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Discussion Starter · #1 ·
Hi all- this is my first post on this board. I have a very unusual problem with the V-8 in my 530 (yea i know this is the e39 board, but there are way many more e39 540's out there than there are e34 540 and 530s).

Been having horrible drivability probs for 2 months now.....no power above 3k. Replaced:
fuel filters, fuel pump, fuel pressure regulator, pcv valve/plate, intake gaskets, spark plugs, o2 sensors. Car throws 4 codes- o2 sensor 1 & 2 and Lambda 1 & 2.

Finally figured it must be a clogged cat when i noticed that at idle the passenger side cat was 450 degrees, and while the driver's side only 150 degrees.....I checked these temps several times over a few days.....always similar. So before I went out and spent the huge dollars to replace a cat pipe, i removed it and bored out the honeycomb......yea i know this is not cool, but it is just temporary. Anyway with a big beautiful 2" hole right thru the middle of the cat i replaced it. Still the same exact deal, with 450 temps on the side with the hogged out cat, vs 150 for the stock side. (Unfortunately that cat i ruined was good, no sign of melting or fouling at all). I did notice that the downpipe on the hot side gets hot BEFORE the cat, right at the first bend, a good 12" upstream of the suspected cat.

So here is my question:
What would caues the right bank of cylinders to make the exhaust 3x hotter than the other? When i replaced the plugs, all 8 plugs looked exactly the same.....much leaner looking than rich. No evidence of oil fouling or richness at all. I also checked compression and fuel pressure all dead on spec.

Gordon

1995 e34 530i 122k
cant wait to dump this pig and get an e39, bot a 528iT for wife, now i want a 530 with that slick automatic......i'm too old to deal with the stick and sloppy loose drivetrain chugging and lurching all around!
 

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Are you getting any misfires? A misfire can easily raise the temp of the exhaust manifol to over 2000 degrees.
 

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Discussion Starter · #3 ·
perhaps i am getting a misfire, but how would i know.......car idles pretty well, could be smoother, but does not visibly move at idle, and car revs smooth enough......just feels like i'm dragging a heard of dead elephants when the reves get much above 3-4k, from a a dead stop at 1/3 or less throttle it is prety much ok.
 
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