matwey

After smoking a Vette, I noticed my car was idling at 550 rpm (norm at 900) and my 3k hesitation problem was much worse. Seems to hesitate mildly at low rpm (1400-3500) and once at 4500 almost cut out. What was once 3k hesitation, is now much broader and more pronounced. Pluggs are NGK 9's (4k mi.)w/ Jacobs wires (15k mi.). Put on a used (guaranteed good from friend)leading pak 10k mi. ago. All piping and vacuum lines seem ok. Ideas?

violator

check the plug wires; i heard that the jacobs wires tend to pop off easily.

matwey

Thanks, but wires seem tight. I will try a known good set from a friend though. BTW, it seems to happen at light to med. throttle. Only the 4500 rpm cut happened under 3/4 throttle. Thanks.

violator

yea i dont know what that problem is. my friend has the exact same problem.

after he rips **** up, the car will feel like someone is holding it back at partial throttle. and at like 3000rpm the hestation would be really bad; but only at partial throttle.
dont know whats wrong with his car but it seems like ur having the same problem.

Rx-Revin

i have this problem at this time to and it is pissing me off.

matwey

Well, if we collaborate, mabey we can get this solved. One idea I have is to upgrade my PFC to a newer one and run it as a stand alone. I've read this will (hopefully) eliminate the problem. I'm meeting w/ someone who also has a PFC Monday afternoon. Mabey we can work something out. Is yours bogging enough to make you lurch, or is it mild? Mine can be both, but usually is severe.
Guess I'll start checking pressure sensor, pressure reg., then move to injectors.... I have a factory manual, but none of the specialty tools.
I have noticed the hesitation get progressively worse. When I got it at 65k it would happen about once every other month at the most, now it's daily!

violator

u have a apexi pfc and it still does this?

matwey

No, I have the Peter Farrell Purple Computer.

WhiteRXseven

I am not sure..

But since the PFS Purple is a piggy back.
and it doesn't intercept signals until
high boost levels and heavy load,
it still runs on the Stock ECU during
light and medium throttle. So it wouldn't
fix the Hesitation problem..
And stock ECU is notorious for the
hestitation and bucking and etc..

I have a PFC since its been in.. No hesitation
not even a hiccup..

Goodluck

maxpesce

Check all yor grounda - make shure all CLEAN and TIGHT - If you have not all ready done so, replace the one from the UIM<>Firewall with one made from 10ga min wire and RING TERMINALS at both ends (get rid of the spade connector)

rotary-tt

Sounds like my problems too. I've cleaned up about every ground I could think of. I've started pulling off connectors, relays, fuses under the hood and using electrolytic grease. It seems like just 1 hesitation on top of another. Mine is more pronounced when the car is cold. I am using Jacobs wires which seem to have problem. I changed my plugs last week and found that the rear trailing plug was not worn at all. I made sure to connect it properly but I'm going to have to use a timing light to check the wire. PS - Rotaries seem to eat plugs every 6 months or so under hard use. I am running much better now but all the multiple hesisations are still there.

I've heard that cleaning the fuel injection ground or replacing the ignition wiring harness helps or fixes the problem in some cars. Time to pull the intake and throttle body off.

Do you guys have very stinky oil? Mine reaks and I suspect the injectors. I wonder if we are experiencing leaky injectors...

matwey

Sounds like we got the same problem home slice. One hesitation after another. My pops had a similiar problem on a BMW motorcycle and he changed the injectors and "poof" no more hesitation! I'm thinking about sending mine out and having them blueprinted. Any thoughts? Only other two thoughts are the wires or the computer. Don't mind changing wires, but the $ for a new stand alone is a bit much. But, I'll do what I gotta do.

kkk93rex

I have a PFC tuned by SR and it it wont currently run anything past half throttle. It just pops jums and wont move or acclerate. I would blueprint the injectors becuase whit what im experianceing the PFC doesnt help. The jumping in my car is so severe it feels awful.
My .02 cents.

blackscorpio

Its your MAP (boost) sensor. When it pops of your idle gets low and eratic and you run really rich. At WOT you basically flood you engine, what you have to do is reconect the MAP Sensor (ties work the best the factory clamps suck). replace spark plugs (they should be pretty fouled by now) and oil(You will have gas in it thus the stinky oil) and reset the computer (negative off battery brake in for 30 seconds) and you should be all set.

