Jerky acceleration...kind of a pulsing feeling.

[Figit090]

Hey, 1986.5 N/A, just did a BHG job, runnin pretty good but...

Sometimes I feel a jerky, pulsing feeling during accleration. what i mean is...the car accelerates unevenly and instead of feeling a constant force applied to me from my carseat i feel bursts of energy. I'm thinking maybe a bad plug wire or two...but i was wondering if anyone could give me another diagnosis for this. if i floor it or give it more gas its fine...but it shouldnt do this...it feels bad and its annoying....

I mostly feel it during accleration, and in 3rd gear. but it's also shown up in deceleration engine braking...but not as apparent, probably because i'm not on the gas.

soo i'm thinking its not a spark plug, or a head gasket leak, because thats all new and bolted down nice and tight . I also have a baisically new distributor cap and rotor, and i've ran two or three bottles of fuel injector cleaner through my car since purchase.

so...maybe i should just shell out some money for new plug wires?

if so, give me some ideas....i dont know if the more expensive or even the performance wires would be beneficial on an N/A...if not i'll save my money and just buy some basic ones that fit...bosh or something.

thanks in adavance

 

[starscream5000]

Plug wires sound good (how old are they?). Don't forget to tighten down the studs/bolts after it's had a good heat cycle (assuming the bolts/studs are new). Have you checked vacume lines or anything that could have been left unistalled after the head gasket job?

 

[Figit090]

I tightened the stock re-used head bolts down to 70ft/lbs after 10 heat cycles.


Plug wires say 1994 or something on them i believe....so they're old. lol

and plug #1 has a rip in the upper portion of the boot...although the wire is still perfect it makes me wonder... i dunno.

i think i'll just invest in some new wires. unless anyone else thinks it could be some other culprit.

 

[starscream5000]

Try that first and then repost if the problem still occurs.

 

[johnathan1]

My car does the exact same thing... Although, It really only does it about half of the time...which leads me to believe it's an electrical/wiring issue? When slowly accelerating, it feels almost like clutch chatter, and the car jerks forward repeatedly, not smoothly, but under 1/2+ throttle it feels great. Also, my car has Autocraft? wires that are probably about two years old, and Nippondenso spark plugs of unknown age, milage...when i did my head gasket I tested them, and they seemed to be okay? I really would like to know.

Maybe the return spring on the throttle body is weak?

 

[born2drv]

my car did that when it ran very rich during boost.

 

[supra90turbo]

Plugs, wires, and report back.

 

[johnathan1]

Does your car idle smoothly? Because mine will sometimes idle perfectly smooth (like you can't tell it's running) during these times, I don't get the jerky acceleration. Then sometimes, it will idle a bit shakily, and will jerk when accelerating slowly.

 

[Figit090]

i need to monitor the conditions more. i'm thinking maybe high-humidity does it? not sure. on days with the BHG (unknown and possibly liquid-repaired at time) my car would run like crud in the morning when it was raining or misty out.

my car still doesnt seem to like running when cool...might start warming up longer before driving to school....

either way my idle is fine as far as i can tell, i havent monotered it....what do you mean by shakily?

i think we experiance the same jerky accel though. it's almost enough to think that there is a tooth or two missing somewhere on a gear in the drivetrain (it wouldn't BE that...but it has that feeling of backlash)

i was thinking backlash in the drivetrain, and i know mine has some...but its not quite that feeling either...has to be the engine.

so i'll try and save for some wires. regretibly i dont have much spending money and since my car RUNS it might take some time before i can work out 40 extra dollars for them. sorry i will be delaying the answer.

i'll also keep better track of my driving experiance and note conditions. thanks guys!

p.s. i'm running new plugs, thanks for the idea.

 

[PimpiNJ253]

well my car did that too but when i ran premium with a octane booster a couple of times it ran like a dream. so try mabe for ur first time TWO octane boosters and premium gasoline. my car HAS TO HAVE A OCTANE BOOSTER FOR SUM REASON. i bought it that way. im new so if i answer this wierd just know im new

 

[SupraDread]

i need to monitor the conditions more. i'm thinking maybe

i think we experiance the same jerky accel though. it's almost enough to think that there is a tooth or two missing somewhere on a gear in the drivetrain (it wouldn't BE that...but it has that feeling of backlash)


i'll also keep better track of my driving experiance and note conditions. thanks guys!

p.s. i'm running new plugs, thanks for the idea.

