High speed engine stutter and bog

[tomsTI]

I have 1998 BMW 318ti automatic. The engine stutters or bogs intermitently at high speeds (75mph – 85mph) on the freeway. After reading suggestions on these forums, I have done the following replacements which have helped the issue quite a bit but not solved it completely:

1. Replaced Mass AirFlow Meter
2. Replaced all rubber tubbing and hose clamps from the airbox to the intake
3. Replaced PCV Valve
4. Replaced rubber hose from the PCV Valve to the top of the valve cover gasket
5. Replaced Camshaft Positioning Sensor
6. Replaced Spark Plugs
7. Replaced vacuum hose to the fuel pressure regulator
8. Replaced Catalytic Converter
9. I drive with the ASC deactivated
10. Not related – replaced Alternator
11. Not related – replaced all belts
12. Not related – replaced idle pulley

Any ideas or suggestions?? I’m considering the following but any advice would be greatly appreciated: Throttle Positioning Sensor, Idle Control Regulator, Spark Plug Wires, and Ignition Coil Pack.

Thanks.

[briansol]

fuel filter and then, fuel pump are probably next on the list.

[tiFreak]

what brand spark plugs did you use? NGK spark plugs work the best in our cars, Bosch plugs don't seem to work as well

[Xenocide]

edit: nvm you did that.

[tomsTI]

Thanks everyone for the ideas. The fuel filter did get replaced 2 weeks ago when the Transmission oil, filter, and gasket were done. Fuel pump never crossed my mind so thank you for that suggestion.

FYI: I did use the oem NGK spark plugs.

Any other suggestions are welcomed. I did attach a SnapOn MODIS computer to the car and believe it or not there are no error codes. It used to throw a CEL for the MAF, CPS, PCV, and Althernator voltage. Those are all gone once replaced. Thanks again.

[trunxgp1224]

o2 sensors? it just seems like you left off the gas and then you get power back.

[tomsTI]

Hello trunxgp1224, have you had this same problem? I was also thinking O2 sensors despite they never pull up as an error code on the computer. When the catalytic was replaced, I had the guy remove both O2 sensors for me to take a look at. On the outside they don't seem too bad but then again that doesn't mean much. Thank you for the suggestion.

[cali_guy_559]

Did you get it fixed?? I have this VERY same problem. and i can't figure it out either. Seems like the warmer it is, the more it bogs down. going up hill is a challenge in 100+ degree weather.

[tomsTI]

My problem became very intermitent and less severe after doing all the repairs/exchanges that I listed on this thread. Unlike your situation, my engine bog could occur at anytime time and temperature: morning, night, hot, or cold. The last few times it happened it was night time and the outside temperature was probably 72 degrees F. I was traveling between 72 and 77mph and for a quick third of a second the engine just bogged.

I'm almost positive it is both O2 sensors. Since it has become intermitent, I've become lazy to really have it checked out. Once I do, I'll post the results.

[trunxgp1224]

Hello trunxgp1224, have you had this same problem? I was also thinking O2 sensors despite they never pull up as an error code on the computer. When the catalytic was replaced, I had the guy remove both O2 sensors for me to take a look at. On the outside they don't seem too bad but then again that doesn't mean much. Thank you for the suggestion.

Sorry, I've been gone a while.
I'm not sure if it really is the O2 sensor or not. But the car has the same symptoms as my Escort did. When the sensors were replaced the problem was gone. It only acts up ever couple days now so im lazy at fixing it.

I dont think they are referring to the outside temp. but the O2 sensor temp. o2 sensors work only when heated up. some high end cars have electrodes that heat them up, but most are simply heated by the exhaust gas. which is why most problems dont occur until the car reaches operating temp.