Unwrapped my 04 Coupe MN6 for a ride today. It's cold but sunny here
in NJ. It's been cleaned and covered for about 5 weeks and decided to
take a little trip.

Warmed it up...drove about 10 miles on local roads....Got gas and
headed out to the highway.
The car felt a little rough to drive but I figured I've been driving my
new Mazda for all this time, I'm just not accustomed to the C5.


Headed up the on ramp and gently got to 70MPH. The road is very
smooth and the car has a pulsing vibration as I accelerate. Pulse for
a 1 second duration about every 1.5 seconds.

I feel it very prominently in the gas pedal and in the car body.

The shifter feels about the same as it always does. (CRAPPY)

Though the vibration is very prominent upon slight acceleration, it
almost (or seems to ) dissipate while coasting or lower speed.

It is speed related (not RPM) and most noticable 70 - 80 MPH. I didn't
go any faster.

I'm thinking something broke or is imbalanced at the rear of drivetrain
rather than engine or clutch.

I don't remember hitting anything with tires prior to putting it under
wraps but I can't remember when the last highway ride was either so
I can't tell if this was present before...But I doubt it.

This is a very noticeable ( to the driver anyway) vibration.

Do you think tire balance could exhibit this?
The steering wheel doesn't shake bu the vibration is felt.

This is one of those diagnoses the dealer will have a hard time finding
on local or bumpy roads. I doubt they'll want to drive the 10 miles
out to a smooth highway.

Got any thoughts on this?

...GeorgeC

 

You Mention the car has been covered for 5 weeks....My Guess is the Tires have flat spots from sitting in one place that long....Pretty common, See what happens after they warm up.

 

Yeah, my first thought, but that would give me a steady
brrrrump brrrrump brrrrump at every tire rotation.
This is a pulsing which lasts about a second.

I had driven about 14 miles before I got on the highway and
drove another 30 miles...It had time to warm...George

 

 

I have heard of this symptom with a rear bearing going bad as well.

 

Patches...I hope not...Here's what happened.

I picked up a buddy and let him drive the same route.

He said he felt a wheel vibration and felt the front end was the culprit.
Didn't feel it tin the shifter or gas pedal as I did early in the morning.

I drove awhile and admittedly it was not at all what it was.

I (we) figured that because the car sat so long and it was about 22 degrees, it really didn't get warmed up and most likely a wheel might
be out of balance and was exacerbated by the cold and
flat spotting. After about 110 miles, it now feel normal with a very slight
wheel vibration.

I think I'll take this opportunity and lower it finally and take it in
for balancing and alignment.

It's going to get cold now for a few weeks and I'll see if it happens again.

...George