Did u set your ignition timing with a timing light as per the TSRM after u repaired your BHG? Did u make sure your Cam timing was correct after u released the tensioner? If u did not do so RIGHT NOW or those conditions will get worse. Please believe.

 

[Figit090]

uhhh...they were pointing straight up as per my notes before teardown. i vaguely remember something about rotating the crank one revolution if its not lined up but i set the cams in how i took them out, added the gears, adjusted so they pointed exactly where they were before, and re-matched the number of belt teeth between the marked tooth on either gear so i had 17 rubber lumps between the marked teeth of the gears....so that spacing was correct and everything seemed fine.

I did do my timing to 10. it was at 12-13 for a while but i fixed it.

so unless i missed something it should be back the way it was before teardown.

this problem was apparent before teardown though so i'm inclined to think it wasnt my error. its possible my base was wrong but it idles fine and it seems to be a on again off again thing....not a consistent timing problem that always shows up.

i did NOT however bend the belt 90degrees to check tension, something i just recently heard about. it was pretty tight and i followed TSRM accoring to plan, releasing the tensioning pulley and bolting it down. the belt seemed to tighten a bit more after running it, eliminating some play in the section between the cam gears.

and again, for those that skim, this was happening BEFORE i touched the engine (although the head has been off prior to my ownership)

 

[Figit090]

well its still doing it. and i still have this funny knocking/tapping on cold starts and when i re-start after a warmed up run and letting it cool off a bit. so i'm thinking it has something to do with how hot the mixture is going into the engine and maybe i have a cylinder that only fires sometimes. i'm going to try and get new plug wires this week if i can get money. i just have to figure out what kind.

 

[johnathan1]

Yea, I would try new plugs and wires. For an NA, just get whatever they have a t Autozone...I put Borg-Warner wires on my NA, with Bosch plats, and it was okay...but if I could do it again, I would go with the Autolite's, or Denso's. Any codes?

 

[Cya]

My car is doing that too, but I advanced my intake timing. It hauls ass at about 4.4 thorottle percent. Im going to set back to stock when I get a chance though, it blows.

 

[Figit090]

4.4 throttle percent? what the heck is that?

i guess its mildly possible my cams are out of timeing but i did it according the the TSRM and it was just like how i found it when i tore it apart so...i dont think its my timing. i set my timing with a light as well. but i'll get new plugs within the week unless something goes funky and post back with results.

i JUST thought of this and it doesnt seem right, but maybe i have an intake leak above the AFM? the rubber up there is looking kinda shoddy because the wires cut through it. i might see if i can buy some rubber plumbing connections, clamps, and a length of 3in tubing. we'll see.

I asked in another thread and as i hear so far, bosh wires are bad and OEM, TRD, or NGK are popular and work well. so i'll look into those.

 

[mkIIIman089]

TRD is probably Denso of some kind, and Denso and NGK are both factory fill options; so either will work well.

As far as your jerky acceleration... how much so are we talking, initially you were talking about spark plugs; if a plug doesn't fire you will hear and feel a sputter and it won't be smooth AT ALL. Are you experiencing more of a surging? Or a bucking like a misfire?

 

[Figit090]

surging. light throttle application sometimes results in a surging feeling instead of a constant force of acceleration...

i get bucking when i shift poorly but thats drivetrain backlash...so i dont think i'm confusing the two.

 

[starscream5000]

NGK's FTW .

 

[Cya]

4.4 throttle percent? what the heck is that?

i guess its mildly possible my cams are out of timeing but i did it according the the TSRM and it was just like how i found it when i tore it apart so...i dont think its my timing. i set my timing with a light as well. but i'll get new plugs within the week unless something goes funky and post back with results.

i JUST thought of this and it doesnt seem right, but maybe i have an intake leak above the AFM? the rubber up there is looking kinda shoddy because the wires cut through it. i might see if i can buy some rubber plumbing connections, clamps, and a length of 3in tubing. we'll see.

I asked in another thread and as i hear so far, bosh wires are bad and OEM, TRD, or NGK are popular and work well. so i'll look into those.

SAFC 2 reading. BTW I fixed the problem, my thorttle cable was bunched up which was causing it to stick. I just spread it out and re-check the tension and we are good.