Does anyone out there still have the 3k hesitation after upgrading their fuel pump?

 

Only way to FIX the 3K hiccup is a NEW ECU..

 

False...

 

I know it's not the ecu, but one member had the idea that it was because the fuel pump ran on two stages, and the problem occured when switched from stage one to two (I think). I want to know if anyone running a Cosmo pump, or a Supra pump, or the RP upgrade is still experiencing the problem. Of course, they had to have had the problem in the frist place.

 

I reading this morning that is was also caused by a ground to the battery? If you either clean or add another ground to the battery it will get rid of this problem.

I am still very new so take this with a grain of salt. I cannot tell you if it worked for me. Haven't had this problem. Hey... Try a search... I love that damn button!

 

not true regarding the ECU -
check steve c.'s site for tons of info on this

 

Adding extra ground to the battery will not necessarily fix your 3k hesitation. Tried this with stock ecu and it didn't fix it. M2 Stage 3 ecu still gives 3k hesitation though it isn't as noticeable. Hear the same things with Pettits unlimited.

I got the PFC and my 3k hesitation is gone.

That was my situation anyway. Like everything else on this car, its different for everybody.

 

I'm not sure who steve c. is. Might you have a URL for that sight?

 

http://www.scuderiaciriani.com/

 

http://www.scuderiaciriani.com/

And yes, the cleaned ground and extra ground do help with the 3k hesitation.

Yes, a replacement ECU (not stock remapped/piggyback) does remove the 3k hesitation completely. In my 94 I still had a slight hesitation but with the adding of grounds it got a bit better. With the PowerFC it no longer exists in my car, as well as many other people with the PowerFC.

 

I heard the best way to get rid of the 3k hiccup is to get a PFC

 

That's not entirely true. Many people do not have the 3K hesitation even with the stock ECU. Even so, the PowerFC may have just made the hesitation less enough that you don't notice it but it's still there.

I'm glad upgrading the ECU worked for you, but that doesn't necessarily mean that the ECU fixes the 3K hesitation.

 

Take a look at this thread, this may be a possible solution.

https://www.rx7club.com/forum/showth...threadid=91818

 

I notice that the 3k hick-up occur when the motor is cold.
So i just let her warm up or just drive under 3k til the gauge reads in the middle(factory). And the hick-up is gone. thats it

94 fd

 

I knew this thread would get a lot of opinions. Most of my grounds are tight. I do have one loose ground from the body to the cat/catback joint. And, it is usually worse when cold. I added an EFI PMC and the problem is still there. I am runnig it as a piggyback, not as a standalone though.
The thread linked by RxJjang, started by DamonB is the reason I started this thread. I wanted to know is after upgrading the pump if anyone still had the problem???

 

I disagree. All of the people that I have talked with, that have purchased a Power FC, have stated that they no longer have any hesitation at 3k.

There is NO hesitation at 3k, not just un-noticeable.

 

How do you account for the people with stock ECU's and no hesitation?

 

I have driven two seperate cars that have stated they did not have the 3k hesitation, with a stock ECU. They did have a very slight hesitation, as compared to my 94 car with the Power FC. My 93 had some hesitation especially when cold, but not as bad as others I've driven in where the car actually bucks. I cleaned all of my grounds, added a ground behind the engine lift bracket to the firewall, and an additional ground from the battery to the chassis; this significantly reduced my hesitation in the 93 car.

I would attribute it to the grounds for the cars that have the stock ECU. The better the grounds the less of a hesitation.

 

1) some/many stock ecu's have 3k hick-up.

2) most past 'fixes' were temporary, or did not work.

3) afaik, the pfc fixed every case of hick-up.

conclusion: stock ecu is the problem. it may well be true that a 'bad' ecu will work better in another car, due to lack of robustness in the oem ecu set-up. The pfc fixes the problem in all cases.

 

Like I said before, I don't believe the ECU is the problem. I believe that in rewiring for a new ECU that the problem is reduced (same is re-grounding or adding new grounds), however I'm more incline to believe that the hesitation is caused by the fuel pump as theorized in the other thread.

The fact is that not all FD's exhibit the 3k hesitation, at least enough to be noticeable. This includes stock ECU FD's, so by theory, that rules out the problem being with the programming in the stock ECU.

 

So how would you explain that the addition of a larger fuel pump, from the cosmo (brand new) still allowed the 3k hesitation in my 93? Then I added that fuel pump to my 94 and no change in hesitation.

There is no rewiring with the Power FC, it plugs directly into the stock harness. There was a study done on the injectory duty cycle where it was noted that it may be a problem with the secondaries and how they come online or not, which is controlled by the ECU. Under light throttle even when cold, the hesitation with a stock ECU is slight to none, under more moderate acceleration the switching to the secondaries may be what causes the hesitation. I believe that this info is on www.scuderiaciriani.com .

 

As for the PowerFC install, I assumed there was some wire cutting and splicing needed for the install. I don't have one, so it was just assumptions.

If you read here:

http://www.scuderiaciriani.com/rx7/3k_hesitation.html

There were a lot of things tested, but everyone seems to agree that the FD's didn't roll off the assembly line with the 3k hesitation (at least not noticeable).

If you look in that other thread posted about the fuel pump, it seems it's more of an electrical thing rather than a pump thing. Which would seem more plausible since extra grounding or re-grounding has fixed the problem for some people.

Then again, what some people may be calling "3k hesitation" may in actuality be different which would also account for the wide variety of solutions.

My point is that there are cars without a "3k hesitation" which are using the stock ECU, therefore the theory of the stock ECU being the problem is invalid. Not saying that the PowerFC won't reduce the effect or make it go away, but that it may be inadvertently fixing the problem.

 

i dont mean rain on any parades, but i actually tested this on my car.
1. the hesitation is always at the same rpm.
2. the fuel pump switch over is not, it is load dependent.
3. cleaning (sanding and applying distributor grease) fixed the problem on my car.
4. it came back about a year later
5. i have had 2 different pfc's in my car, they both did not have the hesitition, and the stock ecu did

mike

 

The only wires that are cut are for the accelerated warmup system, egr and another smog related item; no other splicing done. If these are left connected, the car runs poorly because the PowerFC does not control those items.