If the MAP sennsor is hooked up (all hoses connected on it) and you may have a leak in the line or a bad MAP sensor. PM me If you have any questions.

rotary-tt

I have a rock steady idle and the hesisation comes at the lightest of throttle much prior to any boost. It does seem to run rich. I make good power under boost without any issues. I have the normal 2700-3200 hesitation with 2psi boost but this is not the issue I'm talking about. I get one hesistation on top of another at low speed cruising with no boost. Doesn't seem to be related to the electrical load. I've cleaned grounds and reset the cpu. I'm still stumped but everything is pointing to me pulling the intake and throttle body to get to the fuel injection ground and cleaning the injectors. How do you test the MAP sensor? I'll look it up in my shop manual...

Roo

Hmmm, All very interesting and I cannot but imagine that Mazda must know about this issue and have a solution? Has anyone asked? Well here's my story... I never had the hesitation prob until I replaced my motor with a Jap import. Then as you all seem to suggest the hesitations started. Just to clarify mine seem to occur at low revs around 3000 rpm and only ever under light to medium throttle. Full throttle seems to be fine. It was getting progressively worse over time and although I considered the fuel injectors this seemed unlikely due to the lack of consistency and the spontaneous nature of the problem (it didn't happen every time). My RX-7 also smells rich and I was inclined to think it could be related to the oxygen sensor or MAP. I took it to a reputable performance shop and described the problem with no luck. As a last resort they replaced the computer with another factory unit. (He said the Jap computers were different to other export computers) Anyway, the end result is that the hesitations have certainly reduced in occerence and severity. They are only fairly rare (usually when cold) and the severity of the hesitation has dropped right off. There is no distinct loss off power as there was before.

But beware he could have tweaked something else along the way. I noticed my idle had changed and my boost is now reading a little lower than before the car went in. This could be different factory settings within the computers - who knows. Anyway on Thursday I go out to the track so I guess I can give it a through assessment then.

BTW... I also found this interesting piece of info...

5.2.1 Hesitation at 3000 RPM when cold.
No known cure.

I think it is caused by the double throttle control. Its purpose is to prevent the engine from getting an overly lean fuel/air mix when you first start to accelerate. Now the way this system works is that when the engine is cold, (coolant below 175 degrees or so) the ECU opens the double throttle control solenoid, which supplies vacuum to the double throttle control actuator. This vacuum overcomes the spring tension that normally holds the double throttle butterfly open, and it closes. Now, think about what happens when you accelerate.... the engine pulls less vacuum, and starts to go towards positive manifold pressure as you build boost. With the vacuum going away, the plate returns to its open (normal when engine warm) position. This helps explain why the car doesn't hesitate when accelerating hard, and does when accelerating slowly. The decision by the ECU to operate the double throttle control system is affected by coolant temperature, and the current "map" that the ECU is using. The Double Throttle control only happens during starting, cold engine warm-up, and COLD engine with LIGHT LOAD operation. This map is also affected by the 20k mile switch, which is why many people say that the car never hesitated at 3000 RPM when it was new. The 20k mile switch does the same thing that the EL switch does.... it adds base RPM to the motor... which affects the ECU's decision as to what "map" it is currently operating in.
This is just my personal theory, and may be wrong.

Roo

MORE DETAILS ON 3000 RPM HESITATION...

