I just replaced my o2 sensor because the check engine light was on and the engine was hesitating during acceleration. However there is still terrible hesitation usually in the low rpm's during acceleration and the check engine light still ocasionally comes on for the o2 sensor (I used the motronic code reader). Does anyone know what could be causing the hesisation. Within the last 3 months I put new spark plugs and a new fuel filter in. The hesistation is so bad I will not drive it untill it's fixed. My car is a 92 325i. Thank you everyone
just a couple of q's to narrow down the possibilities:
- does it hesitate regardless of engine temp? or only when cold? or only when warm? or it doesn't matter?
- is it under hard acceleration (heavy load) or moderate acceleration (partial load)? or both?
- any hesitation/stuttering/gasping at idle?
from your description, it sounds like a fuel delivery problem, but there may be more to it if you can provide more info. your engine light may be a completely separate issue.
things you may consider:
1) fuel pressure regulator - regulates low or high pressure
2) injectors - dirty or leaks
3) fuel pump - must provide pressure at least a pressure higher than the regulator regulates
if i interpret your description correctly, offhand it sounds like it could be regulator because it hesitates when you get on the gas. a faulty regulator can cause fuel starvation because of poor delivery or lagged delivery (output) or poor metering of intake vacuum (sensory, it meters off intake vacuum). if it is because of poor input pressure (input), that is actually a bad fuel pump.
Thanks for the quick response. The car has a manual transmission. The car also is rough at idle now. I will try using some "seafoam" to clean the fuel injectors and if that doesn't work I will check the ICV. Thanks again.
The other thing to check is going to be the vacum hoses, if cleaning the fuel injectors (I recommend 44k for that) and the ICV. To check for vacum leaks, just spary carb cleaner slowly on the hoses. If the engine rpms increase, the the hose you just sprayed has a leak. You can isoloate the leak and try to patch if you want, or just replace the hose, its cheap either way.
People always generalize that...when all these things are transmission related fluids:
is it oil, diffs, power steering, brake fluids....?
am I missing something here?
only two of those are transmission related fluids. Gearbox oil is also called transmission fluid. In fact some BMW Manual transmissions use automatic transmission fluid as lubricant. Diff oil is called diff oil. Gearbox fluid is called transmission fluid.
As I'm sure you're aware, brakes and power steering are not transmission parts.
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