Another add to the list of problems with the s2000. Not sure if my problem is common, but its very annoying to the point that I rarely want to drive my s2k anymore. The problem: my s2k jerks back and forth all speed and at all gears. I can be on the freeway going 65 mph and there is a slight jerking motion and slight popping sound coming from the exhaust, the same sound it would make if it were backfiring. From a dead stop, accelerating slowly on first gear the car jerks more aggressively, but if i punch on the gas it goes away, but the car still feels hesitant to accelerate. It will jerk weather the car is cold or at operating temperature no matter the weather conditions outside. There are no CEL codes and no previous codes either. Only mods the car has are bolt ons such as 1)Air Intake 2) Mishimoto Radiator 3) Hi-Flow Cat 4) Invidia N1 Dual Exhaust 5) Light Weight Flywheel 6) Spec Stage-2 Clutch kit. Car has 171K miles, but motor has roughly 70k miles. Things i have done: Replaced Map sensors almost 2 years ago, cleaned IAC valve, cleaned throttle body and intake. Tested TPS, but all checked out fine, however i still keep thinking that it can be the underlying cause of all this. Another thing I forgot to mention was that when I was cruising at 65mph on the freeway, I pressed down the clutch and let off the gas with the car still in gear just to see if the jerking sound and feeling would go away, witch it did, however the RPM'S would rise to about 2k rpm's and then drop. This happens over and over again.

This has been going on for about a year. Anyone know what the problem may be? I appreciate the help in advance.

 

How light weight is your light weight flywheel?

 

A lightweight flywheel wouldn't do this. Sounds like the MAP sensor could be out again...

 

You get no CELs? Wonder if this is a defective clutch issue?

 

Where are you located?

 

get a cheap ass obd2 elm327 and a diagnostic app and log the following:
primary o2
map values
long term fuel trim
short term fuel trim

at least then we can eliminate fuel as an issue

when was the last time valves were adjusted

what do your spark plugs look like

 

I can say I'm almost 100% certain its your TPS. I had this issue over a year ago, replaced my TPS, it went away.

I didn't position the new TPS perfectly because my friend was acting like a little b*tch about 10 minutes of work. Months later the affect of this laziness finally showed itself. I experienced the same exact issues as you are having. I adjusted my TPS to be 4.99 V at WOT and my issue is completely fixed. (My closed voltage is .32 V but it should be .45 V, so idk what to do about that. But it's important you adjust it to the WOT, not the closed position.) And it only got to 4.99 V because it gets stopped by the alternator casing or whatever is right there. I just don't care to go look since it doesn't matter.
The TPS that doesn't fit perfectly I believe is from Omnipower. They might have fixed that but it has only been about a year.

With that being said, this just happened to me less than a month ago and I got it fixed. My idle still drops too low and lets the engine die, so idk if that's my TPS or something else, but definitely adjust your TPS to 5.00 V.

My symptoms were: jerking from 0-85 mph all gears (I didn't test higher than that). Jerking was worst at low speeds in first and second gear, but I think that's just due to a matter of momentum. It felt like it was misfiring, I compare it to this because I had a misfires 2 years ago. It felt EXACTLY like this. It sounds like the engine shuts off for a split second and the transmission jerks hard, then immediately returns to normal operation.

HERE'S HOW YOU TEST IT: If its your TPS, the problem should not be evident if you floor it in any gear at any speed. Put the pedal to the metal and it should be perfectly smooth. That's how it was for my case as well as the guy I found my information from.

For adjusting the TPS I highly suggest only LOOSENING on bolt at a time and lightly tapping the TPS while simultaneously checking the voltage with the car on (not turned over).

Hope this helps!

 

Flywheel is 11.2 pounds

 

Yeah it could be possible. I just ruled it out since it's fairly new, but I guess just because it's new doesn't mean it can't be faulty.

 

No CEL, clutch has about 12k miles, but I get alot of clutch buzz from the Kevlar friction disc. I've learned to live with the buzz untill I eventually go back to the oem disk and still keep to the stage 2 pressure plate. The clutch however wouldn't explain why the rpms rev up and down when the clutch is disengaged (clutch peddle down to the floor).