Terrible missfire 1.8T AGU

[Stanley]

Last week i had a coil go, so replaced it. Problem cured.

A few days later i had the same symptoms, so sourced and fitted another. Problem still exists.

I get a bad misfire all the way from 1500rpm to 5000 under full throttle, accompanied by popping and banging from the exhaust.

If i disconnect the electrical connector for the N75, i get no misfire at all and the car runs smooth.

Any ideas before i torch the *******?

 

[Stanley]

Anyone?

Thanks.

 

[HTC]

So when you are running on wastegate boost pressure only you do not get a missfire. Sounds like the ignition system is working (ie coil packs and ignition amplifier).

When did you last change the spark plugs? Have you checked the fuel pressure lately?

 

[Stanley]

Plugs are newish. Maybe 4 months old. Worth giving them a look I guess.

It's really horrible!

Cleaned up the ignition amps contacts and it made no difference.

Swapping coils around does seem to make a bit of a difference but doesn't make it any better.

Also I noticed my MPG is way down to 12ish....

 

[Prawn]

Plugs!

I had this problem on mine too, boosted fine when cold, then as soon as it warmed up, it miss fired terribly at anything over 10psi.

N75 unplugged and it drove perfectly, just slow!

I swore it wasn't plugs, and even replaced them to prove it, but the misfire continued.

Turned out to be the plug gaps too wide, and above 10psi it blew the spark out.

New standard plugs gapped up fixed it instantly

It's also worth noting, that a big plug gap will give the coilpack more work, thus making it more likely to blow

 

[smokiedee]

sorry to drag up a old thread but did new plugs work as i'm having a misfire now as well and replaced the maf and its still there. i changed the plugs for bosch siper 4s and mpg dropped to 12 and put back in old ngk and is still misfiring but mpg has gon up to 21. please help my old focus seems a lot faster than my a3 right now

 

[16Klappe]

sorry to drag up a old thread but did new plugs work as i'm having a misfire now as well and replaced the maf and its still there. i changed the plugs for bosch siper 4s and mpg dropped to 12 and put back in old ngk and is still misfiring but mpg has gon up to 21. please help my old focus seems a lot faster than my a3 right now

Check the condition of the wires going to the coil packs.

 

[camscockle20vT]

. i changed the plugs for bosch siper 4s and mpg dropped to 12 and put back in old ngk and is still misfiring but mpg has gon up to 21. please help my old focus seems a lot faster than my a3 right now

I would say the mpg thing is due to the short running as i doubt youl be going far in it. Engine missfire will mean lots of un burnt fuel. Try the options suggested as you cant go wrong rather than throw money at it.

 

[DaveA3]

buy a new ignition amplifier (ingnition control module on eurocarparts) thatll sort it most likely. I had the same on mine that thats what it was. Cost £67 quid. I have an AGU also.