GTI Loses Power

Does the tacho needle drop suddenly when power is lost?

Check the wiring to the Hall sensor in the distributor.

The sensor itself doesn't last forever; nor would you, sitting in a hot distributor with 30,000V or more arcing above your head.

If the tacho needle still reflect engine speed, then there's still a signal coming from the Hall sensor. Maybe the fuel pump relay is playing up... electrics differ quite a lot from one production run to the next.

Also check that the rubber bellows between air flow meter/fuel distributor and the throttle body is intact. A broken/weak engine mount can cause the engine to tear open a crack when under load and the engine will suck a lot of air that's not metered, resulting in a very lean mixture.

If so, perhaps it's simply the ignition switch. Jiggle the key next time power cuts out and see if it quickly returns.

Darryl.

Not sure what it is, but what is probably is *not* is ignition. If you lost ignition it wouldn't even idle. Focus on fuel supply issues. The transfer pump is the usual culprit in an A2.

I'm not sure I want to eliminate the ignition system as the culprit yet, as the problem is very intermittent. At the time the sudden power loss occurs, I'm sure the car wouldn't idle either. Problem is, by the time I start moving over to the side of the road, power returns, and it may not happen again for a few days.

I hear what you're saying about the transfer pump, as I've replaced a few of them in the 18 or so years I've owned the car. However, my experience with a failing transfer pump is that the engine tends to surge on acceleration (instead of completely losing power) and there is usually an obvious buzz from the main pump. An earlier post suggested a fuel pump relay problem; that's something I'll be checking out.

Thanks for your input.

You know, I can't tell you for sure if the tach needle drops or not; I'll be keeping a close eye the next time it happens.

Is it your experience that the Hall sensor can experience intermittent, rather than complete failure? The Bentley Manual led me to believe that unless the car has completely lost spark, and will not start, the problem is not likely to be the Hall sensor. I will take a close look at the sensor and its wiring though.

I like your idea of a faulty fuel pump relay; I think I'll pony up the bucks for a new one and see if that does the trick.

I have checked the intake system for obvious leaks and don't seem to find any. I think I'll pull the bellows off the car and give it a good going over.

I'll let you know what I find.

Thanks,

go for the cheap first. a new fuel filter is always a good investment. water in a cis will cause the exact same symptoms. rick.

Intermittent failure seems to be more characteristic than a total failure from the few cars I've seen with that problem in the real world.

The Bentley Manual is good; but it's not gospel. Much of it was written well before the age-related issues came up.

The symptoms you described are fairly characteristic of an intermittent Hall sensor dropout.

The tacho needle is the tell-tale. If the Hall sensor fails to send pulses to the ignition module (or ECU), the coil won't be fired so the tacho needle drops to zero.

It's one of the typical "problem areas"; along with the ignition switch that I didn't think of at the time of writing (dopey me!).

I thought I'd subtly remind you. ;-) My money stays on the switch.

I think both you and Bernd were on the money with this one. The key seems to be very loose in the ignition, and if I wiggle it while the engine is running, it takes a remarkably small amount of up and down wiggle to shut down the engine (without any obvious rotation of the key). I've reproduced the problem in the garage several times, and it seems like normal vibration during driving could do the same. I've never really paid attention to how loose the ignition switch had become. I'm going to do some disassembly over the weekend to take a closer look.

Follow-up question: do you think the problem is confined to the electrical portion of the switch, or do you think the lock cylinder itself is worn and also needs replacing?

Anyway, thanks for the tip!

In the past, I've gotten away with only replacing the switch but take a closer look when everything is apart. In my experience, make sure the steering wheel is straight before you take things apart.

Glad to help.

Darryl.

Just finished removing the ignition switch. Not a particularly difficult job. The lock washer that holds the steering column housing in place took a bit of time to remove by carefully tapping around it with a drift, working it gradually outward. I especially liked the part when the spring under the lock washer launched the washer toward my head at considerable speed after one too many taps. Fortunately, I was ready for it and it ended up in the back seat rather than between my eyes. No harm, no foul. I'm going to try and pick up a new switch early next week; I'll let you all know how it all works out.

-- Kent

glad you are alright! next time replace the steering wheel nut on the shaft. ;-) I think I have been able to use some large pliers and turn that "locking nut" and get it to safely screw off.

I have actually taking the ign switch apart on my 91 Passat and replaced the faulty spring from an earlier switch to repair that switch. Your switch is probably burnt with carbon but the springs are fine. That would require a good cleaning/light sanding. :-) What do you have to lose since you are purchasing a new one anyway??? You will be carefully prying the round cover off. (Key section down, terminals up)

Watch those springs and small metal pieces inside though! lol

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

Put the steering wheel nut on the shaft to keep the lock washer from becoming a dangerous projectile? Duh, that seems pretty obvious. Maybe it would have done me some good to have the washer smack me in the head!

Near misses are better than getting hit. YOU WILL STILL REMEMBER!!!! LOL

And of course others hopefully read this and you save their eyes! ;-)

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris