Hey, a female friend has a 2001 cabrio with an intermitent no-start.
She confused thee hell out of me explaining it, but today I got to see the problem myself, so here's what I know:
Car cranks, often starts fine, but sometimes does not start despite repeated cranking. Codes have been scanned (not by me) apparently four fuel injector codes (I was told by her at one point short to ground, p1225-1228 i think) and three emissions codes. She's been told that it has no spark when it won't start. Yesterday she had it at about the 5th shop she's been to, and the mechanic gave the ecu a rap with a screwdriver to get it to start, and wants to sell her a new ecu.
When it wouldn't start for her today, I looked at it and wiggle tested a couple things, including main ecu harnesses, tapped the ecu with a screwdriver handle, no change during about 5 crank cycles, so I pulled the coil wire, got great spark, put it back on, and this time it started. I do not know if the spark was present during the no-start, or if the problem had resolved itself on the 6th crank attempt.
Intermittent does not seem right to me for needing a new computer. Any ideas? I've suggested cleaning and checking the ecu harness connectors and all grounds, but I'd like to be more sure that it'd fix the problem. Also, can anyone tell me if this car would be one of those models with frequent ground issues? If so, where are the ground points if I get a chance to go through and clean them up.
Thanks for any help.
Check the ground wires in the engine bay. There are several, and some on the front of the block. They rust, lose contact, and you lose start.
Check the fuel pump relay too. You can bypass it with a wire.
Lastly, ignition switch.
There are just too many things it can be. But those 3 are the most likely.
First, where in BC are you and what does she look like?

ECU is obviously a possibility, do you have one you can borrow and try on her car?
Has anyone actually checked the coil? Could be cracked and certain temp/humidity could be affecting it.
Has it ever stumbled to life or is it either working or not working? If it either works or doesn't, the fuel injector codes are strange, might just be coincidental though
I'd say there's a 90 % chance it's poor grounds. The big one from the battery to the block, the ones under the battery tray and even the ones under the dash although I don't remember if they have the same ground point as a Mk4 jetta/Golf, below the steering column. You may be able to find something if you do a google search for where exactly all the ground points are
I'd say there's a 90 % chance it's poor grounds. The big one from the battery to the block, the ones under the battery tray and even the ones under the dash although I don't remember if they have the same ground point as a Mk4 jetta/Golf, below the steering column. You may be able to find something if you do a google search for where exactly all the ground points are
my mk2 used to do the same thing, it was bad grounds, and that finally took my ignition module out. it would have no spark when it wouldnt start, then it would randomly fire right up and run fine..