Help With RPMS
 

so i bought a toyota supra 87 turbo, a few months its working fine then outta the nowhere, 1st gear i could rev till i red line it, 2nd and above, it doesn't pass 3 thousand rpm, it starts stalling. we took it to the mechanics and they couldn't find out. it seems like the wires have been tampered with cause it has lots of mickey mouses and tape all around .... if anyone has an idea with that it is ill appreciate it.

Any codes? (Even with no CEL there may be codes. I'd reset the codes -- unplug the battery for a minute or two, drive it around for a bit, then see if any codes come up). Could be any number of sensors, wires, or the like so codes would definitely help.

In general it could be a sensor screwing up the air/fuel mixture, or even something like a dizzy a tooth in the wrong direction. Definitely sounds like an emissions system issue though. Your Turbo could also have a crack somewhere, causing air to come in (past the maf, which is never a good thing). This would make issues happen when the turbo spools of course.

Check for codes FIRST... Then clear any codes, run the car until it reaches normal operating temp and the fault occurs again and check again for persistent codes. Details on how to check them and what they mean is in a thread in the MKIII FAQ section.

Do not continue to bounce the engine off the rev limiter! You're setting yourself up for nothing but significant damage with this bizarre diagnostic technique.

Yeah hitting redline in 1st I'm assuming he just means it goes all the way up no problem, I think from 2nd on the system chugs at 3k rpm and doesn't go higher.

Trust me... never assume the best when it comes to DIY mechanics... Often they'll blow your mind with what they believe is a good/safe/reliable idea. Like wetting your hands in gasoline and rubbing down intake hoses and vacuum line with them.... seen it.

AFM or an intake leak is possible, so is faulty knock sensor(s) or know sensor wiring or CPS problems. A lot of possibilities though.