I posted a couple of years ago about lack of power at 40 mph. Good power until 40 mph then nothing. It was also making a low thumping sound from the air intake. Well, I replaced the air intake and timing chain and nothing changed until one day on the highway. I had the pedal to the floor (as usual) going 45 mph and all of a sudden, a huge back-fire from the exhaust and the truck shot forward to a great 75 mph. It must have been something clogging the cat-converter. Problem Solved!
1990 4x4 4cyl power problem solved!
Aug 15, 2009
1 Replies
It might have been solved temporarily, but it sounds like you need a new CAT.
I had a similar problem on my 86' PU, 22R carb. It would start to diesel when going up a hill. Could not get past 40 mph. It would rev fine in the driveway, but once under some type of load it, start dieseling. When I mean "diesel", you can hear the valves clicking like on a diesel engine.
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