Surging VS Commo

[goose]

Not fixed.

However... if I disconnect the MAF, it drives exactly the same. Obviously check engine light comes on, but goes back off on restart with MAF re-connected.
Check engine light goes off while driving if I switch it to gas. I thought that was interesting.

[goose]

So it's not the MAF, and it's not the TPS.
If I had a way to check the fuel pressure I'd have done that already, but I guess I'm up to fuel pump and/or fuel pressure regulator.

[MRMOPARMAN]

clamp the fuel return line from the reg back to the tank and take it for a drive. that will tell you whether the reg is fucked.

[goose]

Won't that cause it to run really rich and stress the fuel pump?

[ott308]

LPG backfires can kill MAFs and will also blow the vac line off from under the TB (90deg hose that runs under the plenum). Clamping the fuel return line to test won't fuck anything.

[goose]

Ok, cool.

I've swapped out the MAF so that's ruled out. No signs of vacuum leaks but I'll double check.
Should have a spare fuel reg available to try, otherwise I'll do the clampy thing then.

I'm also of the understanding that there's no MAP on an ecotec, so that's all sensors ruled out.

[goose]

*Think* it's now fixed.

I think it was a combination of the the old crappy fuel gumming up the old fuel pump, and old crappy fuel. Hardly scientific, but just bench testing it against a new one of the same brand showed it was way down on pressure. New fuel pump and some more fresh fuel and so far so good.

I guess the plus side of a VS Commo is parts are cheap. New pump was $85.

We'll be running a bit more petrol through it from now on...