b5 1.8t coil issue

[ivica]

checked spark plugs then after car has been running rough like on 3 cylinders but its normal when idling. i got new plugs and still the same issue

 

[jbh]

It could be a coil pack but you would be best getting the car scanned for fault codes.

 

[ivica]

thanks for reply.
i checked codes and nothing showed up.

 

[aragorn]

yeh these ECU's dont detect missfires unforunately, unless its maybe a really late one with the integrated coils.

The two usual culprits are a coil or the ignition amplifier on the airbox.

Generally, a coil will break down under high load, so it'll drive fine, then missfire when you floor it. Whereas the amplifier will just die, usually on cylinder 2 for some reason.

Occasionally there are exceptions, but for a completely dead cylinder i'd be looking at the ICM first, or for load related i'd do the coils first.

 

[ivica]

is there a way i can test the icm or coils because its hard to find problem it when it idles normal

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[Browett1982]

boost leak was culprit on mine when was running like this so may be work a quick check??

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[ivica]

its getting full boost around 10 while the misfire is happening but i just tried running with maf plugged out and it doesnt misfire through the rev range but its only at 5psi boost

 

[Browett1982]

faulty maf maybe....

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[ivica]

i done a boost leak check and its all good. maf reading 3.4 g/s on idle at 840 and 10.5 g/s around 2500 rpm

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[Browett1982]

not sure then was just a idea as Iv had these issues previous

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[ivica]

here is a video

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[aragorn]

put the MAF back on and unplug the N75 instead. that way you'll still only get 5psi of boost but the MAF will work.

If its still OK, then i'd say its typical coil failure. If its not, then its probably a boost leak.

A boost leak can cause a bog down or hesitiation at mid throttle or initial accellearation that then clears if you keep the foot down. My dads car had a split hose on the inlet manifold (one of the small ones near the throttle) and it was doing exactly that.

 

[ivica]

if there is no misfire with the n75 unplugged would it be safe to drive it?

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[aragorn]

yes

 

[ivica]

still misfiring with n75 unplugged i then tried without maf again and it seems to run much better. is there a way to test the maf sensor?

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[ivica]

found this out by accident


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