hi guys, I have read and searched and even spend cash on this issue to no avail.

when i'm cruising on the highway or in town under neutral throttle the car will some times slow down or speed up on its own with no pedal movement.

other times it will jerk and buck and it gets worse until you either apply more throttle or let off.

It also feels like sometimes its much more responsive and powerful in the top end than other times. sometimes it give you a real nice kick in the butt when you hit 5000rpm, and other times it feels like it just continues up in the rpm without that feeling of power.(but that could just be me)

I already replaced the tps and calibrated it based on what i had read on the forums already. that was an expensive experiment that didn't work.

I'm kinda frustrated because this occurs right where a person normally drives (maintaining constant speed).

car is a 93, left hand drive, basic intake and exhaust mods only. was doing this from time to time wtock also, but the frequency has increased a lot.

 

is it around 2krpm and 3k rpm?

 

no, it isn't the typical hesitation problem.

this doesnt seem to matter the rpm, just under neutral throttle when fully warmed up.

 

Mine has been doing something similar, but I've really only seen it do it in first gear after letting off the gas. It wants to buck unless I keep constant pressure on the pedal. I wonder if it is a similar issue. The only thing I can think is the throttle is sticking or tps needs adjusted.

No exhaust leaks or anything to that affect?

 

I would be looking for vacuum leaks somewhere. Have you ever replaced the lines in the rats nest?
My second guess after that would be electrical, harness with some brittle and breaking wires.

 

The Power FC fixed a few problems like that for me. The car ran like crap before I installed it. Power FC > Factory ECU.

 

its weird that this is happening. it's always out of boost though.

If i do the poor mans non-sequential mod will that remove the rats nest from the equation?

 

you are running stock ECU with stock emissions/underhood stuff? Has anything been done to your engine besides the mods listed in your sig?

 

https://www.rx7club.com/attachments/...p-grounds1.jpg

https://www.rx7club.com/attachments/...p-grounds2.jpg

https://www.rx7club.com/attachments/...p-grounds3.jpg


Might help.

 

You're on stock ECU? At any rate, don't do poor mans non-sequential. Spend the small investment in some silicone vacuum lines and fix what you have. You can do it in a day if you put your mind to it and it's very likely to fix your problems.
If you want non-sequential take the time and do it right.

 

no just basic air in and air out. i have a pettit 14.7psi ecu that i want to install but i want to be sure everything is working right before i use the ecu.

Thank you for the links, i cleaned and checked my stock grounds, but maybe I should add one for the heck of it.

Yest stock ecu for now till i get this figured out. I was planning to do the full parallel mod later. but i just wanted to see if it was in fact the rats nest that was the problem before i pulled my UIM off to redo all the hoses.

If the poor mans mod fixes my issues then i know its either a solenoid or a bad hose right?

 

I don't remember for sure as it's been awhile since I did anything with a stock ecu but you might go in to limp mode if you try non-seq with it.

FD is a touchy beast, you don't ever want to take the easy way out with anything or it will bite you in the ***. With your intake and full exhaust mods it's time for an ECU upgrade and tune anyway, if you want to go non-seq then go all in at once.

 

It will work fine on the stock ecu. i just wanted to make sure it was the rats nest by doing the poor mans version. if the problem persisted, it would be a sensor issue not the rats nest. possibly map sensor.

taht is literally the only reason i wanted to try the poor mans mod.

 

If the problem is occurring under neutral throttle and you're not accelerating or building boost, I don't see how anything in the rat's nest would be the cause of your problem. It does sound like a sensor or ignition component is on the way out. Do you know anyone with a PFC/Datalogit you can use? That would make it easier to identify the culprit.

 

You should be able to see the effects of a vacuum leak if you have a boost gauge. When your off the throttle you should have vacuum rather than boost. If your not getting vacuum its not going to idle right either.
Before you get to much great advice I would suggest seeing what the boost vacuum is doing to eliminate that before going to the electronics aside for checking for broken wires.

Curious which shop you took it too out here. There are only 2 Rotary shops in the GVR and I would not get help from anyone else.

 

No shop, i do my own work. I installed a new TPS because thats what i found to be the culprate on these forums for my symptoms. expensive mistake. lol.

I think it is a sensor, but what one it is i don't know, i redid all my grounds again and added another one and the violent bucking seems to have subsided, but it still feels weak and boggy at random, while other times it feels like a rocket, I cant figure it out.

I have to install my gauge pillar pod soon so i'll hook up my boost gauge and see whats going on.

There are only a couple sensors that could cause it, the tps is new, so that leaves the map sensor, is there anything else it could be sensor wise?

I dont have access to a datalogit, dont have a power fc either. can the datalogit be used on a stock ecu?

 

datalogit is only for power fc

How crispy and crunchy is your wire harness? Can you see bare copper wires at the connectors?
I had an injector wire fail that caused occasional bucking and ultimately lead to a blown up motor.

 

I was kind of having a similar problem before I put my car away for winter.
I kind of avoided the problem by staying in higher rpm.

My issue started after a single turbo build so I would rule out rats nest related items. I actually thought it was caused by an aggressive twin plate clutch and I would have to just deal with it but I guess not. I never even considered a grounding issue.

What exactly did you change or add to help with the issue?

 

It sounds like you're on the right track. I would have suspected the TPS as the #1 culprit as well. Are you 100% sure you calibrated it correctly? Even a brand new sensor with bad calibration could cause the bucking problems under neutral throttle you described.

As far as the car feeling like a rocket sometimes... Issues with not making consistent power under boost would definitely fall under the rat's nest category so you may have multiple issues going on here, or one overarching problem.

Dataloggit is PFC only but it'd only take 15 minutes to swap in someone else's unit and load up the base map to get some data if there's someone local to you.