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Car won't start with new plugs/coil packs?

ctvw14

New member
Car is a 2012 Golf 2.5l. 110,000 Miles. A few weeks ago the car started misfiring/hesitating under acceleration. Threw codes for misfires on all 5 cylinders. I installed new coil packs and spark plugs from ECS tuning and the car will not start. It will crank but not turn over. I put the old misfiring coil packs back in and the car will fire right up, but will still misfire.

I went to a VW dealer and asked them about the problem and they said the newest revision of coil packs (07K905715G) were supposed to supersede the previous versions, but that they had the older models in stock as well. I bought a set of pre-revision coil packs (07K905715F) and installed them in the car and once again, it will crank but won't start. The minute I put the old burned up coil packs in it turns on but continues to misfire.

Any ideas on why either version of genuine VW coil packs will not work in the car, but the old ones start without an issue? I've spoken with two dealerships and two third party companies and nobody seems to have an answer for me. I'm just having a hard time figuring out why simply switching to new coil packs will make or break the car being able to start.
 
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MLue1

Drag Racing Champion
Try doing a double reset of the ECU to ensure that the Long and Short Term Fuel Trims are reset. It is likely that the ECU was compensating for the bad parts and still working with those settings, hence you get the misfires. The double reset should zero the Fuel Trim.

If you have VAG.COM or OBD11, you can monitor this using Engine measuring Blocks 033 and 032. 033 always shows the realtime reading of the O2 sensor, 032 gives a goo indication of the amount of correction that the ECU is making to the fuel trim to keep things in spec. Under misfire correction the correction will be out of spec.
 
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ctvw14

New member
Reset ECU and used OBD to check on the fuel trims. Both trims were within normal range. Had a fault code for the post-cat o2 sensor. Replaced the sensor and tried installing the new coils and once again, car will crank but will not start. As soon as I put the old set of coil packs back in, it fires right up, but will misfire at idle every 15-30 seconds and will break up under load between 3k-5k rpm. Had a few people look at it and no one can tell me what the issue is. Any ideas would be greatly appreciated because i'm running out of things to try.
 
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ctvw14

New member
***(Only components being changed out are the 5 coil packs...can't find a reason why an old set will allow the car to start and a brand new OEM set will crank but not fire...)
 
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MLue1

Drag Racing Champion
***(Only components being changed out are the 5 coil packs...can't find a reason why an old set will allow the car to start and a brand new OEM set will crank but not fire...)
One of the new coils may be bad, put the old ones back in and try subbing in one of the new coils at a time.
 

ctvw14

New member
Yeah, already tried the new coils one by one...car will run with up to 3 new coils and 2 of the old ones, but will barely idle. I also put the entire set of new coils in my friend's car and it fired up right away and ran strong so it has to be something with the car itself, the new coils are all good.
 
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