VR6 randomly stalling -- really need your help

[jolecanard]

Hello everybody,

There are so many things to say...I'll try to be as clear as possible.

The Car:
2000 GTI VR6 12v, 146000 miles, 100% stock

The Problem:
The car stalls randomly. It can happen at a stop sign or light, it can happen while driving 60 mph, any day, any weather, any slope condition. It seems that when the problem occurs, the injection is stopped for ~1-2 seconds (sometimes more, sometimes less).

More Details on the Problem:
It has been going on for more than 3 years now! Unplugging the mass air flow sensor makes the car run perfectly (no stalling at all). Although this is a solution, this only is a temporary one.
When the error codes are cleared from the memory (and sensor calibration is reset at the same time...for what I understand) the car runs good (with MAF plugged) for about 30-40 miles until all sensors go back to a "Ready" status.

Even More Details on the Problem:
There are two typical scenarios.
First scenario, the car is stopped when it occurs (eg. at a light): the rpm will drop and usually the car stalls. If it does not have time to stall, then the rpm will go back up somewhere between 1000rpm and 1500rpm (I am not touching the gas pedal) and slowly get back down to ~750 rpm.
Second scenario, the car is moving: when the problem occurs, the rpm are not going down because the inertia of the car will maintain the engine at normal rpm, but there is no power anymore. If I maintain the clutch pedal pushed, the same things as in the first scenario happen.

The Error Codes (VAG-COM):
17544 - Fuel Trim: Bank 1: System too lean (P1136 - 35-10 -- intermittent)
16486 - Mass air flow sensor (G70): Signal too low (P0102 - 35-10 -- intermittent)
Once in a while I would get a "System too rich" (dont remember the number), but not this morning when I pulled the error codes.

Solutions Tried:
Replacing the MAF with a new one -- did not help
Replacing the throttle body with a new one -- did not help
Check the wires for MAF and throttle bodu -- they are fine
Vacuum lines check for leak -- no leak
Check that wires are properly grounded -- seemed to be fine
Checked the O2 sensor readings with VAG-COM -- they seem correct

What the Car Mechanics Said:
I took the car to three difference mechanics. Each of them kept the car for about a week and ran a bunch of tests on it. All of them finally gave up on the car telling me that they don't see any other solution than changing the parts one by one...this is going to be too expensive.

At this point I am relying on the very experienced people (hopefully still) roaming on this forum.
Any suggestion/idea is very welcome...

[seehaus]

I had a similar problem with a Volvo and it was the Fuel Pump Relay. I'm sure VWs have them,
it would be a cheap and easy thing to try. Have you checked the fuel pressure regulator?

[Kenji]

You might have an intermittent connection somewhere in your MAF sensor wiring harness. With the MAF sensor connected and the engine running, pull lightly on the MAF sensor wiring harness near the sensor connector (since that's the most likely place for an intermittent connection). If the engine stalls, you've found your problem. Good luck!

[jolecanard]

Seehaus> Do you know where is the fuel pump relay? (otherwise I'll look into the Bentley manual)
Also how can I check the fuel pressure regulator? Do I need to take it to the garage for that?

Kenji> I will try that tonight and report.

[Stevieg#1]

in the relay box there are 13 relays on top and 5 on the bottom it is the 4th one in from the left on the bottom. to check pressure regulator disconnect incoming fuel line install fuel pressure guage inline 36psi is spec with vacuum line on regulator 43 psi with line off

[Stevieg#1]

next time you get the p0102 done erase codes get the stored PIDs from when the code was tripped and see what the MAF is reading. 3.00g/sec-5.00g/sec at idle. i have more pin point tests for MAF PM me if you want them

[seehaus]

where is the relay box on a mk4? I know there are a few under the drivers side dash.

[Stevieg#1]

that would be it, drivers side footwell behind lower instrument panel trim

[jolecanard]

I try pulling gently on the wires of the MAF harness while the engine running and it did not make the car stall (I "played" with the wires for a good 5 minutes). This kind of confirmed what the mechanics said (I had asked them specifically to check the MAF wires and they said the wires were fine).

I haven't had time to check the MAF readings.
Stevieg, what do you mean by stored PIDs? Do you mean that I should:
1/ Clear the error codes; 2/ Then check the MAF readings
OR
1/ When the error codes are present, check the MAF readings?

Regarding the fuel pump relay, any easy to check it without replacing it?

Also, I don't have the tools for checking the fuel line pressure...

