Test MAF?

[rweir]

I was wondering if someone can help.

I have a 99 S4 with the full KO4 upgrade, with RS4 intercoolers and MAF, Y pipe etc.

It recently started to 'judder' when it 'tries' to get full boost (1.4bar) it manages to run at 1 bar fine, then if I go for anymore it will get to 1.2 bar if lucky and started to judder. It feels as if the power is coming on and off very quickly.

The judder feels the same as if you where to take your foot off the accelerator while it was running at full boost (You know that jolt you get if you do this?) thats the best was to describe it. It seems to have gotten more frequent, as in the timing between the judders, it is more like a machine gun effect.

I have done over 500 miles with fuels from different garages and no difference. I have changed the N75 Valve and checked as many pipes as I can.

I have ran VAG on it and it says there are no missfires, blocks 14 15 16 if I remember correctly.

Is there anyway to use VAG to test the MAF? Could this be the problem?

I also have the following errors, but, they have been there for ages now and it has been running fine.

Any help would be appreciated guys,
thanks,
Rich.

-----------------------------------------
Chassis Type: 8D - Audi A4 B5
Scan: 01,02,03,08,15,17,25,35,45,55,56

Address 01 -------------------------------------------------------
Controller: 8D0 907 551 C
Component: 2.7l V6/5VT G 0002
Coding: 05611
Shop #: WSC 06325
3 Faults Found:
17866 - Exhaust Gas Temp Sensor 2 (G236): Short to Ground
P1458 - 35-00 - -
17869 - Exhaust Gas Temp Regulation for Bank 1: Implausible Signal
P1461 - 35-10 - - - Intermittent
17868 - Exhaust Gas Temp Regulation for Bank 2: Limit Reached
P1460 - 35-10 - - - Intermittent
Readiness: 0000 0000
-----------------------------------------

[gavsteryoung]

Rich,

I'm no expert but when I diagnosed my lack of boost, I logged block 001 and 032, you need to look at the airflow g/s. Basically start the log and floor it in 4th gear from 1000rpm to as fast as you dare go..... then dump the data onto here.... from what I gather you should be pushing 280g/s.

Block 032 also is useful to see this should be the O2 sensors......

But I would have throught the engine would have thrown an error running lean or something if the MAF had gone.

those error codes you have dont look good.... ERG sensor I think?

[Morpheous]

You don't say if this has just started or if its been like this for a while.
As you have tried alternate fuels for 500 miles, i guess its not a new fault.
Is it ever since the 04 upgrade?
Who did the upgrade and was it set up on RR?
Is the ecu remapped? If so which one.
Have you fitted an RS4 fuel pump and injectors? Is the RS4 airbox with additional air valve fitted?
G235 and G236 (EGT)sensors may be detecting correctly and you may be running lean, the system will try to compensate but if the fuel delivery system isn't up to it, the emergency enrichment will kick in resulting in reduced boost. You could also have a duff EGT sensor. I have a brand new G235 sensor which is for Bank 1 cyls 1~3(offers)?
Sounds like its building boost then shutting off and on etc, as if the specified boost in MVB is being exceeded.
Lets face it, could be loads of things, is the cam adjuster N205 and N208 working correctly?
You can see this in MVB 90 odd.
But yes see the other threads regarding G70 ( air mass meter) testing. I have a new one of these also(offers)?
It is quite rare to get a fault code for G70 when they clogg up.

[UKS4APR1]

EGT Sensor "short to ground" is a common fault on S4's.
I have read about it many times on posts in other Forums.
It causes various problems but often similar ones to yours.
I'd go for changing that.
I have also learned that people run with "intermittent" fault for some time (like yourself) with no problems and then suddenly ..Trouble!
Presumably the EGT Sensor has a slight fault at first and then deteriorates.
Try a Search on the "Audiworld" Forum - you'll find masses of info about it there.

[rweir]

Guys, firstly, thanks for your replies

gavsteryoung

I will do this at the weekend and post the results ... so what it comes back with ...

Morpheous
It has just started over the last week.

The car was originally KO4'd about a year ago by SKN in Germany, it then developed a fault with the oil distributor and the turbo's failed. They have all been replaced now, the injectors and SKN and a custom map. Since then it had the intercoolers and RS4 MAF added, so technically it has not been custom mapped for this, but I believe it is only just not making use of the potential extra power? I believe it has the RS4 Fuel pump.

