Fuel trim error codes.

[ANDTWENTY]

Ive had my 940 on the road a month now after it was sat for 2 years, I had the ECU re manufactured as that was causing it not to run which solved the issue. along the way I replaced the lambda sensor for a guanine Bosch one and got a spare MAF sensor.

About 2 weeks ago I converted the car to gas and it was around this time I noticed some running issues but only on petrol. When first starting up and it was cold outside the engine would jerk like it wasn't getting fuel. It would do this on low revs and low speed but not for long. this seemed to go within a week.

The second issue then appeared in the form of bad idle, when it was very cold outside but the engine was warm the idle would sometimes go up and down between 600rpm and about 1500rpm or it would idle at 1500 rpm. It only occurs once the engine is warm though.

During this time I had an engine light on for fuel mixture, the first time I put it down to the gas as I was getting it set up. The light came on a couple of days later but no codes so I 'cleared it' and it was fine for a day when it came back. this time I got 3 codes:

2-2-1 = fuel trim mid range lean
1-2-1 = faulty signal from maf
2-3-1 = fuel trim mid range rich or lean

I then swapped the MAF with the spare I had thinking this would be the cause for all the issues. I cleared the codes I tried the car again, this time getting the following codes straight away:

2-2-1 = fuel trim mid range lean
2-3-1 = fuel trim mid range rich or lean
2-3-1 = fuel trim idle to rich or lean

As I say the lambda sensor is new and the codes came up on petrol, any ideas? All I can think is that for the gas conversion I soldered a wire to the lambda signal wire so the LPG ECU gets a signal, could this be the cause?

[Laird Scooby]

Originally Posted by ANDTWENTY

Ive had my 940 on the road a month now after it was sat for 2 years, I had the ECU re manufactured as that was causing it not to run which solved the issue. along the way I replaced the lambda sensor for a guanine Bosch one and got a spare MAF sensor.

About 2 weeks ago I converted the car to gas and it was around this time I noticed some running issues but only on petrol. When first starting up and it was cold outside the engine would jerk like it wasn't getting fuel. It would do this on low revs and low speed but not for long. this seemed to go within a week.

The second issue then appeared in the form of bad idle, when it was very cold outside but the engine was warm the idle would sometimes go up and down between 600rpm and about 1500rpm or it would idle at 1500 rpm. It only occurs once the engine is warm though.

During this time I had an engine light on for fuel mixture, the first time I put it down to the gas as I was getting it set up. The light came on a couple of days later but no codes so I 'cleared it' and it was fine for a day when it came back. this time I got 3 codes:

2-2-1 = fuel trim mid range lean
1-2-1 = faulty signal from maf
2-3-1 = fuel trim mid range rich or lean

I then swapped the MAF with the spare I had thinking this would be the cause for all the issues. I cleared the codes I tried the car again, this time getting the following codes straight away:

2-2-1 = fuel trim mid range lean
2-3-1 = fuel trim mid range rich or lean
2-3-1 = fuel trim idle to rich or lean

As I say the lambda sensor is new and the codes came up on petrol, any ideas? All I can think is that for the gas conversion I soldered a wire to the lambda signal wire so the LPG ECU gets a signal, could this be the cause?

I seriously doubt soldering the wire from the LPG ECU Lambda input to the Lambda sense wire will cause the problem.

First thing i'd check is your LPG fuel map, i suspect you've got some multipliers wrong so the petrol fuel trims have now gone out to correct this. Could also be one or more gas injectors are leaking and throwing the fuel trim out. Perhaps because you fed the spuds in the underside of the inlet manifold and there's a pocket of LPG sitting in the pipes to the spuds that is slowly drawn in when on petrol and throws the trims out. I know LPG is heavier than air so will naturally sink but under vacuum will be able to be drawn in.

Did you renew the inlet manifold gasket when you refitted the inlet manifold? If not, it could be leaking air causing running problems on petrol.

Check all of these things and refit the original MAF, ensuring there are no air leaks anywhere between it and the throttle body/AICV.
By the way, if you set the LPG map up using auto-tune, that could be half the trouble, you may need to do it manually with the laptop on the passenger seat while you give it the beans up a few hills as well as normal driving. Get your pterol map first and then compare the LPG map to it.

What plug gaps are you running by the way?

[ANDTWENTY]

Originally Posted by Laird Scooby

I seriously doubt soldering the wire from the LPG ECU Lambda input to the Lambda sense wire will cause the problem.

The actual wire I didn't cut I just soldered the LPG one too it so if anything the LPG one shouldn't work

First thing i'd check is your LPG fuel map, i suspect you've got some multipliers wrong so the petrol fuel trims have now gone out to correct this.

can I see this by seeing if the petrol injectors operate on the LPG software?

Could also be one or more gas injectors are leaking and throwing the fuel trim out. Perhaps because you fed the spuds in the underside of the inlet manifold and there's a pocket of LPG sitting in the pipes to the spuds that is slowly drawn in when on petrol and throws the trims out. I know LPG is heavier than air so will naturally sink but under vacuum will be able to be drawn in.

