I have an 87 SE, all stock except for the bonez superflo kit. Over the course of the last month or two, I've noticed the motor shuddering, getting rougher and rougher slowly over the course of time. The RPM's are at 750 and haven't changed over the last year.

I changed my plugs and wires today (NGK's for everything), and that didn't help. I checked for loose vacuum hoses, wires, etc and everything looked good.

I did notice, however, that by pushing down on the top of the engine with a little force stopped the engine shuddering. Could I possibly have a loose motor mount or one going bad?

Thanx in advance for any advice.

 

It might be the motor mounts, or you could just need one of those engine braces from racing beat. The braces are suppoesed to stop engine shudder. I would try which ever is cheaper.

 

if either of those don't work, get a compression test. my 91 has shuddering due to uneven compression.

john

 

Uneven compression? I'm guessing that's an apex about to go out?......What is an acceptable compression reading before you think of rebuilding?...........

 

the seal is slowly getting tired...my fron rotor has readings of 9,9,9 kPa but the rear rotor has 6.9,6.8,6.9 kPa. once you hit 6.0 or less, it's time to think about rebuilding. 9 is supposed to be a like new reading.

for whatever reason, the rear rotor is more worn than the front one and it causes shuddering at low rpm (under 1k). once you go over 1k rpm, it's fine.

john

 

Yeah.....time for a rebuild.....Seems the the rear rotor is the one that goes south first.....I'm taking an engine out of an 87 apart and will attempt at a rebuild. So far I haven't gotten to the inside. Last owner mentioned loss of compression before he parked it.

Good luck John.

 

Update: Well, thankfully my car doesn't seem to need a rebuild. After talking with Atkins Rotary and another shop, I was down to either motor mounts or transmission mounts (loose or worn out).
They also mentioned it might be running a little lean, so try adjusting the air/fuel mixture.

After adjusting it, the shuddering was reduced almost to nothing. The screw is that one next to the boost sensor behind the air filter (the one with the gunk over the screw). Although Mazda recommends owners not touch it, I did anyway. Did wonders in my case.

I didn't think the engine needed a rebuld. It's only got 40K on it, is bone stock and gets exercise but isn't pushed hard. It doesn't smoke, isn't hard to start (it actually starts easier now after the a/f adjustment), and is rock solid at any rpm above 750 with plenty of power and no hesitation or vibration at all.

I am taking it in anyway to have the motor and tranny mounts checked, just in case. The tranny was just rebuilt about 10K miles ago, so I wouldn't doubt if those are a little loose. Afterwards, I'm going for one of those engine torque braces from Racing Beat. For $65, it couldn't hurt.

Thanks for all the tips!

Jim

 

Let me know how that engine torque brace works out and how easy it is to install. I think I might have to get one myself.