[Stevieg#1]

when the check engine light is set it stores freeze frame data which is what all your sensors were reading at the time the code was set. when you erase the codes it erases the freeze frame data. as for the relay if it was bad you wouldnt get a rich code. i would get a scan tool that reads data stream, it will usually give you freeze frame data. this might help you understand what your looking at http://en.wikipedia.org/wiki/OBD-II_PIDs

[seehaus]

The fuel pump relay will only cost a few bucks and they should have at a Advance or Autozone.
t's worth a try, I put up with the unpredictable stalling on my volvo for a while before I figured it out.
It's worth a few bucks to find out if that's the problem. Always start with the cheapest and easiest fixes first.

[jolecanard]

I am using a VAG-com, which has "freeze frame" and "data stream options". However, the control module of the car does not support "freeze frame" and the sampling rate of the data stream is about 1 sec.

Nevertheless, here are a few more details from the VAG-com. The history of the error codes:

Monday, 01 June 2009, 10:35:49
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
2 Faults Found:
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
        P1128 - 35-10 - - - Intermittent
16486 - Mass Air Flow Sensor (G70): Signal too Low
        P0102 - 35-10 - - - Intermittent
---------------------------------------------------------------------------


Thursday, 04 June 2009, 10:29:15
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
3 Faults Found:
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
        P1128 - 35-10 - - - Intermittent
16486 - Mass Air Flow Sensor (G70): Signal too Low
        P0102 - 35-10 - - - Intermittent
17544 - Fuel Trim: Bank 1 (Add): System too Lean
        P1136 - 35-10 - - - Intermittent
---------------------------------------------------------------------------


Monday, 06 July 2009, 08:46:44
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
2 Faults Found:
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
        P1128 - 35-10 - - - Intermittent
17545 - Fuel Trim: Bank 1 (Add): System too Rich
        P1137 - 35-10 - - - Intermittent
---------------------------------------------------------------------------


Tuesday, 12 June 2012, 20:52:14
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
1 Fault Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low
        P0102 - 35-10 - - - Intermittent
---------------------------------------------------------------------------


Thursday, 19 July 2012, 20:48:52
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
3 Faults Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low
        P0102 - 35-10 - - - Intermittent
17545 - Fuel Trim: Bank 1 (Add): System too Rich
        P1137 - 35-10 - - - Intermittent
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
        P1128 - 35-10 - - - Intermittent
---------------------------------------------------------------------------


Tuesday, 28 August 2012, 11:24:33
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
3 Faults Found:
17544 - Fuel Trim: Bank 1 (Add): System too Lean
        P1136 - 35-10 - - - Intermittent
16486 - Mass Air Flow Sensor (G70): Signal too Low
        P0102 - 35-10 - - - Intermittent
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
        P1128 - 35-10 - - - Intermittent
---------------------------------------------------------------------------

And here is some stream data from when the problem occurs:

Time [s]	RPM/min	Load %	Air [g/s]
2572.76	2560	21.1	14.22
2574.07	2040	11.3	7.28
2575.46	1080	11.3	4.14
2576.65	840	12	3.67  
2577.85	800	12.8	3.56
2579.05	840	13.5	3.47	-> The problem occurs
2580.36	800	13.5	3.42	  rpm drop...
2581.65	1480	11.3	5.11	  goes up...
2582.85	1320	9.8	4.28	  and back down... (keeping my foot on the gas...not full throttle though)
2584.15	1120	9.8	3.56
2585.35	1120	27.8	10.56
2586.76	1400	42.9	18.67	  and there it is over, the car did not stall
2587.94	1680	37.6	19.31
2589.14	1920	36.8	21.28
2590.34	2080	30.8	19
2591.54	2160	25.6	15.86

On the same trip (about 30 seconds later)

Time [s]	RPM/min	Load %	Air [g/s]
2603.14	680	19.5	4.19	coming to a red light
2604.34	680	19.5	3.89
2605.54	840	12.8	3.31	-> problem starts, RPM "bump" up a bit
2606.94	720	12.8	2.81
2608.24	680	12	2.64
2609.54	720	12	2.67	  and oscillate a bit...
2610.83	680	11.3	2.47
2612.03	680	11.3	2.44
2613.23	680	11.3	2.36
2614.43	680	9.8	2.06
2615.63	600	10.5	2.06	  RPM drops... (I am again slightly holding the gas pedal but unsuccessfully)
2616.81	640	15	1.64
2618.13	720	17.3	4
2619.44	600	22.6	3
2620.62	720	17.3	4.25
2621.82	760	13.5	3.28
2623.02	760	13.5	3.44
2624.22	640	20.3	1.75
2625.53	680	16.5	0.56	  ....end eventually succeed to make the car stall
2626.83	920	12.8	0
2628.12	680	12	0
2629.54	880	15	0
2630.83	880	18.8	0
2632.03	800	15.8	0
2633.32	720	13.5	3.94	Waiting for the light to turn green to restart the engine
2634.62	840	18.8	5.64
2635.82	600	26.3	5.97	(engine still not very happy)

I also have the O2 sensor recording and the throttle position (corresponding to my action on the gas pedal). Basically the gas pedal sensor works fine as well as the throttle body/flap.

