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I’ve been chasing this issue since I bought the truck 2 years ago. It’s 90’ F250 with the 5.8 and ZF5. The truck refuses to go over 3k rpm under load; that’s with and without towing. It’s super embarrassing going up hill and losing speed in traffic. No amount of downshifting makes any difference. The truck absolutely refuses. I did do KOEO and KOER tests and did find that my map sensor was reading crazy. Replaced that and did a full tune up (plugs, wires, distributor and fuel pressure regulator). Tested both fuel pumps and the pressures read normal while driving. TPS and throttle cable was also replaced due to inaccurate readings. Only other place I have not tested is the injectors themselves. Is there something I’m missing with the fuel system that would make the truck refuse to speed up past 3k rpm when driving? Truck sounds like it’s cammed and idle is all over the place. Engine also sounds like it is backfiring like crazy when going down hill and downshifting. Any help is greatly appreciated
Incorrect timing.
Verify firing order.
Verify timing.
If thats all good and you still have an issue, verify TDC is #1, and verify your timing chain isn't stretched.
Did previous owner do the timing gears/chain and a different cam?
Timing and firing order is correct. Pulled SPOUT to verify timing is correct. I do have a new timing chain to swap into the truck. That was also a hunch I had that could be the issue. I had a similar issue with my chevelle and it ended up being the timing chain.
Tested both fuel pumps and the pressures read normal while driving.
Whatever that means. I just happen to still have my gauge hooked up from testing the pressure on the B2. I can’t seem to find “normal” anywhere on my gauge
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