misfire codes 540i

[carson03]

i have a 1998 bmw 540i. when i hit the gas pedal real hard(all the way to the floor) the check engine light will flash for a few seconds and then stay on. when this happens the car runs real rough. if i turn the car off and let it sit for a min and restart it runs good but the engine light is on. when i scan it i usually get p0308. and lately i have been getting p0300 and p0306. i have new plugs from the dealer. same codes. i swapped coil #5 with #8 and still get the same codes. i also put a new injector in #8. after all of this i started getting the p0300 and p0306 more often with the p0308. any ideas as to why it happens only on wide open throttle??? please help

[White94RX]

at WOT it takes more energy for the spark to jump the gap due to the larger amount of fuel/air in cylinder.

[carson03]

yes i know that. but it should not misfire.

[White94RX]

LOL. yeah, it shouldn't misfire, but your car does, so there's something wrong.

[jamesdc4]

i have a 1998 bmw 540i. when i hit the gas pedal real hard(all the way to the floor) the check engine light will flash for a few seconds and then stay on. when this happens the car runs real rough. if i turn the car off and let it sit for a min and restart it runs good but the engine light is on. when i scan it i usually get p0308. and lately i have been getting p0300 and p0306. i have new plugs from the dealer. same codes. i swapped coil #5 with #8 and still get the same codes. i also put a new injector in #8. after all of this i started getting the p0300 and p0306 more often with the p0308. any ideas as to why it happens only on wide open throttle??? please help
Clogged cats


LOL. yeah, it shouldn't misfire, but your car does, so there's something wrong.
Well said!:az

[htown540i]

cats

[jamesdc4]

cats
(Was that a question?)
cats = catalytic converters

[htown540i]

sorry, i should have clarified. i was agreeing with you that the problem is his cats.

[robertgu]

There is screen for the fuel pump intake. Could this be clogging? When you let the car sit, the particles that were clogging the screen fall away and it runs good, but the lights stay on. I don't know the codes you indicated, but my 540i had the above problem. The service center read the codes and replaced the oxygen sensor, cam shaft position sensor and one other thing for a health fee to find that none of those was the problem.

[jamesdc4]

Does a misfire at 3-4k RPM's indicate bad cats? (http://forums.bimmerforums.com/forum/showthread.php?t=849545)

Read that thread ^^^ and try the test.

[bmw e36 m3]

that happened to my 540i also. i would accelerate hard and it would start flashing and skipping. it turned out it was one of my cats. if you have a question on where to get a good aftermarket one let me know. if this is even your problem

[BigM62]

I happen to have these in my garage for sale

http://img508.imageshack.us/img508/7101/img0221fn7.jpg (http://imageshack.us)

[BMW 528]

Cats!

[carson03]

i tried the test with removing the pre cat O2 to see if the misfire went away...it did but went to the other bank. so i then removed the other pre cat O2 and i still got misfires on cylinder 8 and 2 and a random misfire. i ordered some aftermarket direct fit cats. i took a $1000 chance this would be the issue. we removed the old cats there were tons of broken pieces inside...whew!!! so far no check engine light:redspot. i hope this worked.

[BSchaefer]

I have a 2002 540i with the same misfire. It has been getting progressively worse, to the point that I don't trust it to go further than 30 miles anymore. The shop has not been able to get a handle on it. The info on the cats might be just what I need.

[chucksrt]

if the cat is clogged the one that is will glow after driving, if it is glowing pull over and turn it off but if your seeing it glow i guess your already pulled over. cel flashing means something major is wrong.

[BSchaefer]

Problem solved (hopefully). Engine coolant leak onto the coils.

[sabir510]

hi i have a 1998 bmw 540i and the problem is the radiator hose upper and lower is getting too hot to the point that you can't even put your hand on in it seems like its too much pressure in it and it's about to blow up . i changed the thermostat thinking it's bad and not opening when the coolant gets hot but its still getting hot though please help.
http://i653.photobucket.com/albums/uu254/carsforsale2009/0212_08zoom1997_bmw_hamann_540iengi.jpg

[sabir510]

i have a 1998 bmw 540i 90,000 miles automatic and my radiator hose are getting to hot. i touched the radiator and the upside is hot but the lower side of the radiator is totally cold seems like the coolant not rotating. i changed the thermostat but the problem is not going away and now every morning my coolant level is low and i keep adding coolant but i dont know where the leak is. please help

[norvel]

hey carson. i have the same problem now with my 98 540i and i cant find the problem so i registered here to ask you how did you fix your problem? what did you change to fix it. please reply asap i really need to know.

Thank you.