[rialnet]

Hi All,

i have got a real problem with my N54 335i. When the engine gets warm it is barley driveable with a bad mis fire and loss of power.

I have had the following done to try and resolve but no joy

new plugs
new coils
new lambda sensor
new injectors

the fuel pump pressures are spot on at 50bar

problem only occurs when the car gets warm, took the JB4 so just left with breathing mods below

mods are AR catless downpipes
forge DV
Burger dual air cones
intercooler
charge pipe
Burger oil catch can

any ideas would really help me out - its been to 3 different garages and no error codes showing.

[zooch7]

Is it random cyclinders or the same one for starters?

[dyezak]

How many miles and how long since the last walnut blast?

[rialnet]

walnut blast done last year, 82,000 miles

[NoQuarter]

You are calling it a bad misfire. But no codes.

Im not sure this is a valid combination.

Perhaps chasing down a "misfire" is the wrong approach and the problem is something else?

[dyezak]

If you are 2007 or 2008 check the DME MOSFETS...

[rialnet]

yes - very possibly. the car runs fine from a cold start up, once it gets warm it suffers from power loss and what 'feel's' like the car is badly mis firing. A strong smell of fuel also suggesting that it isnt all getting used. Poor mpg too

[NoQuarter]

Originally Posted by dyezak

If you are 2007 or 2008 check the DME MOSFETS...

I like the MOSFETS idea also. But when that happens the codes are often pretty clear. Easy enough to check though

[YoungBlood]

Originally Posted by dyezak

If you are 2007 or 2008 check the DME MOSFETS...

THIS^^ mine had those exact symtoms. Did all of the above besides injectors, it threw a code only twice, and it was just a misfire code, no ecu or fueling codes, but misfired hard anytime I tried to get into high loads. One day it shit out an entire bank of mosfets and I thought I blew my motor. THEN it threw mosfet codes lol. Seriously. Check. That. Shit. it takes 5 minutes and a voltmeter.

[NoQuarter]

Originally Posted by rialnet

A strong smell of fuel also suggesting that it isnt all getting used. Poor mpg too

Taking the plugs out right afterwards might lead you to a cylinder that has excess has fuel in it. That will give something to go one.

[rialnet]

thanks all for the replies, ill get them checked and let you know.

[CanadianTSi]

My only when hot misfire turned out to be an Injector. I know you said you replaced them but that's what fixed it for me.

[rialnet]

checked the DME MOSFETS and all appear fine... any other ideas?

[NoQuarter]

If you have gone this far replacing the mosfets is still a good idea

[rialnet]

MOSFETS done, no change.... into BMW we go :-(

[NoQuarter]

Then you are back to the injectors/fuel smell issue... it seems

[HawkeyeGeoff]

Have you done a compression check? I'd hate to suggest it...but I'd do that before you go paying a BMW dealership.

[rialnet]

compression test done when the new injectors went in, all good

[MysticRob]

Originally Posted by rialnet

Hi All,

i have got a real problem with my N54 335i. When the engine gets warm it is barley driveable with a bad mis fire and loss of power.

I have had the following done to try and resolve but no joy

new plugs
new coils
new lambda sensor
new injectors

the fuel pump pressures are spot on at 50bar

problem only occurs when the car gets warm, took the JB4 so just left with breathing mods below

mods are AR catless downpipes
forge DV
Burger dual air cones
intercooler
charge pipe
Burger oil catch can

any ideas would really help me out - its been to 3 different garages and no error codes showing.

I'd be cautious of the code readers those 3 different garages use. It's possible their readers won't see BMW-specific codes. Have you traced and replaced all your vacuum lines? Did the problem start after something else was modified, or just out of the blue?

[rialnet]

2 of the garages are x-BMW engineers that run them, ive had lots of work done by both of them and they are using BMW diagnositic kit

Ive had smoke tests done on all pipes to check for leaks, none found. the problem just started out the blue, no new mods. Ive had all the above mods on for 3 years with no issues at all.

the only error codes present are no cat errors

[NoQuarter]

Time to get logging and see what you see when the poor performance is going on.

Don't put the JB4 back in yet. Get MHD running with the monitoring option and do some logs while things are bad.

[HawkeyeGeoff]

Originally Posted by NoQuarter

Time to get logging and see what you see when the poor performance is going on.

Don't put the JB4 back in yet. Get MHD running with the monitoring option and do some logs while things are bad.

Yeah agreed here.

If you have INPA, reset all those adaptations as well after you log.