I am going to order a fuel pump relay soon, unless someone has a better idea or other tests I can perform with the VAG-com?

Suggestions?

[Roadblock007]

Crank sensor. Sometimes it goes and doesn't ever throw a code. it doesn't jive with your MAF problems but is cheap enough to try it. Mine went and I had the exact same stalling issue the same way you describe it.

RB

[Stevieg#1]

2626.83 920 12.8 0
2628.12 680 12 0
2629.54 880 15 0
2630.83 880 18.8 0
2632.03 800 15.8 0
the car is stalled at this point right?
i would try clearing the codes and running the car with the vacuum line off the fuel pressure regulator and find something to plug the vacuum line that wont get sucked in. i have diagnostic flow charts for diagnosing the codes let me know if want me to post them. best to to figure out what you need before you start throwing parts at it

[jolecanard]

Stevieg, please go ahead and post the flow charts for diagnosing the codes.

Also, could you give me more details about unplugging the vacuum line from the fuel pressure regulator?
Basically: where is it located (if you can take a pic that would be awesome)? Any suggestion how to "safely" plug the open vacuum line? Any special precaution before unplugging/plugging the vacuum line?

I went ahead and replaced the Fuel Pump relay (#409) since I found the replacement part for $20. It did not change anything to the problem....now the part is going back for a -partial- refund.

Also, when I the problem started in 2009 and nobody could figure it out, I drove for ~15000 miles with the MAF unplugged (ECU goes into a "safe mode"). For all the time I drove like that it did not stalled a single time. Basically the problem is due to one of the components which is bypassed when going into "safe mode" (sensors/ECU/vacuum line/...).

EDIT: Yes, when the air flow is 0, the car is stalled.

EDIT2: I found a DIY for the Fuel Pressure Regulator . Still need advice on how to safely plug the unplugged vacuum line...

[Stevieg#1]

for your codes the corrective actions are
P0102 #1 Check MAF sensor #2 check for vacuum leaks upstream of MAF (unmetered air)

P1128 #1 check fuel pressure regulator and residual pressure #2 fuel injectors #3 check for vacuum leaks upstream of MAF (unmetered air) #4 check fuel pump #5 check for exhaust leaks and proper exhaust seals #6 check secondary AIR injection for proper seal #7 check vacuum lines for proper seal

P1136 #1 check fuel pressure regulator and residual pressure #2 check for vacuum leaks upstream of MAF (unmetered air) #3 check fuel pump #4 check for exhaust leaks and proper exhaust seals #5 check secondary AIR injection for proper seal #6 check vacuum lines for proper seal

P1137 #1 check fuel pressure regulator and residual pressure #2 fuel injectors #3 check EVAP canister purge regualtor valve

flow chart for checking MAF
1.Car on in park or neutral all accessories off (lights A/C ect.) and at operating temp.
2.with scan tool or vag-com verify MAF volume is between 3.00 g/s and 5.00 g/s at idle
3.if readings are within specified range turn car off and disconnecct 5 pin connector from MAF and go to step 4.
4. Check voltage supply to MAF. with engine running at idle voltage between pin 2 (counting right to left or rounded side to flat) and engine ground. spec 11v-15v. If voltage ok continue to step 5, if not check resistance of wire between pin 2 and fuel pump relay (key off) spec. 1.5 ohms if wire is open or above spec repair or replace wire
5.Check signal in. with key on engine off check voltage between pin 4 and engine ground. spec 4.5v -5.0v
testing beyond this requires a breakout box

I would suspect #1 vacuum leak #2 fuel pressure regulator #3 fuel pump in that order given you've already replaced your MAF
as for plugging the vacuum line find a machine thread screw that fits nice and has a big head and a zip tie. I would really try and get my hands on a fuel pressure tester though because it seems to be going in that direction

[zuhaelter_82]

Crazy!

[kurpal]

i have the same problem with my 2001 VR6. it started maybe 2 months ago and i am very concerned considering i drive my kids to school. i have stalled on the freeway at 80mph as well as on the streets at 40mph.

let me know if the fuel pump stops the problem.

