Toyota Repair: 1991 Toyota truck engine problem, air flow meter, vacuum lines

Question
QUESTION: I have a 1991 Toyota truck 4x4, manual shift with a 22Re engine. I recently replaced the air flow meter and now the rpm's surge up and down when the clutch is pressed in or in neutral with the brake on. when I let of off the brake, the idle smoothes out. The engine light does not come on. I talked to a mechanic who checked out the truck for the previous owner and he said that he checked the vacuum lines and adjusted the valves. I also can't adjust the idle. It is adjusted all the way clockwise and when I try to adjust it, the rpm starts to surge without the brake on. It idles about 1800 rpm most of the time. Before I bought the used air mass meter, A friend let me try his from his Toyota truck and it did the same thing. Any help you could give me would greatly appreciated.

ANSWER: Does it only act like this during a cold start and improve as the engine warms to operating temp?





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QUESTION: It doesn't do it at cold start. It only runs a very few minutes and then starts the idle surge when I apply the brake and then it does it from then on. It also seems to be running rich because I smell exhaust fumes when It idles. The surge is very fast, about 25 to 30 times a minute. It seems to run very well on the road with a miss ever now and then. I would think it was the used air mass meter if I had not tried one that I knew that was good. It also jumps out of first gear when I let off of the gas. as long as I give it gas, it stays in gear. I also can't park it in first gear with out it jumping out. can this be anything other than a worn gear?

Answer
Wow! It's clear that you have a labyrinth of problems! Anyways, When a standard transmission jumps out of gear, it usually means that the clutch was not aligned properly during installation. Check the connection on your throttle sensor. It could be loose or slightly disconnected. Have your throttle sensor tested as well. The throttle sensor is what advances your timing and controls your injection pulse width during idle and acceleration. You might want to consider obtaining a wiring diagram from you local library and trace the brake wiring circuit to look for faulty a short.