There are numerous "fixes" out there including Engine Control Unit (ECU) replacements, check valve placement, kinked vacuum hoses (See TSB item #17), replacement of the EGR valve with the California EGR valve, etc. While these may help reduce the symptoms, on most RX-7s the problem will remain. There was even an internal Mazda fix which included the adjustment of a rod that controls the "transition" between the primary and secondary turbos, but again, just a bit of help, not a true "fix". The problem seems to be the programming in the factory computer. The RX-7 has two secondary injectors which turn on at aprox 2,700 RPM. While the engine RPMs are rising under light acceleration, the secondary injectors will turn off for a fraction of a second, then turn back on. This seems to be causing a momentary lean condition which we experience as the famous "3,000 RPM hesitation". The secondary injectors are controlled by the ECU at terminals 4 X and 4 Z. By hooking up a digital multi-meter to these terminals and observing the voltages going to the injectors, we may observe this problem directly. At about. 12.5 Volts, the injectors are off. At lower voltages, they are being switched on at varying rates based upon the programming of the ECU. Every time the engine hesitates while going through the 3000 RPM range, we may observe the secondary injectors being switched off, engine hesitation, then injectors back on; hesitation gone, and normal acceleration. It is possible that the only true fix is to reprogram the ECU to keep the secondary injectors from switching off in the 3,000 RPM range. Will Mazda address this problem in an upcoming release of the ECU? Possibly, but only if enough customers continue to complain about the 3,000 RPM hesitation. Contact your dealer service department and also call the Mazda Customer.

matwey

New situation.....car was running ok (mild 3k hesitation) when at 4200 rpm the car stalled (bogged) and made a mild popping noise. Have not had a chance to get any readings from my keypad (Peter Purple comp) , but O2 seemed ok, appeared to not have any vacuum leaks, and otherwise ran ok. Boost was mildly erratic, peaked at 12 or so. Fluctuated 1-1.75 psi. Ideas?

Wade

iTrader: (1)

I would advise everyone to ignore the information below because the vast majority of it is absolutely false...

Wade

iTrader: (1)

matwey, sounds like you might be having the fuel cutout problems that some people have experienced with the PMS. Try disconnecting your battery, standing on the brake pedal for about 30 seconds, then reattaching the battery. Drive around and see if this helps. If it does, you are probably having the same problem as others. Also, what are your fuel and timing settings in the PMS?

Wade

matwey

Wade, here's my situation... bought the PMS used, no manual. Tried to get updated software and manual from PF, no luck. I've had to keep my factory settings b/c I don't know how to read the pad.
Met a guy here (in RichmondVa) who has one and his car is runnig well, except for 3k hesitation. He drove my car and said the O2 is fine, but it could use a bit more fuel. Also my boost fluctuated a bit, never a steady 12 psi, always moving. But to answer your question I don't know what my fuel settings are at.
Friend gave me a RB cat-back and said after that was installed and conv. gutted, he'd help tune it.
I will try the fix you suggested this evening and post back in about 10 hrs. (12:30 pm here). Thanks for the help. BTW, cool site Wade.
I believe my timing was -2 degrees? sound right?

Wade

iTrader: (1)

matwey,

Go to www.efisystems.com and you can download the mazda manual there. That should help get you going in the right direction. I can help you more later and after you read your settings from the computer.

Wade

matwey

Thanks for the info, never thought of going to the source. Mainly b/c I knew EFI wouldn't sell to the public.
Couldn't clear the memory tonight, raining like crazy, will do it tomorrow evening and post back. Thanks again. What are you runnig now, still a purple box?

matwey

OK, just downloaded PMC manual, all 38 pages! Will read by the end of weekend.

matwey

OK, started reading the manual, lots still to go. But, i did "clear" the memory........ seemed to help! Since my problem was somewhat erratic, not sure, but after driving for a few miles it should have happened and didn't.
What did clearing the memory do?
BTW, still have 3k issue, but liked the idea in another thread about the fuel pump, might try it.