sluggishness and cruise control problems

I took my 2003 Passat in for "engine light" service a few weeks ago. They apparantly replaced one of the ignition coils. Ran great until this past week.

Then not only did it suddenly develop bouts of "sluggishness" (poor accelleration, rougher idle), the cruise control doesn't work.

While I wait for the service appointment, does this sound like anything in particular? I was a bit surprised that they both went out at about the same time.

Reply to
Darren Dunham
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Some cruse controls are vacuum controlled. A loss of vacuum could cause both problems.

Reply to
Joseph Meehan

The Passat could be different, but on my '87 GTi the cruise is vacuum operated, but it has its own vacuum pump and does not use engine vacuum.

As I understand it, the cruise control function on newer VWs (with throttle by wire) is built into the ECU firmware. I would imagine that if the ECU detects something wrong, it could automatically cancel the cruise.

Reply to
Randolph

I wonder if some other engine controls are feed off that same vacuum?

I believe mine is as well, but I have not bothered to check. I will have to open up my Bentley CD and find out some day.

Reply to
Joseph Meehan

Check to see if your rear brake lights are working. The brake light switch went in our '02 Jetta wagon recently (and as it turns out there was a recall but we hadn't gotten a notice) and the cruise not functioning is what clued me into a problem in the first place.

As you can imagine, you really don't want to be driving around with no brake lights.

Craig

Reply to
Craig Faison

Some faults will turn off the cruise along with AC compressor. BTW, the cruise is all electric.

Reply to
Woodchuck

Jim B.

Reply to
jimbehning

On some VW's (as you have found out) the cruise control will not work if all the brake bulbs are burned out. Having all bulbs burned out will cause the cruise to "believe" that the brake pedal is pressed. For A2 cars, I know this to be the case for some years, not for others. For the Passat I do not know the details.

Reply to
Randolph

No kidding. In fact, the lights were out.

So the cruise/brake light association I get. What that does or doesn't have to do with the engine performance, I don't know.

It's under warranty and got dropped off at the dealer this morning. Hopefully I'll know soon.

Reply to
Darren Dunham

Let us know what they tell you... we didn't have any running issues when the switch failed on our Jetta.

Needless to say, I wasn't very pleased to find out that my wife & kid had been driving around w/no brake lights for who knows how long. My wife never uses the cruise, and I rarely do, so we really have no idea how long it had been that way.

Craig

Reply to
Craig Faison

Well, I don't think I understand the entire issue, but yes, the brake switch failed and it can confuse the computer to the point that it affects performance.

My wife really noticed the power difference almost instantly. Without that, it would have been a while because she doesn't use the cruise either.

Yeah, I'd like to think you could detect the failure and turn on a dash light. The printout of the work says that the computer code shows a brake switch failure...

Reply to
Darren Dunham

Interesting; we definitely didn't have running issues. IIRC, your vehicle is a Passat... I wonder if the computers are different enough for the Passat to be affected and the Jetta not...

It's a safety feature! ;-)

Craig

Reply to
Craig Faison

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