My girlfriend and I drive an old Toyota Avensis that was produced in 2000. Its engine is Toyota's 3S-FE. Let me spare you my theories and tell you what symptoms arise:
- When the engine is cold, it can barely rev beyond 2,000 RPM, and there is noticeable shaking of the exhaust pipe. The shaking stops when the engine gets to operational temperatures.
- After the engine has heated up, it can rev up to 2,900 RPM, then starts getting very unstable -- it speeds up to a certain point, and it seems to "hit the ceiling" and revs down, this effect is exacerbated with increased throttle position.
- Opening the throttle completely starts this violent revulsion and then quite quickly, the ignition seems to turn off and it just stops dead. Restarting is no problem. This happens with and without load -- the ignition will turn off on the highway, and you have to put the clutch pedal down so the engine stops, only then can it be restarted!
- The engine is very weak, going up hills and such you can "feel it struggling" like anybody who drives stick does, you start getting the feeling that you need to downshift because the engine's power output isn't great enough. Accelerating on highways is dangerously slow because of this, both because you can only drive in the 1,000-2,000 RPM range which has quite poor torque, and because if you accelerate hard, you will get this same "hitting the ceiling" effect.
It wasn't always like this, this happened on a long trip through Europe (and a fair amount of time on the autobahn) -- it started out with the engine misfiring in the range 3,600-4,000 RPM (but not above!) Needless to say, we kept this misfiring to a minimum so as to avoid permanent engine damage.
Loud rattling noise from the generator in the range of 3,400-4,000 RPM
There is a bolt loose on the engine. We're unsure what it does. See picture:
The spark plugs have since been changed, along with their wiring, and I don't know how well it runs now. The spark plugs were previously all different brands.
- Exhaust pipe clogged somewhere. Engine unable to expel exhaust at the correct rate beyond a certain RPM.
- Broken oxygen sensor/vacuum line leak/faulty MAF sensor. This would lead to a lean fuel mixture and explain the misfiring. Also vacuum line leaks could cause poor engine pressure.
- Faulty spark plugs, or faulty timing belt. Could cause misfiring if the fuel isn't ignited properly or at all.
- Faulty fuel pump. Could explain why the engine felt weak to begin with.