Mis-fire causing boost cut

[Chris M]

Having a problem with my 91 S2 3B.

I'm trying to find what enables boost cut other than the ECU, brief story:

Driving along -all fine. Floor it, boost zips upto 1.7 bar then slight misfire, back off and change gear, back on full throttle, boost is now pegged at 1-1.1bar. Quick flick of the ignition off then back on and back to 1.7bar. No faults thrown on VAG-COM either

The car had a slight misfire before but no boost cut.

Anyone had this problem, maybe the coil?

Cheers,
Chris

[CliveH]

No one...???

[spink]

Ive got a couple of coils spare if you wanted to try one?

[220bhp]

3b at 1.7bar, I wish I had your problem,strugle to get 0.8 out of my 3b.If you realy are seeing 1.7bar then I can only think its over boost protection coming in

[valjo]

could be MAF

[Chris M]

Its RS2 spec I think it could be the knock map reducing boost when it misses. Just fitted new knock sensors. MAF has been cleaned.

Cheers,

[T2Andy]

Chris had the same prob this week ,floor it and nothing much happened felt like the power was holding back alot ,then it would surge upto full boost and then cut for a split second.so i cleaned out the miltec DV ,the piston seemed to be sticking cleaned the maf
multiplug and put the standard air filter back in and all is well ,i was seeing about 18\20psi.it shat all over carrado earlier anyway.

[zlobo]

do you run on orig sparkplugs?

[Chris M]

Tried F5DPOR's and also some NGK plugs.

[Ross]

..and still no joy mate?

[spink]

Cris,did you get/try that coil yet?

[Chris M]

Yeah thanks , think the coil has cured the mis-fire, still cuts boost after a WOT blat tho

[CliveH]

Bummer!

[Chris5044]

anyone else any ideas?

[Bjoern]

Hey Chris.
Mine S2 does the same. It's an original ABY '94. It can go smoothly for a couple of days, then it begin to jerk a little, and on the next hard acceleration it cut the fuel. After that it can max. Press 0,4 bar.
I have a mate, his S2 do exactly the same. He has shifted almost everything electrical, pressure hose and vacuum hose.
I mistake the knock sensors. It is practically the only thing he not has shifted.
I will shift mine a.s.a.p.
It’s a very strange problem. Nobody seems to have the right solution. Somebody say it’s a leak in a boost hose, and other say it’s an over boost projection. When I’m think back, I have notice that the problem gets bigger when I drive on 98 octane fuel. That’s why I think it’s a knock sensor problem. I will try to go on 92 octane fuel next time. If it helps, then I know where the problem comes from.
Bjørn, DK.