e34 525 engine problems

[keggy]

hey guys my 95 525 24v has started to run very rough. it started off with a misfire n then completly stoped being able to rev. every time i try to rev it it dies out or nearly does. idle is very rough to. i removed the spark plugs and found that 4 of them are champion and 2 are ngk which wouldnt be helping i guess. also the plugs are very black like it is overfueling. also had quite a strong smell of petrol from the cylinders after removing plugs. can anyone give me so advice on what could be the problem?

[320ise]

maybe the icv valve is dead or one of the temp sesnsors (not sure if its like m20's brown/blue) worth checking, could allso be air flow meter?

[DanThe]

the plugs are very black like it is overfueling

Or not firing, if you have odd plugs it points to a previous ignition problem, inspect the coil packs rubber bits for deterioration, make sure they still have the 'spring' feeling when you press them onto the plugs, get some new plugs put in, only about £12 for a set of NGK's or Beru

[keggy]

cheers guys gonna try plugs 1st anyway although the guy that ibought it off told be he changed the plugs and the car hasnt done 500 mile since. will change them and get back to you guys cheers. any other ideas are welcome:)

[keggy]

ok guy had teh car plugged into teh diagnostic computer and the following code came up:-
knock sensor 2
oxygen sensor 1
throttle potentiometer

now im not sure on these results. the car is revin up and down on idle and missing. would any of these make it do that? i would of thougth it was the temp sensor or something. when the engine misses would the knock sensor code no be fired up anyway?

[stuartgallafant]

its misfiring because the engine is not sure how -
a) How much air is going into the engine, as it cannot dtermine the throttle load - throttle potentiometer fault
b) What kind of mixture is in the exhaust gases - oxygen sensor fault
and last but not least
c) its recieving knock sensor signals from knock sensor 1, but no/incorrect signal from knock sensor 2

The M50's, M52's and even the early M54's all had throttle problems, where the inside of the throttle body, around the butterfly plate, would get clogged up with sh!t and screw the readings up. Remove the throttle butterfly, clean it up and refit it. Disconnect the oxygen sensor on the first bank (from cylinders 1,2,3) and disconnect the knock sensor. Then start the engine. The DME should revert to a pre-pragrammed map and the car should drive ok, but these sensors will need to be replaced, and the DME adaptations will need to be reset

hope that helps

[keggy]

its misfiring because the engine is not sure how -
a) How much air is going into the engine, as it cannot dtermine the throttle load - throttle potentiometer fault
b) What kind of mixture is in the exhaust gases - oxygen sensor fault
and last but not least
c) its recieving knock sensor signals from knock sensor 1, but no/incorrect signal from knock sensor 2

The M50's, M52's and even the early M54's all had throttle problems, where the inside of the throttle body, around the butterfly plate, would get clogged up with sh!t and screw the readings up. Remove the throttle butterfly, clean it up and refit it. Disconnect the oxygen sensor on the first bank (from cylinders 1,2,3) and disconnect the knock sensor. Then start the engine. The DME should revert to a pre-pragrammed map and the car should drive ok, but these sensors will need to be replaced, and the DME adaptations will need to be reset

hope that helps

do i need to replace all the sesnors stated then? also its knock sensor 2 not 1 does that make a difference?

[stuartgallafant]

do i need to replace all the sesnors stated then? also its knock sensor 2 not 1 does that make a difference?

I know. If you read what I put, I wrote that knock sensor 1 is ok, but 2 isn't. The DME know's 2 isnt ok, because it knows 1 is, basically!

Yes, you will definately have to replace the oxygen sensor and the knock sensor, but you may be able to salvage the use of the throttle pot. And, as said, you will need to have the air/fuel adaptations reset.

However, before you go changing sensors, check that the wires are ok first. You could have a chaifed wire somewhere thats causing these problems, in which case, changing the sensors will do sod all!

Hope that helps

[DanThe]

Have you put new plugs in yet?

[hongkongfuey]

hello mate, i had the same prob on an e36 325i , i changed the oxygen sensor in the exhaust, that fixed it

[keggy]

Have you put new plugs in yet?

yeh i changed them on sunday but no change at least i got a full set of the same plugs now tho!

sorry never read it right will check out those sensors etc and hopefully thatll be it.

thanks for all the help guys

[DanThe]

If you unplug the lambda the ECU will run on a default 'protection mode' fueling map.

Usually gives a good idea as to how well the lambda is doing its job

[keggy]

must try that. does it leave protection mode after the sensors plugged bak in or do i have to do summin?

[DanThe]

No, the ecu will sort itself out, very basic system, mine didnt even know the cam sensor was unplugged!!

I wouldnt take any fault codes too seriously

[keggy]

yeh ano what you mean ive worked of vauxhalls for around 3 years and know not to believe everything the computer says lol. but would be too sure on bmw engines something i never really worked on

[stuartgallafant]

as DanThe says, its a basic system, but it works well.

i mentioned earlier, if a sensor goes down or loops out completely, the DME (engine management module) uses a pre-programmed fuel n spark map so it doesn't launch itself. It only gets confused if the sensors all jumble each other by putting some wrong signals, some right signals, etc

the adaptations i was talking about is basically the way the DME has adapted the air/fuel/spark control to allow it to run. when everything is as it should be, these adaptations must be reset so it performs properly. resetting these will also make the engine feel a whole lot different in general, as these adaptations occur during everyday driving too

[keggy]

ordered all the sensors today. will be here sat on this preprogrammed fuel n spark map can i drive teh car home as its stuck at a garage or will i need to tow it?

[DanThe]

this preprogrammed fuel n spark map can i drive teh car home

Thats what its for

Like I said, disconnect the O2 sensor first to be sure your on the default map

[stuartgallafant]

yep, Dans absolutely right

a BMW dealers, or a garage with really decent diagnostis equipment will be the only way you'll get the adaptations cleared