njkrause

So i have this hesitation/stumble/jerking between idle and 3k rpm. The hesitation goes away under acceleration or deceleration. The hesitation is most prevelent when trying to maintain speed, aka between accel and decel and below 3k. READ: It is absolutely not the 3k hesitation that most 3rd gen rx7's have, my car has this too and has had it for the last 2.5 years and it does not bother me at all. The problem i am having now makes the car impossible to drive between idle and 3k rpm once the car warms up. In order to make it up a hill i have to spin the motor up above 4k rpm. When i initially had the problem i searched for hesitation in this forum and found numerous similar descriptions of the same problem where the o2 sensor seemed to be the culprit. I immediately went home and unplugged the o2 sensor and went out for a drive. They were right, sort of, with the o2 sensor unplugged the car did run fine. Well now it is time for me to go through DEQ in Oregon, so i went out and bought a new o2 sensor, installed it on Friday, drove home and the problem is back. Here is a little info on my car

93 R1 Rx7
68k miles
M2 Stage 3
in other words:
M2 Medium intercooler
Downpipe
Racing Beat Dual Tip Catback
Has Catylitic converter in it right now
M2 Stage 3 ECU
M2 Carbon Fiber Intake
Intake hard pipes
Greddy Elbow
Stock Turbos
Stock Motor
Running Stock boost

So like i said i put a new o2 sensor in it and plugged it in and the problem came back. I took the car to deq with the o2 sensor unplugged and it failed miserably on the rollers (load situation like normal driving), I took the car straight from there to my dad's shop and used his gas analyzer to see if the cat was working. with a no load situation at both idle and 2500 the cat was working, about 45 ppm HC at idle and .01% CO, about 50 ppm HC at 2500 and .02% CO. So it looks like the cat is working. I would guess that with the o2 sensor unplugged the car used the base maps on the remapped ECU to run on the rollers at deq and being a remapped stage 3 ECU i could see how it could fail. By the way the car did pass with the same modifications 2 years ago. When i first talked to my brother (mechanic) about the problem and how i found on this forum that unplugging the o2 sensor was a common fix (because the o2 sensor fails), his first response was that it would run full rich and that added fuel could potentially mask a lot of problems. Basically telling me it might not be the o2 sensor and now i found out that it isn't. So, if you've made it this far, any suggestions, more questions to ask me, i would definately like some input.

Also, the car will turn the check engine light on after about 5 to 10 minutes of driving with the o2 sensor unplugged, and i have not been able to plug the car in to see what has actually flagged the check engine light, i will be working on that thursday or friday this week.

thanx,
Nick

MrRx

iTrader: (1)

check the boost sensor near the TB, If that hose came off it would explain your jerking and so on...

njkrause

I will check that out tonight! thanx

STIKYHANDZ

i had exactly the same problem when i was completely stock, it was sooo annyoing. when just cruising it would tumble and buck real bad. so i bought the hyperground wire kit and it INSTANTLY went away.. just something to try..

E.J.

4Fun

iTrader: (8)

How is your idle? Smooth? Bouncing?
You might want to check for some vaccum leaks. Spray some carb cleaner around the TB, UIM, and LIM

J.S.J

I am sure the smart thing to do is test the basic set up. Fuel filter and pressure. Something which is easy to do is just connect a digital volt meter to the 02 sensor. Keep it connected to the ECU and tap in on one lead and ground the other. Set the meter on 2volts DC. Drive it with the meter in the car. I used some speaker wire, the load on the system is low so resistance is not a problem. If its rich or lean during the hesitation it will show up on the meter. If you have a EGR I would look at that as well. This may give you a base to start.

njkrause

Idle is smooth, no bouncing, boost pattern is normal, drives perfectly under boost, all the way to redline, i am leaning toward the grounding being an issue and will be my first issue to address. I checked the boost sensor and everything looks as though it is hooked up. Based on searches done on the boost sensor i think i would have serious problems while in boost if it was disconnected. I also checked the check engine light codes last night and came up with 15 and 17, which are oxygen sensor, and oxygen sensor feedback system respectively. Based on searches for similar problems i will run a good ground from the downpipe to the frame and a good ground from the frame to the negative battery terminal. I will also hook up a DMM to the o2 sensor to see whether the problem is caused by being overly rich or lean prior to addressing the grounding issue. I will try looking at the voltage or resistance linearity on the throttle position sensor if none of this works. If anyone has other ideas let me know, thank you all for your information.

kilroy440

Hi All, I have been experiencing this exact problem for over a year now on my 94 RX-7. Driving me nuts. I recently replaced the O2 sensor, the Water Thermo Sensor and the EGR valve due to codes from the computer. None of this helped and the problem hasn't gotten any better. I've owned the car since '99 and this is not the 3K hesitation. More like whiplash at 2500rpm...

