Hey guys,

Recently got a '94 EF XR6 and after putting it onto lpg i've had some serious idle problems.

When I put the clutch in and stop at the lights the car often drops to 2/300 rpm and sometimes stalls if i don't catch it. I've replaced the ISC which seemed to help the problem but not fix it completely. I recently blew a hole in the air intake (may have given it gas when starting on lpg ).

I replaced that but it has reverted back to running real rough - not sure if that has to do with running around with the broken air intake. The problem is much more noticable when running on lpg.

The odd thing is that it doesn't always drop in the rpm - sometimes it will idle at around about 1000rpm - its almost as though something gets stuck and stops it from working properly and then on a whim decides to play ball. When it is idling properly though if i rev slightly over 1000rpm and back off quickly it'll drop down to about 6-700 and then go back up to about 1200 before it'll even out.

When taking off it has like a flat spot - as in you can't take off gradually or coast along in traffic jams. Once you get over the spot where its either on or off it drives fine and i don't seem to have any problems with actual driving.

I've done a fault code check and its come back with 214 and 227 - CMP & Knock sensor faults. I've heard varying opinions on the usefulness of a CMP sensor - but could this be causing the issues that i describe?

I'd be looking at lean LPG setup,
The knock sensor will generally does display a fault when using Non-Factory LPG systems.

What system is it? does it have a balance pipe (to air box) etc?

Its a Landi setup, and yes it has a balance pipe going to the snorkel just after the mixer ring (airbox end).

(Fizzer is here now - we're trying to get it to go a little better)

It runs 100% on fuel, ISC is being controlled perfectly, no stalling.

The Gastec controller shows a continual rich condition on idle, and goes to lean momentarily when blipped. Going to try the tune instructions suggested by MacGyver on a previous post and see how it goes.

Just to clarify the Landi converters, is the top larger screw with spring the sensitivity screw, and the smaller one the bypass? Are they effetively the same screw, but one is a fine, and the other a course adjustment of air bypass? (ie is it the same as the screw on a complex mixer to control air bypass?)

Seems that the lpg was a bit of a red herring.

Gizmo and i had a play and managed to tune the lpg so it was running perfectly last sunday... but alas it had reverted to its old ways by monday.

I took a video of the taco to show you guys exactly what its doing... usually it'll gradually go down further and further until it almost stalls then rev up. This is running on petrol by the way.

http://www.leetbix.com/tacho.html

If you can borrow one, or source a cheap one, try swapping over ECU's. EF ECU's blow components all the time, especially when the ISC is problematic. If it goes away after running the relearn procedure you've found your problem.

As a test only, i'd like to see how it goes for a week without ISC control at all.

Run engine until normal temp achieved, unplug the isc and up the idle to a comfortable 850 or so. Expect the engine to bog down a little with AC on or steering turned, and to run a little low when cold started.

What I'm interested in finding out is if the ECU is trying to control RPM using spark or similar (if it senses a failed ISC or ISC circuit)

Run it this way, thro a timing light on it on both lpg and petrol and see if the spark is jumping around at idle when it starts to lope.

Let me know what you see. Do this both before and after you unplug the ISC and set idle.

Hey guys, sorry i haven't updated in a while been too busy to play cars.

EBGizmo and I had another look at it on the weekend and i did the no ISC test like he suggested. I unplugged the ISC and upped the idle using the idle screw. Ran it for a while and it didn't seem to really make a difference.

I can now confirm that the problem happens on LPG and Petrol but i'm convinced the problem only started occuring when i had the gas installed.

I recently had the head gasket replaced as it was leaking into the oil chamber thinking that was the problem. I no longer lose coolant but this idle thing is still happening. Also when i got it back from the mechanics after having the head done it seemed to run sweet for like 2 days - gradually getting worse. I noticed that the battery had been disconnected - i don't know why that would make a difference.

Gizmo also said it smelt like petrol (when running it on lpg) and it seemed to be running real rich and vapour coming out of the exhaust. He said it could be an injector leak? Does that fit the MO and how would one test for that?

Car engine seems to run really hot - you can really feel the heat radiating off of it - the temp in diagnostic mode is only reading ~78 degrees and when i d/c the coolant temp sensor the thermo fans work.

I'm going to take it to a lpg specialist when i have the cash but i'm eager to try any suggestions you guys might have.

One thing I didn't check was how the installer wired into the oxy sensor.

I may be wrong (i'm sure someone will correct me if I am ) but if the installer has simply "tapped in" so the oxy signal instead of using a relay to move it between the lpg and ecu, the ecu might still be trying to change the fuel maps based on the lpg mixture (if its too lean or too rich)

I could definately smell fuel out the back when it was on lpg and idling crap, so either you have a really leaky injector, or the ECU is seeing a lean lpg mixture and going "i'll try and fix this" and upping the fuel map or other tables. Once put back onto petrol, it will be using this incorrect map and unlearning over and over again each time you change over.

We'll have to test this with a known good ego sensor and maybe my Jaycar mixture display kit (i'll have to dig it up - lost it in the move)

One mistake your installer made was wiring the "pump saver" relay (fuel pump killer) into the dash switch, and then saying he connected fuel start assist to the lpg computer.

Sure, he wired the LPG side of it up correctly, but he had the dash switch controlling the fuel pump cutout directly. In other words, once put on LPG and left there (on the dash switch), you have available however many fuel assisted starts you can use with the fuel pressure left in the lines. That pressure will probably be gone overnight, or at the end of the week. The switch was controlling the fuel pump, not the LPG computer or some other arrangement.

While the install itself is very neat and tidy, the wiring and logic was not well planned at all.

*bump* Any ideas guys?