What the crap is wrong with my car?!

[hoss331stang]

Sometimes when i'm driving around at low RPM's it bucks like crazy...it feels like its skipping on like 4 cyls or something.....and when i try to speed up, it just does it faster....The engine wants to pull but it just keeps on bucking and sputtering...This is a brand new motor, i prolly only have about 300 miles on it. I haven't been that rough on it yet, even tho i've got on it a few times....It really only does this after driving it for awhile......What do you think guys?

 

[MAC'n89Blckstng]

My brothers does that, he tried to check his timing and it wont stay at a number, it just skips up and down. Maybe your timing chain is somehow loose, try checking the timing, maybe its too advanced or too retarted.
Hope this helps,
Jesse

 

[HO93LX302]

Be sure you have the correct firing order with the wires 13725648 counter clockwise.. I would douple check that first

 

[95kobrah]

Hey, when u find out, let me know, my cobra does the EXACT SAME THING... heres what ive done since, and still hasn't changed
New EGR, Fuel Pressure Regulator, Fuel Filter, Thermostat, Plugs, Wires, Dist. Cap and Rotor, header gaskets, fluids, oxygen sensors, cleaned MAF, cleaned Air Filter, cleaned AIC, checked timing (solid 12*)... still running like chit. I feel bad that your car is running crappy, but im sorta glad mine isnt the ONLY one... oh yea, all plugs and wires are in order, and there are no cracks or leaks anywehre

 

[bradranger]

bucking

Pull the codes from the computer, it maybe tps sensor.

 

[SmockDoiley]

well that may work on 95Kobrah, but I hear those TPS sensors are really tricky on the carbureted cars, lol!! Hey, I thought you were going to run the supercharger, or are you waiting for the engine to break in?

 

[Greenracing]

check the carb bowls.

 

[88GTStreetRod]

Ok. I just had the same problem and spent many nights on this site trying to figure it out. I also spent $$$$$$$ trying to figure it out. My problem started when I put on new heads and intake. I Replace o2 sensors, etc. The (very easy) fix for my car was clocking the Mass air meter 90 degrees. I have the X3Z cobra computer. You are suppose to run 24lbs injectors with a 19lb mass air meter for the cobra computer. I put on a 24lb mass air meter and clocked it 90 degess and it runs perfect. The new set up I have pulls in more air. The air comming in the car was missing the sensor in the mass air meter.

Sometimes when i'm driving around at low RPM's it bucks like crazy...it feels like its skipping on like 4 cyls or something.....and when i try to speed up, it just does it faster....The engine wants to pull but it just keeps on bucking and sputtering...This is a brand new motor, i prolly only have about 300 miles on it. I haven't been that rough on it yet, even tho i've got on it a few times....It really only does this after driving it for awhile......What do you think guys?

 

[88GTStreetRod]

Sorry, I am a dumb A__ I did not see that you are using a carb!

Sometimes when i'm driving around at low RPM's it bucks like crazy...it feels like its skipping on like 4 cyls or something.....and when i try to speed up, it just does it faster....The engine wants to pull but it just keeps on bucking and sputtering...This is a brand new motor, i prolly only have about 300 miles on it. I haven't been that rough on it yet, even tho i've got on it a few times....It really only does this after driving it for awhile......What do you think guys?

 

[90 lx convert]

Assuming this is not ignition related it sounds like the problem is a lean off idle-low rpm condition. What happens is the vacuum signal across the venturis is not enough to bring in the main power circuit. The throttle is open too far for the idle circuit to be effective and so with the idle circuit not effective and not enough signal to pull in the mains you get a lean condition during off idle-low rpm. The reason why it gets worse when you give it more gas is when you open the throttle more the vacuum signal gets worse. The solution is to increase the amount of fuel delivered through the accelerator pump shot. This will help cover that lean area untill the mains come in. You can tune this by adding the larger 50cc pump kit, changing the pump shooter and the pump cams. A good starting point would be buying a Holley trick kit and a 50cc pump kit. This will get you the parts you'll need. The rest is just tuning for your setup. Hope this helps. Mike