P38A MAF woes

[romanrob]

Diesel or petrol? If diesel, I'm missing something, I have never seen anything about resetting MAF adaptive values in Faultmate.

V8

 

[pwood999]

In that case it's easier. Pin-1 = 12V, Pin-3 = Ground, and Pin-2 is the output to the ECU.

The description in RAVE is not quite correct, because the IAT is in the air-filter housing. The attached LR System doc has the correct description on 4th page.

MAF voltage should be about 1.4V at idle. (see P41 in "GEMS by Poole")

 

[romanrob]

Only use a gems maf, and better 2nd hand oem than a new one which is supposed to do the same job. Re your screenshots...in pic1 there shd have been air flow, i guess the engine was off. Probably unconnected, but your idle ref voltage is quite high...using Write settings ( as in one of ur pics) you can write it to 0.625V. Current air flow at 32 was quite high for idle. Pls be aware that adaptive settings only learn above min tank level, not sure if 1/4 or 1/2. IAT temp i looked at it in detail in the past...v8s all read wrong ( or nano does), but doesn't seem to do much ( I have put additional resistance in line on mine to get better temp reading) so that is a distraction. Poole by Morgan and lucas gems nanocom guide are your best refs. I will probably be in Corfe C next weekend if you want to try a "known good" maf off mine. Cd be worth removing/ cleaning the iacv and the ports on the throttle body. Leave the tps in place

 

[romanrob]

Also in the write settings screen you have 245 st idle... i thinks that's v high...i have 3 old pics of that screen on mine: one at 6, one at 49, and one at 235....i wd try and write it down to 50

 

[pwood999]

For info, here's my GEMS at idle. No faults stored, and adaptive not cleared for many months.

 

[cornishboater]

Thanks guys, there is something to get on with then

 

[cornishboater]

Only use a gems maf, and better 2nd hand oem than a new one which is supposed to do the same job. Re your screenshots...in pic1 there shd have been air flow, i guess the engine was off. Probably unconnected, but your idle ref voltage is quite high...using Write settings ( as in one of ur pics) you can write it to 0.625V. Current air flow at 32 was quite high for idle. Pls be aware that adaptive settings only learn above min tank level, not sure if 1/4 or 1/2. IAT temp i looked at it in detail in the past...v8s all read wrong ( or nano does), but doesn't seem to do much ( I have put additional resistance in line on mine to get better temp reading) so that is a distraction. Poole by Morgan and lucas gems nanocom guide are your best refs. I will probably be in Corfe C next weekend if you want to try a "known good" maf off mine. Cd be worth removing/ cleaning the iacv and the ports on the throttle body. Leave the tps in place

Many thanks, lotsa info to get on with there, the engine was idling on the old MAF for all screen shots, odd about the airflow bit, I did wonder but I am not au fait with using engine diagnostics so I wouldn't fully know what I am looking at!

 

[pwood999]

Also check that GEMS is set for the correct engine size. 2nd screen in settings menu.

Once you get the settings in the right ballpark, you should do some drive cycles to train the ECU.

 

[Mark Piercy]

If any one can interpret these, they are readings on the old MAF after clearing the fault and doing an adaptive reset

Those short fuel trims are really low

 

[cornishboater]

Just to update. I have again tried the 2 new MAFs with the same ending, chugging black smoke and backfiring. I have now fitted a good used one from James Coleman (SAGEM OEM) and tried it, it started but was really rough. I checked for any faults (none) and then did the adaptive reset, suddenly we jumped to a nice even tickover. I also have numbers coming from the Nano that although don't meet the norm I have to yet drive it to get the ECU to adapt. It also revs cleanly and idles perfectly!! I then again tried one of the 2 "new" ones (the one from Island 4X4) and straight back to chugging, black smoke and backfiring.
It seems that the GEMS setup is very fussy as to what you stick in it, a good used OEM rather than a chineseum replacement, well, lesson learned now and a heads up if anyone is thinking of doing the same

 

[Mark Piercy]

Unfortunately some parts ain't worth the cardboard box they turn up in
Job well done lad

 

[cornishboater]

Unfortunately some parts ain't worth the cardboard box they turn up in
Job well done lad

Believe me there were a multitude of cuss words, some really, really naughty ones
Funny thing is a local chap pulled in in a s3 Landy and asked if I wanted to sell it, hmm, the thought had been crossing my mind, trouble is it would be like selling one of my kids, however, it all depends on the greenbacks methinx.

 

[cornishboater]

Believe me there were a multitude of cuss words, some really, really naughty ones
Funny thing is a local chap pulled in in a s3 Landy and asked if I wanted to sell it, hmm, the thought had been crossing my mind, trouble is it would be like selling one of my kids, however, it all depends on the greenbacks methinx.

One thing is that I didn't expect 2 "new" MAFs to be totally useless!

 

[Datatek]

One thing is that I didn't expect 2 "new" MAFs to be totally useless!

Duff new parts are sadly all too common these days