MAF or Not??

My car keeps flagging up the same fault with a MAF, even though I tried a brand spanking new Bosch one, which was then exchanged for another with the same result!

It seems to come & go. Last time the actual fault was a loose pipe (IACV to after MAF intake to inlet) so I fixed that and it's still fixed, but I once again have the MAF fault logged

So, giving the benefit of the doubt to the new MAF, the wiring seems to be fine, although I only checked the bit to the plug. Now, on saying that, the plug has been taped up from a previous repair, but no visible signs of breaking, chaffing or splitting.

So is there another place the wiring would normally get damaged on these (like in the Clio it chafes at the ECU guard for instance)??

Or is it possible the LPG system causes some fault (doubtful)???

I can't seem to locate any fault

Whats the fault?

Starts & runs on petrol, drives ok. Once warm & switched to LPG, it runs fine, but when you demand a little juice it feels hesitant as if there's no fuel! Sometimes it even cuts out, like when I was going onto the roundabout the engine died It started immediately on petrol and ran fine until it switched and although it didn't cut out again, it was still hesitant.

I put my code reader on and it showed MAF so I binned it and it came back.

Yes, but what did it say about the MAF?

Well, it was a generic reader so just MAF fault. However, it flagged up same fault when read by RR dedicated code reader. That's why I changed the MAF then got an exchange a few days after...

But this seems to have been going on since I got the car

Thing is, it starts on the button, it doesn't blow black smoke, uses normal amount of fuel, doesn't seem to hunt on petrol, only LPG but the LPG system is otherwise fine. It only seems to be on demanding fuel like a hill or accelerating hard.

Thought perhaps an air leak, but that would cause revving and falling....

Are you able to read live data with your device - I have a generic ELM327 device with the EasyODBII software and that can read certain live data parameters on the P38 Petrol - maybe you could hook up and read the MAF air Flow information and see if it rises and falls with acceleration.....

BUT, the fact it runs well on petrol suggests it is an LPG issue - what make is yours?

My mate has a pretty good system that reads live data (found my mates sons Clio is chugging at idle and the ignition timing is advancing a lot +35, then retarding by -2.37 then it settles to approx +6. I think that's a compromised O2 sensor as the head gasket went before the timing belt snapped. It shows no other faults and a brand new crank sensor was fitted because they are a known fault on Renault's in general, but especially the Clio...).

Anyhoo, I thought that too, but the fact it flags up a MAF fault when the car is running on petrol (I manually switched off the LPG) would have an effect on LPG as it runs lean anyway, so I think if it is running leaner would cause the O2 sensors to go crazy.

To be clear, it runs fine at all times & under all conditions when on petrol?

Ratae said:

To be clear, it runs fine at all times & under all conditions when on petrol?

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I think so... Trouble is, I start on petrol then it switches to LPG.

Sometimes I switch back to petrol to keep it reminded of it's true nature, but only for a few miles of foot to the floor overtaking or up some steeeeep hills with a tow on. So to say it cruises along fine may be a bit of a misnomer as I very rarely just trundle on petrol.

Saying that, I hope to take it twelve miles to mates garage tomorrow or the next day to get it live data read and see what's actually going on.

However, I wish to reiterate, I cancelled the MAF fault code (0101 if I remember correctly) and it came back soon as I started the engine.

Convinced it's wiring, but not sure "where" exactly to start looking as I've checked the spur to the MAF

when were the filters changed on the LPG?

My 2001 4.6 Thor runs like a bag of crap with poor acceleration, and misfiring when the plugs get worn. LPG eats them. a new set of BPR6ES and it runs like a smooth v8 should. the fault codes thrown up from bad plugs is usually a misfire.

i would say first port of call is LPG filters. until you get a smooth flow through to the engine you'll be chasing ghosts

ukadamwest said:

when were the filters changed on the LPG?

My 2001 4.6 Thor runs like a bag of crap with poor acceleration, and misfiring when the plugs get worn. LPG eats them. a new set of BPR6ES and it runs like a smooth v8 should. the fault codes thrown up from bad plugs is usually a misfire.

i would say first port of call is LPG filters. until you get a smooth flow through to the engine you'll be chasing ghosts

Click to expand...

Brand new less than 1000 miles ago, that and new plugs and the MAF.

This started around the same time as the lights staying on and the ABS & TC stupidity as soon as I start reversing.

it cant be the wiring if it runs fine on petrol and not on LPG !

ukadamwest said:

it cant be the wiring if it runs fine on petrol and not on LPG !

Click to expand...

But whats causing the MAF fault code?

Unless its sucking air after the MAF which is causing both a MAF fault code "and" a weaker than normal mix. After all, it doesn't take much to weaken an already weak (LPG) mix.

unmetered air is a possibility are all the HT leads on properly?

throwing a MAF fault code is intersting especially if it presents with different Bosch MAFs.. on your generic code reader can you look at the O2 sensor readings live ? they only function when engine up to operating temp so you'll have to check with a warm engine.

