Sooty Lambdas on Petrol, wont LPG

[rewmer]

We did buy a genuine MAF didn't we?

 

[DanClarke]

Genuine Chinese MAF you mean?
Is there likely to be a difference, it's such a simple device in essence and was sold as being suitable by that nice Mr. Wong on Flea-Bay.

Plan B is to clean the old Bosch one and re-install it to see if there's a difference in behaviour.

 

[Datatek]

Genuine Chinese MAF you mean?
Is there likely to be a difference, it's such a simple device in essence and was sold as being suitable by that nice Mr. Wong on Flea-Bay.

Plan B is to clean the old Bosch one and re-install it to see if there's a difference in behaviour.

There is your problem The cheapo ones often give different readings to the genuine article.

 

[DanClarke]

There is your problem The cheapo ones often give different readings to the genuine article.

Well, I have thoroughly cleaned the Bosch MAF that was on there and I have the same symptoms as with the cheap-o MAF. Which can mean both are no good, or that both are fine and the problem is not the MAF at all (although it is suspicious that playing in the MAF area produces positive results).

Sometimes it will work fine on LPG and changeover nicely; and other times it just dies. I will re-run the LPG calibration (when it stops raining) the next time it successfully does an initial change over. It may be that the LPG system is out of whack and so running is "borderline". However, this doesn't explain the rich-running on petrol.

Basically, I think she's a sick-puppy. Perhaps it is time to get a LR specialist :fighting2: to connect diagnostic kit to it and clear all codes and reset the fuel trims.

I am however very grateful for all the advice & guidance from all of you good folks on here.

 

[rewmer]

We need to get some readings from the MAF before you decide it (they) are no good.
The below figure are confirmed good readings from a 4.6 THOR. Make sure all loads are off the engine and its up to temperature.

Idle 680rpm - 22Kg per hour
1200rpm - 32.5Kg
2000rpm - 55Kg
3000rpm - 92Kg.

The Chinese MAFS are ****e.

Forget the LPG for the minute and get her running on petrol first

 

[DanClarke]

Thanks Rewmer,

I will have another crack at her tomorrow.
The cheap reader I have said that on my idle (which is not 680RPM) there was 6.325g/S at idle RPM and no-load.
So, if that's true 6.325g x 3600/1000 = 22.77Kg/Hour

I have not tried any other RPM's, but I certainly can do.
Thanks for providing the sample figures above I will try to get the readings as best I can although getting exact RPM's isn't always easy.

Thank you very much though for your continued help.
I shall report back in due course. Yes I agree that getting it running right on Petrol is the first step. LPG can wait.

 

[DanClarke]

UPDATE
=====
I checked the MAF functions across a range of RPM values and it looks to be working.
It is very hard to get steady RPM's because the fuel trims seem to be so out of whack but here is what the scanner reported (just a few points, but seem to be consistent).
735 RPM 7.35g/s = 28.44Kg/Hr
1357 RPM 11.01g/s = 39.64Kg/Hr
1805 RPM 15.39g/s = 55.40 Kg/Hr
3032 RPM 25.95g/s = 93.42 Kg/Hr

This would suggest to me that the MAF is working fine (old BOSCH one cleaned up).
Still running incredibly rich so I think it needs a Nanocom (or similar) to reset the fuel trims.
I also now have persistent EAS & Traction messages I cannot clear (although the brakes are fine).

 

[ovalandrover]

UPDATE
=====
I checked the MAF functions across a range of RPM values and it looks to be working.
It is very hard to get steady RPM's because the fuel trims seem to be so out of whack but here is what the scanner reported (just a few points, but seem to be consistent).
735 RPM 7.35g/s = 28.44Kg/Hr
1357 RPM 11.01g/s = 39.64Kg/Hr
1805 RPM 15.39g/s = 55.40 Kg/Hr
3032 RPM 25.95g/s = 93.42 Kg/Hr

This would suggest to me that the MAF is working fine (old BOSCH one cleaned up).
Still running incredibly rich so I think it needs a Nanocom (or similar) to reset the fuel trims.
I also now have persistent EAS & Traction messages I cannot clear (although the brakes are fine).

Do u mean ABS and traction message ?
If so it might be an easy fix by adjusting the brake light switch by pulling out the plunger while holding the brake pedal down and then releasing the pedal and it should self adjust.

 

[DanClarke]

Yes, I did mean ABS & Traction LOL. Not EAS & Traction. Oops!
I will give your suggestion a try. Thanks.

 

[martyuk]

Save the messing about and buy a genuine Bosch MAF.

I had a load of the same problems when I first bought my 2001 4.6 (also with LPG). I had a load of rough running issues, and replaced the MAF with an aftermarket Bearmach one, which wasn't one of the cheap and nasty ones - it was mid-range in price. as I couldn't afford a Bosch one at the time.

It got me back up and running, and after resetting the fuel trims, everything seemed fine. After awhile checked engine ECU and saw that I was getting rich running codes all the time, and the fuel trims were jammed all the way in one direction.

Finally worked out that the aftermarket MAF was showing a very slight increase in air flow at idle, which meant it was overfuelling all the time and in the end the ECU runs out of adjustment and it just runs worse and worse.

Managed to get the money together for a proper Bosch MAF. Reset the adaptive values (you don't *have* to do this as the ECU will relearn over time - approx 100 - 150 miles I've been told, but resetting the adaptives gets the ECU back in spec from the start) and after a bit of mileage, no codes came back.

I tried cleaning my Bosch MAF aswell, but didn't make any difference. I think they are calibrated to such a precise amount that when they get old and drift out of spec a bit then it's just replacement time. The earlier GEMS vehicles seem to respond a lot better to cleaning of the MAF than the Bosch ones do.

Hope this helps