I have a 1990 chev p/u with a 4.3 and 135,000 2 wh drive. The engine runs good and has plenty of zip, but when on the highway doing about 60 mph, the vehicle loses speed and becomes very doggy. When I let off the accelerator just a bit, it will start to pick up. when I press down a bit more , it gets boggy till it downshifts, then it goes good. Once in lock up, same thing...... .Any ideas?
Might try higher octane fuel. There is a possiblity that as engine heats up a bit under load it wants to knock but knock control is retarding spark before you hear it and power sags. When you get out of it, it cools combustion chambers a bit and starts cycle over. Octane requirement is not constant and it increase with load and temp and generally decreases a bit with RPM and why it feels better when it downshifts.
----------------- TheSnoMan.com
When was the last time you changed the fuel filter? Had a similar problem with my '97 Yukon, new fuel filter brought it back to life. Regards, JR
This has merit too!
----------------- TheSnoMan.com
I've got a 93 4.3z at and the same thing happened to me at 90k but a bit worse. I parked it (working) for two weeks for when our fist baby was born...then started it up on a cold winter morning and it had no power. You could rev 5k in neutral but when you loaded it, it sputtered. So I changed the fuel filter (which had been changed several times before) and nothing. So I pulled the cap and each terminal was loaded with little fuzzies standing on their heads. I blew it out with air and fixed it all. Then changed the cap to get me another 90k.
skimmer
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