So when you turn the key all the way to the left, the engine doesn't immediately shut off? Hmmmmmm....ignition switch faulty maybe?

 

Sometimes it does and sometimes it won't. When I step on the brakes a couple of time it will shut off. Any clue?

 

I believe this is called dieseling. (don't quote me on it ) Might wanna search that.

 

I don't think so cause it's running as if the ignition is not switched off.

 

hey just think of it as a built in turbo timer:lol:

 

yes what a new discovery and save your turbo for free!!!:lol:

 

After you switch it off, how long does it run if you don't do anything? Don't touch the brakes or anything, just let it run its course.

I believe this is called dieseling. (don't quote me on it ) Might wanna search that.

Interesting idea passatboy. I think what your getting at is more of an uncontrolled ignition (also known as pre-ignition) due to hot carbon deposits on the piston heads. If there are carbon deposits, I don't know how they'd get there. Perhaps the computer is running the engine so lean that carbon is building up.

With that.....dinofg7171, what type of fuel are you using? If your using anything lower than 91, it might be contributing to the problem.

 

I am pretty sure you have a faulty ignition switch. Dieseling did indeed happen at one time, but I don't see it occurring with a modern fuel injected engine without other obvious problems occurring.

Excess carbon deposits can cause pre-ignition, but not dieseling. For dieseling to occur, you need actual fuel, which the injectors cut off when you turn the key.

SirWired

 

True.

 

after switching it off, it will keep running till I step on the brakes or till I run out of fuel.

 

I'm using 91 octane fuel

 

Hook up a timing light, run the engine for a couple of minutes, then observe whether you still have a spark as the engine continues to run with the ignition turned off.

This differs from your problem, but when my son was unable to shut down his S4, the problem turned out to be a shorted starter lead. We replaced the starter and repaired the starter/alternator/battery cabling. This experience was definitely a first for me.

 

Will a timing light work with a coil-on-plug engine? I can't say I have ever thought about it before...

SirWired

 

Was your son's S4 having that problem on and off? Or did it just happen onw time?

 

I've got agree with the ignition switch theory group.

 

I'll be replacing the ignition switch and see what happens

 

It is the long sought after invisible turbo timer.

 

finally got to replace the ignition switch but the same problem is still happening. Any more ideas?

 

I had this happen to one other car and it ended up being a bad ECM. What engine do you have? Might try looking at the starter relayand others, it could be a stuck relay. When the car is running try pulling out the stut off relay and see if it will shut of.

 

1.8T

 

Is your fuel pump still running when this is happening?

Your ignition switch cuts power to the fuel pump relay and the injectors. So when the key is turned to off, the injectors will not operate and hence the engine will shut down immediately. If your engine is not shutting down, then positive is still getting to that circuit either via a faulty ignition switch or a short to positive. That circuit connection is labeled "15" in the instrument panel wiring harness.

Have you done any recent work under the dash?

Stepping on the brake tells the ECM to cut throttle. There is a possibility that if the brake light switch terminal 1 which is a fused positive (fuse 13) is shorted to terminal 4 that positive would be able to get back to the circuit mentioned above through the normally closed brake light switch to fuse 7 (which gets it's positive via the ignition switch positve mentioned above). Then when you step on the brake, the contact opens and the car stops. So either pull fuse 13 or disconnect the brake light switch and see if the problem goes away.

 

I would think that it is cause it revs when you step on the accelerator. I haven't done any work under dash. I'll try your suggestion and get back with an answer tom.

 

that's a great breakdown ken, but what about the thought that the car's relays are getting stuck?

with our age, and vw's history of relay issues, it's plausable to believe that the relays are old and sticking closed.

 

There are no relays in the circuit to the injectors. In order for the car to run, the injectors have to operate. The only common thread is the brake light switch (or wires to the switch). That's the only logical device / wires that can backfeed positive to the the injectors (and ignition switch and fuel pump relay) yet cut the power to the injectors when the brake is depressed.

 

ah. ok. i don't have a diagram on hand right now, so i don't have a full grasp of what all goes around what parts of the frame, and to where.

but it sounds as if you have a definite lock-on to the target failure.

i have another scenario in my head of how this could happen, but without diagrams, i can't spit it out, let alone proof my theory for correctness. (i need a bently :banghead: )

 

You may want to pull some of the ignition or fuel fuses to see if it shuts off. I would tend to believe it is a relay or a switch as anything with moving parts will have a finite number of cycles until it fails. By pulling fuses one at a time you can narrow down which circuit is the problem.

 

Would you possibly have a turbo timer that you don't know about?

I'm getting that it's running like normal, not Dieseling (putter-putter...just BARELY running and sounds like a Diesel truck). Good lucking tracing around your electrical system for that. Pulling single fuses and such will probably kill the engine every time, but is worth a try.

 

i don't have a turbo timer.

 

I pulled out fuse 13 and true enough, the engine stops. I put back the fuse and the dash lights were as if the ignition was on switched position till I stepped on the brake again. It's definitely got something to do with the fuse 13. What should I do next?

 

I pulled out fuse 13 and true enough, the engine stops. I put back the fuse and the dash lights were as if the ignition was on switched position till I stepped on the brake again. It's definitely got something to do with the fuse 13. What should I do next?

My guess it's the brake light switch but could be wiring. To check the brake light switch, take the lower dash panel off under the driver's side and disconnect the electrical connector on the brake light switch which is mounted on the pedal cluster. If the problem goes away, it's probably the brake light switch.

To check the switch, get an ohmeter and remove the brake light switch and test the contacts for continuity. Termials 1 to 2 should be open and terminal 3 to 4 should be closed. Push the switch in and terminals 1 to 2 should close and terminals 3 to 4 should open. Also, check to see if there is a short between terminals 1 and terminals 4 (which is probably the case and causing the problems).

If the problem does not go away then there is a problem with the wiring to the brake light switch. With fuse 13 pulled, check the wires for shorts to each other at the connector especially the red green wire (teminal 1) and red/white wire (terminal 4).

 

Had the same problem on my 2003 Passat GLS 1.8T. I went to the dealer and they noticed that there was a open recall "Break Light Switch" on the car. After the recall was done the problem was solved. Zero costs for me