recently, my car, when cruising in any gear and accelerating at anything but WOT, it starts to jerk violently, jerks like when you were first starting to drive a manual, even in 5th but not as violent. it doesn't do it all the time,

what could be causing this?

 

I am no expert but let me take a crack at it..
First of all you should list your mods or is it stock?
and Mileage???

Does the jerking at or around 3.5K rpm???
or is it 4.5K rpm.. Correct me if I am wrong.

Could be the Transition from primary to secondary
injectors. New ECU will fix that.

Replace that puny ground strap in the engine
compartment, with some 12gauge from autozone.

Or Dirty injectors.. put in some Injector cleaner.
Clogged Fuel filter?? when was it last replaced??
Maybe faulty fuel pump??

Those are the first place to start look.

Well hope I helped.

 

here my signature

my car has 70k, engine was rebuilt at 65k, it was done at pineapple racing, so im pretty confident he replaced the fuel filter, the injectors were cleaned and balanced 5k ago when the engine was rebuilt.

the jerking/bucking is around 2.5k-3.5k, and only only durring moderate acceleration, when i open it up, and accelerate at WOT it drives fine.

 

From what you are describing.

I think its your Transition from
Primary to Secondary Injectors.

ALL FD3S with stock ECU has that issue.
Ok maybe not all, MOST do..

I am no authority on Rotaries or RX7's
But my advice to you is to.
UPGRADE your ECU. ASAP..
Stock ECU is junk.. Get reprogrammed ecu
or stand alone soon.. Its a shame that you
have street port and rebuilt Motor and etc,
and not being able to use it to its potential
with the Junk Stock ECU. Not only a New ECU
will make your car Run and FEEL totally different
for the better, It also gives you peace of Mind,
knowing you are less likely to blow your motor.

Oh yea get a boost gauge too...

 

Sounds like the "3k hesitation"...

What will help is if you check all the grounding locations and make sure they are clean. Also, you might want to add one or two more extra grounds.

That will help smooth out the hesitation, but it won't get rid of it.

 

There was an ECU recal for early 93's that was designed to fix the 3k hesitation (and the Stall w/AC on at idle problem) so check w/ MAZDA to see if your ECU was (is) the upgraded unit. But since this is a NEW (I understand it started AFTER your rebuild?) problem - first check all the Engine<>Chassis Grounds for CLEAN TIGHT connections - Upgrade the strap from the uim<>firewall to min 10ga (or larger) wire with RING terminals on both ends, get rid of that spade connector! connect the firewall end under the bolt that holds the existing connector - check that ALL the connectors on the Injector harness are CLEAN & TIGHT!. Also check your Spark plugs & wires - worn/fouled plugs can sometimes cause midrange hesitation

 

cash money i think with all these problems that you have had a string of bad luck. I hope you fix this one.

 

i got a PFC on the way, so not to worry, but i'll cehck the grounds, is there a how to on this anywhere?