Akyota49

Long time forum reader first time poster. Anywho I picked up this 86 Toyota 4runner for 300 bucks. It had extreme power lose (like no power at all) in 3rd or 4th gear and couldn't get past 50 mph. (don't even ask about going up hills) I pulled the codes it was throwing and fixed them accordingly. (tps and knock sensor) replaced and adjusted TPS and the knock sensor wire was just undone. No more codes. Here's we're it gets interesting. If I Start from a stop third gear will just shake the truck and Chug. But if Im downshifting into 3rd gear it work fine. As long as the vehicle never comes to stop 3rd gear seems to work. Also, I still can't it over 50mph and the clutch on this thing is weird. If I don't hit the clutch like I'm driving a race car it won't engaged. Would that have anything to do with this?
What I have done...
Timing (good)
Cheacked compression (all good)
Tps sensor
Knock sensor
Previous owner put a new cap on it and a new/used MAF
Any thoughts?

myyota

Welcome to the board

The first thing I would do is give it a complete tune up, plugs, wires, cap/rotor, and fuel filter. The fuel filter is one of the most over looked parts on these trucks. Check for vacuum leaks. What size tires do you have, and what gearing do you have ?.

As for the clutch, its either worn out or there is a problem with the clutch master cylinder or slave cylinder.

These trucks don`t have a MAF, they have an AFM (air flow meter), there is a huge difference in the two.

abecedarian

Well, you shouldn't be in 3rd below around 20-25 mph anyways so the coming to a stop in 3rd thing makes no sense to me.

As for your clutch, check the clutch pedal bracket under the dash and if that's not broken, the next things to do are: bleed the clutch, well, don't bleed it- flush it and if that doesn't help the clutch master cylinder and/or slave cylinder are bad.

As mentioned, these trucks have an AFM, or more accurately a VAFM (Volumetric Air Flow Meter). It measures how much the air coming into the engine displaces a "door" in the air stream (the volume of the air) and has an air temperature sensor the ECU uses for density correction- cooler air is more dense, warmer air less dense.

MAF sensors directly measure the mass of the air entering the engine by calculating how
much electrical current is necessary to maintain a constant resistance in a heated wire placed in the air stream, which makes the air temperature correction for density mostly unnecessary as the temperature of the air directly influences how much the air can cool the sensor: warmer, less dense air won't cool it as much as cooler more dense air.

Akyota49

OK first of all I'm not starting in 3rd gear from a stop. What I mean is when I start from a low gear (1st or 2nd) and shift into 3rd it dosnt want too work but when I'm going at a highway speed (55mph) and start down shifting (5th-4th- and then into 3rd) it seems to work normally. I did my tune up and replaced plugs, cap, rotor, air and fuel filter. Runs a little better then before but still acting up on me. What I did discover is when I remove the first cylinder wire from the spark plug the engine dosnt catch is tune. But when I remove other wires it bogs down like it should. So I'm basically running on 3 cylinders. Compression is good on that particular cylinder (180) which seemed a little high cause the others sat around 160-170. Bent valve maybe? I guess the easy thing to cheack first is if fuel is getting to that cylinder. Anyone know the procedure for that and how to cheack injecters? Was gonna dump in some fuel tank cleaner tomorrow and hope maybe I get lucky. Any thoughts?

Akyota49

I ment change not catch. Sorry doing this from my phone so autocorrect gets me from time to time. Also I have spark on the first cylinder. Not sure if I mentioned that.