Symptoms of a bad ignition wiring harness?

[virgoavant]

I am curious about the most common symptoms of a bad ignition wiring harness. I had someone scan my car with vagcom and we noticed a short spike in voltage on one of my ignition coils and then it went back to normal so I am trying to diagnose if it could be an ignition coil or the harness that caused it. The original reason for having the car scanned was because I was having some startup issues that were not consistent. I replaced a few things that may have been related to the issue with no success, crank position sensor, coolant temp sensor. Alternator and battery scanned and all good. Only issue with that scan was a very small amp leak of about .6 amps. Usually this issue happens from a cold start and it's very random, I could go weeks without it happening. I replaced my ignition coils with the red R8 coils Sept 2014. If I remember correctly there was a specific spark plug that was supposed to be run with the R8 coils. I can't remember what it was and couldn't find it with google searches. I would really like to know what they were and possibly the average cost of having the ignition wiring harness installed just in case I need to have that done I can budget for it.

[chad99]

If you can wiggle the harness while the car is running and either cause misfires of cause misfires to go away, that would say the harness is bad or swapping coils from one cylinder to the other.
Although even if it does not cause a misfire, if you have close to 100k miles, your wiring will be cracking by now, and getting it fixed will help in the future.
If you are handy with a soldering iron you can easily fix it yourself or you can find the harness repair kits that come with crimp connectors for each coil plug.
I have no idea what it would cost to have it repaired by a shop.
If you know someone who works with electronics or building circuits, I am sure they would be more than qualified to fix it for you.

What kind of starting problems do you have?

[texasboy21]

A replacement harness is $85 and will take a shop a few hours to replace it, so it should be $500 or less all said and done.

http://www.uspmotorsports.com/1.8T-C...placement.html

I, however, would start with the usual suspects - boost and/or vacuum leaks. Start with a boost leak test and visual inspection.