Weird Highway Situation? Please Help

[grlaneriejr]

Hey guys, a question maybe you can help me with.

At around 3000rpms to 3400rpms, cruising on the highway, my car seems like it's hesitating. I can't see the tach needle bouncing, but it just feels like it's losing rpms for like a second and then catching back up.

Does anyone know what causes this?

Thanx

[StereoInstaller1]

foot spasms?
Luke

[nando]

is the engine check light flashing, for a split second? if so, it's your O2 sensor.

[grlaneriejr]

No, no lights flashing or anything. It almost feels like it's hesitating, just not on acceleration.

Any ideas?

[Mystikal]

Sounds like timing. When was the last time you had the valves set?

[nando]

well, the light only flashes for a split second (doesn't stay lit), you probably just missed it. I still think it's the O2 sensor, maybe do a code check to be certain. I had this same problem last year (at the same RPM, cruising down the freeway), as did a bunch of other people (at the same time, which was odd). in every case, it was the O2 sensor.

otherwise, check your ground connections, and for loose wiring. could be something shorting out.

out of adjustment valves wouldn't cause a hesitation while cruising down the freeway either (although it wouldn't hurt to adjust them!).

[grlaneriejr]

Adjusted the valves about 3000 miles ago.

Changed the o2 sensor, timing belt, plugs, cap/rotor, about 4500 miles ago.

Could I have gotten a tooth off on the timing belt? I can time my engine to run great any other RPM range, just this damn highway "blip"

Any other ideas, or should I look at this stuff again?

[grlaneriejr]

Question: could it have something to do with the tension on the butterfly valve inside the airflow meter thing?

I heard something about that on another kind of car.

[grlaneriejr]

Guys, please. Any help is needed on this.

[Mystikal]

Do you know anyone nearby with the same or compatible ECU?

[Kondour]

is this a recent occurrence? my dad had a problem on the highway, where it would hesitate/be fine/hesitate/ and it turned out to be a bad tank of gas....

[grlaneriejr]

I don't know if anyone has a ECU I could swap in. I live in Lafayette, LA and have a 85 318i.

I don't think it's a bad tank of gas, b/c it does it all the time on the highway.

Any ideas?

[PanamaE30]

Just out of curiosity.. Is it only on the highway?

what about just normal city driving.. does it stutter in that rev range too? What kind of throttle is being applied?


and lastly, any chance you're accidentally kicking in the cruise control or anything like that?

[grlaneriejr]

Yes, only on the highway. Don't have cruise, runs fine in town.

[PanamaE30]

WOT or only partial throttle?