OK....be forwarned this is a looong post :P

anyways first the car....
1988
BMW 530i
3.0L straight-6 5-speed
additional info=IMPORTED FROM GERMANY....(taillights were burnt out and on the dash came up...Rucklicht....which apparently means taillight...go figure)
but yeah

got this car cause i figured upgrading from a 1980 toyota corrolla to a BMW is pretty smart....until i found this little issue with it

in the most basic explaination without having to be in the car to feel/hear/watch this happen would be a misfire....it feels like a misfire it sounds like a misfire...but it only happens during hard accel between 2k-4k RPM.....also very slight misses in first in second almost like one cylinder is constantly missing....then in 3rd,4th,5th it will occasionally miss....like...

vroooooooo..putt putt putt...ooooooooo..putt......putt putt......oooom

anyways ive checked the wires....all snug....checked the distributer cap...on snug and wires fine (actually it looks brand new)......used car lot where i got it said they put new plugs in cause it did it on the test drive too....so i told em to fix it....i guess the plugs wernt the problem.....i got no cracks/leaks anything before or around the mass air sensor thinger :P.......air filter is clean (new)....and personally is the only issue with the car....besides the door locks but that a different topic.....

in WOT in 3rd it will "stutter" "misfire" "jerk" WHATEVER until about 4k rpm then its like full power and i feel like im about to launch off the ground ;) so please give me anything you can think of...by the way LIMITED BUDGET....im not gonna go out and buy a whole wack of parts that wont fix it....

as a side note....sometimes...not always my exahust has a bit of sulphur smell to it....which leads me to think o2 sensor? or broken cat?....i dunno i just love this car.....so teach me your wisdom :confused

bump :( :( :(

Sulfur odor is the catcon working to process a rich or incompletely combusted fuel mixture.
I believe on your year/model you had the MAF which is shaped a bit like a box and has a square vane/flap that rotates ~90 degrees inside the box when the air flow increases through the MAF housing.
These units were suspect in regards to your symptoms due to the fact that the shaft of the vane passes through the bottom of the housing to a small compartment that contains a contact arm that sweeps across a rheostat.
This rheostat is what sends the signal to the ECU for MAF input.
After time the contact arm either loses tension on the rheostat windings or the rheostat windings become glazed or gummy from all of the oily vapor and fine dust in the engine compartment. Even though this small rheostat compartment is fairly well sealed it is not completely sealed due to the fact that the shaft must pass from the chamber through which the air flows, down to the rheostat compartment.
I had a similar symptom with a 1985 635, and from previous postings heard of a technique of opening the rheostat compartment and carefully cleaning the rheostat with alchohol etc. The post also suggested a very careful bending of the contact arm to increase continuity of the sensing mechanism.
Of course most responses to the post were of the opinion that if this was truly the problem then it was time for a fresh MAF.
I tried it and it worked for me, drove the car for another couple years and then sold it. The guy that bought the car kept it for about six years, (we stayed in touch by email), and never had a problem with the MAF.
To let you know, I am an electronics tech so I have a familiarity with working with these types of devices.
andrew

well then the sulphur smell means the cat is working to break down uncombusted fuel...which is going right through the missing cylinder...

if you could sorta go into more detail on what needs to be done to possible fix this or see if that in fact is the issue...please do :D id rather not have to take it to a bmw dealership and sell my soul just to get a tiny sensor cleaned


:devillook BMW :devillook


ill see what i can do about maybe getting some pics :D might make things easier

can an EXTREEEEEMLY loose negative clamp on the battery cause this problem.....cause i went and disconnected my battery for the night to clear the memory....and well....my negative clamp was just basically sitting on the post very loose and easy to pull off.....o.O :banghead:

A loose negative clamp at the battery is not usually considered a good configuration. Bear in mind though, that if the connection was sufficient to provide the current necessary to engage the starter motor then you had enough contact to run the electronics which require significantly less current.
That being said, vibration over the road could have had an effect also.
Regarding the cleaning of the MAF rheostat, I don`t believe that most mechanics would attempt such a repair. The potential for less than a succesful outcome with the associated labor cost could only produce an unhappy customer. The recommended repair in this case would be to replace the MAF unit. These types of MAF units were known to become intermittent over time and increasingly so when the mileage was higher.
Not what you wanted to hear I know but I will assume that your car being a 1988 it has some mileage?
Stay on the discussion board, let us know how you make out.
andrew

ok so the car has 270k on it....the dealer told me that there was a part that was replaced (apparently 300$ CAD) and he pointed at this cylindrical looking unit with a harness that plugs into it....which from the outside looks like it connects to the vane inside the intake plumbing....(im hoping on getting some pics here tommorrow) that you mentioned in your last post....it also looks like the first major sensor of the intake system...then it basically runs to the intake manifold where the throttle body is with a few other sensors i assume throttle position sensor...:D look im learning already...:D:D

well here is a pic of what i think you are talking about...and this is what the dealer guy said he replaced

That's the idle air valve, which won't affect off-idle operation.

If you're trying to locate the air flow meter, it's under the black plastic cover just to the front and right of the idle valve. It was incorrectly called a MAF sensor, which stands for mass air flow. However the type of air flow meter in question measures volume, not mass.

Before replacing parts you should do some basic diagnosis, like check fuel pressure and measure the resistance of various sensors and the ignition coil and compare your readings against a spec table.

ok so what "various" sensors and i only have one coil....also i have a round sensor around the 6th cylinder wire off the distributor that runs to a plug that goes to who knows where but where it goes to is another harness style plug thats slightly loose but its plugged in and there have been times ive jiggled it and things have gotten a bit better but then there are the days that its just HORRIBLE

well just an fyi just i figured out some stuff with regards to the car itself:

Chassis number 3521577
Vehicle code HC51
Series E34
Model 530i ( 530iM30 )
Body type saloon
Catalog model ECE
Production date 1988 / 03
Engine M30
Transmission Manual
Steering Left
Catalyzer YES


Additional Information for Vehicle code HC51
Production FROM : 1988/01/01 TO : 1990/04/30
Engine M30 B30
Engine Oil 5.75 Liter
Transmission Manual
Transmission Model Getrag 260/6
Transmission Oil 1.25 Liter
Rear Axle Oil 1.70 Liter
Coolant(w/o Air Conditioner) 12.00 Liter
Coolant(with Air Conditioner) 12.50 Liter
Brake fluid 1.00 Liter

also can i clean my "air flow meter" with throttle body cleaner or what? cause i pulled it off and there looks to be a sensor in front of a big flap...and when i open the throttle a bit the flap moves (ok so i thought it was neat) anyways the little sensor in front of it is slightly grimey.....least it looks like that...what can i spray on there safely?

There's no need to mess with the air flow meter -- that grime isn't hurtinig anything. It can't hurt to clean the idle air valve and throttle plate with carb cleaner though.

The sensor on the spark plug wire is so the DME can identify TDC of the compression stroke. If that fails the DME reverts to parallel injection instead of the normal semi-sequential. You may not even notice any difference in the way it runs, but exhaust emissions will increase.

Other sensors include coolant temp, air temp which is located in the air flow meter I think, and the crankshaft sensor at the front of the engine. I'd be especially suspicious of the crank sensor. It plugs into the harness next to the TDC sensor. It would be best to have a manual with the specs and test conditions.

I don't think I saw fuel pressure mentioned. That should also be checked. While doing that also check for maximum pump pressure by momentarily pinching shut the return line. It should read 8-10 bars.