m30 535i Part Throttle Flat Spot

[Derek A.]

My car has had this affliction for a while. Did a new o2, cap + rotor, air filter. Valves were done not to long ago, injectors are good. Under part throttle conditions 2-4k it almost feels like someone shuts the fuel off for a milisecond. I was thinking maybe the Airflow meter is the problem. All the little repairs helped the overall smoothness of the car - but there is still this part throttle gremlin. It does not seem to be there at WOT.

[epj3]

My car has had this affliction for a while. Did a new o2, cap + rotor, air filter. Valves were done not to long ago, injectors are good. Under part throttle conditions 2-4k it almost feels like someone shuts the fuel off for a milisecond. I was thinking maybe the Airflow meter is the problem. All the little repairs helped the overall smoothness of the car - but there is still this part throttle gremlin. It does not seem to be there at WOT.
Is it when you barely have your foot on the gas? All SOHC bmw motors I've driven do this... i'm sure there's something that is the problem, but my car seems to 'surge' a VERY little amount (just enough to make the car feel unsmooth) while applying barely any gas...

[632 Regal]

Derek, did you replace that #6 pickup deal too?

[Derek A.]

It does it even as much as half throttle. Definitely not that first tip in feel. I think that has to do with how the injectors are turned on and off. This is while you are under way. I am wondering if there is a spot on the Airflow meter trace that has gone bad or is dirty.




Is it when you barely have your foot on the gas? All SOHC bmw motors I've driven do this... i'm sure there's something that is the problem, but my car seems to 'surge' a VERY little amount (just enough to make the car feel unsmooth) while applying barely any gas...

[krzysiom5]

Derek,
Check the ignition wires, sounds like misfire (how old are the wires)? I've had the same problem with my 325, changed the wires problem solved

[JAlfredPrufrock]

Derek,
Check the ignition wires, sounds like misfire (how old are the wires)? I've had the same problem with my 325, changed the wires problem solved

Would you miind going through the details of changing the ignition wires?

I've been over at my stealer's parts dept and had them look up ignition wires but it seems like I either have to buy the entire harness or buy ignition wire by itself by the yard.

So do you just simply measure up how long each ignition wire is, make the proper cuts, and replace the wire or is there more to it than that?

[Jeff N.]

Worth a shot swapping AFMs - find someone and swap and see if it makes a difference.

[niall]

ive seen a few with similar symtoms, where
the carbon contacts in the air flow meter wear out

[shogun]

Ignition wires never go bad in my opinion. What goes bad are the resistors at the end of the wires which can be replaced for about $7 at any internet parts place. Try bimmerparts.com. You have to destroy the old endand then insert the wire in the new end. Hope this helps.
Or check out this page, good stuff
http://www.kingsborne.com/
this also might help you
http://shrubbery.student.utwente.nl/sean750/Replacing_sparkplugWiringV12/ReplacingSparkPlugWireSet_V12.htm

[Derek A.]

My wires actually had cracked insulation near the plugs, coupled with the ripped up #6 sensor wire it was time to replace them. I also did the cap and rotor - so I am notw good for anothr 200,000 miles.

[632 Regal]

so the hesitation is finally gone??

[ryan roopnarine]

bump

curious if i should maybe change coil boots.

[Robin-535im]

bump

curious if i should maybe change coil boots.

No coils on the M30 though. Well, there is one of course - but not one on each lead.

[ryan roopnarine]

No coils on the M30 though. Well, there is one of course - but not one on each lead.

i understand that the m30 uses plug wires and a single coil. i have the same symptoms with a leaky valve cover gasket (i clean the oil out of there if it spills), but im thinking the boots might be dead from the oil.