MAF Sensor

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Doo

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I know I have said I am getting George on the computer some time next week, but in the meantime I wanted to ask if the MAF on these are robust?

I am having issues on both petrol and LPG the fact it is disappearing quicker than our Government makes me think I have a MAF issue.

After all, everything else has been replaced.

I am using 10/15 quids worth of petrol to drive 40 miles, so I "KNOW" something is amiss.

She fires up no problem, runs fine for a few minutes then starts with all the lumpy running and huge fuel usage and it just points to Mass Air Flow defaulting to rich mixture.

I'd be interested to hear if anyone else has suffered the same fate o_O
 
What year P38?

If it's a GEMS engine - then it's worth trying to clean the MAF - they can get crudded up over time - but generally respond to a good cleaning.
If it's a THOR engine - then the MAF doesn't really respond to cleaning and just goes out of spec. I had it happen to mine after I first bought it, and it got to the point it was running so rich, that the fuel trims were at the end of their adjustment and the engine would almost stall when idling at the lights. A replacement MAF and reset of the adaptive values sorted it out.

Also, the Thor engines do NOT like the cheap aftermarket MAF sensors... spend the extra and get a genuine Bosch one. I used a Bearmach one in mine to start with (as I didn't have the money for a genuine one) and it was over-reporting the amount of air coming in, so it was still making it run rich (but not as bad as the bad original one!) and eventually would pull the fuel trims out again as it tried to compensate. Bought a genuine Bosch MAF, fitted that, reset adaptive values - and then rich running codes disappeared, and she's been happy ever since.
 
When I put it in for the MoT the emissions level was 7.1 on CO2 :eek: and that was on LPG!?!?!

Did the O2 sensors, and 5 of the 8 plug leads as they sent wrong ones and some were too damn short. Went back and it only just scraped through the emissions on LPG.

Following day, replaced the plugs (couldn't get Champions so settled for NGK) and it ran better, but still rich on both fuels.

I suspect the MAF but I had a thought, she sat 5 years so is it possible the temp sensor is goosed?

She starts on the money, sounds lovely, revs cleanly with not a hint of missing or hunting.

Within a few minutes, she's lumpy as last years custard and hesitates under acceleration until you get to about 2500/3000rpm then she's away like a fat kid to a sweet shop :D

Again this is on BOTH fuels, but slightly less so on petrol...only slightly, but I think it's because it has more power than the LPG...

Normally we'd remove the MAF plug to see what happens, but not sure what will happen on this beastie.

Not sure which engine, but here a photo



I'm guessing that is little or no help so it has a aluminium manifold that resembles an octopus as opposed to the big black square box I've seen on older models....
 
Changed the MAF on our 4.0 THOR a couple of months ago and it made a stellar difference - changed from lumpy and unresponsive to instantly responsive and power restored.
 
Changed the MAF on our 4.0 THOR a couple of months ago and it made a stellar difference - changed from lumpy and unresponsive to instantly responsive and power restored.
Sounds about right. I have to floor it, wait for a kick down and she will pull, some what lumpily until the revs hit around 2500/3000, then it's all hands to the pumps. She goes, she just throws petrol straight out the back...

Getting a MAF next week, can't make it any worse :D
 
WTF?

Drove her to a gig on LPG and as I left I was aware the LPG was low, so switched back to petrol.

Watched the needle on the fuel gauge expecting it to ping off the end with such speed I could feel the judder...but No! The gauge actually barely moved!??!?!?!?

I drove all the way home at 50mph, up a few long steep hills, but she behaved immaculately! Smooth and sweet.

The only difference was the weather, it was night, cold and damp (9 degree's C outside temp) so this has me confused now, unless the cold air has "numbed" the MAF :D

I'm going to spray it with brake cleaner today and see if it does the trick in the short term til the new one arrives.

In the meantime, What The Flip? o_O
 
Lulling you into a sense of false security.
Aye, the sneaky witch o_O

Towed my Doblo on the "A" frame to mates garage and my Clio back home, am left with half a tank (bare in mind the so called petrol tank barely holds 30 quids worth :mad: )

The LPG system is a joke. Donut tank is more than enough in my humble...

Seriously needs a service and I would love to bin the two tanks underneath and re-install a proper size petrol tank.

If anyone has a full size petrol tank I may yet be a customer ;)
 
Spoke to Kenny, our works mechanic, a genius.

Told him of the petrol drinking woes and he suggested that the ECU may need a kick in the butt because the LPG runs lean so the (new) O2 sensors are telling the ECU to up the mix and therefore the serious petrol usage.

I am not 100% certain this is the case, but soon as I get her to Hamish I will know.

