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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 12-20-2013, 07:24 AM
NoMercy346 NoMercy346 is offline
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Question exhaust manifold glowing after spirited drive on a stock e46?

over the past few months had to do lots of shorter trips and started to see the usual yellow mayo building up again on the oil cap.
the 1 hr drive home every weekend never gets rid of the condensation so yesterday on my way home I started to gradually drive it harder as it warmed up.

had in in manual mode, with high revs and lots of throttle over the last few miles... kept it idling, got out to check the oil cap and pcv line and noticed the red hot glow coming from down where the headers are but couldn't make out whether it's the cat or the manifold as there is too much in the way, just the glow reflecting off other parts

is that normal on a stock car?

took it for a short cool down drive after that as well...
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Last edited by NoMercy346; 12-20-2013 at 07:26 AM.
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  #2  
Old 12-20-2013, 11:58 AM
wdaveweaver wdaveweaver is offline
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Mein Auto: 2004 330i ZHP
Quote:
Originally Posted by NoMercy346 View Post
over the past few months had to do lots of shorter trips and started to see the usual yellow mayo building up again on the oil cap.
the 1 hr drive home every weekend never gets rid of the condensation so yesterday on my way home I started to gradually drive it harder as it warmed up.

had in in manual mode, with high revs and lots of throttle over the last few miles... kept it idling, got out to check the oil cap and pcv line and noticed the red hot glow coming from down where the headers are but couldn't make out whether it's the cat or the manifold as there is too much in the way, just the glow reflecting off other parts

is that normal on a stock car?

took it for a short cool down drive after that as well...
No it's not normal. I have a stroked v8 383 with long tube headers that don't get that hot. Typically when the exhaust manifold is that hot you have a clogged cat or too rich a fuel mixture (excessive fuel is burning in the exhaust primaries) and the second can also lead to the first over time. Are you throwing any codes or does the care feel down on power?
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  #3  
Old 12-20-2013, 06:31 PM
NoMercy346 NoMercy346 is offline
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yeah cat's was what I was thinking too with the glow. No codes and it's only a 325i so not much power to speak of anyway. If it is then not by much... Wouldn't a clogged cat seriously cut your power, though?
two other things: fuel economy seems to have taken a hit lately but it's also colder outside and I'm not talking much, only like 10-20% more.
The car has a problem that I thought to be drivetrain related and no one can diagnose so far, rpms bog down under certain light load conditions coupled with drivetrain vibrations, not happening under more throttle/higher load (where I guess a clogged cat should be even more noticeable?)
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Old 12-21-2013, 08:11 AM
GoForthFast GoForthFast is offline
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What condition are your oxygen sensors? Replaced lately? Take a look at the live data.
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  #5  
Old 12-22-2013, 11:53 AM
NoMercy346 NoMercy346 is offline
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hooked it to the scanner... live data on the o2s looks miserable but no codes stored (go figure) one bank tends to hang at low values the other at high value.

had another look with a flashlight and it's the rear bank cat that's glowing. Only takes one 0-70 run and about a mile of 4k+ rpm (but still staying within speed limits so little actual acceleration) to start getting red.
hard to imagine why it's not throwing a code by now...

guess it's time for some O2s.

Does it adapt fuel trim for each bank according to it's O2 readout or equally for all cylinders?
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Old 12-22-2013, 12:20 PM
wdaveweaver wdaveweaver is offline
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Quote:
Originally Posted by NoMercy346 View Post
hooked it to the scanner... live data on the o2s looks miserable but no codes stored (go figure) one bank tends to hang at low values the other at high value.

had another look with a flashlight and it's the rear bank cat that's glowing. Only takes one 0-70 run and about a mile of 4k+ rpm (but still staying within speed limits so little actual acceleration) to start getting red.
hard to imagine why it's not throwing a code by now...

guess it's time for some O2s.

Does it adapt fuel trim for each bank according to it's O2 readout or equally for all cylinders?
Yes o2 input will adjust the fuel trims on each bank. If your values are hanging the O2's are probably done and need replacing. Try swapping from side to side and if you're value hangs on the other side that O2 is your problem. Personally I'd replace all the O2's at the same time to keep consistent values.
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Last edited by wdaveweaver; 12-22-2013 at 12:56 PM.
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  #7  
Old 12-22-2013, 02:57 PM
NoMercy346 NoMercy346 is offline
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Quote:
Originally Posted by wdaveweaver View Post
Yes o2 input will adjust the fuel trims on each bank. If your values are hanging the O2's are probably done and need replacing. Try swapping from side to side and if you're value hangs on the other side that O2 is your problem. Personally I'd replace all the O2's at the same time to keep consistent values.
by all do you mean post-cat as well? Was only planning to replace the pre-cats. With 105k on the originals it's about time anyways.

Just hope the cat itself didn't take too much of a hit.
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Old 12-22-2013, 04:18 PM
wdaveweaver wdaveweaver is offline
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Originally Posted by NoMercy346 View Post
by all do you mean post-cat as well? Was only planning to replace the pre-cats. With 105k on the originals it's about time anyways.

Just hope the cat itself didn't take too much of a hit.
Sorry, precat is what you should be looking at. The post cat O2's don't have anything to do with the fuel trim adjustment.
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