Vibration when accelerating

RIDEORDIE0719

MEMBER
1992 LINCOLN TOWN CAR
V8
2WD
AUTOMATIC
97,000 MILES

I’ll be driving/accelerating and all of a sudden the car will vibrate intensely for a few seconds then resume to normal. This vibration feels and sounds like the engine is going to fall out of the car when it does happen. It also reminds me of driving over a defective part of asphalt or driving over speed bumps. The speed bumps that are at some cross walks or airports. The kind that are only an inch or so off the ground and very close together. The vibration only lasts about 5 seconds when it does happen at any given time. I haven’t been able to pin point a pattern in regards to how frequently these episodes take place. It does happen more than once during a trip.

Tuesday, July 14th, 2020 AT 8:18 AM

2 Replies

STEVE W.

MECHANIC
15,236 POSTS

That description sounds like an intermittent misfire while under load. When was the last time it had a full tune up with plugs and wires? It could be something like a loose connection as well. The catch is to test it while it is acting up, which on a random problem can be tough. If it does it mainly when you are accelerating it could also be low fuel pressure that starves the engine when it needs fuel the most, but if that is the case it should act up pretty much every time you hit the gas hard.

This guide should help us fix it:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

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Tuesday, July 14th, 2020 AT 10:01 AM

4DRTOM

MECHANIC
467 POSTS

Hello,

Your description matches a shudder caused by the lock-up torque converter. To identify that, hold the accelerator pedal perfectly steady at highway speed, then tap the brake pedal with your left foot. You'll hear the engine speed increase by 200 rpm, the go back down a couple of seconds later. If you feel that shudder when engine speed goes back down, it's the torque converter locking up.

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Tuesday, July 14th, 2020 AT 10:06 AM