Car jerking when accelerating??? - SR20 Forum
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#1 (permalink) Old 12-22-2007, 02:49 PM
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Car jerking when accelerating???

I am having some major issues with my car right now. Everytime I accelerate the car starts to jerk out of control, The only way to stop it is to press in the clutch and start over. I can't seem to figure out if its clutch,fuel,or motor/turbo related. I am first going to replace the clutch cable to see if the clutch just isn't disengaging and maybe sticking?? Another weird thing it does is when you try to accelerate it'll start to jerk, but if you gun it it starts to stumble and jerk, then take off. After I change the clutch cable I am not sure what else to try and will just do the engine swap, change out the clutch, etc.... Any input would help.

btw I am planning on swapping in a jdm de soon and bigger turbo set-up;, but wanted to atleast get through the winter to do the swap(to damn cold), and right now the car is basically undriveable.

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Last edited by jonwepa; 12-22-2007 at 02:56 PM.
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#2 (permalink) Old 12-22-2007, 04:37 PM
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Have you checked the ecu for codes? I would start there and see where that takes you.
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#3 (permalink) Old 12-22-2007, 04:51 PM
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sounds like a fuel problem to me....
plugs possibly?
what's the a/f look like?

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#4 (permalink) Old 12-22-2007, 05:50 PM
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plugs vac leaks and check your timing!

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#5 (permalink) Old 12-22-2007, 05:56 PM
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Originally Posted by philipn126 View Post
Have you checked the ecu for codes? I would start there and see where that takes you.

Have no light on, but no I haven't checked that. Didn't even think of the obvious

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#6 (permalink) Old 12-22-2007, 05:58 PM
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Originally Posted by nsusammyeb View Post
sounds like a fuel problem to me....
plugs possibly?
what's the a/f look like?
A/f seems to be good by looking at the plugs, there nice and rusty colored.

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#7 (permalink) Old 12-22-2007, 05:59 PM
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Def. check your plug gap if you put them in recently and check for vacuum leaks.
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#8 (permalink) Old 12-22-2007, 06:03 PM
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Originally Posted by zipstrips View Post
plugs vac leaks and check your timing!
Plugs are perfect, I've had a vacuum problem since day one and just can't seem to find the culprit, but it never caused any problems before and my timing is fine although I really can't get it running right let alone put it into timing mode.

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#9 (permalink) Old 12-22-2007, 06:05 PM
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most likely a vacuum issue then.
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#10 (permalink) Old 12-22-2007, 06:15 PM
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Originally Posted by doner005 View Post
most likely a vacuum issue then.
I am positive its not because its been the same since i turboed the car (a year ago) and the car ran great. It is the reading the same at idle as it was before.

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#11 (permalink) Old 12-22-2007, 07:06 PM
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so there's no cel's? Sounds to me that it is either flooding when you put it to the floor or leaning out and detonating. Most likely flooding the cylinder with fuel, and then once it gets more air in there in leans out enough to run smoother. Check your injectors, any of them leaking or stuck open? How's the compression??? Throwing out ideas, but i agree with zips it's most likely a vacuum leak. Car idle at all? Here I have a video of mine idleing with a really big vacuum leak... http://s71.photobucket.com/albums/i1...t=HPIM0929.flv
It would do the same thing really rough until I got high enough in the rpms to overcome the vacuum and it would smooth out... http://s71.photobucket.com/albums/i1...t=HPIM0928.flv

hopefully this helps you some.

What clutch is in the car? What turbo set up do you have? How much power you putting down?

http://www.sr20-forum.com/members-ri...ebs-build.html

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#12 (permalink) Old 12-22-2007, 07:10 PM
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what ECU do you run?

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#13 (permalink) Old 12-22-2007, 07:21 PM
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When is the last time you changed the cap and rotor? I would just for the piece of mind change the plugs. You would not believe how many times it was just a simple plug change...even though they looked o.k. If you could list your setup it would make other diag.. easier. If you have sometime you can use to datalog that would be great also.

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#14 (permalink) Old 12-22-2007, 07:50 PM
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Originally Posted by nsusammyeb View Post
so there's no cel's? Sounds to me that it is either flooding when you put it to the floor or leaning out and detonating. Most likely flooding the cylinder with fuel, and then once it gets more air in there in leans out enough to run smoother. Check your injectors, any of them leaking or stuck open? How's the compression??? Throwing out ideas, but i agree with zips it's most likely a vacuum leak. Car idle at all? Here I have a video of mine idleing with a really big vacuum leak... http://s71.photobucket.com/albums/i1...t=HPIM0929.flv
It would do the same thing really rough until I got high enough in the rpms to overcome the vacuum and it would smooth out... http://s71.photobucket.com/albums/i1...t=HPIM0928.flv

hopefully this helps you some.