If I turn the gas off and let it run out the lines then clear codes and re start the car this should point to a gas issue, right?

Did you renew the inlet manifold gasket when you refitted the inlet manifold? If not, it could be leaking air causing running problems on petrol.

I didn't, I gave it a check over and it looked good, it came off nicely and there were no tears or anything.

Check all of these things and refit the original MAF, ensuring there are no air leaks anywhere between it and the throttle body/AICV.
By the way, if you set the LPG map up using auto-tune, that could be half the trouble, you may need to do it manually with the laptop on the passenger seat while you give it the beans up a few hills as well as normal driving. Get your pterol map first and then compare the LPG map to it.

the other MAF seems to run better if anything and I haven't had the code for a bad signal come back though. The gas map was done using the auto calibration but has been running well so I haven't changed anything. the other thing is the hunting on idle is on the gas which makes me think its a sensor issue.

What plug gaps are you running by the way?

I can't remember off the top of my head but I think it was you that suggested the gaps when I changed them not long after getting the car.

When I set up the LPG I can see the lambda reading on the software and it was all over the shop, but the car has always run smoothly and well apart from the couple of idle issues

[Laird Scooby]

What was the Lambda reading doing on petrol?

*** EDIT *** Have you also checked what the Lambda reading is doing now?

[ANDTWENTY]

Originally Posted by Laird Scooby

What was the Lambda reading doing on petrol?

*** EDIT *** Have you also checked what the Lambda reading is doing now?

It was going from about 0.3 to 0.8 volts constantly up and down (on idle), when I did my other car it was smooth and constant. Not sure what is is now i'll hook the computer in and see.

[Laird Scooby]

Originally Posted by ANDTWENTY

It was going from about 0.3 to 0.8 volts constantly up and down (on idle), when I did my other car it was smooth and constant. Not sure what is is now i'll hook the computer in and see.

That's how it should be, give or take a smidge, sounds like your other car was in Limp Mode (even if it hadn't put the MIL/EML on) if it wasn't cycling up and down at idle.

Either way, first thing to check is that it's doing what it should now. Wouldn't be the first time a new Lambda sensor has failed in short order, had a few of those myself!

[ANDTWENTY]

Originally Posted by Laird Scooby

That's how it should be, give or take a smidge, sounds like your other car was in Limp Mode (even if it hadn't put the MIL/EML on) if it wasn't cycling up and down at idle.

Either way, first thing to check is that it's doing what it should now. Wouldn't be the first time a new Lambda sensor has failed in short order, had a few of those myself!

My v40 always had the engine light on, could never find a code or clear it but ran fine so left it.

The voltage may be slightly different I can't remember exact values but thats roughly what it was so sounds about right then.

I replaced the lambda sensor on my v40 before the gas conversion as I thought that was causing an issue I had, turns out it didn't work so put the old one back on and it gave a reading again. This one was working on the computer but will check what it says now the rain has passed.

[827Roverman]

Originally Posted by ANDTWENTY

Ive had my 940 on the road a month now after it was sat for 2 years, I had the ECU re manufactured as that was causing it not to run which solved the issue. along the way I replaced the lambda sensor for a guanine Bosch one and got a spare MAF sensor.

About 2 weeks ago I converted the car to gas and it was around this time I noticed some running issues but only on petrol. When first starting up and it was cold outside the engine would jerk like it wasn't getting fuel. It would do this on low revs and low speed but not for long. this seemed to go within a week.

The second issue then appeared in the form of bad idle, when it was very cold outside but the engine was warm the idle would sometimes go up and down between 600rpm and about 1500rpm or it would idle at 1500 rpm. It only occurs once the engine is warm though.

During this time I had an engine light on for fuel mixture, the first time I put it down to the gas as I was getting it set up. The light came on a couple of days later but no codes so I 'cleared it' and it was fine for a day when it came back. this time I got 3 codes:

2-2-1 = fuel trim mid range lean
1-2-1 = faulty signal from maf
2-3-1 = fuel trim mid range rich or lean

I then swapped the MAF with the spare I had thinking this would be the cause for all the issues. I cleared the codes I tried the car again, this time getting the following codes straight away:

2-2-1 = fuel trim mid range lean
2-3-1 = fuel trim mid range rich or lean
2-3-1 = fuel trim idle to rich or lean

As I say the lambda sensor is new and the codes came up on petrol, any ideas? All I can think is that for the gas conversion I soldered a wire to the lambda signal wire so the LPG ECU gets a signal, could this be the cause?

Can you show photo's of the installation please.

[Laird Scooby]

Originally Posted by 827Roverman

Can you show photo's of the installation please.

There are some on Pg51 of this thread David :

https://www.volvoforums.org.uk/showt...44#post2572644

You might even see one of your pics too!