matters but ive had no trouble with it for ages apart from the increased fuel economy which is fine.....rather be running richer anyway.

Can anyone help me?

Regards
John[/list]

[djpkins]

lol..this seems to be my answer to everything but.....air leak between AFM and throttle body....this will also make you run too rich, to the point of misfiring

[Jonnie1987]

lol..this seems to be my answer to everything but.....air leak between AFM and throttle body....this will also make you run too rich, to the point of misfiring

Cheers for that, I'll go have a look today at some point and make sure everything is tight.

John

[SFLee]

i would say bov is source of your air leak using afm and atmospheric bov dont mix

but have you check the gap of the new spark? some ime new plug gap can be out, and ignition lead? change back to your old set and see? (sometime they do strainge thing)

[Jonnie1987]

i would say bov is source of your air leak using afm and atmospheric bov dont mix

but have you check the gap of the new spark? some ime new plug gap can be out, and ignition lead? change back to your old set and see? (sometime they do strainge thing)

I think the gap of the new plugs (which im yet to fit) are around 0.7. The leads i had on before were tiny and all corroded so the new ones should have been much better. Im not sure about tge bov as its been working find for ages and hasn't caused me any trouble.

Im thinking its something that needs tightening up as the boost peaks at 0.64 bar. If I try and set it back to the standard 0.8 it'll miss when it goes over 0.64. Ive got a couple of days off work so i think im going to take the inlet pipes off between the afm and the turbo and have a look to see what condition they're in.

Cheers for the replays, ive got a few ideas as to what it may be!

Regards
John

[Jonnie1987]

Yesturday I took apart the whole inlet (from the AFM to the throttle body) making sure everything was done up tight when I put it back together.

On the test drive there was a big improvement, however it still misses a bit under full boost and WOT. Im going to turn it back down again for the time being.

Im planing on fitting the new plugs today but i doubt they will make any difference.

John

[mikey2]

Check your lambda mate, i had almost exactly the same problem, turned out i was limp wristed when i plugged it back in. solved all hesitation and missfiring.

[Jonnie1987]

Check your lambda mate, i had almost exactly the same problem, turned out i was limp wristed when i plugged it back in. solved all hesitation and missfiring.

by limp wristed do you mean it wasn't tightened up enough? funny you mentioned the lambda as i took mine out a while back to clean it up and found it had two gaskets. I thought this was strange and removed one of them then shortly after the problems started.... I may put it back and see what happens. Cheers!

John.

[mikey2]

It was the plug i didnt do up properly, when i checked it to fit an afr, the plug came apart, once i plugged it back in in a more manly fashion it worked no problems.

[Jonnie1987]

It was the plug i didnt do up properly, when i checked it to fit an afr, the plug came apart, once i plugged it back in in a more manly fashion it worked no problems.

Well Ive just replaced the plugs for the 4th time this month and fitted the second gasket back on the lambda (also in a more manly fashion!) and the misfire has gone! I turned the boost back up and felt that nice kick again!

cheers for your help guys.

Regards
John