'Jerking' while Accelerating - Need Help
Thread Starter
Intermediate
Joined: Jul 2022
Posts: 34
Likes: 10
'Jerking' while Accelerating - Need Help
Hello,
I recently bought a 1986 Corvette (L98) with the 4+3 transmission. I have been experiencing an odd issue. Occasionally when I accelerate, the car will like jerk or hiccup, is almost seems like it is misfiring. It's a pretty distinct sound and you can feel it clearly while driving. I've experienced this in all gears at all speeds.
The issue 'seems' to be worse in overdrive but this might just be my imagination.
I would love any input that anyone has. I can provide more details if necessary. Thank you.
I recently bought a 1986 Corvette (L98) with the 4+3 transmission. I have been experiencing an odd issue. Occasionally when I accelerate, the car will like jerk or hiccup, is almost seems like it is misfiring. It's a pretty distinct sound and you can feel it clearly while driving. I've experienced this in all gears at all speeds.
The issue 'seems' to be worse in overdrive but this might just be my imagination.
I would love any input that anyone has. I can provide more details if necessary. Thank you.
Popular Reply
Aug 2, 2022, 10:12 AM
Safety Car
Joined: Mar 2017
Posts: 4,188
Likes: 1,310
From: LeClaire Iowa
Seems kind of dangerous "jerking" while accelerating. Maybe better to pull off to the side. Dan
Melting Slicks
Joined: Aug 2003
Posts: 3,389
Likes: 391
From: Lakeville MI
First thing would be to verify/check the timing with a timing light. Might be knocking and pulling timing due to knock retard. Also get a cable and log data to see what is going on.
Example products:
http://www.moates.net/aldu1-and-cabl....html?cPath=64
http://www.tunercat.com/DataCat/datacat.html
Example products:
http://www.moates.net/aldu1-and-cabl....html?cPath=64
http://www.tunercat.com/DataCat/datacat.html
Last edited by tequilaboy; Aug 2, 2022 at 04:10 AM.
Drifting
Joined: Nov 2018
Posts: 1,738
Likes: 635
From: USA
Agree^^^^^! First verify timing! Next question, how do the plugs, wires, cap and rotor look? You may have a bad spark plug or plug wiring grounding out. Would likely be worse in OD as the motor is more "lugging" (lower rpm's). If visually the ignition parts are old, I don't feel it's "throwing" parts at it, even if it doesn't solve your issue....a tune-up to the ignition system, done properly is usually beneficial! If timing is correct, my guess would be a plug wire melted or rubbed through the insulation.....Open the hood at night or in a dark garage while it's running and look around for arcing from a wire! Cap could be so bad that the spark intended for one cylinder is jumping to another. Tune it up! For good measure, throw in a fuel and air filter👍
Le Mans Master
Joined: Jul 2004
Posts: 6,219
Likes: 696
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
Hello,
I recently bought a 1986 Corvette (L98) with the 4+3 transmission. I have been experiencing an odd issue. Occasionally when I accelerate, the car will like jerk or hiccup, is almost seems like it is misfiring. It's a pretty distinct sound and you can feel it clearly while driving. I've experienced this in all gears at all speeds.
The issue 'seems' to be worse in overdrive but this might just be my imagination.
I would love any input that anyone has. I can provide more details if necessary. Thank you.
I recently bought a 1986 Corvette (L98) with the 4+3 transmission. I have been experiencing an odd issue. Occasionally when I accelerate, the car will like jerk or hiccup, is almost seems like it is misfiring. It's a pretty distinct sound and you can feel it clearly while driving. I've experienced this in all gears at all speeds.
The issue 'seems' to be worse in overdrive but this might just be my imagination.
I would love any input that anyone has. I can provide more details if necessary. Thank you.
Thread Starter
Intermediate
Joined: Jul 2022
Posts: 34
Likes: 10
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Safety Car
Joined: Mar 2017
Posts: 4,188
Likes: 1,310
From: LeClaire Iowa
Safety Car
Joined: Mar 2017
Posts: 4,188
Likes: 1,310
From: LeClaire Iowa
Racer
Joined: Aug 2021
Posts: 321
Likes: 44
I started experiencing the same thing with my ‘86 L98, 4+3, yesterday. Mine was the overdrive engaging and disengaging on its own. Service Engine Soon light is on too, but that could be another issue. Once mine decided to stay out of overdrive the lurching quit. If that isn’t it with yours, try setting your timing a couple of degrees advanced and set your TPS voltage at the middle to top of the spec. This will give better off idle response but the Control unit will still limit maximum advance.
Burning Brakes
Joined: Nov 2004
Posts: 1,193
Likes: 176
From: Hillsborough NC
My vote is on a misfire as well. I had a similar issue that I chased on my 86 (automatic) for several months. I went as far as replacing the torque converter as I thought the lockup was non-functional. Same issues, seemed like it was only happening in overdrive at highway speeds.
For me, it turned out that the ignition wires on the passenger side got too close to the manifold and burnt some of the insulation, allowing any of the four plugs on that side to randomly misfire.
What I did notice is that after fixing the issue, at idle the engine does not move (shake) at all. Even though the miss was not felt in the lower gears, it was there even at idle, just barely noticeable.
For me, it turned out that the ignition wires on the passenger side got too close to the manifold and burnt some of the insulation, allowing any of the four plugs on that side to randomly misfire.
What I did notice is that after fixing the issue, at idle the engine does not move (shake) at all. Even though the miss was not felt in the lower gears, it was there even at idle, just barely noticeable.
Safety Car
Joined: Apr 2016
Posts: 4,648
Likes: 1,059
From: N.E. Ohio OH
Finalist 2020 C4 of the Year - Modified
Have you taken the distributor cap loose and looked inside ? Back when I had cars with that kind of distributor, a buildup could occur on the electrodes causing firing issues. Also a cracked cap can cause an issue. Then there is a coil starting to go bad.
Do you know how long it has been since the car had an actual good tuneup with new wires, new cap, new plugs, etc ? It would be worth the investment to do so.
If you have a place where you can have it be really dark, run the car and look. You can see if there is any voltage leaking out from either a wire or the cap.
There is a reason different folks here have mentioned misfire as being a possible culprit.
Do you know how long it has been since the car had an actual good tuneup with new wires, new cap, new plugs, etc ? It would be worth the investment to do so.
If you have a place where you can have it be really dark, run the car and look. You can see if there is any voltage leaking out from either a wire or the cap.
There is a reason different folks here have mentioned misfire as being a possible culprit.
Thread Starter
Intermediate
Joined: Jul 2022
Posts: 34
Likes: 10
Issue fixed!
So I took your suggestions and checked out the plugs and wires and one plug wire was loose. I snugged it back up and the car's running AMAZING! It's like a whole different car!! Thank you everyone for your suggestions.
So I took your suggestions and checked out the plugs and wires and one plug wire was loose. I snugged it back up and the car's running AMAZING! It's like a whole different car!! Thank you everyone for your suggestions.