Right, so, get the error codes sorted, failing that MAF, failing that a good car doctor!

Offers on the parts, my mechanic is pricing them for as we speak, I don't have an idea of costs so far for them ...

UKS4APR1
Yes, I think I tend to agree, clear these faults first, they may be red herrings, but they are there to do a job, so I may as well get them fixed so they can do their job!!



Thanks Guys!

[gavsteryoung]

Rich my mistake its Block 002 not 001, that should show the mass air flow!

[rweir]

OK guys, managed to get the blocks VAG'ed in the S4.

I have posted them at http://www.typesure.com/CARS/VAG/

All where from 1000 RPM upwards in 4th gear

LOG-01-002-032-005.CSV - It happened in this one
LOG-01-114-115-116.CSV - Another run with other data, it seemed to be ok in this one, generally. [Note its the bottom one here, 16th Jan]
LOG-02-114-115-116.CSV - Problem with this run.

Let me know if you guys can think of anything.

Rich

[S2tuner]

Rich, when you swap the MAF from stock to the RS4 unit, you definitely need the ECU remapped ASAP to take care of this, because otherwise nothing is right for the ECU anymore and it can lead to lots of problems, like lean running and eventually ruining the engine. With the RS4 MAF, the ECU will see less air mass going into the engine, thus fire the injectors to dump less fuel into the cylinders, which is always going to lead to running problems.

IMHO, you should either get a stock MAF back in, or get the ECU remapped, ASAP!!!


Hope this helps,


Mihnea

[rweir]

IMHO, you should either get a stock MAF back in, or get the ECU remapped, ASAP!!!

The idea was I have a couple of more parts to fit, ie the RS4 intake manifold then I was going to have a modified RS4 chip put in the car.

From what I can gather it is going to cost a fair amount of money for a custom remap.

Also, if a remap was needed to solve this problem, would it not be fair to say that the problem would have been from when I first attached the new MAF. As it was, I did over 600 miles before it started ...

Cheers
Rich

[KayGee]

You don't mention your fuelling, is this RS4 stuff as well including FPR?

Has it ever run correctly, not sure if we are trying to get a modified car to run correctly or fix a car that was working correctly and has developed a fault.

Could try unplugging the MAF to eliminate it from the equation.

[KayGee]

ECU will learn and adapt so thats not necessarily true. Uprading only the air intake side without doing the fuelling side to match would require remapping.

[KayGee]

One last suggestion, have you double checked your TBB for splits, splits are usually located under the clamps...

[S2tuner]

This is a wrong statement. The ECU will only adapt to some extent. The MAF is the main load input to the ECU. If it sees the air mass is low, it will trigger the injectors to run the mixture it "thinks" is right for the aforementioned air mass. The actual air mass will be much higher though (his logs show 230g/s, this is even lower than a stage 1 S4 chip), thus the actual mixture will be lean. I'd be curious about a log of group 031 together with 003 just to see how lean the car is running.

He said he had done the RS4 injectors then had it mapped, then he upgraded the MAF. Upgrading the MAF definitely needs remapping.

HTH,

Mihnea

ECU will learn and adapt so thats not necessarily true. Uprading only the air intake side without doing the fuelling side to match would require remapping.

[S2tuner]

Rich,

You are right about the RS4 IM and so on. This is the right way to do it. However, until you get the car remapped, I'd suggest putting the stock MAF back in.

The 600 miles issue could be to the ECU's long term fuel trim adaptivity. If you had reset the ECU since day one, it could have started 600 miles ago IMHO...

Custom mapping doesn't cost as much as you'd think

Cheers,

Mihnea

IMHO, you should either get a stock MAF back in, or get the ECU remapped, ASAP!!!

The idea was I have a couple of more parts to fit, ie the RS4 intake manifold then I was going to have a modified RS4 chip put in the car.

From what I can gather it is going to cost a fair amount of money for a custom remap.

Also, if a remap was needed to solve this problem, would it not be fair to say that the problem would have been from when I first attached the new MAF. As it was, I did over 600 miles before it started ...

Cheers
Rich

[KayGee]

What statement is incorrect? Bosch Motronic does adapt.... AFAIK it can adapt fueling, boost, timing and throttle position.

If it is MAF related any ideas on why it may take 600 miles to start miss behaving if it isn't due to ECU's adaption?