# Random misfires, rough idle



## brilliantwagen (Mar 5, 2009)

I have been tracking this problem for a while, I have misfires on Bank 1, random cylinders, random counters. I can watch them using VAGcom on MVB 15. No misfires on Bank 2. Misfires are not constant, check engine light never comes on. My long term fuel trim is showing rich. Here is what I have done to try and isolate the problem
New plugs, twice.... first set had red powder subsatnce on them so I replaced, no effect.
swapped fuel injectors, random, from bank to bank. No change. 
swapped MAF and drove for weeks, no change. 
Swapped plug wires from bank to bank, no change.
checked for a plugged cat by checking temperature pre and post cat, nothing noticed to indicate a plug. 

Any help is appreciated!
135k on clock, runs very well at highway speeds.


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## walkingfool (Mar 24, 2008)

*Re: Random misfires, rough idle (brilliantwagen)*

I'd check the compression, and if that didn't show anything off, check the vacuum (I know, so old school)


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## matc (Apr 2, 2009)

*Re: Random misfires, rough idle (brilliantwagen)*

What type of spark plugs and wires are you running if I might ask? I had this similar problem and a friend of mine who is a vw/audi mechanic told me this particular engine is extremely temperamental when it comes to the ignition components. When this happened to me I through a set of factory spec NGK plugs, a resistor plug, NOT platinum or any other type, and a set of factory wires made by Karlyn and presto problem solved. You can get the wires any where on the internet for way cheaper than vw/audi will ask for them and they're the same part number. Just make sure they are made by Karlyn


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## dangerous_dave (Jun 28, 2006)

*Re: Random misfires, rough idle (matc)*

if your car still uses an ignition module, you should replace it. its the little module that is on the top of your air box. 
most 30v cars stopped using the ignition module but some may have it. if you have a 12v, you have the module and it is bad. it will cause misfires on just one bank if it goes. i forget if 98 cars came with the 12v or just the 30v. what motor do you have?


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## brilliantwagen (Mar 5, 2009)

I have a 30V with the ignition coils above the PS pump. There is no module on the airbox. I had a set of original plugs from the factory, and i currently have some NGK platinum in now. The wires were recently replaced, I have swapped them from side to side but the problem still remains.


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## brilliantwagen (Mar 5, 2009)

I am going to order some of those plug wires and get the right plugs in to make sure.


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## matc (Apr 2, 2009)

*Re: (brilliantwagen)*

I hope that works for you, let me know how it goes


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## Skimmer0220 (Oct 12, 2009)

*Re: Random misfires, rough idle (brilliantwagen)*

some times with a missfireing it could be you ignition coil, also diffrent people recomend changing your ignition coil when changing the wires.....maybe this will help


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