Thread: MAF ?? 94 V8i

The engine will start with the MAF unplugged, but you be lucky to get more than 150ks out of a full tank of fuel and if it needs the MAF for gas, I wouldnt even think about starting.

Revving to 1900rpm on start up is a little high but this is a trait of the V8 and its not abnormal. When you turn off the ignition, the idle stepper winds back to a full open position. The next time you start it, it revs higher until the stepper adjusts the idle speed.
The 1400rpm max is a bit odd though. Try this...

Depending on how often you run it on petrol, I would take a look at the fuel system first. If it sits stagnant over time from running on LPG, fuel will go off in the rail and can get water and rust deposits in the rail. Subsequently the fuel reg can block and generally end up stuck open resulting in a low rail pressure.
A problem with the fuel system is the way the fuel filter sits with the outlet side sitting lower. These filters also arent water separation type filters, just standard everyday paper filters no different to a Z14 filter, just in a metal can so water does pass straight through affecting the rest of the fuel system.
The water ends up pooling in the filter, subsequently rusts the inside of the filter housing and the element, which is only glued to the inside of the filter by the sponge rubber you normally find on the ends of filters, lets go and your system is chokka with crap. I have had this happen twice in succession with Cooper fuel filters which are from the same factory as Daewoo OEM ones (they even have the GM part number on them) and are absolute rubbish. I still have crap floating around in my tank now.
Should have taken some pics of the filter after I cut it open. Changed it as a routine thing and ended up straight back out to the workshop and stripped the entire system short of dropping the tank. I got gallons of crap out.

Anyway....... try this and see how you go....

Plus, if you have never had the rail off, its time to do it and clean everything out. You will be surprised at the amount of crap that gets caught up in the injector cups.

Cheers

Andrew

Thanks for the imput Andrew,

The thing is, the car runs & revs fine on petrol, idles perfect, but the only way to get it on petrol is Driving or reving on LPG and then change to petrol, and you wouldn't know there was a problem.

If you try to start it from scratch on petrol, then i have the problem,

Electrically there's something not right with the efi starting procedure,
Thats what lead me to test the TPS and MAF settings.
(It was me who e-mailed you yesterday)

The MAF is now set to 1.3 volts but made no diff, but as stated the TPS goes from 0.3 right up to 8.9 volts at WOT.

I thought maybe the TPS was crook and causing the problem (going up to 9 volts) but tested with engine running and it's only on about 2 volts when engine wont rev any further.

Also when i unplug the MAF it will rev again, maybe the MAF is stuffed although it shows to be putting out voltage

Luke

Think you have a problem somewhere in the LPG wiring.
The MAF and TPS are inputs to the ECU and are not interconnected.
If you disconnect the MAF while running, the ECU reads a fault and goes into "limp mode" being the richest settings. By plugging the MAF back in while its still running, it will receive MAF signals, however it will stay in limp mode.

How long have you had the LPG on for?? The 9V is in my mind the issue and if the LPG is hooked into the TPS for any reason, this may be the problem.

I would suggest putting the TPS and MAF on another car if you know another AULRO member close by who is willing to help, and test them in a different environment. I would even swap the ECU as well and see if things change.
Be aware that you will need them to be same model.

Cheers

Andrew

Well,
Problem solved
I was suspect this was the case,
Got a second hand MAF, off a vehicle thats never been on LPG, cleaned it up, and presto

I wonder if it will alter the LPG consumption??

The old MAF was causing the petrol start problem.

It looked fine and regulated voltage, but it seems you can't go by that.

Thanks again Andrew for your help.

Cheers Luke