91 S2 limiter fault

[Welshboy]

Hi I'm Nick and been a member and owner for a year now.
I have a fault that i initially thought was a misfire at 4500RPM, I've took the old girl to a local garage and they say it's more like a limiter fault and say it's present at 3000 when cold but can't read the ECU. Any ideas what could be causing this as i'd love to get it into the fun RPM's
Thanks Nick

[Tractor Dave]

Where in Wales are you?
Boost leak and proper vcds code read a good place to start.

[Welshboy]

Thanks Dave i'm from Wrexham so i'll try and find someone up here who can check it and read it. are you up this end?

[Tractor Dave]

Unfortunately the other end near Carmarthen.
Anyone with vagcom or vcds should be able to read the codes for you. However, a boost leak often leaves no codes at all.


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[newsh]

Things that can cause a misfire on the 3B engine.

Has it got the correct rotor arm in the dizzy?

Is the dizzy timing spot on,m? needs to be checked to the zero mark in the bell housing window. Roll the engine forwards onto the zero mark then adjust the dizzy so it’s exactly on the marks.

Does the IAT sensor measure correct resistance at 20deg C?

Check your dizzy cap and spark plug leads, run the car in the dark and look for sparks tracking.

Fit new genuine spark plugs from a proper supplier, there are lots of copies on eBay!
Torque them correctly.

Check for boost leaks with a proper boost leak test kit, you cannot do this without a compressor.

You should be able to read the ECU, you can get a cheap OBD lead and adapter on eBay. You only need the freeware version of Vagcom .. and any old laptop PC

Do you know if the ECU has been chipped?
It’s extremely unlikely it’s actually the rev limiter in the ECU causing this.

[Welshboy]

Thanks Newsh for the info, i don't think it's chipped but i'll get the others checked. I did read on Audi world somewhere that a faulty Knock sensor can give "impact-like power loss like a misfire so have got one on order along with a new rotor arm (it can'y do any harm to give the old girl new)

[LHD_Kid]

Faulty knock sensor (of which there are 2) usually just result in reduced boost, not a misfire... (and don't always trigger fault codes)

Good advice on checking plugs, leads, dizzy cap and rotor arm. Make sure you have the narrow tip version (the correct version).

I agree, is unlikely to be ECU rev limit related...

[Welshboy]

Thanks LHD Kid

[newsh]

Distributor timing is crucial on the 3B, if it’s out you can get a big misfire sometimes with a cloud of smoke out the back!

As the Kid says, narrow tipped rotor is essential.