91 passat stalls...help!

i've got a problem with my 91 passat gl stalling out. i was on the highway doing about 65 mph and the engine just cut out. rpm slammed down to zero! attmpted to restart..no luck. had it towed, about 2 hours later... started up with no problem. this is about the 3rd time this has happened. even had a mechanic keep it for 3 days, couldn't find a problem. i hope you guys can give me an answer. thanks in advance

Do you have any idea if it was a loss of fuel or spark when it died?

I have a 92 Passat GL that is doing the same thing to me, stalling out erratically. It cranks afterwards and sometimes fires but usually will not run untill a couple hours later. I just had my fuel pump and filter replaced so i know those are good and i installed a new distributor cap, rotor, and plug wires. I scoped the ignition system and that turned out strong, no problems. I tested my ignition coil and it failed one of the three tests, the primary circuit resistance test but i don't think that is the problem. I took it to a shop four days ago and I haven't heard back from them yet. If i find out anything solid I'll let you know.

Same exact problem here. If anyone finds an answer, please post it!
I have had this problem occur intermittently for about a year. Super PITA.

Anyhow, since it is notoriusly intermittent, it is very hard to diagnose. By the time that I get the thing home, and into the shop and begin doing diagnostics, it starts right up, no problems, thus all of the diagnostic work is normal.
I have the Bentley manual, and have been through all of the tests on the Hall sender, coil, coil power stage, ignition wires, etc... Everything tests normal when I have done diagnostic work on it. In addition, I have had the codes pulled as I know a guy with the old vag 1551 scan tool. No codes (except for an EGR code that has always been on). No check engine light, no nothing.

On the roadside, where it is not so convenient to do diagnostics as trucks careen by you at 80mph, I have found that the secondary coil voltage is non-existant when the thing has died (no spark while very irritated wife/kids turn the key, and I hold kilovolts in my hand under the hood while looking for a spark).
However, when it has been broken, I have not been able to test the primary voltage at the roadside. And of course, when it gets towed home, it starts just fine, either a few hours later, or the next day. I have also tried the "mist the coil/wires/etc.." test which reveals no arcing, and no problems.
The thing runs great normally, no miss, no hesitation, plenty of power (for a 2.0 anyway).
Additionally, I have removed/cleaned/reattached/retightened all of the grounds that I can find under the hood and on the interior under the dash.
Fuel system diagnostics have revealed no abnormalities. Good spray pattern, reliable functioning of injectors, including cold start, and two functional fuel pumps. Requires guage set for testing pressure, which I do not have, thus have not tested, but the problem is clearly in the spark side, not the fuel side.

OK, I'm sure that someone out there is thinking ignition switch,which is a classic problem on these cars. Well, mine does not give those type symptoms. It is not possible to reproduce the symptoms while driving by moving the ignition around (unless you actually turn the key off), and the only thing that is lost when the thing fails me on the road is the ignition. Tach to zero, coast to stop. No problems with lights, radio, wipers, or anything else electrical when it dies. Just tach to zero, and pissed off driver/wife/kids. Occasionally, the thing does not make it all the way to "coast to stop" and re-fires before the motor coasts down, then drives normally for a day or week or month, until it happens again.

One thing that I have noticed, is that it does this in the winter almost exclusively. All spring/summer/fall no problems. But now that it has gotten quite cool some mornings here in KC, it's happening again.

Possible suspects:
distributor/hall sender
coil power stage (what does this thing do, and is it temp sensitive?)
ECU (unlikely but possible)
Knock sensor with severe malfunction?
How about the throttle pos. sensor? Bad signal intermittently?
Something else?????????

Anyhow, please help if you can, or else I either have to part with the car or move to a warmer climate. Hmmmmm, maybe both? Hope my workup saves someone some time/money.
Thanks in advance for any replies.

Does it hesitate or engine knocks when it goes to reverse, before your engine stalls. This problem could be neglect of the air intake boot above the air filter. There may be a hole in the rubber boot check it carefully for holes cracks. Some mechanics take it off and break the boot unknowingly thus the problem in the intake the car chokes and stops running simple problem first then look at a sensor intake later.

A&E

--Problem with air intake boot would cause a completely different array of symptoms.
Not complete and intermittent ignition electrical shutdowns. My intake boot is fine, as are all of the rest of the rubber connectors in the intake air path.
--Intake cracks would allow unmeasured air into the combustion chamber, and may result in a variety of engine abnormalities from rough running/idling to variance in idle speed, to complete non-starting of the engine depending on the severity of the air leak. However, a cracked boot would not result in occasional loss of ignition, followed by subsequent selfcorrection and resolution. Also this would not expalin the seasonality of my problem.

