Topic: Car hiccups when driving at pace

[aw12345]

pinion angles are easy to figure out. With an SYE it has to pint straight at the yoke on the transfercase, without one simply turn the driveshaft so the yoke on the pinion and the transfercase is vertical then measure yoke ear to yoke ear if it is the same at the top and the bottom the angles are correct and it should not cause vibration

[Eucalypta]

Ok...driveline angles are not ideal but ok for now.
Saving for a SYE 

Because the hickuping or bucking of my car while driving slowly is still not cured I analysed it some more:
It seems the throttle is extremely sensitive.
When driving slowly on a bumpy road this triggers the bucking ride. When hitting a bump the throttle is pressed slightly by my foot and results in surging forwards. When the cars jumps forward the pressure is slightly relieved from the throttle wich makes it slow down quickly what results in pressing the throttle again a bit, surging forward etc.....

I got an MOPAR TPS and mounted this, no cure.
Then I thought to take off the 4.0L TB and place my old 2.5TB back. I noticed that there is a slight difference in angle of the  valveshaft of a 2.5 and the 4.0. Has anyone noticed this or is it just a coincidence?
With the 2.5TB the bucking gets worse. Don't know if less air is the problem or that more air camouflages the problem.

What I also notice is that at idle the engine doesnt run at a constant rev. The revs go slightly up and down.
Don't know if it is caused by the same problem or if it has another cause.

The PC doesnt throw any codes out of the obvious 12 33 and 55.

So, what now? Does anyone have a suggestion?

[sharpxmen]

Ok...driveline angles are not ideal but ok for now.
Saving for a SYE 

Because the hickuping or bucking of my car while driving slowly is still not cured I analysed it some more:
It seems the throttle is extremely sensitive.
When driving slowly on a bumpy road this triggers the bucking ride. When hitting a bump the throttle is pressed slightly by my foot and results in surging forwards. When the cars jumps forward the pressure is slightly relieved from the throttle wich makes it slow down quickly what results in pressing the throttle again a bit, surging forward etc.....

I got an MOPAR TPS and mounted this, no cure.
Then I thought to take off the 4.0L TB and place my old 2.5TB back. I noticed that there is a slight difference in angle of the  valveshaft of a 2.5 and the 4.0. Has anyone noticed this or is it just a coincidence?
With the 2.5TB the bucking gets worse. Don't know if less air is the problem or that more air camouflages the problem.

What I also notice is that at idle the engine doesnt run at a constant rev. The revs go slightly up and down.
Don't know if it is caused by the same problem or if it has another cause.

The PC doesnt throw any codes out of the obvious 12 33 and 55.

So, what now? Does anyone have a suggestion?

i'm thinking the O2 sensor but could also be a ground reference or signal loss/noise related to the sensor as well

[Eucalypta]

O2 sensor...would that not be a problem at any speed?
And would that maybe also be the reason that at WOT, it feels like I am smothering the engine?

[sharpxmen]

O2 sensor...would that not be a problem at any speed?
And would that maybe also be the reason that at WOT, it feels like I am smothering the engine?

not at any speed (speed won't matter) it's more if you're in closed loop or open loop - at wot it doesn't use the O2 feedback. If you get an up-down revs at idle it is usually (but not necessarily) a result of too rich mixture and that's why i was thinking O2 or something related to the O2 feedback.

[Eucalypta]

Ok.. If I remember correctly the O2 from a 4L is the same as one from a 2.5L, I can swap the sensor with the one from a friend and see if it helps.
Also will replace the fuel filter and broken FPR.

[sharpxmen]

Ok.. If I remember correctly the O2 from a 4L is the same as one from a 2.5L, I can swap the sensor with the one from a friend and see if it helps.
Also will replace the fuel filter and broken FPR.

just be careful when you take the O2 off, i have seen them go bad sometime when removed and reinstalled.

[Eucalypta]

just be careful when you take the O2 off, i have seen them go bad sometime when removed and reinstalled.

ok, going to be extra carefull (cannot afford to buy 2 sensors)

[Bones]

Having the same issue on mine at the time. Replaced my fuel filter and though I could still blow through the old one it was restricted when compared to the new one. This seemed to help reduce the frequency of the surging and bucking but I am still having an episode every once in a while. This leads me to think that perhaps my fuel pump might be dying or having issues. Anyone had a similar experience with a confirmed bad fuel pump?

[Eucalypta]

My pump is new, as is my filter, FPR, all lines and tank are clean.
New bougies, distributer cap and rotor, spark plugs and wires, K&N airfilter (helped a bit), 4.0L TB (helped a bit), new TPS, cleaned TB+IAC housing.
It is not the loose throttle cable (installed the TJ spring), no vacuum leaks, no worn out gaskets.
Thinking about the O2 sensor, maybe the coupling (it is a bit worn out, needs to be replaced within 1K-2K km)

Is the following plausible?
Maybe the IAC is not workign correctly; not shutting down as quick as it should? When driving, the engine running on idle, IAC is open to get enough throttle for the engine not stalling while driving. When I press down the throttle the IAC should close completely (or should it stay wide open all the time?) but it stays open and there is too much air flowing into the engine, thrusting the car forward.

I'm clutching straws here, it is REALLY anoying when it bucks like this.

[aw12345]

You need to find a way to look at the data stream to see where the fuel trim is at
As well as looking to see how well the 02 sensor toggles. If that is all happy it's time to look at the ignition, but I am sticking with a fuel related problem, could be as simple as low voltage at the fuel pump

[dwtaylorpdx]

Throttle position sensor, and FYI I bought one a while back and it was bad out of the box, ended up buying a second one.

Dave

[Eucalypta]

Throttle position sensor, and FYI I bought one a while back and it was bad out of the box, ended up buying a second one.

Dave

That was also what I thought...even bought a mopar one istead of the shitty crown.
Still no difference, have tested them with my multimeter; both checked out to be ok...

I am going to do some more analysis before throwing more parts at it.

[Jeffy]

That was also what I thought...even bought a mopar one istead of the shitty crown.
Still no difference, have tested them with my multimeter; both checked out to be ok...

I am going to do some more analysis before throwing more parts at it.

The Mopar part will be the exact same as Crown.

[Eucalypta]

The Mopar part will be the exact same as Crown.

Ya under the skin Im sure they are.
The mopar was of different color than the crown though.
Well they both checked out to be ok on the multimeter...
So, throwing parts at it, doesn't solve the problem.

Would worn out spark plugs or spark plugs with a too big gap be responsible for this kind of behaviour?