Engine probs (overboost protection)

[Jas11n]

Hopefully someone may know WTF is going on with my bro's car (I'm posting as he is shy and hasn't a clue when it comes to stuff like this )

Ok, the car is a 95 ABY coupe, miles are 60k.

The car keeps on getting overboost control coming in. The car has recently had the following; (just to rule these items out)

1/ new WGFV
2/ New Bosch 710N TBV
3/ New Bosch F5DPOR spark plugs
4/ and a recent service with new oil, coolant etc.

Fault codes from Vag-com are,

00544 - Maximum Boost Pressure Exceeded.
...........13-00 Adaptation Limit (Mul) not Reached.

00561 - Fuel Mixture Adjustment.
............27-10 Implausible Signal - Intermittent.

Now, looking up in the official Workshop Manual for the Motronic Fuel Injection and ignition System edition 09.92

It gives the following solutions (the stuff I'm asking for help on)





As I say, the TBV is fine, and I've also tested the WGFV with the output tests in Vag-com, and it's clicking away like a good un.
We've ruled out a boost leak by pressure testing the whole system, which holds pressure quite well.
Would a faulty/dirty G70 (Maf) cause this type of problem, or could it be something like a blocked fuel filter or duff fuel pump (not noisey BTW) which is maybe causing fuel pressure to be to low? again would the fuel pressure being to low, trigger Motronic to cut boost?
What else could cause the fuel pressure to be too low?

Next on the cards tomorrow is to swap Maf's with mine, would this be a good idea?

I've tried to give as much info as I can, just need help interpreting the above possible solutions.

Sorry for all the questions I'm learning all the time

TIA
Jas

[BRY]

Glad to see something is working well matey
VagCom
Swapping the MAF is fairly quick and easy, BTDT. May aswell to see if makes a difference.

[Jas11n]

Vag-com worked before Bry mate, just not all of it

[audiman]

Do these fault codes come back everytime after being cleared???

When you say it held pressure fairly well. How well?? Swapping Mafs is dead easy and wont do any harm (unless you drop them).

[Jas11n]

Yes Tom, same codes everytime, plus the normal G28 if doing test with engine off but ignition on.

Putting 1.2bar of pressure in, it slowly disappears in around 5/6 minutes, no hissing.

Ta
Jas

[S2central.net]

Such a slow leak could be thru turbo seals - assume you can't hear bubbling noises...

Changeover the MAF for sure - you'll need to run it for a while for adaptation to settle down. Make sure to clear all fault codes before trying new MAF.

Another thing to change at 60k is the lambda probe - they can cause mixture problems.

Fuel pump & filter should be OK at 60k but the filter is cheap and easy to change on a COupe for piece of mind.

[audiman]

Thats what i was gonna suggest Paul

[Jas11n]

I couldn't hear any bubbling noises Paul,
What length of time is sufficient for the adaptation to settle down after the Maf swap?
IS it just a case of driving calmly for 3/4/5 miles and then giving it some big handfulls of WOT.

Thanks for the advice
Jas

[audiman]

Just pull the ECU fuses and then take it for a drive for a few miles. Then give it large and see what happens. Sounds like the system is leak free. Might be worth checking that the line to the ECU isnt trapped or blocked? Maybe?

[S2central.net]

Ideally you need to give the ECU some time at all part throttle / load positions for complete adaptation. MIhnea is the resident guru on this stuff. I'd say about 15-30mins normal driving thru all conditions should be sufficient for adaptation.

Its worth hooking up a DVM to measure the o/p voltage from each MAF at some repeatable conditions. S2central.net will tell you the pin to probe. Expect signals in range 0-5V.

Another QnD check is with a DVM on the output of the lambda probe - even at idle on a warm engine you should see it skip under and over the 0.7V mark at least once per second. If you see the probe output 'stuck' for a few seconds then its on the way out.


Paul

PAul

[Jas11n]

Thanls gents, I'll grab a DVM tomorrow night.
The line to the ECU is fine, also the hose from the recently fitted boost guage isn't kinked either.
New Lambda will be ordered tomorrow too, IIRC they should be changed every 40k anyway. We'll also whack a new fuel filter on, as you say, very easy on the coupe.
I'll also give his Maf a good clean with IPA, just have to make sure I don't try the local chemist, as last time the girl behind the counter accused me of wanting it to drink seriously

[pjeast73]

they are the 2 fault codes I got when my MAF was faulty - and same symptoms. good place to start

[jon_91_s2]

I'll also give his Maf a good clean with IPA, just have to make sure I don't try the local chemist, as last time the girl behind the counter accused me of wanting it to drink seriously

Maplins £9.99 a litre. They wont accuse you of wanting to drink it. Then stop at boozebusters on the way home and get some vodka to drink while the maf is soaking.

[BRY]

Maplins £9.99 a litre. They wont accuse you of wanting to drink it. Then stop at boozebusters on the way home and get some vodka to drink while the maf is soaking.

There speaks a voice of experience

[Jas11n]

Lets just hope I don't get them mixed up and drink the IPA whilst the Maf soaks in Vodka