Random Stalling + Codes
 

Merry ChristmasAF,

I have driven my 1998 A4 2.8L quattro tip for about 3000 miles of it's 180k.Everything has been great untila week ago, I hadn't driven my car for about 4 days. And when I went to start it up it didn't fire right away, infact I had to crank it for awhile about 4 times before it fired, and the battery seemed very weak. It started and idled very rough, and a CEL followed shortly. It now stalls (or almost stalls) randomly while parking or at stop lights.

Codes:
P1127
P1129
P1141

Cleared codes and CEL came back within 30 miles.

Tried a throttle body adaptation - just left the ignition on for 10 minutes.

Cleaned the MAF - was a bit dirty, still runs rough and stalls at idle

Checked codes, same + P0103 (I think this code was in there because I unplugged the MAF with the keyon - or fubarred the MAF while cleaning it, but I don't think so) CEL came back within 5 minutes.

Help please!

RE: Random Stalling + Codes
 

Change your air filter and spark plugs.
Add Seafoam to the fuel to clean your fuel injectors.
Clear the codes and see if they return.

RE: Random Stalling + Codes
 

bumping with more info:

Need your input!!

Now have VAG-com so here comes the data, same codes keep coming back:
Saturday,05,January,2008,16:27:27:01024
VAG-COM Version: Release 704.1
Data version: 20071016
Chassis Type: 8D - Audi A4 B5
Scan: 01 02 03 08 15 16 17 25 35 37 45 55 56 57 67 75 76 77

Mileage: 291210km/180949miles
-------------------------------------------------------------------------------
Address 01: Engine Labels: 078-907-551-AHA.LBL
Part No: 4D0 907 551 AH
Component: 2.8L V6/5V MOTR AT D01
Coding: 06251
Shop #: WSC 42272

3 Faults Found:
17549 - Load Calculation Cross Check: Implausible Value
P1141 - 35-00 - -
17535 - Fuel Trim; Bank 1 (Mult): System too Rich
P1127 - 35-00 - -
17537 - Fuel Trim; Bank 2 (Mult): System too Rich
P1129 - 35-00 - -
Readiness: 0000 1101
---------------------------------------------------------------------

Group032 display
Attachment 61230
(O2S control learning curve, @idle -14.1% @part -1.6%)

---------------------------------------------------------------------
Logging of Group002_MAFvsRPM_idle (linked to google docs no login required)
idling in Park.
(ranging from normal 5ish g/s to 12-15 g/s in idle)

Logging of Group_002_MAFvsRPM_WOT (linked to google docs no login required)
WOT several pulls on to freeway on ramps.
I've read that MAF should be 0.80*Max Horsepower at WOT. MAF appears to be reading high as I got a few readings over 200 g/s and I think we all know that's well over the Max HP of a stock 2.8 30V.


Can you guys with lots of experience take a look at this information please? I am guessing that the MAF is shot. The codes indicate a vaccum leak is possible too but seems unlikely with the engine trying so hard to trim from rich back to lean.

Suspect parts at this point:
MAF
Evap Purge Valve
Fuel Pressure Regulator
Less likely:
Vaccum leak
Fuel Filter
Fuel Pump
Injectors leaking

Thanks for your help!!

edit: fixed docs links

RE: Random Stalling + Codes
 

clean the MAF and check for a vac leak. your running rich and i doubt your getting too much gas, most likely not enough air

RE: Random Stalling + Codes
 

I cleaned the MAF already. DPO had a K&N air filter on there for the last few months, the filter was replaced with paper stock, and then I cleaned the MAF with contact cleaner, an I think i need to replace the MAF no matter what. If I had a big vaccum leak wouldn't I be running lean since there would be more un-metered air getting in?

Any reason to avoid the remanufacted MAF from ECS tuning?

Macro shot of a MAF for those entertained by such things...
after cleaning with contact cleaner
Attachment 61228

after cleaning with rubbing alcohol + qtip
Attachment 61229

edit: fixed image links

RE: Random Stalling + Codes
 

the reman ones are fine. replace your CTS too. it's only 7 bux a autozone.

RE: Random Stalling + Codes
 

i'll look into the CTS too.

Thanks for the replies hiwords!

RE: Random Stalling + Codes
 

It's amazing how different your two logs appear - split personality car.

I'd be more inclined to take a look at your fuel system. +1 on the seafoam to clean injectors, but go further and pull a fuel pressure (flow and volume) test before scrapping the MAF. It could uncover whether you have a bad FPR or a failing fuel pump/clogged filter. Those pulse widths are REALLY high. As are the load reading for an idling stock car.

RE: Random Stalling + Codes
 

Indeed. I only posted the idling log of when it was stumbling around though, and "marked" each time that it stumbled badly and almost died. (left most column) It idles fine sometimes, other times not. I think the MAF was still reading very high even at the top end of the WOT test though.

Well I already ordered a new MAF late last night, which is fine since I didn't see new MAF any where in the service records I have for the car. But if the problem isn't fixed, I'm definetelymoving on to the fuelsystem...

I didn't notice the load reading until you mentioned it. Can anyone explain to me how load is calculated for this engine? Are there any other sensors that can throw off the calculation besides the MAF... air temp? I know speed density systems use RPM, Air temp, TPS, and MAP. but I'm a bit less familiar with the MAF type system.

RE: Random Stalling + Codes
 

It very well may be your MAF. You're right about them reading abnormally high and they will generate rich codes. Given it's the original unit, I don't think you can go wrong with replacing it.

One other, but I seriously doubt both would have gone bad, is that the 02 sensors could be responsible for the rich signals and the implausible signal. They can be ruled out by checking your trims and MAF/Load reading before you go into closed loop.

Post back if it indeed turns out to be your MAF. I hope that it is!