Stuttering at higher RPMS - why?

[Vilhelm]

Hi.

I'm about to buy back my old car - Audi 100 with 400HP but before I do that I want it to work like it should.

Mods are in signature.

The owner has just replaced the rotor, cap, ignition wires, spark plugs.

There are no leaks in the pipes.

It is currently running 1.5 bars of boost.

The problem starts when you hit 3rd gear and 5000+ RPM.

The first pull of the day (after warming up), it goes like hell, but the more pulls you do the worst the stuttering gets from 5000RPM-> Redline in 3rd->.

Do any of you guys have an idea as to what the problem can be? We are out of ideas.

Thanks for your help and suggestions,
Vilhelm

[Rusty]

Sounds like a thread recently by Topsparky... his problem was an overheating lambda probe. Other usual suspects are fuelling and spark plugs / coils.

[GazzaG60]

AIT, knock sensor expansion, wiring to spark. poor earth.

[Error404]

AFM also worth a clean unless you are running a map sensor?
I had a similar issue with a knackered lambda on an old S14 too, didn't want to rev past 5k

[Andyh-R6S]

Overboost

Check the wastegate diaphragm spring has not been tampered with as well, too much compression of this spring and the ECU will start protecting the engine due to overboost.

All the best.

Andy H.

[Vilhelm]

Thanks for the suggestion guys! Will forward the suggestions to the current owner

[EspenW]

Sounds like a fuel delivery problem. Ignition trouble usually manifest itself at lower rpm, around max torque/max boost, because the charge density at resistance in the chamber is at its highest at max torque

[Vilhelm]

Sounds like a fuel delivery problem. Ignition trouble usually manifest itself at lower rpm, around max torque/max boost, because the charge density at resistance in the chamber is at its highest at max torque

Thanks for the tip Espen.

But why does it run good and hard on the first 3rd gear pull of the day? I don't get that. It starts stuttering on the 2nd pull. The more pulls you do in 3rd gear - the worse it gets.

[magarv]

Do a check with a WB lambda or/and Fuelpressure gauge. Check if there is any difference in numbers between 1, 2 and 3 pull.
The fuel pressure should increase 1:1 with boost pressure, if you have "bad" fuelpumps or clogged up fuel filter you will see a drop in fuel pressure compared to the boost pressure. (This causes the engine to lean out)

[Vilhelm]

Thanks!

Thanks for all your help guys! I really appreciate your time and effort.