Rough Ride when Cruising

[mainnor]

I have a strange problem that my car has had for the last 8 years that not even 2 seperate BMW Dealers and various independent mechanics have been able to diagnose.

1991 535i E34 with 173,000

I bought the car from the original owner and he told me of the problem as he tried to get it fixed as well.

If I am driving between 50-55 MPH, all of a sudden the car starts to shake like if someone is hitting it from behind. This happens only when I am not stepping on the accelerator too hard (just cruising). I had the transmission looked at and have replaced fuel and air filters as well as the spark plug wires and new plugs, but nothing has changed. Once I step on the accelerator harder and speed up, the problem goes away. The same is true if I let go of the accelerator when the car starts shaking.

My cruise control sometimes kicks me out at whatever speed I am going so I don't know if it's related to this problem at all or not.

Later.

Mainnor

[Kalevera]

Hello, there. Welcome!

We discuss this problem all the time -- do a search and you'll find more information than you can probably handle in one sitting.

Forget about what the PO told you, he probably made all of that up, anyway. Find a good indy, one that actually knows what he's doing, and use him (http://www.iaibmwsp.org). The problem you're experiencing is typical; we've all had it at one time or another and it relates to one of three things, in order of likelihood: 1) front suspension -- thrust arm or control arm bushings and ball joints, 2) warped rotors, 3) bad wheels or tires.

So, do a search. Read http://www.bmwe34.net and get your bimmer back together ;)

best, whit

[mattyb]

hi ther and welcome also. dont know much about ur problem.im only posting to let u know that what lowell says is always the case and what he dont know about these machines aint worth knowing.

[jjw]

Might be a long shot. Could it be a bad TPS? dead zone somewhere in its travel? Just a wild guess

[Beemr750]

You did not say is it body/chassis shimmy/shaking
related or is it a engine bucking type of "shaking".

[mainnor]

Thanks to all of you who welcomed me and replied to my problem. I was away for a couple of days and did not have a chance to check the forum.

I don't know what the TPS is?????

Also, the noise seems to be engine/chassis related.

[shogun]

TPS = throttle position sensor
http://paulaxford.com/bmw730i/images/eng_sensors.jpg

[Gayle]

TPS = throttle position sensor
http://paulaxford.com/bmw730i/images/eng_sensors.jpg

Shogun--You do the BEST pics!

[Kalevera]

Mainnor....

TPS = Throttle Position Sensor. I don't have a pic; someone else may. It's located on the front (headlight) side of the throttle body, which is bolted onto the intake plenum (the thing with the "3.5" on it). Diagnosis may be a bit tricky without some mechanical inclination.

I'll still put money on it being one of the three things I mentioned in that earlier post...

best, whit

[mainnor]

I appreciate all the help you guys have been given me. I will try most of the suggestions to see if they fix my problem.

[nyc525iTe34]

Sometimes noises are difficult to locate - even though you might be certain that it is coming from a specific area. While the TPS sounds like a good place to start you might want to check your drive shaft/line (maybe one of your CV joints have worn away). Often, when a CV joint has worn away you will experience moderate to heavy shaking of the car at various speeds. However, when you press the accelerator the problem seems to disappear.

Good luck!