RPM Problems
 

A buddy of mine just gave me his non turbo-ed 86 Supra. I don't know much about these cars and i generally work on domestic vehicles. Any way i was wondering if you guys might have an idea of what would cause a vehicle not to go over 2500 rpms. I though maybe it has a built in rev limiter that is malfunctioning. A bad sensor, bad computer, not enogh fuel and a few other things. My bud already pulled the engine out of it though so i don't know for sure until i reinstall it. I did not think it was going to be neccessary for him to do that but oh well we shall see. Let me know what you guys think. NE and all help would be most appreciated.

Well, it could be timing, either cam or distributor. It could be a clogged fuel filter too. Make sure the butterfly is opening all the way and that there is nothing clogging the intake anywhere. Was it missing or running smmoth but just not revving up?


The cams and pistons are non-interference so they could be set wrong and still run but very poorly. Oh yeah, a clogged exhaust could cause that too, especially the cat. converter. Let us know.

Russ

Is the 7m a non-interference motor in that a piston at TDC wont slap a valve in its complete open position?

Yeah, that's it. The valves won't catch each other nor will they contact the head if the belt breaks. It is a nice feature, but it does mean there is room for a compression improvement either with the head or with high compression pistons. Of course then you will give up that safety margin, but the extra power may be worth it.

Russ

not going over 2500rpm = limp home mode

timing belt jumped... ign timing way off

along those lines more than likely :)

have you checked for vaccum leaks?? try by the head/manifold gasket & injector rubber o-rings. mine was loose by two bolts did the same thing.

Tps bad
 

You should check your TPS. Try cleaning it or replace a new one. if tps is not good, rpm wont go over 2500rpm

So what did you find?


Russ

i have had same problem it will stutter a bit then sit on 2500 the more u accelerate the lower the rpm goes ....... the only way to stop it without replacing n e thing was to turn off the car and re-start i wasnt too shure what solved my problem after i had a full service but my money is on your throttle position sensor ... give it a thorough clean and check your fuel filter.....

A plugged exhaust will cause an engine to not rev past a certain point. I repaired (replaced cats and mufflers) many on the 22R engine from the late 70s and into around 86 Celicas and trucks. Not many supras, but a posibilty.