ok for the past 2 weeks it's been getting grdually colder here, i bought my car at the end of summer time so it was still hot out, it had a bad alternator, and old plugs and wires, as it got colder i began to develop a high speed jerk, kind of like a miss fire but not consistint enough to call it that. i finally got around to replacing all the parts and then it ran like crap. So i checked my timing and after i changed out the old stuff with the new my timing advanced 9 degrees. SO i re-timed it and thought it was doing good. TOday i got in and started driving and i got that jerk again. anytime i hit 50 in any gear, 3rd,4th or 5th, and if i drive through it it goes away...then comes back again in lessa than a minute, form what i can tell warming up my car does nothing, anyone have any ideas as to what it is?

I put on a new autolite alternator, new champion plugs, and new nascar(i think) wires or whatever checker sells you. I timed it to 4BTDC like alldata said and it hasnt helped...WHAT IS IT???????

I'm not that familiar with TBI but I would check the TPS sensor. It may have a 'bad spot' in it that you notice around 50mph.

Hope this helps!

If you can drive through it, check for clogged egr valve eternally.

cant be a clogged egr i have a new ac delco that was just put on by my local shop and they cleaned out my entire intake manifold too

How did they go about that?

i wathced them pull my manifold, spray it off in their parts sink with a solvent, and use like large pipe cleaners to scrub it out, it was bad before like clumps of black gunk came pouring out, then they pluged up the holes except one and let it soak, put it into a parts washer, the water kind where it sprays it with extremely hot water, and then put it back on

Good, I wouldn't have been surprised to hear, "coat hanger jabbed into the holes."

I assume they cleaned out the ports in the heads, too.

to my knowledge they did