Diagnosing bad coil pack

[MugatuVR6]

I think a coil pack went bad but when I unplug each one individually the engine runs worse all six times. If one were bad, wouldn't the engine run the same when it was unplugged. I had all the symptoms of the bad coil though. I had a flashing CEL while driving in the rain and it ran poorly but it went away after the rain. A month later I started seeing the CEL blinking while accelerating or going up a hill, it had a loss of power and I felt a vibration through the car. I can tell the car isn't running on all 6 cylinders and there is definite loss of power but the idle is only a little rough. Is it possible the coil is okay enough to idle the car but under a load it fails?

[jaso028]

yeah you got a bad pack or a couple somewhere.., can you get it scanned?

[Wolfschnee]

getting it scanned is the best idea. One csn start to fail under stress. I had this happen. But it went really quick after the first time i felt it under stress. When was the last time you changed your spark plugs? Did you put them in yourself?

Use this link, if they all look the same its not a coil pack, if one or two look different then its probably coil pakcs or something else.

http://www.ngksparkplugs.com/tech_su...qs/faqread.asp

[MugatuVR6]

Will the scan tell me which cylinder is failing? Will an obd scanner work or does it have to be a VAG COM?

[jaso028]

VAG should tell you what pack is bad.. but an OBD scanner would tell you too.. but it wont pin point the exact one.. usually when one fails it throws the system in some weird mood.. lol
1 coil pack went bad on me and I used a generic scan tool cause my VAG was home and the OBDII scanner tossed up like 8 codes and 4 of them were for misfires in different areas..

you could also unplug a coil @ a time.. if the idle changes, that specific pack is good...
if you unplug one and nothing happens, you just found your bad pack...

[miniyazz]

Will the scan tell me which cylinder is failing? Will an obd scanner work or does it have to be a VAG COM?

OBD will do fine. It's unlikely to pinpoint the exact problem but will certainly tell you e.g. which cylinder has a misfire.

Edit: beaten.

PS I had a misfire on cylinder 3 according to OBD (car was running really bad). I suspected a faulty ignition coil so swapped over 3 and 4, and lo and behold, OBD reported a misfire on cylinder 4 too (had to drive it a short while). New ignition coil = problem solved.

Just don't drive it too far with a misfire as you can damage the cat.

[Wolfschnee]

my $50 wireless obd2 scanner and a $2 app will tell you exactly which cylinder is misfiring. Its pretty damn good.

[millerlite3421]

i've heard of the plug getting cracked as well, and during rain, moisture may cause it to short. Could be why it was acting up in the rain, but not after. Either way, get it scanned and let the problem be solved. Might think of buying another one just in case as I did. Dont want to have to drive too long without a replacement.

[MugatuVR6]

my $50 wireless obd2 scanner and a $2 app will tell you exactly which cylinder is misfiring. Its pretty damn good.

What scanner and what app do you use? Is it a smartphone app?

[miniyazz]

i've heard of the plug getting cracked as well, and during rain, moisture may cause it to short. Could be why it was acting up in the rain, but not after. Either way, get it scanned and let the problem be solved. Might think of buying another one just in case as I did. Dont want to have to drive too long without a replacement.

Definitely buy a spare, it's a common problem on these engines. £35 for a new one from a supplier or ~£25 on eBay for two used ones.

What scanner and what app do you use? Is it a smartphone app?

A cheap Bluetooth OBD II adapter and Torque (Android only) which is an epic app.

[MugatuVR6]

I don't see a lot of follow ups from OPs to what the problem and solution was so here it goes... I got an OBDII scanner and boom it was the #5 cylinder. I replaced the coil and it's all good. FYI that #5 coil was already replaced by a previous owner and it was a non VW part so in case you were wondering, the cheap Chinese parts are inferior.

[miniyazz]

I don't see a lot of follow ups from OPs to what the problem and solution was so here it goes... I got an OBDII scanner and boom it was the #5 cylinder. I replaced the coil and it's all good. FYI that #5 coil was already replaced by a previous owner and it was a non VW part so in case you were wondering, the cheap Chinese parts are inferior.

No guarantee of that given that VW's coils are known to fail. Did you check the other coils to see whether they had also been replaced?