What clutch is in the car? What turbo set up do you have? How much power you putting down?


Your explanation sounds like the most accurate, but the only thing is wouldn't the plugs show signs of the detonation?? The plugs are about 1 month old and look really good(gapped to .028. My compression has been steadily declining(175,000+ miles), but is still reading 150 across all 4 cylinders and the vacuum problem has always gave me issues with my idle, but not my acceleration or drive ability, which can be seen by my 1/4 mile times.

My main guess is the clutch. It feels like its not disengaging properly and sticking maybe ??? Almost like when you don't let the clutch out right and it jerks like crazy and I am using a cheap xtd ebay clutch, which has never given me a problem and held up to multiple track runs and a 13 flat @ 110mph.

My next guess would also be a leaky injector, but would it start to misfire? and not jerk??

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#15 (permalink) Old 12-22-2007, 07:58 PM
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btw this is my set-up: usdm w/ 175,000 miles, bb manifold, avenir t25, 370cc's, nismo fpr, bored se-r maf, hot shot fmic w/ hks bov recir., jwt s3 cams, jwt ecu tunned for the above set-up @ 4bar fp, 3inch dp w/ side exit exhaust, etc.... I run at the track pretty frequently and run low 13's @ 108-110mph. I have never been to a dyno yet, but by my traps and times I am guessing around 250??

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#16 (permalink) Old 12-22-2007, 08:37 PM
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i actually have one of those stage 3 xtd's in my car and i like it haven't had any problems so far, and it's very streetable. When you say jerk you mean like "jerk" not just a gap in the power band? I mean you're the one driving what's it feel like? It's hard for us to troubleshoot haha, we're just throwing ideas out there. My girlfriends car has oil on one of the plugs and it kinda jerks when you give it some gas, but doesn't do it if you really get down on it. You may just have one cylinder misfiring somehow. I'd check the injectors with a 9 volt battery and a couple wires, you'll hear them click open and closed, it's pretty cool actually.

http://www.sr20-forum.com/members-ri...ebs-build.html

U13 SR20DET, Turbonetics 60-1 hi fi .63 ar, Brian Crower Stage 2's, 875cc injectors, .3 bar fuel pressure, log manifold, Tial 38mm wastegate, 3" downpipe-3", PLX Wideband, Megasquirt v3.57

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Last edited by nsusammyeb; 12-22-2007 at 08:40 PM.
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#17 (permalink) Old 12-22-2007, 08:42 PM
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you have a boost guage on the car don't you?? does the vacuum on it bleed off while it's idleing?

http://www.sr20-forum.com/members-ri...ebs-build.html

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#18 (permalink) Old 12-22-2007, 08:54 PM
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I had a TPS that went bad. It would stumble as it accelerated. Does it feel like it's cutting in and out real fast with it normal in between the times it cuts out? You can watch the TPS on a consult and see this happen. It did not show when I did a tps setting but if you watched the voltage as you slowly opened the throttle you could find dead spots.

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#19 (permalink) Old 12-23-2007, 01:06 PM
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Originally Posted by nsusammyeb View Post
you have a boost guage on the car don't you?? does the vacuum on it bleed off while it's idleing?
At idle my boost gauge reads about 10 and usually stays there.

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Originally Posted by 98sr20ve View Post
I had a TPS that went bad. It would stumble as it accelerated. Does it feel like it's cutting in and out real fast with it normal in between the times it cuts out? You can watch the TPS on a consult and see this happen. It did not show when I did a tps setting but if you watched the voltage as you slowly opened the throttle you could find dead spots.
I did check my tps and it read .44 with the ignition set to the on position and at WOT it reads 4.15. I took it off and cleaned the contact points, but still nothing. Now my idle is just plain crazy one minute its idling at 900rpm the next its stalling and then its idling at 2000rpm. I know that my low vacuum is probably not helping this and maybe even causing this.

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Last edited by jonwepa; 12-23-2007 at 01:07 PM.
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#20 (permalink) Old 12-23-2007, 01:12 PM
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i actually have one of those stage 3 xtd's in my car and i like it haven't had any problems so far, and it's very streetable. When you say jerk you mean like "jerk" not just a gap in the power band? I mean you're the one driving what's it feel like? It's hard for us to troubleshoot haha, we're just throwing ideas out there. My girlfriends car has oil on one of the plugs and it kinda jerks when you give it some gas, but doesn't do it if you really get down on it. You may just have one cylinder misfiring somehow. I'd check the injectors with a 9 volt battery and a couple wires, you'll hear them click open and closed, it's pretty cool actually.
Thats the one I have and I haven't had any problems with it either. I think its a little of both. It feels like a dead spot and a jerky clutch

I think I will do a injector test next.

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