# Random Back-and-Forth Jerking in 1st and 2nd Gear



## dbsoundman (Feb 3, 2013)

I'm having a somewhat frustrating, random problem with my 88 pickup. Occasionally when I'm driving in 1st or second gear, the vehicle will be accelerating along just fine, and all the sudden it starts jerking back and forth, like I'm gunning the gas. The only way to get it to stop is to let off the gas or shift gears, which as I experienced the other day on the freeway ramp, is not such a good option. It doesn't always seem to happen, so I'm wondering if it's maybe just me tapping the gas pedal at an inopportune time, but the way that it seems to gain its own "momentum" makes me think it something else, maybe something in the fuel delivery? The throttle body assembly on this truck is all new, the only thing I haven't done yet is that brass idle stopper thing, but I don't think that would come into play. I still need to run some Seafoam through the fuel system, but I didn't know if perhaps the clutch could be out of adjustment or something? I'd appreciate any ideas. Thanks!


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## wilburk (Dec 29, 2012)

Say more about the 'jerking back and forth'...do you mean like bucking forward and then back?


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## dbsoundman (Feb 3, 2013)

Yes, that's exactly what I mean! It bucks back and forth.


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## wilburk (Dec 29, 2012)

Can you make it die like this/has it ever? Or does it just buck...


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## dbsoundman (Feb 3, 2013)

Never Dies, just gives me some whiplash!


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## smj999smj (Jan 1, 2006)

What engine?


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## dbsoundman (Feb 3, 2013)

It's got the z24i.


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## TheRepairMan (Jun 30, 2009)

Do the symptoms get worse as you accelerate harder, or can you accelerate through the problem? If you let up on the gas slightly does it go away? Questions I have to ask to help determine if it's a secondary ignition misfire, or a fueling problem.
-R


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## dbsoundman (Feb 3, 2013)

It seems that sometimes I twitch my foot down which causes me to accelerate harder, rather suddenly. If that happens, I tend to pull my foot right off, which sort of sets up the jerking. If I take my foot totally off the gas for a second or two, it usually stops jerking.


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## wilburk (Dec 29, 2012)

I know you said the throttle body is new, but is it possible that the throttle cable itself is sticky? When you say that it's also kind of jerky when you release the pedal makes that sound like a possibility.


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## dbsoundman (Feb 3, 2013)

I had definitely thought about looking after the throttle cable. How should I lubricate that?

I'm also wondering about the fuel delivery system...today I was driving up a hill and accelerating in third gear. I kept noticing that it felt like I was losing a bit of power, then it would come back, then it would go away...I was accelerating the whole time, but I could just feel the acceleration going up and down against the hill, if that makes any sense. I had about 1/4 tank of gas at the time. The previous owner replaced the fuel injectors, spark plugs, etc., but could I be having a fuel pump issue perhaps? I do know there is a leak somewhere in the fuel filler neck, but it only leaks when I'm filling up at the gas station and point the nozzle the wrong way, it never leaks on the road or otherwise.


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## rogoman (Dec 16, 2004)

dbsoundman said:


> I had definitely thought about looking after the throttle cable. How should I lubricate that?
> 
> I'm also wondering about the fuel delivery system...today I was driving up a hill and accelerating in third gear. I kept noticing that it felt like I was losing a bit of power, then it would come back, then it would go away. The previous owner replaced the fuel injectors, spark plugs, etc., but could I be having a fuel pump issue perhaps?


With the engine shut off, operate the throttle cable from under the hood at the throttle body. Check for smooth operation from wide open to closed. Not sure if you can lubricate the cable; may be a sealed unit.

You need to first determine if it's a fuel or ignition problem. Since the injectors and spark plugs were replaced, check the condition of the distributor cap/rotor and the ignition wires. Might be a weak coil. Measure the fuel pressure; should be around 36 psi. Consider replacing the fuel filter if it's never been done. Make sure the air filter is clean.


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## dbsoundman (Feb 3, 2013)

Fuel filter has been replaced, I'm pretty sure the air filter has too but I haven't had a chance to open it up (it's been cold the last week or so here). How would I identify a weak coil?


