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[bootzey]

Hi All.
Been awhile since I was on. I've still got the same problems...EML on, fuel trim codes but runs fine with MAF disconnected and doesn't go it to limp home. Brought a Chinese MAF off ebay and fitted to car when hot, result EML light off after about 30 miles but still rough starting. Then brought a MAF of Steve at Omega Spares, car exactly the same as my MAF
Here's what's happening:-
Car now won't start with MAF, any MAF, plugged in when cold.
Car starts perfect with MAF unplugged.
Car continues to tick over after plugging the MAF back in immediately after starting, even though it's cold. But when engaging drive, car coughs, splutters, pinks then stalls. Unplug MAF - restarts perfectly.
Plug in the MAF when at driving temperature and car starts and drives until I hit a bump or turn a corner too vigorously. Then runs bad so I have to pull over to unplug....you guessed it..the MAF.
Plug in the MAF when at temperature...ticks over. Then turn off, leave for 2 minutes and attempt restart...and doesn't...plug MAF in and it does.
Got a code reader...yep, a Chinese one and Android Torque. It switches EML off and clears codes but...it's telling me the oil temp is -44!!! But indicates coolant temp the same as the temp gauge. Does anyone think this might be confusing the poor old ECU? Also, where is the oil temperature sender please?
This seems to be a progressive problem. The EML came on along with Check Engine Oil on the MID about 10 miles into the 233 mile journey home from Chester in August. The starting problem has got worse and worse since and now won't start at all, even after 30 odd goes. Can't help thinking that the muppet I brought the car off did something as when I started the car the EML wasn't on but the engine was warm. It's all rather confusing and very expensive on fuel.

Now to confuse things even more I decided to use an amp meter to test the resistance of the 4 MAF's I now own. I haven't got a clue about electrics and the dial switch on the tester totally baffled me. So I just turned it to the ohms section pointing to 20K as it seemed to give a steady logical looking result.
I placed the red lead on the connector for the blue wire and then touched the black wire to the other connectors in turn and made a note of the readings. Then moved the red connector to what I noted as No.2 which is the green wire. Then continued until I had readings for all combinations of connectors. The car's MAF and the one from Steve gave very similar results. The chinese MAF's (yep, I got the ebay seller to send me another) also gave similar reading. However, the readings were completely different to the original Bosch MAF's. Would anyone like me to put the results on here? Can anyone inform us as to what the readings when testing a MAF should be please?

Many thanks if you have read this.

Cheers

Dave

 

[Kevin Wood]

Measuring the resistance of a MAF won't tell you anything and could damage it.

What you need to do is get it idling, plug the MAF in and have a look at the live data with a code reader. The following parameters would be of interest:

MAF air flow rate in kg/h
Intake air temperature (measured by the MAF)
Fuel trim values
Lambda sensor activity and open / closed loop status.

I suspect a MAF problem has caused the fuel trims to get so high that it's preventing starting but need to see the live data to confirm this.

Also have a look for any stored fault codes in the engine ECU.

In my opinion, non genuine and 2nd hand MAF sensors are a false economy, as they often give problems after very little time.

[aaronjb]

Dave, whereabouts in Surrey are you? If I'm passing I'm happy to stop by and sanity check your Chinese code reader with my reader (although mine reports MAF flow in a nutty unit rather than kg/h, sadly)

[bootzey]

Cheers Kev.
I might get the chance later to plug in the code reader.
Is there any way of clearing the stored fuel trims so it has nothing to compare and starts logging again? The last time I had Torque connected it sometimes indicated a fuel trim of 100%! Also showed an intake of 12.5g. The Lambda's were flipping nice and regular between .1 and .8 and were closed loop until it warmed up a bit then they went open.

Could a wiring problem blow a MAF? A dodgy earth or something maybe? Is there a wiring diagram for the MAF indicating which of the 5 wires do what and where they go in existance?

Also, I forgot to mention that after blasting my original MAF with a carb cleaner it worked for a while and the mpg went upto 28 in town! However it didn't last long and hasn't worked again since....that's 20 quid on cleaner wasted lol

What do you reckon on the Oil temp reading?

Thanks again

[bootzey]

Cheers Aaron, I'm just south of Guildford 

[Kevin Wood]

Not so far from me, then. I'd be happy to look over it with the real McCoy Tech 2.

[aaronjb]

Yep, not much further really than from my usual route (Bracknell->Chobham->West Byfleet->Chertsey and back) 

[car5car]

I bought 95 Mercedes with new Chinese MAF, which didn't work. I bought another cheap MAF, which didn't work either. Finally I bought used MAF sensor from ebay and it worked fine.
I got smarter and when I needed MAF for Catera I got it from junk yard, worked fine!

