The front motor mounts are bad. This has been confirmed. When I am cruising at a constant 45 or 55 mph and choose to accelerate because traffic is clearing, etc. the car will thump a bit and only slowly creep faster. It feels as if there is very little response other than the mild thumping. Getting to 65 mph takes time. The car has 70k miles and performs almost flawlessly at slower speeds. Is the thumping/lack of acceleration a symptom of the bad front motor mounts?
" Is the thumping/lack of acceleration a symptom of the bad front motor mounts?"
I have a very hard time seeing any connection between the two problems.
What can you tell us about the car’s maintenance over the past 3 years?
Is the Check Engine Light lit up?
The thumping can be a symptom of a bad motor mount, the slow acceleration is not.
Possibly a wire or vacuum hose is getting pinched b/c of the extra movement allowed by the defective motor mounts. While replacing the motor mounts, also look for something that could be getting pinched by motor or transmission movement.
It is a used Regal I recently bought for a fair price. I do not have any maintenance records. I didn’t think there could be a relation between the lack of acceleration and the motor mount but I had to ask. I will see what else may be ailing the car. It runs seamlessly with no strange noises until the mild thumping at a 55 mph roll. As I accelerate the engine does not sputter or appear to misbehave at all. It just does not increase in speed at a reasonable rate. I will update this post after I take it out on the freeway again (which may be days away). Thanks all!
Absent it being associated w/the motor mounts, ffor the lack of acceleration the first place I’d look is a clogged engine air filter or a clogged cat. Easy enough to replace the engine air filter. A mechanic has a backpressure measuring gadget and could check for a clogged cat. Or you could just remove the cat and see if that fixes the problem, as an experiment I mean.
Bad motor mounts can absolutely cause acceleration problems on a '94 Regal. If the engine rocks out of place, it can easily affect the operation of the throttle cable.
Newer systems use an electronic signal to the ECU which drives the throttle plate via a signal to a motor, so a rocking motor won’t affect throttle operation, but in '94 some things were still hard-wired.
Change the mounts. I’ll bet that’ll help. I say that at some risk, knowing full well that a '94 probably has other problems too. For the other problems, start with a compression check. Post the results.
mountainbike
I like your thinking . . . yup, electronic throttle was still fairly uncommon in '94
Thanks.
I’m leaning toward @GeorgeSanJose 's diagnosis on this one. Poor performance at higher speeds points to poor “breathing”. This could be caused by a partially plugged catalytic converter or air filter. It could even be a rodents nest in the intake duct. I’ve seen it happen.
I’m skeptical of the accelerator cable. Bear in mind that the engine end of the throttle cable housing is secured to a bracket which is mounted to the engine so it moves as the engine moves. The cable itself is very forgiving of engine movement. That’s the whole point of these kinds of cables
Now if it were a much older car using all rod type linkage then I could see it.
These suggestions are all extremely useful. First and easiest, I will replace the air filter. Could use a new one regardless if it is the problem or not. The other things I will have assessed (my tools were stolen and I have no place to work on my car) somewhere soon.
Bad motor mount affect throttle cable? NOT!
Bad motor mounts triggering the knock sensor, however is a strong possibility. If the knock sensor thinks the motor mount knock as pre-ignition knock, it could be retarding the timing, causing acceleration issues. Replacing the motor mounts will cure this.