[zuhaelter_82]

Sounds like a MAF or a coil pack.

[kurpal]

thanks for the help. i'll work on it this weekend.

[zuhaelter_82]

Not the fuel pump?

[kurpal]

thanks for the heads up. i am going to check my plug wires. i had changed plugs, cleaned my air filter and throttle body when i started to feel sputtering about a year ago, but the stalling started after that.

[zuhaelter_82]

Throttle body alignment maybe?

[jolecanard]

I would suspect #1 vacuum leak #2 fuel pressure regulator #3 fuel pump in that order given you've already replaced your MAF
as for plugging the vacuum line find a machine thread screw that fits nice and has a big head and a zip tie. I would really try and get my hands on a fuel pressure tester though because it seems to be going in that direction

I finally disconnected the vacuum line from the fuel pressure regulator and duct-taped it. Since then I drove about 200 miles and the car did not stall. A couple times it stuttered while I was stopped (foot off the gas pedal), but as soon as I would put my foot back on the pedal it would be fine (which was not the case when the "problem" occurred). I guess the stuttering could be due to the fuel pressure regulator being disabled...?

From my past experience and the previous posts this means nothing until I drive another 500 miles. However, assuming disconnecting the FPR from the vacuum line "solves" the problem, what does that mean? That the FPR is faulty?


Also...my gas mileage went WAY UP. I mean. On my commute I used to do 25mpg, now it says 29.2mpg!

[jolecanard]

Drove around for 2 hours and had to almost force the car to die before it started up. The throttle angle sensor shot up to <17deg and with my foot off the gas the RPMs shot up to 1700. Next step will be to clean the TB and see if that fixes the issue. I kept thinking that it felt like an ISV from a MKII and this may explain it. Just another hunch though.

Edit: I took the TB off today and cleaned the sh*t out of it. Drove 138 miles and so far no issues.

Very nice pic!!

About the TB, I really hope this solves the problem for you, but for me it did not:
- FIRST, I removed the TB, cleaned it, put it back. Everything was fine....for 2 months and more than 1000 city miles (I was not driving much back then). Then it occurred.
- THEN removed the TB and replaced it with a new one ($$$). Things were fine for 2 days and 60 miles...then it occurred.
I checked the wires (voltage) and they returned the expected values. I even took the TB apart and made sure the electrical motor was working fine using an external power source.

My catch regarding the fuel pump is: if when you unplug your MAF and drive without it, the car runs just fine, then the fuel pump should not be the problem. If it was faulty, it would fail regardless of having the MAF plugged or not.
For me unplugging the MAF has been the best way to have a reliable car those past two years...but gas mileage is 10-15% worse and you cannot pass emission tests.

[jolecanard]

Another 150 miles and then the engine died at a stop.
15 miles later it was while cruising at 50 mph, the revs would not go up.

I guess unplugging the FPR did not solve the problem BUT it improved my gas mileage by 20%!!

Any suggestion?

[jolecanard]

The problem is definitely not solved by unplugging the FPR vacuum line.

Yesterday it was pouring rain, and for the first time ever, instead of dying, the engine went crazy and would make the car accelerate by itself. When "idling" the rpm were around 4000. And then I got the usual lights going on on the dashboard. I stopped, pulled the codes, cleared the codes, restarted. Similar issue 20 minutes later. I finally cleared the codes again and plugged back the vacuum line. At least now the car stalls instead of accelerating.

The error codes from yesterday:

Thursday, 04 October 2012, 15:56:50
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
2 Faults Found:
17550 - Load Calculation Cross Check: Lower Limit Exceeded
        P1142 - 35-10 - - - Intermittent
16485 - Mass Air Flow Sensor (G70): Implausible Signal
        P0101 - 35-10 - - - Intermittent
---------------------------------------------------------------------------


Thursday, 04 October 2012, 16:15:07
VAG-COM Version: Release 409.1-US

Control Module Part Number: 021 906 018 M
  Component and/or Version: MOTRONIC ME7.1  G   6760
           Software Coding: 00031
            Work Shop Code: WSC 26084
1 Fault Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low
        P0102 - 35-10 - - - Intermittent

It still looks like the MAF is not working or the wiring is faulty, but I know replacing with a new MAF did not solve the problem and that the mech guy checked the wires and said it was all right.

[zuhaelter_82]

After all the BS I went through, I finally went to Pick N Pull for a used crank sensor and fuel pump relay. I replaced them both, with used ones! 2 months has gone by, 3k miles later and no issues! I could not tell you if it was the crank sensor or the relay.