Anyone else with any ideas? Seen this problem before? Want to buy my car?
Thanks in advance for any replies!

Same exact problem here. If anyone finds an answer, please post it!
I have had this problem occur intermittently for about a year. Super PITA.

Anyhow, since it is notoriusly intermittent, it is very hard to diagnose. By the time that I get the thing home, and into the shop and begin doing diagnostics, it starts right up, no problems, thus all of the diagnostic work is normal.
I have the Bentley manual, and have been through all of the tests on the Hall sender, coil, coil power stage, ignition wires, etc... Everything tests normal when I have done diagnostic work on it. In addition, I have had the codes pulled as I know a guy with the old vag 1551 scan tool. No codes (except for an EGR code that has always been on). No check engine light, no nothing.

On the roadside, where it is not so convenient to do diagnostics as trucks careen by you at 80mph, I have found that the secondary coil voltage is non-existant when the thing has died (no spark while very irritated wife/kids turn the key, and I hold kilovolts in my hand under the hood while looking for a spark).
However, when it has been broken, I have not been able to test the primary voltage at the roadside. And of course, when it gets towed home, it starts just fine, either a few hours later, or the next day. I have also tried the "mist the coil/wires/etc.." test which reveals no arcing, and no problems.
The thing runs great normally, no miss, no hesitation, plenty of power (for a 2.0 anyway).
Additionally, I have removed/cleaned/reattached/retightened all of the grounds that I can find under the hood and on the interior under the dash.
Fuel system diagnostics have revealed no abnormalities. Good spray pattern, reliable functioning of injectors, including cold start, and two functional fuel pumps. Requires guage set for testing pressure, which I do not have, thus have not tested, but the problem is clearly in the spark side, not the fuel side.

OK, I'm sure that someone out there is thinking ignition switch,which is a classic problem on these cars. Well, mine does not give those type symptoms. It is not possible to reproduce the symptoms while driving by moving the ignition around (unless you actually turn the key off), and the only thing that is lost when the thing fails me on the road is the ignition. Tach to zero, coast to stop. No problems with lights, radio, wipers, or anything else electrical when it dies. Just tach to zero, and pissed off driver/wife/kids. Occasionally, the thing does not make it all the way to "coast to stop" and re-fires before the motor coasts down, then drives normally for a day or week or month, until it happens again.

One thing that I have noticed, is that it does this in the winter almost exclusively. All spring/summer/fall no problems. But now that it has gotten quite cool some mornings here in KC, it's happening again.

Possible suspects:
distributor/hall sender
coil power stage (what does this thing do, and is it temp sensitive?)
ECU (unlikely but possible)
Knock sensor with severe malfunction?
How about the throttle pos. sensor? Bad signal intermittently?
Something else?????????

Anyhow, please help if you can, or else I either have to part with the car or move to a warmer climate. Hmmmmm, maybe both? Hope my workup saves someone some time/money.
Thanks in advance for any replies.
Don't know the yr of your car but I have 97 passat vr6 w/ same problem .Changed everything possible and nothing until Bochanm told to change the speed sensor and guess what? ,, It runs fine now.. Hope it will help you ..

It's going on three weeks now that the shop has had my 92 passat with this problem. They still have not given me a positive ID on the problem but they do suspect my idle regulation systems, they say a sensor may just be dirty and may not require replacement, but other than that, theres nothing new on my situiation. Soemthing to go along with the other replies listed here would be that I understand ignition coils with high internal resistance will heat up from engine temp during operation and increase the resistance in the coil until it opens the circuit and you lose all spark until the coil cools down again and resistance lowers. I may try throwing a different coil at my car when i get it back and see if that changes anything but once again, I'm just guessing here. The specifics of my car are posted in the thread 92 Passat GL erratic stalling/rough running

I at one point last year tried the coil swap. Died a few blocks away from an O'reily's and stopped in, dropped the 60 or so bucks the y wanted for a new coil, and swapped things on the roadside. Guess what? Still no spark with new coil in place and car dead. So at least for my vehicle, the coil is not the issue.
Incidently, at that time, I reinstalled the old coil, walked back to the parts store, returned the new coil that I had just purchased, and walked back to the car, and true to the intermittentcy of the problem, it started right back up, no problem.

