Why does my car buck below 3000rpms?

[1990LXDropTop]

If I put it to the floor in any gear except 1st below 3000rpms my car will buck a bit before the rpms start to climb. My car runs perfectly fine and pulls hard, but for reason it has always bucked a bit, especially after my H/I/C swap last winter. Could it be bad motor mounts? What would cause this?

I have edelbrock performer heads, performer intake, e-cam, C&L 76mm maf/pipe, 70mm tb/spacer, 24# injectors, 255lph fuel pump. Timing is set at 14* initial and fuel pressure is at 40psi. For rest of mods click the link in my sig and go to page 3.

Maybe I just need a tune?

 

[86bluecobra]

wierd i would say tune up time. mine used to buck in fith below 200orpm 3.73 gears fixed that. Thats not your problem. Is it missing intermitenly perhaps?

 

[1990LXDropTop]

Also, sometimes when the motor is cold I will get a slight misfire when accelerating in 2nd and 3rd in low rpms.

 

[86bluecobra]

i would say time to look at the plugs and wires cap and rotor.

 

[86bluecobra]

usally you only really notice the misses at lower rpms seems like they go away at higher ones. Im sure they don't but they are much less noticable.

 

[1990LXDropTop]

The plugs have less than 5000 miles on them. The wires have less than 10,000, as well as the dist cab/rotor.

 

[86bluecobra]

isn't there an issue with plug wires sometimes cross firing? I was missing and it turned out that the condensation had rusted the pickup in the bottom of he distributor. could be your problem. get any water in the dizzy?

 

[Euphoric306]

my car always bucked when cruising below 2k. setting my tps helped that, but i doubt thats your problem unless yours is WAY off... in which case you might have different problems

 

[2002BLGT]

pull the distributor and check it out , replace the PIP and if the shaft doesnt spin VERY ,VERY smooth , just get a reman distributor from a local parts store , I had a terrible bucking in my car from about 1100-2000 rpms and when I changed intakes I pulled the distributor and let the shaft hang and spun it by hand by the distributor gear and it felt a little rough , went to local parts store and got one off the shelf and felt how smoothly it turned compared to mine , I figured what the hell atleast I will eliminate one more thing that could be causing it , spent the money , dropped it in the car and now it doesn't buck at all ....just my experience ......hope it helps

 

[1990LXDropTop]

I wanted to get a new dist. in the future so I might as well spend the money on an aftermarker one. Which is the best aftermarket dist.? MSD? Accel?

 

[2002BLGT]

I wanted to get a new dist. in the future so I might as well spend the money on an aftermarker one. Which is the best aftermarket dist.? MSD? Accel?

I would get the MSD ....

 

[Paul Perreca]

what kind of spark plugs are you using? try autolite 3924's and see if it makes a diff - that is my next thing to try - similar set up and same problem lol

 

[rustang87]

I have the same problem after H/C/I. If i downshift in to 2nd or 3rd when I am coming to a stop, it starts bucking into a rythm. Same thing when cruising through a parking lot or in traffic. Its smooth when you you are accelerating, but if I let off it starts bucking in any of the first 3 gears. I always have to hit the clutch and let it back in and keep consistent pedal pressure. I wonder if it has something to do with the fact that I can't get the car to idle below 900-950. Cap and rotor are stock, is that the problem? If not, any body have any advise?