4.3 Surging

[muff34]

Hi Guys
I`ve got a 2000 Silverado with the 4.3 . 145,000 miles on it . The engine rpm at 60 M.P.H. is about 1500 , lately I have noticed it seems to be surging between 1500 and 1750 or so in OD. There is no cruise on truck so it is all foot feed (that ain`t the problem ......lol). The engine starts and runs fine fuel mileage is good. fuel filter is 5 months old and may have 2500 miles on it tops. I read an old post where if you were to touch the brake peddle lightly the surging would quit .when I do this the rpm jumps up about 400 rpm and engine does not surge anymore. no ses light is on yet . Thanks for any imput
Muff

[wrparks]

Mine was doing something similar a few weeks back. It's a 04 w/ 4.3. Anyway, it was more of a lurch on deceleration. It was low on atf fluid, so I suspect it was the torque converter not acting properly??? Anyway, added fluid and it's gone away. Slightly different, but may be worth a look for you.

[muff34]

Originally Posted by wrparks

Mine was doing something similar a few weeks back. It's a 04 w/ 4.3. Anyway, it was more of a lurch on deceleration. It was low on atf fluid, so I suspect it was the torque converter not acting properly??? Anyway, added fluid and it's gone away. Slightly different, but may be worth a look for you.

I`ll check it out, trany fluid and filter was also changed about 3,000 miles ago. This doesn`t lurch and seems to shift ok. also when I step on the brake lightly and it picks up the 300 to 400 rpm it is not downshifting and I doubt the brakes are even starting to apply . Thanks for your input.

[wrparks]

I think that the simple act of hitting the brakes at hwy speeds should disengate the torque converter, even when the pads don't engage, maybe explaining the 300 to 400 rpm pickup. Kinda like the cruise cutting off with a tap. So maybe it is a torque converter problem. Hopefully somebody with a bit more broad knowledge can help here.

[gremlin96]

check your dist cap. I bet it has gone bad. probly arking in side.

[muff34]

Originally Posted by gremlin96

check your dist cap. I bet it has gone bad. probly arking in side.

It was changed two months ago ,cap and rotor . O.E.M. parts ,thanks . Was kind of hoping that some others with lots of GM knowlege on this forum would have chimed in but it didn`t happen........oh well. Went back to GM garage and both mechanics(Guess I won`t call them Technicians) did not have enough knowledge about the problem, so were reluctant to comment on it . At least they were honest enough to admit it. They were thinking Transmission issue, but would go no farther.

[gremlin96]

GM garage mechanics. i have found a lot of shops will not pay for good mechanics. so thay get the low end of the tech field. if thay can not find the problem with the computer thay will not do any thing.

[MT-2500]

Start with the basis.
Tune up and fuel pressure?
How many miles on plugs and what kind?
Get it on a good engine and transmission scanner on it and check things out.
Lot of good info and information in them and some test to run.
MT