95 gt engine vibration

Hi StangNet community. I have been getting help here for a long time as a reader (much respect and thanks!). This is my first post.

I have had a 95 GT convertible for 11 years and 35k miles (currently 195k on the odo). I try to keep it in good enough shape to lend it to my mother in law with confidence. It has always been super smooth and a pleasure to drive. I have worked on it a lot, and I have taken a lot of advice from this forum.

A couple weeks ago, out of the blue, I started it up and it had a new vibration. It's pretty mellow at idle but give it any gas and you can feel the whole car rumbling. It rattles the dash and trim inside. It doesn't matter if it's driving or parked, so I rule out everything downstream of the engine itself. There are no trouble codes, so I want to rule out anything related to injectors or ignition as well, assuming I would get lean/rich mixture codes if those were failing. Other than the vibration, it is driving great, I don't think it has lost any power and it idles smoothly.

After some research, I thought it could be the motor mounts or the balancer wearing out. The balancer looks fine to the naked eye (although it does vibrate with the engine) and there is no belt noise. I put it on stands to check the mounts- the driver's side mount had a big crack in the rubber. I replaced the mounts. The job went well but sadly it still vibrates. I just read this one with a similar issue, and it seems like their next step is to check the harmonic balancer.

I am just looking for opinions. Would you go after the balancer next, or is there something else to check? Would you go after spark or fuel even though there are no trouble codes? Are there other possible issues that I'm not thinking of?

Thanks in advance!

I took enough stuff out to get some pictures of the balancer. The rubber is looking pretty old. You can see some cracks, and you can see that the rubber is not flush with the front surface of the damper on the left and bottom. Didn't want to do it, hate pulling the radiator and stuff, but I probably should.

I would still love to hear any opinions!... but I think I will go ahead and order a balancer.

For what it's worth, just because it's easy to do, I also checked all 8 plug wires with my timing light. All are firing.

Edit: I don't think the radiator has to be pulled out for this. For whatever reason, I have always had the radiator out when pulling a balancer, but it looks like I'll have enough room to leave the radiator alone.

Well, the balancer was certainly shot, the outer donut was working towards coming off the hub, the rubber donut was coming apart, etc. You can see it compared to the Dorman replacement part here.

Unfortunately you can also see that the tapped holes on the Dorman balancer are too small. My pulley bolts are 3/8-16, these seem to be M8 or 5/16. I would have thought 5/16 but it seems to have a metric thread. I was tempted to just use it anyways, but I don't like how loose the M8 bolts are in the pulley clearance holes.

I filed for a refund and am now looking for a balancer with 3/8-16 holes, but nobody specifies this hole in their product details... making me think it shouldn't be a thing that varies among balancers. I may try ordering the Pioneer and see what happens.

Any ideas out there? Happen to know the size of your pulley bolts?

With the new balancer in, the vibration is gone.

The Pioneer balancer was not as pretty as the Dorman but it had the correct mounting holes and feels like it is doing its job correctly. Much easier job than the motor mounts, 5x easier, would have done the balancer first if I had known. Although in my case, the mounts were definitely needed anyways.

On the mounts:

• The gymnastics of getting to the bolts and nuts got pretty old. Wish I had a lift.
• It felt like the engine lift was uncomfortably high. The engine is missing one of its hoist loops, so I used a jack under the front sump. Disconnect the air duct, remove the crossmember between the struts over the intake manifold, loosen the transmission mount, remove the bolt that retains the tranny shift cable to the bottom of the car, lift a little at a time and keep an eye on all the exhaust pipes and lines/wires/hoses topside.
• The alignment nub on the driver's side mount was not finding its hole at first. I got halfway through installing before I noticed it wasn't lined up. I lifted the engine back up, loosened all the bolts on both mounts, then slowly dropped the engine back down, little by little, and at each step I hit the mount with a hammer and drift in the direction I needed it to go. This worked, everything lined up, I tightened it all back down.

On the balancer:

• I read somewhere that I should mount the pulley in the original orientation on the new balancer. I figure the overall balance will never be as good as it was off the line, unless I take it to a shop and get it re-balanced with the pulley on? It feels nice and smooth now and that's good enough for me.
• Smear a line of RTV into the keyway of the new balancer, clean the crank snout with acetone, rub a little bit of oil on the crank snout and on the outer surface of the balancer hub where it slides into the seal. Take care to align the key to the keyway and not mess with that front seal, torque the center bolt to 125 ftlb against a prybar across a pair of 3/8-16 screws in the balancer mounting holes.
• Torque pulley bolts to 45 ftlb against a prybar wedged into the center hub.

I should have taken more pictures. Thanks everyone for comments and information, hope this helps somebody later on.