Need some assistance BMW 535 hesitating

[Mrsmadcow18]

I have an 89 BMW 535i and recently its been having a hesitation problem through all the gears in the 1000 to 2500 RPM range while accelerating. Once above 2500 it calms down a bit. It just got back from the shop after some overheating issues namely the water pump, radiator, head gasket. T-Stat and fan clutch all got replaced. Leaving the shop it was alright a little noticeable but now the problem is slightly worse than to begin with. Any help would be greatly appreciated. Thanks

[moroza]

Describe your problem in more detail. It sounds like what I've been having on and off: if you give too much gas, especially at lower RPM's regardless of gear, the engine stumbles (I think that's the correct term) and the car actually slows down. It'll rev as high as usual, but can't take full throttle until higher RPM's.

If that sounds like it, read on:

The culprit seems to be the AFM, since cleaning that out made my problem go away completely. The bit in question is the heated bulb with two wires, protected by a plastic cage in the front of the AFM. I cleaned it with canned air, and later with a very fine piece of twisted tissue paper. It seems to be sturdier than it looks, but I still wouldn't use an air compressor. There's a slight chance you may have to replace the AFM, and 'tain't cheap.

While you're at it, I'd disassemble, clean, and reassemble the filter box, both airflow hoses, the throttle body, the rest of the AFM, the IACV, and the blowoff hose (at least, I think that's what it's called. It's the 3cm-wide hose running from the second airhose to the valve cover). With how old your car is, some of the hoses might need replacing anyway.

The AFM is liable to get fouled up if your filter needs replacing or if there's an air leak, such as a cracked or loose-fit first intake hose. Using a low-restriction filter like K&N evidently makes it not only foul up faster by filtering less crap, but adds its own oil to the grime that bulb likes to collect.

[Mrsmadcow18]

Yeah like the car just bogs down until higher RPMs almost like its stalling. Even right now its not totally in the clear above 2500 its just smoother and the jerks seem to weaken. The air filter got swapped out prior to everything else getting swapped out by the factory air filter. Thanks for the fast respose i will give this a try and see what happens.