car bucks 1st few miles.....
 

OK, here is my problem.....

Car sits overnight (12 hours). Start engine put it into gear and drive away. No problems at all.

Get to work after a 20 mile drive around 6:45 am. Leave for lunch at noon. Car bucks and jerks for about 3 miles. Even after the engine temp has hit the mid mark. Goes away.

Leave lunch 45 minutes later. Same thing but not as bad and for not as far.

Leave work at 5pm and same thing again. Jerks and bucks then goes away.

Again. Leave for work in morning and engine runs fine.

Has been doing this for about 2 weeks not. Does not matter what the outside temps or if it's sunny or raining.

Things that have been done to the engine within the last 6 months.

new plugs, wire, cap rotor, fuel system o-rings, all hoses both coolant and emissions (ALL OF THEM!) water pump, air filter and full oil and fuel system cleaned with seafoam.

I regapped and installed my old plugs and double checked the wires and cap. still jerks.

Could it be the O2, fuel filter or EGR?

Car runs fine afterwards and still getting great gas mileage.

Thanks everyone. I know it's a long post but wanted to be as complete as possible.

P.S. I wired in a tach about a month ago. 2 weeks prior to this problem occuring. Double checked my connections for loose wire to ignitor. Seems fine to me. Still tight and no corrosion.

I'd place my bets on the fuel filter. The o2 sensor would just give you worse gas mileage. The EGR might be it, but I doubt it.

i am just curious; why would it jerk at first if it was the fuel filter wouldn't it keep doing it while you drive?

I second the fuel filter. When it sits over night or while you are at work, all the junk in the filter has a chance to fall back into the tank. After driving a bit the pump sucks it back up and the filter clogs again.

If it is independent of throttle then it is not the fuel. If it runs smooth with light throttle then bucks with more throttle it could be spark breaking down. Wet distributor cap is often the problem if it clears up with temp.

It bucks in all gears while appling throttle. If I rev it while out of gear than it spools up fine.

It did it this morning on the way to work. It usually doesn't do it then. However it was very light bucking. it feels as if there is no power at all then I fell a short (1/2 sec) burst of power than no power. Repeats a few times and goes away.

I just remembered that my jeep would do this. A friend was under the impression that it might be a clogged catalytic converter, or a clogged exhaust system.

Just an idea.

Could be possible?

The truck is a 1992. I had the head rebuilt 2 years ago but the exhaust has only had a muffler changed.

I hear that when the cat gets clogged it will run VERY hot! So far the cat seems to be running at a normal temp.

I have been thinking about running 2 cats anyway. So I might just change it?

The fuel filter needs changing. Been putting it off because my filter runs $30!

After I do that I'll see what happens.

Check your PCV valve - I heard once that the engine block pressure vented into the poor seals of the distributor blowing moisture up into it - a poor PCV valve would do this. Also when it starts doing it just stop and pull the distributor cap off. Also check on the ignition connections to make sure you get good grounding to the distributor or else you could be misfiring the coils or not firing them at all when you loose power. Check for the smell of gas in the exhost too since that would indicate a failing spark - smell that all the time when I hear a car go by skipping a lot. Soot in the tail pipe would indicate a cat problem too. Spark plug gap too big can cause problems with high voltage wiring breaking down under less than ideal a/f mixtures.

After it's been driven awhile and bucking, what is the combustion looking like? Any smoke? What do the plugs tell you?