I tried to do a search but got a message that the admin had disabled that function, so I am coming to the experts for assistance.

I have a 93 FD with 61k miles on the engine. It has a catback and downpipe. The previous owner put a super big ground cable on it negative battery terminal to the frame.

I am still gettin a really bad hesitation at 3k RPM until the car really gets warmed up. Has anyone found a sure way to get rid of this hesitation?

Thanks in advance for the tips.

 

That is a common problem with many theories as to why. I won't go into those, but the common thread seems to be that an aftermarket ECU will either smooth out or fix the problem altogether.

I know of several people with piggyback computers (a la PFS) that still have the hesitation. I think the best way to eliminate it is by purchasing a stand-alone computer like a Power FC or Haltech. Both units are expensive and require tuning, but you'll need one anyway if you plan on modding further.

 

I think someone posted about it being the primary to secondary injector switching.

Just as stated above, you can get a programmable ECU to help smooth it out, but I don't think it's ever "completely" gone. Just less enough that it's not noticed.

 

I am very new to modding, in fact I have not done any myself yet.
What would be the best ECU to get that would not require me to get a college degree to learn how to use it?
It is real bad. Any improvement would be a big improvement.

Thanks again!

 

Probably the most popular aftermarket programmable ECU is the PowerFC.

The problem is that when you start changing your car, *if* you want to tune the ECU yourself, you really need a dyno and a wideband O2 to make sure you aren't going to pop your engine. You can use other people's maps, but to me that just sounds bad. You can also have it sent away, tuned and returned (for a price) so that is always an option.

 

I had the same 3k hesitation problem, at times it was quite severe. I also tried the usual easy stuff....grounding, vacuum hoses, blah blah. Others recommended putting in a 94 ecu (i have a 93). Well, I finally gave in and put in a PFC. Completely solved the problem, and the car runs better than ever.

I did have the PFC pre-tuned by SR Motorsports for my modifications (intake, DP, CatBack). It is an easy plug and play install, but does require a lot of knowledge, research and committment to go further with it. Having said that, even if you do nothing more than the "pre tune", your car will likely run better than it ever has.

Good luck...

Fabian

 

Thanks for the tips. I will give that a try.

What would it cost (approx) to get it re-tuned if I make more mods?

Twyatt

 

When you say PFC you are referring to something along the lines of the Apexi Power FC w/commander right?

 

Yep, you don't need the commander and unless you plan on doing you own tuning or trying to also use it as a boost controller.

Nice to have either way though...

 

Thanks again for all of the tips. Does anyone know about how much it is to have one of those rascals reprogrammed?

 

One thing I never got about the 3k hesitation, is that if it really is a problem with the ECU, then shouldn't a new ECU or an ECU from a car that doesn't have the problem solve it? But this never seems to be the case. No new RX-7s ever had the problem, so something must be happening between when the car is new and when it develops the 3k hesitation. I think the PFC doesn't actually solve the problem, what is does works around it by staging the primary/secondary transition differently. I have a feeling there are multiple underlying causes for the 3k hes. problem, and we just haven't figured all of them out yet. IMHO if a new RX-7 doesn't have the problem, there is no reason an old RX-7 can't be fixed to eliminate it. Its just a matter of figuring out what is going wrong.

 

I think it's like $150-200. Give SR Motorsports a call. I would also purchase my PFC from them as they modify the PFC to fit the wiring harness exactly. Their price is not bad either.

www.srmotorsports.com

 

You should check the 3 main grounds, and replace them with a heavy guage quality braided wire (such as good stereo cable.)

1. from the block to the frame (driver side, bottom)
2. from the throttle body to the frame (along the firewall, closer to the pax side)
3. at the cat back exhaust and main cat junction to the frame.

make sure you have clean metal to metal contact for the grounds.

then you MUST reset the ECU. modern car ECUs can "learn" a behavior and exaggerate it. to reset the ECU, disconnect the battery and hold the brake pedal down for at least 30 sec. (some people say 15 sec., some say 30 sec., i have never found a definative answer).

also, i found it made all the difference in the world to unlpug the ECU. (it is located behind a kick panel on the pax side) take your time when you pry the connections loose, as it uses a softer type plastic.

anyway, if this doesn't work, we can try some other things -