NJKrause, were you able to solve this issue? Anyone else?

Thanks in advance,
Jonathan.

jkstill

iTrader: (11)

Yes, cured it with TPS adjustment.

I can drive my FD at 2K RPM in 3rd gear, which was impossible prior to adjusting the TPS.

dhcernese

I stopped reading after the quote below. It's exactly what many car owners call the 3k hesitation problem. I had this.. ..and completely solved it with improved/multiple grounds.

DaveW

This thread may apply:

https://www.rx7club.com/showthread.p...ght=fixed+idle

Dave

twilsonbpa

might be your secondary injectors sticking

Veger

I had same problem when near stock but i had a HKS piggyback on and found i was over fuleing lots, turned it down, replaced the o2, replace check valves with Dale Clark ones and adjusted the tps, added a ground kit all at once so i aint a clue what made it better but it worked.

You allready have the o2, Dale clarke check valves are ony $20 for 4 and you could clean and check your grnd or simply grnd the engine via some thick cable for test and adjusting the tps costs nothing, so they are all cheap easy fixes to find out if they work, the only other problem i had was overfuleing , it was bogging down big time, pull your spark plugs as you can tell by them if you got 2 much fuel going in.

kilroy440

Thanks guys, sounds like two things to try first:

1) Check TPS settings
2) Upgrade grounding

For the grounding, I found these Hyper Ground Wires http://store.racinglab.com/hygrsyformar.html here. Do you guys recommend these?

Also, can someone provide more info on these Dale Clarke check valves?

I'm hopeful on the TPS settings. As jkstill said, I often cannot drive the car at 2K rpm in 3rd at all. It bucks like crazy as though the fuel is getting cut off. TPS could make sense.

Hope to try these out soon and report back...

Mahjik

iTrader: (1)

https://www.rx7club.com/showthread.p...25#post6643725

rotaryinspired

iTrader: (3)

I had a similar problem. My TPS was acctually toast. Replaced then adjusted and things are going good. I need to add a few grounds as well. Good luck.

dhcernese

You can spend $115 on nice looking wires for your engine or you can go to any parts store and buy a couple battery ground cables.. ..either bare braid or just heavy wire. I know of no reason why ground cables should be shielded, but they look nice!

Roto7FD

Could running too rich, cause violent jerking and shaking in 1st and 2nd? Everything was fine before this until I did a couple of pulls this weekend. Came back, car sat for a couple of hours. I started up the car, idle was fine (single turbo, no air pump) at 1000-1100k rpm, waited for car to warm up then proceeded to drive. One block later, the symptom I described above started happening for the first time. In 1st at 2k rpm it starts to buck violently, shift to 2nd same thing. Then car just dies. I started it back up and it took a couple of seconds to fire up. Thought to myself, maybe plugs are fouled. Limped it back to friends shop around the block, same ****, couldn't even drive 10mph as it was still bucking.

Changed the plugs, running 11.5 NGK's all around, gonna switch to 9's this weekend, those plugs are too expensive. Anyways, I switch the plugs and everything was fine, drove it around the block and it did not buck anymore. So at that point I figured everything was cool, I drove about 7 miles back to the apartment. On the freeway no problems. But as I'm 2 blocks away from home, the car starts to act up again. Bucking again on low rpm, but not as bad as earlier. I limp it again, but the car dies as I'm coming up on a stop sign. Made me run the bitch before I realized the car died. Started it back up and parked it haven't touched it as of late.

Forgot to mention that after I changed the plugs, there was a fuel smell from the exhaust that was more pugnent than before. The type that makes your eyes tear, don't know if there is any relevance by mentioning this. It wasn't like that before I swapped the plugs. I know my car is running too rich as I think the PFC is set to 850's and 1500's right now, don't have a data logit to change it to 1600's yet. Waiting for my tune in end of may with steve to fine tune it and dyno. Boost is fine by the way.

I'm thinking of grounding the car better this weekend and see what happen's. I could only think of a grounding issue and running too rich that might cause this to happen. I'm pretty much a newb so forgive me, I don't really tinker with the PFC, but i have owned the car for several years now, recently gone single. What pisses me off was it was fine before, can it randomly just act up like that. Please give me some insight as to the bucking and dying issue with the car. Thanks!

Roto7FD

Also, I like to note I did search "bucking" in single section...nothing. Keyed in "hesitation" but only 1 page of nothing that really relates to me. I opted to choose the 3rd gen section to continue on this thread as most of the symptoms OP posted somewhat related to me under hesitation.