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Discussion Starter · #1 ·
I'm trying to sell my Passat. Of course, right before the sale went through, my check engine light came on. Someone took it to Advance Autoparts to "run the codes." They told him that three cylinders were mis-firing. He then took it to a local VW authorized service station. They told him that the car needed two new catalytic converters and an ignition coil.

I can understand the ignition coil -- which I'm told will cost about $280 to replace.
But the catalytic converters cost more than the car is worth. And, I had the 2 catalytic converters replaced about 4 years ago. And then, I learned here that there probably wasn't any problem with the catalytic converters, but it was probably a software clitch.
The car drives fine.

Should I take it somewhere else for a second opinion? Thoughts?
 

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To be certain, you probably need to find someone with VCDS so you can pull any stored trouble codes.

Only the post-cat oxygen sensors can tell you whether the cat(s) need to be replaced (without removal/inspection of the cats). Even if the post-cat trouble codes are stored, you should locate the harness connector for each post-cat sensor, disconnect the harness plugs, then use some contact enhancer (Caig Deoxit) on both sides of the harness, then reconnect both post-cat sensors and drive the car for a while to see if the codes come back.

If you didn't live in "salty roads NY state", the potential for poor connector contact causing DTCs probably wouldn't be an issue.
 

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Discussion Starter · #3 ·
I received a little more information. The service guy said that due to three bad ignition coils, three cylinders were mis-firing and allowing unfired gas to flow into the converters. He said that this is what eroded the converters.
Still seems odd to me. The check engine light has gone on and off in the past -- usually, I would play with the gas cap to correct it or it would just go off after a few days.
 

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Your VW-authorized service guy apparently doesn't know how the 2.8 ignition system works. Each coil fires two plugs at the same time, one plug on the compression stroke, so if three coils were bad, the engine would misfire on all six cylinders. Also, if those are stock coils, they tend to be pretty realiable. My old '96 A4 2.8 had the OE coils and plug wires, and at over 270K miles never missed a beat. As Electron Man said, you need a more complete scan. If the autoparts guy was telling the whole story, that only three misfire codes came up, then why wasn't there cat codes too if those are bad?
 

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If you do actually have misfires on 3 cylinders of the same bank, I would check the CCT to see if the pads have broken. With a misfire, you can not count any codes for cats as they are only made to clean up normal combustion gases, not un-burned fuel.
 

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3 cylinders on passenger bank? This could usually be 2 possibilities on the 2.8: bad cat or timing off (usu. caused by bad belt tensioner). In either case you should get more codes, but would confirm either situation before buying parts. Replace old plug leads before touching the coil in any case.
 
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