Off to look for a petrol tank now.....
 
I was having this issue not so long ago aswell with running it on LPG and the map not being quite right and a couple of kinks in the hoses.. As the Multipoint LPG systems slave off the petrol system, if the LPG map is wrong and running too rich/lean, then the petrol ECU will adapt its fuel trims to get the mixture right, but will then obviously run stupidly rich/lean on petrol.

In my case as 4 of my 8 cylinders were getting naff all LPG (kinked hoses - it's a long story, but it's running great now!) the fuel trims got rammed right to the limits, and then going back to petrol it ran like a dog and stupidly rich, because the trims were totally maxed out.

When you boot it, the system goes back to running open loop, so will naturally run a bit richer and the ECU ignores the lambda sensor inputs until the engine load decreases, which may be why it runs better with a heavier right foot, and uphill when the engine is under some load.

Ideally it would need the fuel trims reset, run about on petrol for a bit for it to adapt itself to running on petrol happily, and then get the LPG re-tuned once it's happy on petrol - so that way it won't be constantly forcing the fuel trims out of whack.

Either that, or it could still be the MAF, as I've been through that saga aswell (incidentally on the day I picked it up after buying it!)
 
Yes, it was funny it ran fine for a bit, then a bit smelly again.

However, I can't really tell what my fuel usage is thanks to that feckin egg cup of a tank :mad:

But I towed my Doblo about 10 miles and my Clio the same on the return journey and she ran sweet as (obviously under load while towing).

I want to run it on petrol until the LPG system is repaired and those silly tanks removed. I can buy a tank on ebay for 45 quid, but not sure what is missing exactly. Breather pipes and whatnot....

Worra pain o_O
 
You have a Thor engine there with the Motronic Ecu. On cold start it will run open loop, that is setting the fueling to a good guess based on previous drive cycles. After warm up it will go closed loop and adjust the fueling depending on the feedback from the sensors - MAF, Lambda etc.
Simple test for the MAF- should read about 22 kg hour on tickover ,warm with no loads on the engine.
Dont buy cheap !
 
You have a Thor engine there with the Motronic Ecu. On cold start it will run open loop, that is setting the fueling to a good guess based on previous drive cycles. After warm up it will go closed loop and adjust the fueling depending on the feedback from the sensors - MAF, Lambda etc.
Simple test for the MAF- should read about 22 kg hour on tickover ,warm with no loads on the engine.
Dont buy cheap !

I bought an E320cdi Mercedes estate and for a whole year I ran it ONLY on BP Ultimate diesel.

My emissions were allowed 3.50, the gas blast reading was actually 0.22. Not bad for a car with 197,000 miles on it ;)

I will only use good fuel, Tesco can go shove it's bonfire fuel up it's rectum :p

I will find if the MAF is knackered at some point in the next week or two.

But thank you for your input :)
 
I know I have said I am getting George on the computer some time next week, but in the meantime I wanted to ask if the MAF on these are robust?

I am having issues on both petrol and LPG the fact it is disappearing quicker than our Government makes me think I have a MAF issue.

After all, everything else has been replaced.

I am using 10/15 quids worth of petrol to drive 40 miles, so I "KNOW" something is amiss.

She fires up no problem, runs fine for a few minutes then starts with all the lumpy running and huge fuel usage and it just points to Mass Air Flow defaulting to rich mixture.

I'd be interested to hear if anyone else has suffered the same fate o_O
 
I know I have said I am getting George on the computer some time next week, but in the meantime I wanted to ask if the MAF on these are robust?

I am having issues on both petrol and LPG the fact it is disappearing quicker than our Government makes me think I have a MAF issue.

After all, everything else has been replaced.

I am using 10/15 quids worth of petrol to drive 40 miles, so I "KNOW" something is amiss.

She fires up no problem, runs fine for a few minutes then starts with all the lumpy running and huge fuel usage and it just points to Mass Air Flow defaulting to rich mixture.

I'd be interested to hear if anyone else has suffered the same fate o_O
I seem to have the same problem I have an RR Supercharger SE Vogue. 2006 , Just had a service, car ran ok, after a week , began to run rough, took back to garage, no faults on there comp, so they suggested it may need a new MAF sensor, have ordered one Denso, as that's whats already on the car, will let you know if it works,
 
Checking the maf... Disconnect whilst running a slight stutter then normal running is good. No change means maf fubar.
This is a cheap rule of thumb. In fact disconnect most sensors(not crank though) if the fuelling improves bingo! Most sensors have faila safes in place that when disconnected trigger often resulting in better running hence exposing the out of spec but still working sensor. Obviously a totally gone sensor will throw a code or 6!
Jb
 
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