I have been trying to track down what feels like drive line play for about a year now, with little success.


Symptom is when coming on and off the throttle, lets say between 0% and 5% I get a very noticeable buck/jerk.

the best I can do is explain the butt feeling in the seat.

When you come off the gas to 0%, is like the suspension is unloading and the body has slack compared to the tires.

Then when you come back onto the throttle, the the slack comes out of the drive line. The suspension loads with the torque.

That slack causes a very rough jump in the front end.

Nose of the car raises then the car springs back and starts to hop till I slip the clutch.


It is a really weird elastic feeling, nearly like the torsion bar/traction bar is made of rubber when there is a drastic change in speed.


This makes driving in a parking lot a huge pain, because I have to rev, slip the clutch, then coast.


I threw parts at what I thought was giving me free play.


*drive line parts*

OEM Clutch

Innovative solid (street) motor mounts

FandF type 1 Coil overs, Skunk2 adjustable upper control arm (to stop the front of the car jumping up and down with the jerking)

Innovative Traction bar (had to take off the front oem motor mount when I did this)

OEM drive shafts (they had play in the cv joints, I gained a shake under acceleration after these were installed)

HardRace front lower control arms


*air fuel parts*

TPS (was the second thing I replaced)

Fuel injectors (junkyard parts)

Throttle cable

Adjusted idle


With all the drive line parts it has improved, but is still very hard to drive at low speeds.


I have not done the O2 because I can't get it off.

I have not done spark plugs because they look in great shape

I have adjusted the TPS a ton of times I also ran into a ton of issues dealing with it.


In the past when I had this EXACT jumping problem with my CRX, adjusting the TPS fixed it.

.45V closed and it came close to 4.5 WOT (which you cant really adjust for from what I know)

When I adjust this one. the small vacuum module gives a little bit of slack in the throttle plate.


So I would adjust to .45V not running, start it, and the sensor would read .30 because the vacuum would let the throttle plate close a bit more.

Adjusted it to .45V running, everything acted the same.

And no matter what it will only read 3.0 to 3.4V at WOT.


The TPS is the 80$ Ebay DPFI one.

When I went to install it, I could not get it to read .45V and get the screws in.

I noticed the spring was going the wrong way VS the stock one.

Swapped the spring between them and got it to read the .45V when in the center of the adjustment range.


I opened up the ECU, the board looks brand spanking new. the caps are not leaking.


I have checked for voltage drop, with nothing really jumping out as an issue.


Alternator seems to be working just fine. Reads 13-14V when running.

Only weird thing is the alternator has a slight hum when the key is on run.

Assuming that is normal.




Where I am at right now, I am thinking maybe the play is normal?

The only thing between the flywheel and the tires that have not been changed is the transmission.

When the car is on the lift in gear, I can grab both left and right tires and rock them forwards and backwards.

There is about a 1/2 to 1 inch of tread movement, till you can see the pulley move. which I think is normal?


I would be happy with any suggestions of things to check.

I don't remember any of my other EFs having this much of a slack feeling in the drive line.

Searching has only came up with people talking about IACV causing erratic idle (I idle just fine), and TPS having dead spots (mine does not)


I am looking at doing a D16Z9 swap for this car(already have the motor) but I don't want to spend the time if something mechanical is going to make it keep jerking.

 

 

Rockauto is where I got the Flywheel, Clutch, Driveshafts, and throttle cable. They ship to APO, and have decent prices for shipping.

I think the drive shafts are re manufactured.

But, they sent me a MPFI TPS (rotates other direction), and a ABS style drivers side drive shaft (maybe why I have a shake under acceleration)
The shake is only under acceleration which makes me think Air/Fuel more than unbalanced drive shaft. But started when I put the drive shafts in.

 

 

You are fine man, any help is good help. As far as a design flaw. The OEM shafts come with a little rubber dampener. I am pretty sure none of the aftermarket stuff has the little rubber dampener on them. Which is what made me think drive shafts. It just feels like under tourque, it's binding, and causing a shake.

Today I swapped the IACV and TPS from the junk yard parts. Adjusted it to 0.45v not worrying how the trottle plate closed a little more. It can now read 4v WOT.

I forgot to put the Fuel pressure regulator vacumv line on. And the car drove like a bat out of hell. Didn't notice a ton of low rpm hopping. It still did it, but it was easier to modulate the peddle on and off. When I popped the hood I saw it was missing and put it back. And the low . Idle hopping came back.

I had a friend basically launch the car and back up hard from a roll. The motor does shift around quite a bit. I think the harsh on and off might be normal. But the 3 solid motor mounts are letting the engine twist and "spring" under load.

Because 3k getting on it. Then letting off to coast, is like a big rubber band between the engine and tires.

 

It feels like this is happening. But it's a stock motor. On solid mounts.

https://m.youtube.com/watch?v=CRHS0_Bglfk&t=5m28s

I just ordered the innovative mounts front torque mount for my traction bar. I'll see if it is the motor rolling around like that video.

 

 

I really hope this is it. That video is the closest thing to what I think is happening. Because it has this springy feeling under heavy load. Like the whole nose of the car is lifting and sagging with the engine torque and engine braking..

Shipping from CA to APO will take like 2 weeks tho.
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Front motor mount in, it helped stop the bucking from bring so noticable in the car. But I am still getting a jerk coming on and off the trottle.

I guess I'll try the O2 sensor next. But I will have to have someone cut and weld a new bung. That thing is not budging.

Also, thinking fuel/ ignition issues i did the spark plugs, plug wires, and fuel filter. Seems to have smoothed the car out. No change to the jerking tho

 

 

you know after reading the first post this sounds as simple as blown rear struts
that would explain everything your car is doing
so?

 

I am thankful for all the help. I got the O2 sensor to break loose by trying while the engine was still hot.

The car has smooth out a ton with that being replaced.

The parts I have replaced so far.
Physical stuff
OEM clutch kit.
All 4 motor mounts are inovative solid mounts.
Inovative traction bar.
Hardrace front lower control arms with harden rubber bushings.
Skunk 2 adjustable upper control arm.
Function and Form type 1 coil overs.
OEM Rear trailing arm bushing.
Drive shafts.

Air/fuel stuff
Trottle position sensor
O2 sensor
Sparkplugs, wires.
Fuel filter.

I have not really considered the sub frame, I will give that a look next time it's on a lift.

After about a month with the traction bar, I've noticed the two bolts holding it to the LCA can move under really high stress braking or acceleration. It was popping till I got a breaker bar on those two bolts.

My next thing to check out is wheel bearings and lower ball joint. Something in the front end is still wonky

Going over potholes and stuff I can hear a loose sounding rattle from the front end. Almost like the rack end bushing. Sadly when I am on the lift doing a shake down, nothing is loose.

The low rpm jarring is so little now, the O2 sensor helped the most. The only time I get bucking is when I am rough with the trottle. I'd say "it's fixed" untill whatever is loose reveals itself.

 

It may not significantly help the symptoms, but you should re calibrate your tps. TLDR: Start at WOT, line up to 4.5, then adjust throttle stop (small allen set screw on the front of the TB) to hit your target minimum voltage. Once that's done adjust the bypass to set your idle speed.

The calibration proceedure explained (with loads of pictures) in this thread is the way to do it:
https://honda-tech.com/forums/tech-m...e-tps-2947986/
EDIT: Just realized you have DPFI, so the pictures won't be so helpful. Principle is still basically the same though.