[seanzook06]

I have a problem with the g13ba in my 93 sj70. every time I start it up it takes multiple attempts, and when it does start it immediately revs to 3500rpm. more recently everytime it went straight to 6500rpm, then when driving it seems to calm down a bit, but revs back to 6500rpm when the clutch is pushed in. after about five minutes of extremely high revs it seemed to calm down and rev normally. the only thing I could diagnose after driving was exessive heat near the exhaust manifold. my thoughts is it could be either an automatic choke problem, or some kind of blockage in the exhaust manifold. the zook is my daily drive so some help would really be appreciated.

[fordem]

There's no way an exhaust blockage will cause an engine to rev to 3500 or 6500 rpm, if anything it's going to restrict the vehicles ability to rev freely, the same goes for a choke problem - the only way an engine is going to rev that high is for the throttle to be open and damn near full open.

I'm not familiar with the SJ70, but a 93 G13BA is most likely a carbed engine, possibly a double barreled Aisin - the secondary throttle plate could be binding.

[seanzook06]

I am fairly sure it is a double barrel Aisin. If the throttle plate was binding, wouldn't there be restricted movement or stuck accelerator pedal

[Gwagensteve]

Not necessarily. Do you pump the accelerator before starting?

[fordem]

Please note I suggested the secondary throttle plate might be binding - on the Aisins I've seen, the secondary throttle plate is vacuum operated - I've seen them bind to the point where I've had to slip a long screwdriver in the bore and push them closed to bring the idle down to where the car could be driven safely.

If the primary were binding, you probably wouldn't notice the difference in the accelerator pedal - you're pushing against a spring, the throttle will open but may not close, the cable would just be loose.

I'm just sharing what I've experienced in the past on my own vehicles.

[seanzook06]

From the sound of it, my secondary throttle plate is the issue, aside from unbinding it, is there a way to guarantee it doesn't happen again

[fordem]

That would depend on what's causing it to bind, which is usually a build up of dirt & grime on the linkages - keeping them clean and lubricated would be the solution if that is what your problem is. Just be aware that dust sticks to lubricants so use them sparingly.

[seanzook06]

Thanks for your help guys, it was the secondary plate that was stuck. All fixed now, car starts, idles and revs normally now

[Gwagensteve]

Ha, I was 1/2 way through typing a response and got distracted yesterday afternoon and now I see you have it sorted.

Cool outcome.