JEDlocks

well i've searched and searched and i cant seem to find the right answer to my
particular situation. Well first off, I'm at about 1400 miles on a rebuilt motor.
At this point, from what i've read and from what i have been told, it's safe
to rev up to 5000 rpms and give the car about 2 - 4 psi of boost. so, my problem is:

at around 3300 rpms (give or take a couple hundred) my car seems to lose power.
boost pressure is steady, but i get some sort of "stumble, or restriction" from 3300 rpms and on.
My car seems like it's struggling to gain speed. The stumble/restriction/ hesitation isn't the common
"jerk" most get, but it's more of a series of mild surges in power and power loss.

at first i thought i had fouled spark plugs, so i replaced them (all 9's) and the problem still exists.

here are my following mods (that may have something to do with the problem):

-rebuilt motor (new housings w/ street port, and TB port)
-apexi PFC (untuned, ran base map before rebuild and never had this problem)
-3" dp, pettit hi-flow, rb duals (i still have the airpump)
-stock turbos with sr motorsports smic
-indigo pulleys
-stock injectors and pump (guessing this is the main problem, but note that i am
not maxing the injectors out yet, no more than 55% injector duty so far)



sorry for the long post, but im bringing my car back to the shop on tuesday
to get it checked out. just trying to eliminate any possible problems. cant
afford any more down time with this car.

any advice would be appreciated.
thanks

Dusted RX

Too much timing with street port and base map?

JEDlocks

too much timing?

JEDlocks

anyone??

DaveW

I had similar problems with a bad plug wire - not a distinct miss, just a power loss. A bad coil will also cause that.

JEDlocks

hmmm i doubt it's a bad plug wire, i just replaced them in april.

i'll look into the coils.

thanks for the help


anyone else?

JEDlocks

****UPDATE****

after 5000 rpms the car smooths out and after i shift up to
the next gear, it still drives smooth. but once the rpms get
down to 3000 rpms again, the car starts to hesitate once
again.

DaveW

I don't know anything, except for what I've read on here about the PFC, but from my experiences with other cars, I'm guessing that it is running too lean (or too rich) in the 3000 RPM range. Do you have a wideband O3 sensor to see if the mixture is way off when this happens? Does it change with car or ambient-temperature changes?

JEDlocks

i do not have a wideband sensor
and no it does not change with car or ambient-temperature changes.

i think it runs too rich when this happens, because i seem to get a lot of backfiring
after i let off the gas.

im hoping the problem is the coils though

DaveW

The fact that it smooths out at higher revs MAY indicate that it's not an ignition problem. Those usually get worse as the revs increase.

Dave

KBSRX7

This could be anything, BUT. I know this is going to sound funny, but it could insuffient grounding. These cars are know for its poor ground paths and also these cars are getting old which means copper corrosion. I had the same problem. Run several ground wires from the engine to engine bay. If you moved the battery to the back you must run a ground wire from the NEG to the engine bay. Bigger grounding at the fuel pump harness helps too. The problem was GONE! you never know, plus it wouldn't hurt also.

JEDlocks

yeah my second guess was bad grounding, but im going back to the shop today to
get the coils checked and tested. we'll see what happens

pinkrx7

iTrader: (2)

check your plugs and plug wires. having the same problem and im sure its my plugs/wires

JEDlocks

coil packs and grounds are good.
even checked map sensor.


next guess is a bad solenoid because i tested the car out
again today, and i noticed that i dont make any boost at
around the time the secondaries are supposed to come in.
i tried flooring it once i got to 5000 rpms, but i was not making
any boost at all. correct me if im wrong, but this may be a bad
solenoid or a hose that popped off.
cant get that checked until next week though.
dont want to tinker around with the car myself, i'd rather have
an expert do it right the first time.

JEDlocks

solenoids checked. vacuum lines messed up? stuck wastegate? secondary turbo doesnt kick in at all. AFR stays at a constant 12.

HELP!!

MAZDASPEED08

try this

Bulletin No.: 005/97
Issued: 03/10/97
Revised

CategoryF

Applicable Model/s
1993-95 RX-7

Subject:
HESITATION (JERKING/BUCKING) WHILE DRIVING

APPLICABLE MODELS
1993 - 95 RX-7

DESCRIPTION

A jerk or bucking condition may occur under any of the following conditions:

^ Under light to moderate acceleration

^ Cruising at engine speed of 2000 - 2200 rpm

^ A/C ON


This concern may be caused by improperly grounded engine harness, creating high resistance in the engine ground circuits. This condition affects the fuel control system.

Customers complaining of this concern should have the vehicle inspected and if necessary, repaired according to this bulletin.

REPAIR PROCEDURE

1. Clean and retorque harness ground.

^ Locate ground on left side of engine, mounted to bracket behind A/C compressor. Refer to the applicable BETM or wiring diagram.









^ Tightening Torque: 69.5 - 95.4 in-lbs (7-11 Nm).








2. Clean and retorque main battery ground and bracket mounting bolts (bracket used for mounting the ground).

^ Tightening Torque:

69.5 - 95.4 in-lbs (7-11 Nm)









^ Remove the Original ground strap and terminal bracket between the engine hanger and the bulkhead.

^ Install new style ground strap using the original bolts.

^ Tighten Torque:

12 - 17 ft-lbs (engine hanger side) (16-23 Nm) 69.5 - 95.4 in-lbs (7-11 Nm) (engine room bulk-head side).

3. Verify repair.

MAZDASPEED08

pics did'nt show but hope this helps you. i'll be doing it this weekend!

pulabear

iTrader: (1)

Hey guys, I'm reviving this old thread so I don't have to create a new one.
I am experiencing the same problem, did the above method or adding grounds help the condition?

spoolage

iTrader: (2)

+1, I am currently experiencing the same issues... new motor so I cant boost yet but if I am at 3000 rpms and try to accelerate at all, I get power break up and it feels like fuel / ignition cut