My Toyota 4 Runner (old model) misfires and seems lazy especially while climbing hills. There is also a delay in changing from gears 2 - 3 and 4. Can someone please help to advise? Thanks in advance.

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    Sounds like 2 different problems. When is the last time the vehicle had a tune up - plugs, wires, cap, rotor, coil, fuel filter, air filter, oil – rpmerf Jul 27 '16 at 12:12
  • A month ago I had the fuel filter and plugs changed. You mentioned about wires, caps, rotor, coil and air filter. Can you explain more about them please. – Paul Damba Jul 27 '16 at 12:57
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    Spark plug wires, distributor cap & rotor, and coil pack are all part of the same system that delivers electricity to the spark plugs. If one of them is faulty, it could cause the engine to miss, especially under heavy load (climbing hills). The air filter removes dirt/dust/particulate before the air enters the engine to prevent excessive wear. If the filter is clogged, it could starve the engine. Not sure of your location, but in the US, wire/cap/rotor/coil will cost ~$150 + labor, and a basic air filter is $10. You can do all the maintenance yourself with basic hand tools. – MooseLucifer Jul 27 '16 at 13:18
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    Delayed gear changes might be solved by changing the automatic transmission fluid and filter. I'd say you should probably only have it changed, rather than having the transmission 'flushed'. – MooseLucifer Jul 27 '16 at 13:20
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    Jumped timing could explain these symptoms if they started suddenly. – SteveRacer Jul 28 '16 at 4:07

I know this sounds crazy, but I think that you need to fix/replace the exhaust. Basically, in my humble guesstimation, you don't have enough compression in the exhaust system. Either you have a non-factory muffler or a hole in the pipe or your catalytic converter has been stolen, or something along those lines.

Toyota and Nissan (and probably a few others) behave like that when they don't have the right amount of banana in the tail-pipe (back pressure).

In my experience, when I replaced the exhaust system of a '92 Toyota truck and '92 Nissan truck (in the years of our lord 1998 and 2002, respectively) with cheap muffler replacements, I initially experienced an increase in power... which eventually subsided after a couple months and became the problem that you described.

Then, after replacing the one-size-fits-nothing muffler with factory exhaust parts, both vehicles had an inital loss of power, which eventually subsided and became normal operation.

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