[bootzey]

Hi Guys

Sorry, not been here for a while thanks to BT, my boys xbox and an unaffordable BT bill.

Thanks for the offers of help but (not wanting to insult you) I wouldn't expect you to do it for nothing, which is all I have at the moment so can't reimberse you.

I just done a bit more testing as there's been some updates from Android Torque. Got some weird scenario's happening :-

Running with MAF unplugged.
3 O2 sensors flipping nicely but bank 2 sensor 2 lags behind and just flips between .1 and .2 volts. Fuel Trim dials show 1x2 and 2x2 unmoving at 92%, Intake temp of -40 degrees C, oil temp -44 degrees C and No injector pulse width reading. Runs closed loop.

Now the confusing bit:-
MAF plugged in....has to be done with car running and up to temp:-

Scenario 1. O2 and fuel trim dials stop working as soon as MAF plugged in, like plugging the MAF in switches them off, fuel trim at 25%. Injector pulse width 71.3ms. Oil temp -22. However...flip the throttle and revs to 1800ish and won't drop until...I turn on the head lights and air con then revs drop!!!!! I cleared the P0100 fault code and the thing runs rough for a while.

Scenario 2. Lights and Air Con off revs to 950, F/T 25%, MAF 3.8gm/second, injector pulse width 71.3ms, oil temp -22

Scenario 3. Lights and Air Con on revs at 750, F/T 16.4, MAF 2.8gm/second, Volume Efficentcy 15.8%, Boost (assume it means vaccum) -12.3%, injector pulse width 71.3ms, oil temp -22.

There seems to be a connection between DB Wire throttle, Plugging the MAF in, turning Air Con and Lights on which will reduce voltage. Can't think why the O2's and Fuel Trim sensors shut down when the MAF gets plugged in unless there's some kind of voltage overload somewhere.

Going to try same scenarios with Omega Spares MAF (ohm performance the same as mine and Steve assures it came of a well running 2.6) and then chinese MAF's (ohm performance the same as each other). I reckon if I get the same thing happening regardless of which MAF is in then it has to be a bad earth or cross wire somewhere.

Phew! Sorry, yet another long post for you to read but I think the devil is in the detail somewhere.

Thanks for reading and understanding.

Dave

[Kevin Wood]

Could be something odd with the wiring but they are also classic MAF sensor issues, and the 2.6 seems very sensitive to a degrading MAF sensor. It would be good to get the MAF sensor reading at hot idle, and see if it varies when pulling the wiring around a bit, but I don't trust the readings from that code reader. Sounds like it's confused by some of the data it's getting.

Bit of a shame I've just passed by the south of Guildford and could have chucked the Tech 2 in the car.

[symes]

I had similar problem on my 2.5 getting fault code for Lamda/maf & throttle Pos sensor ran like a pig -it was plug on egr - Got another plug from scrapper and 10 mins soldering-car fine now

[Kevin Wood]

By the way, the lambda sensor activity sounds pretty normal. The post cat sensors shoudn't cycle as readily as the pre-cat sensors as the cats damp their response.

Are you getting any fault codes? (do the pedal trick if the code reader isn't reporting any)

[dbug]

I had similar problem on my 2.5 getting fault code for Lamda/maf & throttle Pos sensor ran like a pig -it was plug on egr - Got another plug from scrapper and 10 mins soldering-car fine now

Ops got a 2.6 - no egr on a 2.6 mate

[bootzey]

That's just my luck Kev...don't tell me...you went through Chilworth lol

MAF readings are @ 600 revs 2.8 grammes/second so by me reckoning that's 60secsX60minsX2.8/1000 = 10.08Kg/hour
                        @ 950 revs 3.8 grammes/second = 13.68Kg/hour
                        @ 1845 revs 6grammes/second   =  21.60Kg/hour

All O2 and F/T readings stop dead when the MAF gets plugged in, DBW throttle doesn't decrease when foots off the pedal but turn lights and Air Con on and revs drop?

Can't understand why the Injector Pulse Width is always the same regardless of revs @ 71.3 milliseconds surely it should change with the revs? And there's no IPW reading unless the MAF is plugged in.

Is there anything behind the dials/dash that would be at risk if a large Latte was split then runs down through the grill by the windscreen then out through the fusebox?

Dunno why but I'm convinced there's a wiring problem.

What replaced the EGR on the 2.6 and 3.2?

Cheers for the in put Guy's

Dave

[TheBoy]

Sounds low. But that bluetooth based system often talks 'dangle berries', so slightly reluctant to suggest buying a brand new, genuine GM MAF at this stage.

Don't use 2nd hand or pattern (even if it claims to be Bosch). Dealer only, in GM hologramed box.

Worth fully checking for air leaks as well.