Incidently, mine has not acted up in the last few weeks, and I have done nothing to it but drive it. Maybe she knows that I am searching for a cure for her bitchyness, and she may be subject to surgery soon if she continues to act up. ;)
Thanks for the update, Gregg, and good luck finding the problem.

I got my car back from the shop two days ago, they couldn't find anything wrong with it. Since then, I have driven it nearly 170 miles without a problem besides a little difficulty with starting it cold. However, I had it idling in the driveway just today while I was putting air in my tires and I heard it start bogging down and losing rpms. I shut it off and tested my coils resistance and the primary circuit was 7,800 ohms, I remember the specs being a lot lower than that somewhere around .6 ohms or .6 kilo-ohms. The secondary circuit showed the same resistance as the primary so I ordered a new coil. It'll be in tomorrow so I'm going to install that and see if it does anything for me or not, it's all I can think of besides the witch doctor and exorcist that I have scheduled to check my car out next week. I did have somebody reply to my thread suggesting I replace my O2 sensor, what do you guys feel about that? Thanks for your input!

I have to make a correction to my previous reply. Since that posting I have realized that I had performed the resistance tests on my coil incorrectly. WIth the proper procedures, my ignition coil tested within specs so I no longer believe that the coil can cause the stalling problem. I checked the resistance of my coil cold and then idled my passat until it stalled out upon which i tested the resistance of the coil again and found it was the same as when it was cold. After stalling, the engine would crank but would not fire, I spark tested all the wires and I had strong spark at each of them. I gave it WOT and cranked it and it fired up fine and ran without a problem. So I still do not know what the problem could be. My next idea is to call a VW dealership and see if I can talk to one of the techs and ask if they have encountered this problem before because it seems to be somewhat common, or at least not just one individual incident.

Have you looked at the ECM power supply relay or the fuel pump relay? See if they get hot or don't click when the key is turned to the on position during a no-start event.

Alright, I spent all day picking my car apart and I found some things that may have been causing the problems. First, I removed my sending unit and priming pump from the gas tank and inspected the filter screen, it was clean so it was not restricting fuel flow at all and causing stalling. Underhood, I was checking out my fuel distributor and noticed that it was leaking a little bit of fuel on the engine side around the differential fuel pressure terminal. The connector was soaking with fuel so I cleaned it and dried the terminals and found that the two torx head screws that hold the differential fuel pressure unit onto the fuel distributor were a quarter turn loose each. I tightened them and cleaned the dust off that was stuck to the fuel so I can see if it still leaks later. Now, the most probable and useful problem I found with my car was in the wiring harness for my distributor, coolant sensor, and warm-up/idle control. This harness is below and to the passenger side of the ignition coil. All of the harness tape had been rubbed off and the wires were resting against a metal coolant flow pipe, (I believe its for the heater). The insulation of a red wire with a black stripe had been rubbed through and the wire was shorting to ground on the metal pipe. (Inspect all wires in harness regardless) The wire supplies information from the distributor to the computer which monitors ignition and fuel supply. I repaired the insulation and put the entire wiring harness in a plastic wire loom to protect it from further damage. I'm not saying that was the cause of my car stalling out but it makes sense. Shorts to ground can be intermittent and in this case, humid weather or water can improve the connection of the wire to the ground and therefore the problem becomes worse/more prevelant in wet conditions. If the wire were to make contact with the short while driving down the road it could easily disrupt both my ignition and fuel systems and stall the car and prevent it from starting again. I haven't road tested this correction any more than 5 miles so far, so I don't know if this did fix my problem or not. SO, I would recommend inspecting this wiring harness on your vehicles, the short was below the distributor cap and towards the firewall on a metal pipe 1" in diameter or slightly bigger. Good luck, let me know if any of you find similar problems with your wiring harnesses.

:biggrin: So far I haven't experienced the same symptoms as I had before I found that short, things are running smoothly, confidence in my car is once again building.

This sounds eerily familiar. I have a 94 (I know this is for earlier models, but this is relevant) Passat GLX VR6 and have been experiencing this very frustrating issue that sounds an awful lot like the same things I have read in this thread. A month ago, my engine bucked on the highway, which made me very worried since she NEVER bucks, misses, or stalls. About 10 miles later, tach went dead, and I pulled off an exit ramp just in time. Tried to start it for about 20 minutes (battery's almost new and starter is great). Sounded odd at first and I thought I had snapped the timing belt/chain, but something told me it was something electrical since I had been hearing a buzzing, almost like sparks arcing, under my dash near the fuse block for a while.

