Engine Harness - Bucking/Hesitation
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.






PARTS INFORMATION

WARRANTY INFORMATION

(Applies To Verified Customer Complaints On Vehicles Covered Under Normal Warranty. Refer To The SRT Microfiche For Warranty Term Information.)

Warranty Type: A

Symptom Code: 08

Damage Code: 95

Part Number Main Cause: FD02-67-E70

Quantity: 1

Operation Number: XX899XRX

Labor Hours: 0.2 Hrs.



Hope everyone enjoys

 

very nice thanks

 

Wow, what a find! 12 years after the dealers should of known about this and it takes an owner to find and read the service bulletin. Ovcourse the dealer would prefer to put in a new engine and destroy your harness and what not in the process, but they could allways charge you for a new one of those to.

USDM Mazda dealer =

 

That's nothing new. All it's really saying is 'make sure you have good grounds.'

Even doing all that, the only surefire way to eliminate the 3k hesitation is to junk the stock ecu. I never had a pronounced 3k issue, and moving to a pfc cleared it right up

 

That's funny because I have a really pronounced 3k hesitation and I have a G-Force ECU...

 

Good info! The grounding system on our cars isn't very good. The design of the engine with multiple layers increases resistance at each surface through the entire engine end to end. On My rebuild I used allot of holamar on the housing surfaces. No to mention the rubber coated washers that insulate all the tension bolts. Rubber motor mounts. Too many things isolate our motors from the frame. All these area caused my starter to turn over when it felt like it. Sometimes I had to cycle the key five or six times before it would turn over. I moved the ground shown in the first picture back onto a starter bolt and now Its good as off the show room floor, maybe better.

 

The G force is just a re-chipped stock ecu, so I would expect it to have the same problem. The PFC is a replacement ecu, nothing like stock.

 

Aw man I thought somebody actually solved it after all these years LOL! Like Rich said, the PFC is the sure way to get rid of the hesitation. I have never felt it ever since I installed mine.

 

My hesitation disappears after the engine warms up. How is that a grounding issue?

 

This is a 'fix' that has been known for a long time and only works for some people (and often the problem comes back).

Only 100% reliable solution is a PFC (or other non OEM based ECU).

 

With the PFC your A/C won't work right 90% of the time, and finding someone to tune it correctly is a problem. Trade offs.

 

Can you explain this, I've never seen an A/C issue with my PFC?

 

I currently have the 3k hesitation after changing the engine wiring harness. I am going to re-ground everything this weekend and I'll post my success next week sometime. I have often found that information is not always accurate on this forum and the only way to check things is to do it myself. I have a feeling that if I ground everything very well my problem may go away. It is minor anyway.

I have had a PFC in the past that had the A/C issue and tuning issues. A "tuner" (and I use that term loosely) tuned my PFC in PA and the "tune" left with a blown engine and a messed up turbo from an apex seal piece. With a re-mapped ECU I have had no issues ever even when running almost 15 PSI at the track.

I prefer the re-mapped stock ECU.

 

This is as common as the 3k hesitaiton. What year is your car? The 94-95's have a less frequent occurance of this problem.

 

This problem can be solved with additional proper ground improvement. The solution from Mazda is insufficient, but a useful step in itself.

Using a PFC does also appear to solve the problem, most likly because the PFC is much more tolerant of out of range sensor readings (my observation, not experitise).

 

ok, never mind then.. ..I have a '95.

 

Ditto. I've grounded the hell out of mine and no difference.
My 3k hesitation is gone after the engine has completely warmed up.

 

mine was the same way. So I didn't mind it much. But interesting enough and after a few years of ownership the hesistation all of the sudden began. So something certainly degraded. Just like you grounding didn't make a difference.

With the PFC no more hesitation. I was also a little concerned with the AC because I had read about this problem before, but it works just fine. Maybe because I have a 94

 

Well in a previous post of mine i was told to ground the cat and do the same fix as this by Twisted7.
Well i did both today and sevear hesitation is compleatly gone thanx Twisted7 and the other guy who told me to do the cat, it feels like a compleatly diferent car.
Worked for me so it may work for you.

Btw i also have the car grounded at 8 other points as well but the hesitation was still there (had them on for 3 months), grounded like Twisted7 said and on the cat and its gone.

 

A remapped stock ECU will not solve the hesitation problem, so I am not sure why you would prefer it over the PFC. Dismissing the PFC because you had a bad tuner blow your engine with one is odd.

Since they have dropped in price to around $600, a PFC is probably even worthwhile on a stock car for the hesitation fix, generally smoother engine operation, and monitoring capabilities alone.

 

How did you ground the cat? From where on the cat to where on the car?

 

just connected a HKS grounding wire from one of the cat fixing bolts then routed it up by the spark plugs the the engine bay where i have a HKS grounding kit connected directly to the battery.

Bear in mind i dont have a cat just decat pipes but the bolt is the same.

 

Wow, loooong ground wire. What gauge? Thanks!

EDIT: Found it, 8 gauge wires.

 

Nah not 2 long.

To hid it i pushed it under the cover for the break and fuel lines then ya cant see most of it.

 

Think I'll give it try. Clean up and add the "earth" wire to the cat. Seems like my 3k hiccup has been getting worse lately. Thanks!