vw new beetle misfires cylinder 1 puzzle

Happy Sunday to everyone, back to it tomorrow.

Daughter's 00 Beetle, she tells me CEL is on and running rough mostly at idle.
You can hear it missing.
Code comes back cylinder 1 misfire. Plug looks still new, about 5K miles. Wires look new, car has 55K
Get out the Haynes manual, start looking at the coil, weak spark on #1 compared with other three. It says weak spark means no spark. Check resistance.
So I put the meter on the coil and the wires and it resistance checks good.

Coil still bad? Replace it? Its a $100 part. I'd love to look at something else..... I hear these cars have emission parts issues, and it had to have a mass airflow about 7K ago. It really ran bad then, but the dealer didn't charge on that one.

Thanks

Vincent

 

Only a back yard mechanic but a spark plug that looks good can most certainly be bad.
For a couple of bucks you have nothing to loose.

Messed with my Honda pressure washer for three hours that has started 1st time every time for eight years.
The "new" plug I put in last fall was the problem.

 

IS the spark weaker on that cylinder than the other? Absolutely? If so, finding this should be easy. That means the problem is confined from the rotor-cap in area of terminal of cap, through plug, only. Unless there is also something I am not thinking of regarding the induction, during rotation in the distributror, that is affecting that cylinder

 

ecman51, it is weaker than the other three, absolutely, and it's also weaker right at the coil tower on #1, a lot weaker.

Here's something else, I pulled off the wire to the fuel injector and at idle it ran the same. Maybe that means nothing.

I'll try a new plug, whynot?

Thanks a lot.

 

Are you dealing with individual coil packs? I've never had to deal with these yet and others here are more in the know about these.

(Or are you refering to the distributor cap tower?)

Regarding no change when removing fuel injector wire makes sense because naturally if you have no/weak spark, no matter WHAT you do regarding that cylinder, will have no effect on that (dead) cylinder.

 

If you find the plug isn't at fault, it's probably the coil. I believe that one has individual coils.

Since we're not on the clock, I would swap coils with one of the other cylinders. If the poor spark moves with it, replace the coil. If not, check wiring and connections.

Hope this helps,

Bob

 

What engine is in the beetle? 2.0 or 1.8T?
If it's a 1.8T the individual coil pack is probably bad, If it's a 2.0, I'd replace the plug and wires before a coil(it may need coil anyway).

I used to work at a VW dealer for 7 years, I hope this helps.

 

For some reason I saved those original plugs, so I threw one in # 1 after brushing it off. Running right.

Greg, you nailed it. 5000 miles is too short for a $9 spark plug, but I guess they go bad sometimes. If I'm learning here (and I always do) I guess it's stick with original plugs, NGK. They didn't have em when I changed em and the part guy sold me the "E" brand. Now we know they're good for 5K.

Thanks to all for chiming in. That's what makes this forum great!

vincent