[george a weitz]

Does anyone know if the ignition is cut off when the overboost protection activates? Because I'm trying to get my head round whether the ignition system has a fault (the garage thinks possibly the crank sensor is going bad) or the overboost is just doing its job. The tacho drops and effectively the engine is cut off for a fraction of a second, creating a violent jolt - this happens when boosting and not all the time. The DI cartridge is brand new and fuel pump a year old.
Thanks
George
'93 LPT

 

[mark e]

Normal operation of overboost cuts the fuel by interrupting the injector pulses. This does result in a very violent jolt, but I'm not sure I've ever noticed if the tacho dies too.

 

[Voxan2001]

Hi, George.

I experience the same problem. The garage told me it's the ignition cut off. It happens at my car (9K 2300 turbo 91)when turbo boost is at the end off the orange zone. I can't even give it a full throttle because of the hard jolts. Very annoying when you want to give a Golf 1.9 TDI a good run for his money. I think the APC valve isn't working correctly. But I still have to find a good one to prove I'm right.

Does anyone else have an idea?

Steve

 

[TURBODATA]

Hi, I have the same problem with my '96 2.3fpt auto. It keeps intermittently overboosting causing a severe jolt as you describe.I have been told it's the APC valve that is probably faulty (new one £98+vat!) Told by main dealer to disconnect wiring to it and run with reduced (base) boost until I can find a good secondhand one. ps. always seems to happen when taking on a VW GTI though: funny that!!!!!!

 

[mark e]

Originally posted by Voxan2001:
[qb]The garage told me it's the ignition cut off. [/qb][/b]

The garage are wrong. It is fuel cut off. The reason for this is to avoid hefty amounts of unburnt fuel being washed through the system, which is what would happen if just the ignition were cut.

As turbodata says, the best diagnosis is to find a known good APC solenoid.

 

[Andy Bowles]

Hi,

Not very technical, and maybe not exactly on the right lines here, but I have fitted a manual bleed valve by doing the basic manouver of cutting the wastegate actuator hose, and plugging it in.

It takes a while and lots of welly, lots of cut outs and tweaking the valve untill the spring loaded top was set just right, enabling the full boost possible without actualy cutting out on me at all.

The turbo needle now regularly goes to (and stays at) the 3 oclock position without any cutouts. I have not had to adjust it again in over 2 years (just replace a melted gearbox last Autumn)


Cheers,
Andy.