Jetta had trouble starting, then was jumping while braked and at low speeds, now it's fine?

jetta
volkswagen

#1

So I haven’t driven my 2003 Jetta in about a week and a half. Today when I started it it struggled to start, and then at a stop light while my foot was on the brake it was jumping/stuttering. it continued when I moved at 5 mph, but did not happen while driving at higher speeds (15 mph) and went away when j shifted from drive to park. I got on the highway and drove for 15 minutes with no issues, and now the problem is gone. Is this a sign of a failing part?

edit: the spark plugs and wires were replaced 6 months ago. I had them changed because the car has always had a small intermittent rough idle that would sometimes happen when stopped and at low parking lot speeds, but it’s never been so noticeable. it was really lunging this time


#2

Perhaps, but there are a number of possibilities. Its’ possible that your fuel system lost pressure during the 1-1/2 week rest and it took a minute to get it back up to where it needed to be. That might have had a secondary effect of causing bad readings from the upstream oxygen sensor, manifesting themselves as erroneous fuel metering inputs to the injectors. Or, the throttle plate could have been sticking and loosened up once it began operating again.

Chances are that you have stored fault codes in your ECU. Have them read and post them here.

But, honestly, I think you’re likely good to go at this point.


#3

Not driving in a week could have discharged the battery enough to cause some ignition system problems. Keep driving it on a daily basis, see if the problem returns or not. It could also be the mixture is too lean from a vacuum leak, and that would show up most when the engine is cold.


#4

As @the_same_mountainbik mentioned, have the codes read. I’m pretty sure your car has a coil pack and not coil over plug design. I think you may have a failing coil pack that is causing the problem. If the coil pack is cracked it can cause these symptoms especially on humid days and in the morning when dew may have dampened everything.
After a minute or so of the engine running the coil drys out and the symptoms disappear untill the next damp day.
That may have been your original problem and not the wires that you changed.

Yosemite


#5

Solved: A few months later after sitting for a few days in heavy rain the car had the same problem, only much worse and the check engine light started flashing. After doing some research we settled on a cracked ignition coil pack. We removed it and saw a very tiny crack with what looks like the beginning of rust. Rather than replace the entire thing we coated all of the cracks we could see with a rubber based sealant and put it back in. The car has been fine ever since and I’m pretty confident that that was the problem.


#6

Hey, thank you for reporting back! And congratulations on the sleuthing and the low-cost solution!


#7

Thanks for letting us know. I would replace all the coils when you have money… if one is bad the others are soon to follow.


#8

I wholeheartedly agree.


#9

I assumed that she was referring to a single coil pack (with multiple coils), rather than individual COP’s.