First off put your flames away, I know what your thinking--jk

I've been through all the crap trying to fix this hesitation and nothing works--this crap is pissing me off.

My hesitation is now at 3500 rpm since I have the Rtek 1.7. Had it very slightly before the chip upgrade, but significantly more prounounced after the chip install--sometimes even bucking. I've read everything in 2nd and 3rd gen sections about this (yea they got it too). The 3rd gen section says pretty much the only "sure" way to rid yourself of it to go with a stand alone (Power FC). Right now that's not for me but someday I'd love to have another gadget to play with.

Just for grins I tried something out this morning. I have adjusted the TPS all three ways so I am well versed in how it works and how to adjust it. I watched the TPS plunger as I opened up the throttle and sure enough the TPS was wide open well before the secondaries started to open. So I cranked the TPS screw out about 5 turns and now the TPS plunger is wide open just after the secondaries have opened a little. I thought what good is putting in secondary fuel if there is no (or little) secondary airflow--at least now I'm sure there is enough airflow to carry the fuel into the engine.

What I did is lied to the ECU about the primary throttle position. After the adjustment it tells the ECU it is LESS open than before. Hence I don't think it will make it run richer (making it run richer is a common band aid way to minimize the hesitation). I'm not sure how the ECU really uses this throttle position but I surmise that it is a component of when to turn on the secondaries.

This TPS tweak seems to have helped alot, I barely get the hesitation now and when I do it is much less severe. I've only had a day with it and today was unseasonably cold, so I need to get some more driving time with it like this. First impression is the low rpm throttle response is much more abrupt, i.e. its harder to feather the gas and go slow. Really so far that's the only drawback I've seen.

More driving time will tell, but I thought I'd see what you guys have to say.

Scott

 

The TPS has nothing to do with this problem. On the S4 pretty much all it does it tell the ECU if the throttle is closed. It does not tell the ECU when to turn on the secondaries, that's the job of the CAS (rpm) and MAP sensor (load). Really all you've done is changed the point in the throttle travel where the injectors are turned on and off (closed throttle fuel cut).

 

True, that. I unplugged my TPS completely for a while working on that problem, runs fine without it.

 

how do you know that its not something mechanical, or i guess what im saying, non ecu related. Im not familiar with the turbos as much as N/A's but could it have something to do with the secondary injectors being either bad or just plain dirty. Do turbos have the diffusers??? Those could be gummed up as well, you may want to try having the injectors cleaned...just a thought.

 

I say all of this after pulling my injectors out of a car that did actually run before being rebuilt. Well when i got em out, two of them barely clicked while two others made no sound when powered up. Not to mention how nasty the diffusers were when i pulled my engine. And this was all after 115k. (Took lots of penetrating fluid and some pliers for the 6pi sleeves, but thats another story!)

 

Just put in freshly cleaned secondaries, so it's not that. Also, if the secondaries were clogged up then it would always do the hesitation.

There is so much info about hesitations it isn't funny. Many contributing factors can seemingly correct the problem. Some fixes work for some people, others get no improvement.

Thanks for your input.

 

Well, lets see:

1) Running rich is a known bandaid fix for the problem
2) Unplugging the TPS causes your car to run rich
3) Unplugging the TPS fixes the problem

Do you conclude that the TPS itself is the problem? I think the information gathered there is insufficient to determine that. :p

But the first post indicated that turning it out five turns could have fixed the problem. I wonder if the TPS is just flat out BAD. (As I have seen on almost every RX-7 I have ever seen)

 

Like I said, I've been through all the easy checks--TPS is good--checked ohms and volts and backprobed the ECU while driving. I saw nothing bad.

This hesitation problem has many "contributors" where one small thing that's not working exactly perfect can bite you. For some reason the root cause is not being found by the community.

I've never ever seen anyone consider that the top end of the TPS could be a factor. I know it is not the cause of the hesitation. I'm just trying to get it to where it doesn't happen every time I go across 3500 rpm. So far it works most of the time--maybe I can tolerate it like that.

Probably shouldn't have put "fix" in the title--this is really just another band aid--but if it helps...

 

I had HUGE hesitation/Bucking problems with my Rtek 1.5 in my car.

I added extra grounds and it was gone.

I added a firewall,tranny, and main - terminal to strut tower.
They didn't really do anythign but do help.

The instant I grounded the boost sensor to the strut tower ALL hesitation went away.

When I stripped the ground wire I saw some really corroded aged wiring. So I figured the wires themselves are just too old and have contact problems.

I have yet to add a ground to the ecu since I'm lazy.

 

what all have you done to fix this hesitation problem???? You probably already did but did you check the water thermo sensor?