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## wilburk (Dec 29, 2012)

One thing you might try is shooting some cable lubricant up from the accelerator pedal towards the throttle body (that sounded confusing). A similar sounding thing happened on my Honda and I shot some wd-40 upwards from the pedal--though it just got on PART of the cable. Seemed to help. 

You can identify a weak coil by testing ohm resistance with a multimeter. Visually inspecting the coil could work--may be obvious rust, cracks, etc.


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## burnt03 (Mar 22, 2005)

dbsoundman said:


> Fuel filter has been replaced, I'm pretty sure the air filter has too but I haven't had a chance to open it up (it's been cold the last week or so here). How would I identify a weak coil?


If you don't have a Haynes manual or similar I can scan the picture of where to test on the coil if you want?


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## wilburk (Dec 29, 2012)

Found a post that goes more into depth on coils (in a z24) and may help your quest:
http://www.nissanforums.com/truck-suv/114979-before-i-replace-my-power-transistor.html

Also, here's the detailed, albeit rather confusing, diagram from the fsm for your truck. How to test coils, etc.


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## dbsoundman (Feb 3, 2013)

Thanks guys! I do have the Haynes, just haven't gotten a chance to check it out yet. That FSM page is sort of helpful, but it is definitely confusing...

I may check the movement of the accelerator pedal and cable as well, I've wondered about that too since sometimes when the engine is up at higher RPMs and I take my foot off the gas and put in the clutch, the engine revs still stay high for a second, and slowly come down. I have come to expect the revs to pretty much immediately react and come down under those circumstances.


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## wilburk (Dec 29, 2012)

FSM page is confusing, and doesn't list ohm tolerances. 

I'd definitely check pedal and cable--an easy thing to do and there's another similar post and the guy is lubricating the throttle cable.


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## dbsoundman (Feb 3, 2013)

I think I isolated part of the problem today. I was doing some city driving, meaning I was using the clutch more than usual. After a while, I found that I just could NOT get a smooth start in 1st. I did some test starts in the neighborhood and found that it seemed like the clutch was engaging sooner than it should, and rather suddenly, as if I just totally took my foot off the pedal. I have noticed the friction point seems a bit further in than I'm used to from my Ford probe long ago, but this seems to be more than that. Is it possible my clutch cable is stretched or otherwise messed up? How do I go about fixing it? I haven't read the FSM or Haynes yet but I didn't know if you all had suggestions or thoughts...


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## dbsoundman (Feb 3, 2013)

OK, so I think this is half operator error (I'm still getting used to clutching), and half mechanical issues...check out what I found today when I looked at the accelerator pedal and cable under the dash:










There's about 1/2" of play in the accelerator cable, between where the pedal goes out and the cable is actually pulled out. I also noticed I could push down the cable right by the throttle without actually moving the throttle at all. Is my cable stretched out or something? How can fix that? I did put some spray lube around the cable entrance by the accelerator pedal but it didn't change anything.

I did adjust the clutch today as well, I could push the pedal in 1-2" before it would actuate before, now I have it closer to spec, I only push the clutch pedal down 1/2" or less before it starts moving the clutch. Something else to get used to while driving, but it does feel better, the friction point was REALLY close to the floor before...


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## yellowrosefarm (Dec 11, 2011)

No clutch cable. There is a clutch master cylinder and a clutch slave cylinder. Maybe the master is low on fluid and you have some air in there.


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## dbsoundman (Feb 3, 2013)

yellowrosefarm said:


> No clutch cable. There is a clutch master cylinder and a clutch slave cylinder. Maybe the master is low on fluid and you have some air in there.


Yeah, I had a *duh* moment when I posted that one...need to look in my Haynes manual so I can check those tomorrow.


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## rogoman (Dec 16, 2004)

dbsoundman said:


> There's about 1/2" of play in the accelerator cable, between where the pedal goes out and the cable is actually pulled out. I also noticed I could push down the cable right by the throttle without actually moving the throttle at all. Is my cable stretched out or something? How can fix that? I did put some spray lube around the cable entrance by the accelerator pedal but it didn't change anything.


There's an adjusting nut at the end of the throttle cable next to the throttle body.


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