The O2 sensor could be weak, thus throwing a spurious reading to the MAF resulting a MAF fault code. i've had that happen to me. Look atthe readings and compare, you might find one lagely different to the other. i cant remember the reading range off the top of my head but its easily sought out with some googling.. or Wammers could tell you the readings, backawards, upside down and back to front

ukadamwest said:

unmetered air is a possibility are all the HT leads on properly?

throwing a MAF fault code is intersting especially if it presents with different Bosch MAFs.. on your generic code reader can you look at the O2 sensor readings live ? they only function when engine up to operating temp so you'll have to check with a warm engine.

The O2 sensor could be weak, thus throwing a spurious reading to the MAF resulting a MAF fault code. i've had that happen to me. Look atthe readings and compare, you might find one lagely different to the other. i cant remember the reading range off the top of my head but its easily sought out with some googling.. or Wammers could tell you the readings, backawards, upside down and back to front

Click to expand...

That was my thoughts. I'll get Ian to read it soon as I get there. She's mint on cold starts as it runs open loop (as you know) so no O2 sensor input. However, a thought... I am certain there is a slight exhaust leak, possibly somewhere near the manifold or the 1st joint at the cat. I can hear it some days, but not others

So I guess an exhaust leak would cause a similar problem!

I know an exhaust leak can cause an MoT emissions failure!
If it's before the O2 sensors it's going to upset them too.

Ratae said:

I know an exhaust leak can cause an MoT emissions failure!
If it's before the O2 sensors it's going to upset them too.

Click to expand...

Found the leak. It's the tiniest pinhole blow from the joint between the left manifold & the cat down-pipe. New gaskets should fix that.

It would appear the front right ABS sensor is faulty... Then not, then faulty... I saw the fault on the screen, it said FR sensor, but I can't recall "what" it was about. Anyway, I undid the plug and the pins were gleaming! Retested the ABS and no fault. Drove it and ABS & TC lamps went out, but the Traction Failure legend still came up on the dash. So could that "still" be the FR sensor?

Did live data and NO MAF fault found! That's after I drove it 12 miles. Drove fine too.

Drove home and on both petrol (although not to the same extent) and LPG was showing hesitation on accelerating. Hunting and hesitation much worse on LPG.

The Cruise Control system had about eleventeen million faults

Power out to the pump low when should have been high - Intermittant

Internal ECU fault - Permanent

Power out to the pump is high when it should have been low - Permanent

Power out to the valve is high when it should have been low - Permanent

Power out to the valve is low when it should have been high - Intermittant

Control out to the pump is low when it should have been high - Intermittant

Power out to the pump is high when it should have been low - Intermittant

Speed input fault - Intermittant

Power out to the valve is low when it should have been high - Permanent

Control out to the pump is Low when it should ahve been high - Permanent

Speed input fault - Permanent

Internal ECU fault - Intermittant

Power out to the valve is high when it should have been low - Intermittant

Control out to the pump is high when it should have been low - Intermittant

Brake lights - OFF

Brake/clutch switch - Pressed (except it wasn't and I don't have a clutch so could this be one of the problems, switch faulty as well as ABS sensor??)

Cruise Control - Inactive

Resume Switch - Released

Set Switch - Released

Speed Input signal - not detected (because I was parked)

Read again with brake pedal pressed:

Brake lights - On

Brake/clutch Switch - Pressed

Cruise Control - Inactive

CC manufacturer is HELLA, part number is AMR 5700. Production data (date?) 990927. Serial No @. Software No 00000001. Diag Index 01. Coding Index 01.

So, does any of that lot help?

Run the vehicle on petrol only. No gas. ..none. ok any issues? If yes you'll need a proper diagnostic device( nano) if no it's your lpg system. Find someone with proper manufacturer software and see what's happening. Of course you could just take a punt on plugs filters etc etc. But it's basically a waste of time and money.

johnnyb70 said:

Run the vehicle on petrol only. No gas. ..none. ok any issues? If yes you'll need a proper diagnostic device( nano) if no it's your lpg system. Find someone with proper manufacturer software and see what's happening. Of course you could just take a punt on plugs filters etc etc. But it's basically a waste of time and money.

Click to expand...

There's no one here who can diagnose the LPG, but I'm not convinced it's a fault with it. As I said, it does the same on petrol, but to a lesser extent, but you can feel it. I deliberately left the garage on petrol and as I was going up the hill I felt a slight hesitation and I looked to check if it was on LPG. It wasn't.

Anyway, I went to wash my hand before dinner (which is why I've been a while, was eating) and I wrote on my hand as my phone died so I couldn't photograph the screen of the code reader (not some shite btw, it cost 1400 quid and read all the stuff I needed apart from LPG...).

Anyway, it stated that Purge Canister High Load.

I'm guessing that's a problem?!?! Could that explain the pressure coming out of the petrol tank when I undo the cap?? Never had this problem before in my life with any car

I also recently replaced the plugs with decent ones. As well as oil, filter, air & pollen filters. I look after this car. Two sets of plugs in two years, 4 oil & filter changes, diffs both done with expensive oil, gearbox oil too when I replaced the cooler. Coolant changed twice too.

https://www.google.fr/amp/s/www.aut...-of-a-bad-or-failing-canister-purge-solenoid/
Is this any help doo?