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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Fuel trim error codes.Views : 441 Replies : 8Users Viewing This Thread : |
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Dec 8th, 2019, 16:16 | #1 |
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Fuel trim error codes.
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? |
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Dec 8th, 2019, 20:54 | #2 | |
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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?
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Dec 8th, 2019, 22:09 | #3 | |
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Dec 8th, 2019, 22:20 | #4 |
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What was the Lambda reading doing on petrol?
*** EDIT *** Have you also checked what the Lambda reading is doing now?
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Dec 9th, 2019, 09:28 | #5 |
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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.
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Dec 9th, 2019, 10:45 | #6 | |
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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!
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Dec 9th, 2019, 12:18 | #7 | |
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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. |
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Dec 10th, 2019, 12:48 | #8 | |
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Dec 10th, 2019, 13:50 | #9 |
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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!
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