VR Commodore stalling when coming to a stop or taking off

[joe123]

Hey guys, been searching around the forums for a solution to my problem but haven't had any luck.

The car is a v6 executive commodore automatic, dual fuel; it runs fine on gas. However, on petrol, it stalls when coming to a stop or tuning a corner, not always, only sometimes, usually when the engine has been running for five minutes. A detailed description of the problem:

So far I've had three occurrences all slightly different. First time the engine stalled when I completed a right hand turn at a set of lights, I attempted to accelerate out of the corner, but it died.

Second time it happened when I was slowing down to merge into the left lane, I was braking not accelerating.

Third time I did a left hand turn at the traffic lights, it died whilst turning, power steering obviously disappeared which wasn't a good feeling.

So I'm guessing it's something to do with the idle control, but I can't be sure. It's only started happening after I got a new radiator installed, and I filled up at a Safeway fuel station recently. So I want to empty the tank and fill up with some better stuff to eliminate that issue.

But my theory is since installing the new radiator, the engine is running cooler, thus the computer isn't recognising that the temperature is cooler? Is there a way to test the coolant sensor?

To top it off, my diagnostic system does not work; the engine light will not flash at all when I insert a paper clip into pins 5 and 6. The fan turns on, but the engine light display comes on for a second and that's it.

Any input would be appreciated.

EDIT: Fuel tank has been between full and 3/4 when the stalling's occurred.

 

[Bourbonated]

Is the globe blown on your CEL? That's pretty easy to replace if it is. It will be much easier to diagnose that way... Otherwise I would suggest:

1) The first one sounds like what my car is doing at the moment.. Get your Fuel pump looked at. It is (obviously) working but might have slipped out of its well and/or the hose inside the tank has moved.
2) Disconnect your battery for a few minutes to reset the IAC valve. Your car will idle high when you start it up again.. Just take it for a drive until it settles (Not really necessary you do it right away.. Any time you need to go anywhere, just do it before hand). If your problem subsides after doing this, it's probable (But certainly not definite) that you may need to replace it.
3) As for your coolant temperature sensor, it's probably "easier" to go buy one from Holden.. Last I heard they were like $25. Cheaper if you shop at any of the major Auto stores.

 

[joe123]

Is the globe blown on your CEL? That's pretty easy to replace if it is. It will be much easier to diagnose that way... Otherwise I would suggest:

1) The first one sounds like what my car is doing at the moment.. Get your Fuel pump looked at. It is (obviously) working but might have slipped out of its well and/or the hose inside the tank has moved.
2) Disconnect your battery for a few minutes to reset the IAC valve. Your car will idle high when you start it up again.. Just take it for a drive until it settles (Not really necessary you do it right away.. Any time you need to go anywhere, just do it before hand). If your problem subsides after doing this, it's probable (But certainly not definite) that you may need to replace it.
3) As for your coolant temperature sensor, it's probably "easier" to go buy one from Holden.. Last I heard they were like $25. Cheaper if you shop at any of the major Auto stores.

Thanks for that, I haven't attempted any of the above yet but I have adjusted the engine idle so that it idles a bit higher and filled up with 95 RON petrol, so far so good. Regarding the diagnostic system, the CEL light is working, but as to why it does not flash, I think it has something to do with the car being converted to gas.

 

[Bourbonated]

Also! I forgot to mention, if its happening while you're braking, your master cylinder MAY have a vacuum leak between it and the Throttle body. While idling, stick your foot on the brake and if your RPM's drop, you will have to get that checked out, too.

 

[Cheap6]

I have adjusted the engine idle so that it idles a bit higher

Unless you moved the throttle stop screw a very long way, actually you didn't adjust the idle. The idle speed is controlled by the IAC valve with the idle stop screw merely determining the slowest idle speed (throttle opening) which the opening IAC valve then increases to varying degrees. You will, at some point, need to put that screw back to where it was or at least adjust the base idle speed (almost the same thing).

What you have described is symptomatic of a dirty or sticking IAC valve. There are "How To's" and posts on how to clean that valve, the throttle body and throttle plate. Do not use carb. clean, at least where it can run into the spindle bushes or bearings that the shaft for the throttle plate rotates in, as it can wash away the lube for the shaft. Remove the IAC valve to clean it and the air flow passage it blocks properly. Lubing the screw thread for the IAC with Lithium based spray grease is possibly useful but you may do more harm than good. You will have to make judgement call on that based on what the old grease is like.

When you have cleaned the IAC valve and assuming that there are no other tune problems such as vacuum leaks, ignition or mechanical induced misfires, you can readjust the base idle/throttle stop screw. There are also posts and "How To's" on that.

I think it has something to do with the car being converted to gas.

Possibly. The air:fuel mixtures on LPG can be different to those on petrol, affecting the idle speed. The PCM learns IAC valve positions - every time the car runs - while on one fuel and then is "caught out" trying to use those positions as a baseline when the other fuel is used.

 

[joe123]

I'm not sure if this is related but the other day when I had a full carload travelling approx 90km/h, a kangaroo jumped out, I slammed the brakes, abs didn't kick in, but I noticed the brake light appeared on the dash. I checked the brake fluid level it was fine, however the cover seal had fallen down into the reservoir. Could this have had an effect on the brake vacuum/performance?

I tested the brake vacuum level by turning off the engine and pressing the pedal a couple of times to deplete the vacuum, and with the pedal pushed in, i turned the vehicle on, in which the pedal pushed in further, which means the booster is ok?

As for engine idle on petrol, when the brake is applied, the engine rpms do not drop, however on release, the engine revs up for a second, then returns back to normal. On gas, when the brake pedal is released, the engine almost stalls, then returns back to normal.

Might take a look at IAC valve this weekend, the car has not stalled so far this week. Thanks for your input.

 

[mattyb220992]

I didn't read the whole thread cos I couldn't be bothered, I used to have issues with my VS automatic with stalling. It used to stall at random times and refuse to start for any amount of time. Try cleaning out the automatic transmision fluid I did this and this temporarely fixed the problem I was having but it shortly started again. After that I replaced my crank angel sensor, this completely fixed that problem and I haven't had the stalling problem since.

 

[Nathan kenny]

Thanks for that, I haven't attempted any of the above yet but I have adjusted the engine idle so that it idles a bit higher and filled up with 95 RON petrol, so far so good. Regarding the diagnostic system, the CEL light is working, but as to why it does not flash, I think it has something to do with the car being converted to gas.

 

[Nathan kenny]

I have a 96 vs commodore acclaim I go to slow down for a set of lights get to about 20-10 even lower the car likes I wants to stall it sounds like it missing I have changed the DFI new coil pack new leads and plugs

 

[Nathan kenny]

I have a 96 vs commodore acclaim I go to slow down for a set of lights get to about 20-10 even lower the car likes I wants to stall it sounds like it missing I have changed the DFI new coil pack new leads and plugs