GOt the beast towed home and she would not even sputter for me. Called mechanic and checked with the car again and thought that it was the fuel pump after I checked the fuse readings and all seemed okay (I was getting voltage as I cranked the car, but it died shortly after while still cranking). I thought that it was fine like that and it just shut off because the fuel pump was not pressurizing or something. TOok that blasted little round door off the trunk floor and after much work, got the retaining ring off. Ordered a new fuel pump and readied to put it in. When I looked at the new one, they were not even close. Plusk, I would have had to buy an additional $120 new sender unit to make it work (I guess that they don't make that exact pump anymore). Had a useless new pump, so I took the old one apart and cleaned it thoroughly and tried it with leads from the battery and it worked! CHecked the voltage and it was no good. Went to the VW dealer to pay $25 for a $5 relay and put the relay in. Put the pump in and it started. Victory, yes sir. Well, that was short lived.

Car died again and I put the old relay in and THAT worked. A few miles later, it died again, but I pushed on the relay and it started again! This happened repeatedly over the next few days but got better and better. Had to travel 60 miles to Boston today and as soon as I had gotten farthest from home, it died. I ran a wire from a working fuse to the FUel pump fuse and it worked. I felt like a GENIUS. Off I went. It died when I stopped for coffee and went to start it again. This time, I took apart the fuse block--just dropping it down and it appears as though I am getting intermittent voltage at the fuse. VW said that the fuel pump relay for the early 90's Passats where extremely popular, but I think folks just think it is the relay. When the beast starts to die, the relay makes a buzzing noise, like it is getting power to switch, then not, then power again, very fast.

I am at a total loss here. I am going to a junk yard tomorrow to remove a fuse block from a 94 Passat that I have picked almost clean and I am going to use that as a guide so I won't have to disconnect the whole block. Next I will check the ignition switch. ANy suggestions? Please help!
Thanks!

Its A Fuel Pump Had This Problem With Audi 90 Same Thing.

Good idea and probably the right diagnosis in a majority of cases, but in mine, it turned out to be the ECM relay, one which VW says is VERY popular in their parts department. I had already been charged $28 by the stealership for a $3 fuel pump relay, so I ordered the ECM relay from Europarts direct for $4.30. VW had wanted $34 for the ECM and I checked the relay I received against the dead one and the two were IDENTICAL--same numbers, same manufacturer, everything. That's an almost 800% markup over e-retal!

Not one stall, or skip since the relay replacement. However, drving on the highway the other day, I hit a small pothole and noticed that the back end skittered sideways. Yep, shocks went. Back shocks totally blown with struts needing replacement soon too. That makes the one month total for my baby as follows: Ball Joints --estimate: $370, second opinion $140, clutch: first estimate $860, second opinion $625, fuel pump: estimate: $760, misdiagnosed by stealership, relay $28, top radiator hose: estimate (VW) $300, hose $198, web price $50, 20 minutes installation, back brakes: estimate $185, self install of web-bought pads, 1 hour and $30 struts and shocks: estimate $810, professional install with my web-bought parts $430 total.

WOW!

The grand total for one month if I went with the mechanic's recommendations and "just had it done" (instead of getting other opinions and/or doing it myself) was: $3,285.00

The actual total, arrived at by second opinions, asking questions, buying parts on the web, and doing some repairs myself came to: $1,303.00 I estimated that I spent about 11 hours extra making calls and doing repairs. I think that 11 hours is worth almost $2000 in savings, don't you?

Thanks for the suggestions folks!
LAZARUSvw

FOUND THE PROBLEM, very difficult to find without swaping parts. The powerstage when it goes bad on this sometimes won't work in the cold or not well. It cuts out on the highway because it is cooling off. It will start up after sitting because the very hot manifold heats it up again, but it is intermitten and may work fine in the shop or not start even heated up. Even though your coil is good you still have to buy it to get the power stage. If you notice in the book carefully there is no check for the powerstage itself only the signal and wiring from the computer this tricked me for a while. The powerstage handles the ground to fire the coil's spark. I'm talking 90 Passat. Good Luck

Yea, that happened to me a couple of times. I soon realized that if I unplugged the diferential pressure regulator the car won't stall, and it will just take a few times to get it started (it will stall right away at the beginning, but will run smooth eventually). Try it and let me know.
By the way, those who don't know which the differential pressure reg is, you will find the plug beside the air filter housing. I believe the wires are red/white and blue/brown.

I've had problems anywhere from fuel pump relay to an alternator pulley ribbing the fuel distributor "differential pressure regulator" to a fuel pump on vw's