Losing Power on 5th Gear

bobome · 08-04-2008, 12:15 PM

My 87 325is is losing power on the 5th gear. When I'm driving on the freeway, if there a incline or if I need to slow down, my car is not able to pick up speed, I must shift back to 4th gear and run it up to 4000-5000 rpm before I could shift to 5th gear to have power. Can anyone tell me what's the problem? 1st to 4th gears are able to pick up power if slowed down but not the 5th. Your help are always appreciated.

Wayne 962 · Wayne 962's Garage

Well, 5th gear is the least leveraged of all the gears. What you are describing is common with *all* cars. Do you think there is an ongoing problem with power in your engine that is causing this? Is this relatively new (down on power)?

-Wayne

bobome · 08-06-2008, 03:57 PM

Thanks Wayne for answering my question. Yes, this is started recently, before I was able to pick up speed on the 5th gear if I slowed down a little. Now, seem like as long as I put my foot on the gas, it runs fine. Once I release the gas, I can't pick up speed, I must down shift to 4th and run it up to 4k rpm before shifting to 5th. The car vibrate a little and I noticed my gas mileage is not as good as before. I cleaned the O2 sensor. Is it possible for my 87 325is to have only one o2 sensor? I can only find one by the exhaust manifold, can not find the one after the catalyst converter. Last night I jacked up the car to change the transmission oil, then I found out I didn't have the tool to take the plugs off. I drove to my friend's house to borrow the tool and the car SEEM to drive a little better. I was able to pick up speed on 5th gear but the car still vibrate. Could the transmission oil be the problem? Like no enough inside the transmission? What would cause the car to vibrate and lose gas mileage? I'd think is the o2 sensor, how do I test the o2 sensor to be sure? Thanks for you input.

Wayne 962 · Wayne 962's Garage

Have you run the codes on your system, to see if anything is popping?

http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm

-Wayne

bobome · 08-09-2008, 01:39 AM

Hi Wayne, I read the article and did the test at least 5 times. The results are the same each time but is different from what the article mentioned. It only gave me three flashes. The test results I got are - FLASH PAUSE FLASH PAUSE FLASH (that's it, the engine light remained on after this point). All the test I did the results are the same. I changed the transmission oil last night and the power returned. The car runs beautifully 1st to 4th gears but when I shifted from 4th to 5th gear, the car started vibrating until it able to reach 3k rpm, then the vibrating stopped. Does the air flow sensor have anything to do with this? How about the cap and rotor? Thanks for your help.
Bo

Wayne 962 · Wayne 962's Garage

It may be some type of harmonic dampener in the system, that is wearing out and introducing vibrations. It may be something wrong with the 5th gear in your transmission. This one is tough, because it's so subjective...

-Wayne