surging and bucking

[Psychokinesis]

I did the search, so decided to ask the question. My 93 Cobra, Mods are KB2.1 Flowzilla, MSD distributer and Coil, everything else is stock, well cam from a 89 5.0, but everything else stock Cobra. I have bucking and jerking at slow speeds with light throttle. More noticeably around 1500 RPMs. Good acceleration, but once it reaches speed and cruising, I can feel/hear a skip here and there, but worst at low speeds. One more thing it does, while normal accelerations, once it reaches speed, it seems like everything stops as if I remove my foot off the gas, very noticeable, like it is hitting a limit or something. In third gear it is the worst, I go through the gears, hit third, once it reaches a point where the acceleration should stop due to throttle position, it seems like it just hit a headwind, like instantly. I don't know what is causing this. I have new plugs, wires, IAC, and TPS. Reset idle, TPS at .96. Also cleaned the MAF with MAF cleaner and cleaned the throttle body thoroughly. VAC holds steady at 17-18. I tried looking for vac leaks, none to be found (used the propane and carb cleaner methods) It idles kind of roughly, it will skip here and there, but sometimes it will stumble so bad, it will almost die, then rebounds. sometimes I start it and it will die instantly. If you experienced this, chim in and let me know what you done to fix it. My next step is to pull the dizzy from my other cobra and see if the MSD distributer or coil is giving me the issues. After that, maybe putting in my 60lb injectors and remove the 24s. Any help is appreciated.

[1986Browns]

I'd be interested to know what the distributor drive gear on the cam and the gear on the end of the distributor shaft looks like. How much play do you have between them?

[WillyB93]

Double check the vacum lines, also check to make sure the supercharger made a good seal with the intake. I had one at a point doing similar things and was a leaking intake gasket, might even be able to spray around the intake with carb cleaner to see if it affects it.

[Romo93]

Double check the vacum lines, also check to make sure the supercharger made a good seal with the intake. I had one at a point doing similar things and was a leaking intake gasket, might even be able to spray around the intake with carb cleaner to see if it affects it.

I agree, sounds like a big lower intake (supercharger) leak to me. All the symptoms point to a vac. leak. I fought similar symptoms in the past and it turned out to be my lower intake leaking.

Other possibilities: Check for a spark plug boot that may be unseated, fuel-pump on it's way out? Bad cap/rotor, I doubt it but, worth a check. I once had a plug wire melt on my header and it took me a little bit to figure out I was running 7 cylinders

Good luck

[Psychokinesis]

I'd be interested to know what the distributor drive gear on the cam and the gear on the end of the distributor shaft looks like. How much play do you have between them?

The distributor gear looks good, no wear I can see and no play.

Double check the vacum lines, also check to make sure the supercharger made a good seal with the intake. I had one at a point doing similar things and was a leaking intake gasket, might even be able to spray around the intake with carb cleaner to see if it affects it.

I agree, sounds like a big lower intake (supercharger) leak to me. All the symptoms point to a vac. leak. I fought similar symptoms in the past and it turned out to be my lower intake leaking.

Other possibilities: Check for a spark plug boot that may be unseated, fuel-pump on it's way out? Bad cap/rotor, I doubt it but, worth a check. I once had a plug wire melt on my header and it took me a little bit to figure out I was running 7 cylinders

Good luck

I have sprayed and sprayed, just cant find a leak. I dont know any other way to find the leak. I plan to remove the blower soon and put insome bigger injectors, so maybe I will double up on the gaskets, check for straightness on the blower and intake, maybe use some silicon to seal the two together.
I did switch out the MSD distributor with an OEM one and it seems to idle much much better. I will use the OEM for a while to see how it acts. Hopefully that fix some of my issues

[Romo93]

I would always use sealant on the lower intake, especially around the front/back edges. I tend to use quite a bit as it's a PIA to redo.

Kyle

[Psychokinesis]

I would always use sealant on the lower intake, especially around the front/back edges. I tend to use quite a bit as it's a PIA to redo.

Kyle

Are you referring to lower intake to block/heads or lower to sc?

[Romo93]

I would always use sealant on the lower intake, especially around the front/back edges. I tend to use quite a bit as it's a PIA to redo.

Kyle

Are you referring to lower intake to block/heads or lower to sc?

Lower intake to block. I bet this is where your problem might be coming from. I've had this issue and had the same symptoms. Good luck!