Thread: '91 SE-R - Engine Wants To Take Off

I finally have the new motor firing up on all four cylinders! However, I have a new problem - it wants to rev right up the moment it gets going. I don't know exactly how high it wants to rev because I don't want a cold engine 'potentially' hitting the rev limiter. The tachometer isn't getting signal either, or it is broken, so I don't know where it's getting to before I shut it down.

(On the upside, it sounds excellent when it fires up!)

-I tried disconnecting the MAF sensor and it made no difference
-The throttle isn't moving when it revs up, so it could very well be an air leak after the throttle, to my knowledge
-The intake manifold was visually in excellent condition - better than the outgoing engine. Cannot completely rule out a cracked intake manifold, but seems unlikely.
-Tachometer is either broken or not getting signal, so I cannot watch the RPMs climb on the gauge.

It seems to most likely be an air leak after the throttle body, but I need to decide where to look first. Are there any common issues related to this, even related to "New to SR20" folks hooking up a line incorrectly? Could the MAF sensor still be the issue?

Is the cable stuck?

The throttle is actually closed and does not move while the engine is revving up, so that has led me to the ideas about a post-throttle intake or vacuum leak.

make sure to set timing/idle only in timing mode. Make sure tps is at .38v closed and 4v WOT. after that is sorted out spray the vac lines with carb cleaner and listen for dips/raises in the idle. our cars are very fickle with vac leaks. If you are having trouble in timing mode keeping idle steady could be your CAS in the distributor,but since this is just now running its probably not in time or vac leak or tps adjustment.

huge vacuum leak or idle adjust screw on tb moved

Ironically, I am very glad to hear that because it gives me something to go on! I am going to look into compressed air / smoke testing the intake system for leaks first, and if nothing there I will look into testing for vacuum leaks.

I am leaning toward a large intake leak at this point simply because it may very well rev all the way to the limiter if I were to let it.

did you put the fresh air to iacv line pre throttle body? the big 3/4" hose.

I have both of the large hoses (that attach via metal fittings to the intake pre-thottle body) attached, however I can take a look next time I'm at the car as perhaps it detached from the IACV side.

This happened to me once.

Turns out the O-ring from the MAF housing became lodged in the throttle plate and upon start up revved all to 7500rpms until I shut it off the motor and discovered the problem. Take off your intake tube and check your throttle plate, worth a shot.

Definitely a good thing to remember, but in this case I've confirmed that the throttle plate is not moving and is in the closed position while the engine is revving up.