Severe engine vibration

[Lbert]

'96, 3.8L, 160k miles, part-time transport, not used much lately.

My van has a severe engine vibration problem. The engine vibration is so bad that vibration can be seen on the front tires.

No engine codes and the idle is nice and steady as indicated on the rpm gauge, around 800 rpm. In addition, I do not hear any engine sputter or misfire.

Below are due maintenance and misdiagnosed replacements that I have done to address the problem:

- cleaned the mass air flow sensor and air intake
- new spark plugs, spark plug wires, and new coil pack
- replaced the engine mounts (all 3)
- new synchronizer

The spark plugs and wires were due for replacement and it initially reduced the vibration slightly. Next I checked the coil pack. The secondary resistance was very close the 11.5k ohm limit per Hanes manual. Since it is very close to the max I thought the coils maybe on the way out. I got a new Motorcraft coil. Low and behold, the secondary resistance to the new oil is 13k, over the limit. So much for Hanes specs. Vibration retuned hard as before. Next I replaced the engine mounts and that did not help either. The mount close to the radiator was most worn of the 3 so replacing the mounts was not a wasted effort. Lastly, since the synchronizer is old and it cost around $40, I decided to gamble it could be the problem. Needless to say I lost the gamble, engine still has severe vibration.

What is left? I suspect it maybe the harmonic balancer but it is hard to tell if it is wobbling due to the engine vibration. There is no serpentine belt or drive bearing noise that may indicate a bad harmonic balancer.

I need some suggestion where else I may look or should I tackle the harmonic balancer. Could the harmonic balancer cause such severe engine vibration when it goes bad? I hate to replace the harmonic balancer and find out I am back to square one.

I about ready to give up and have the mechanic hook up the car to their scanner.

Thanks in advance!

[12Ounce]

If (IF!) the spark cables are routed correctly, I would use an inductive type timing light on each cable ... there should be a steady flash of test-light, while engine idles ... no "skips". That would be my starting point.

[scubacat]

I have to agree with that. It really sounds like a timing/misfire type of issue, especially if the motor mounts are new. No codes? Does it vibrate when driving or just when idling?

Slightly off topic -- I hope you didn't put an aftermarket motor mount one like "anchor" brand or something in the front. It will snap in half at the weld at a bad time if you did. I'd bite the bullet and get a motorcraft one in there in the next few months if at all possible.

[tempfixit]

I would also take a look to see if the harmonic balancer rubber between the outer and inner parts of the balancer are not cracked. DOes the transmission work properly??

[Lbert]

12Ounce, scubacat, and tempfixit. Thank you for you guys' suggestions!

12Ounce,

I will get an inductive timing light and do the test. Hopefully I could find a local store that has one on their loan program. The severe engine vibration occurred before I messed with the replacement of spark plugs, spark plug wires, and ignition coil pack. Vibration remained even after said replacement.

Scubacat,

Vibration is less pronounced as the vehicle speed gets higher. Above 40 - 45 mph is the point where the vibration is almost gone.

Thank you for the warning. I am sorry to say I got an Anchor brand mount next to the radiator. You are right, quality is no where close to Motorcraft. The metal frame (thinner) and rubber are subpar. I was not able to compare until I had the old part out and compared them side by side. By then I was not up to mailing back the mount for a refund. It looks like I will have to redo the mount, urgh!

No engine codes.

I too believe it is likely an ignition issue or at least a combustion issue. I wonder if one of the fuel injectors is malfunctioning. When I removed the old spark plugs, all looked pretty much the same. Not one looked oily and wet.

Tempfixit,

The rubber between the inner and outer parts of the harmonic balancer is so thin that it is difficult to see if it is cracked or not. There is not enough material to view to make the determination.

Transmission is in good order and shifting between gears is relatively smooth.

[scubacat]

Did you hook up a code scanner and check for codes? It vibrates when idle right? I'd also spray some carb cleaner around the intake while idling to see if it changes at all.. Could have a vacuum leak. Are EGR ports clear?

Sorry about the motor mount. I replaced two due to them breaking in half before I got a motorcraft. Check ebay; I got mine for a bit less there from a dealer somewhere out west. On the bright side, the two hydraulic anchor mounts are still ok 3 years later!

[tomj76]

A vibration associated with a misfire SHOULD be recorded as a code and the MIL will blink while the engine is misfiring. The PCM records misfires by checking that the crankshaft is rotating at an even rate. The car/engine can jump with the crankshaft rotating smoothly.

With no code, it implies the problem is somewhere else (such as the previously mentioned harmonic balancer). Other possibilities are a problem with the flywheel or the torque converter, basically anything that could create an out of balance spin (like a washing machine that is out of balance during the spin cycle). The other place to look is the motor/transmission mounts (as you have already done).

[Lbert]

It was the harmonic balancer after all!

Although the crankshaft pulley did not wobble and the thin rubber on the harmonic balancer looked intact, the weighted balancer portion (outer section) of the harmonic balancer is out of place against the inner ring or section. Both sections were free floating against each other. As a consequence the engine vibrated severely.

To test the harmonic balancer, clamp the inner section of the harmonic balancer on a vise to hold this section of the harmonic balancer down. Grab the weighted outer ring with both hands and turn it. If you are able to turn the 2 sections against each other, then you have a bad harmonic balancer.

Thank you to all that have responded!

[DeltaP]

Or you coulda just run the engine without the balancer and belt/ accessories. Then start a process of elimination.

[Lbert]

Originally Posted by DeltaP

Or you coulda just run the engine without the balancer and belt/ accessories. Then start a process of elimination.

The engine will not start or run without the harmonic balancer.

As I already posted, the harmonic balancer was the source of the severe engine vibration.

[12Ounce]

Glad you got if running well. I am surprised it turned out to be the harmonic balancer ... as I never thought the weight amounted to that much. On the Windstar the balancer weight carries the markings for the timing reference ... but not the actual teeth that trigger the crankshaft positioner sensor.
.
Do you think the weight being off-balance was causing the problem .... or was it the timing markings being off location?

[Lbert]

120ounce,

The counter balance weight is huge - see 795b.

The outer section (black) which has the counter weight is out of place against the inner section (silver). As you can see at the pics provided, I clamped the inner section and I was able to spin the balancer out of place.

I do see the timing markings you mentioned on the balancer outer ring as you mentioned. Perhaps they are only valid only as long as the balancer stays in place against the inner section that has the timing gears. I say this because the engine was not miss firing nor sputtering. Idle was in good order expect for the severe vibration. Besides the timing mark, I also see a notch on the balancer so it maybe a trigger for a sensor. Oh well, at least the van is working again.

[12Ounce]

OK .... if it was that loose, I can see how it was a problem. I have seen them move a bit ...to the point that the markings were no longer usable, but I've never seen one I could move by hand.