I've been trying to track down a slight engine vibration. Not severe, just enough to shake the steering wheel and mirrors. It varies with engine speed, but can usually be felt around 1500 rpm. It happens when parked, so it isn't a driveline problem. It also seems to get worse when the engine heats up.

I thought the cause was a warped flex plate, because the starter would grind occasionally and the ring gear ran out about .050. I replaced the flex plate this weekend, but the vibration is still there.

My next thoughts are the harmonic balancer or torque converter. Does anyone have advice on testing these components, or further tracking down the source of the vibration? I would love to have some better direction before taking the front end apart or pulling the transmission (again ).

Thanks,

Chris

 

Harmonic balancer spin okay or dose it look funny. The stock ones do come apart and spin funny. Hows your power, its not injectors is it.

 

crankshaft pully maybe? i cant recall if those are balanced or not.

 

I'd be looking at how your engine is running. Issues with tunes and injectors give those same symptoms.

 

I checked the harmonic balancer last night. It does look different than the other pulleys when the engine is running, it has a slight wobble.

The engine power is good, but seems to drop off a little when the vibration is worst. Would one of the AE tests show if an intermittent weak injector was the problem?

 

There's been more then one replaced because of wobble. I'd change this even if it isn't the cause. Very bad for the internals.

Chet

 

Update: New harmonic balancer, same problem .

 

You say power drops off with vibration. Dose it miss also? Vibrations could be lots of things, drive train etc., at least you took care of a bad harmonic balancer before something really happened. It could be electrical if its misses and lack of power.

 

No miss, just a very slight drop in power. It isn't a driveline problem, I can feel the vibration while sitting still. It's actually worst at mid throttle; when I really get on it she smooths out and has lots of power.

Glad I changed out the balancer. I'm sure the wobble wasn't going to go away, and it couldn't be good for the bearings.

Think my next step will be to get out the laptop and see if anything looks strange when the vibration is happening. If there is any interesting looking AE data I will post it.

 

I'm interested in what you find. I also have weird vibration or loud hum.

 

Because of my recent experience, I'll suggest you at least check your EBP, MAP, and BARO before you crank it... make sure they match.

KOEO, KOER, and Cylinder Contribution Test (full engine oil temp) are good ones.

 

EBP, MAP and BARO are all at 14.7 +/- 0.1 psi with the engine off. However, I discovered something very interesting, and hopefully the source of my trouble.

I was going to run KOEO, but hit the injector buzz test by mistake. All 8 sticks sounded great (thanks to Rosewood Diesel), but take a look at this:

99 F350 7.3 Buzz Test w/ Tach.MOV - YouTube

The tach is all over the place when the injectors fire, even without the engine running! My guess is that the injector vibration is getting picked up by the CPS or the injector drive voltage is getting coupled into the CPS wiring some place. In either case, I hope someone can verify that this isn't normal. If the tach shouldn't move during a buzz test, then I have a place to start troubleshooting.

Chris

 

Latest update: I replaced the torque converter and threw in a new flex plate and the vibration is the same. The flex plate still wobbles around, maybe even a little more than the old one.

After I installed the new TC on the transmission and rotated it to seat the shafts, I could still rock it up and down about 3/8 to 1/2 inch. Is that normal? I thought maybe there was a bad bearing but I don't have much transmission experience. The front seal looks good and it doesn't leak.

Chris

 

I just saw that tach. Mine smoothely goes up and down, but it looks like yours doesn't have a buffer on the tach. Loose connection? Software issue? Truck issue? If the truck was 100%, I'd ignore it... but a vibration? I'd look at communications and connections to the PCM, 42-Pin, IDM, etc....

 

Well, here's the weekly bump of my vibration thread.

Pulled the trans (again) for a closer look at the torque converter and took a video of the converter play in the transmission:

TC bearing play - YouTube

Does that amount of play look normal? I don't have any transmission experience so I really don't know how it should fit. My thought is that the pump bushing is shot from the TC running off center.

I posted this in the transmission forum as well, maybe someone down there will know.