3000RPM Idling Problem

[strgas]

i have found in the past that most gas fitters are lazy and dont follow instructions to well and take a short cut by running the LPG processor earth wire to a body earth using a tek screw this in time can become a point of high resistance and a poor earth connection is now the cause of the problem as this will now force the power in the processor to seek another point of earth and can put voltage back thru the O2 sensor wire giving higher voltage readings , TPS voltage can be higher up to 12 volts depending on the resistance at the dodgy earth wire , can be intermittent at times when the car hits a bump and knocks the earth connection and it makes contact once again till such time as the resistance builds back up again , Im not saying this is your problem to the letter just a common problem i see most days , some systems can run with their processor disconnected altogether and may never have a problem plug it back in and the problem soon comes back . intermittent faults are the hardest one to find or even reproduce in the workshop .

 

[Sheriff69]

OK, the wife has just texted me with news that the car is playing up again! Seems to only do it when she's driving it cos I cant get it to do it!

Now the car is running on Petrol this time so we can now confirm that it does it on both fuel sources, LPG and Petrol.

When the car played up there was no engine warning light on the dash.

Are we getting closer to the problem now that we know it happens on both fuel sources or has this now made this problem more complicated?

Thanx for your advice strgas, totally agree with you on intermitant faults and not being able to reproduce them in a workshop environment. What do you now think?

 

[strgas]

your problem may be a result of a burnt out wire , dodgy connection or poor workmanship and now is present on both fuels given time the fault may become bad enough to stop the car running altogether .

 

[Sheriff69]

Oh great, the wife will be real happy then!

Do you think the problem could be computer related?

 

[strgas]

hard to say from behind the keyboard could be related to the ecm or just dodgy workmanship or part related ,

 

[Sheriff69]

OK, appreciate that. I'm going to PM you strgas to see whether your able to give us some further assistance.

Many thanx for your time in answering my questions.

If anyone else has had this problem then I sure would like to hear from you, please!!!

 

[strgas]

ok no worries

 

[Sheriff69]

strgas

PM sent.

Cheers mate : )

 

[Sheriff69]

Here we go again!

The wife has just dragged me out of bed to hear for the first time the car revving ta 2500rpm and not 3000rpm as first stated. I popped the bonnet and checked the throttle cable and the cruise control cable, both were slack and under no tension.

Electrically I wiggled every electrical connector I could from under the bonnet with no change in RPM. I checked the dash for any warning lights as the car is still on Petrol and there were no dash lights to indicate any problems.

I turned the engine off, waited 10 seconds and restarted the engine. The engine then revved at around 1500rpm, gave the throttle a quick 'squirt' and it then began to idle normally.

Apart from taking the car to an Auto Elec to look at does anyone have any other thoughts on what could be causing this?

Cheers

 

[VesperZ]

From memory the gas system uses a "piggy-back" ECU and uses that to control your gas system. If your car is running fine on Petrol then that pretty well isolates your issue to your gas system and it may very well be your gas piggy-back system causing the issue. The other thing is you should probably not be starting your car on gas as you really need to be running gas on a warm engine, not a cold one. But that is the extent of my knowledge with gas systems.