i have a 91 ef hatch with a jdm dohc zc swap that i have been busting my *** off to finish up and i need one last problem solved...
My car hesitates/ stumbles when i press the gas too quick but when i slowly open the throttle it revs up just fine. Before ot would stall with full throttle but i replaced vacuum lines and that fixed the stalling. I replaced plugs, injector seals (was leaking a good amount through injector 1)cleaned out throttle body and did a lot of minor tune ups but this hesitation is bugging me. I was looking to see if maybe i had another vacuum leak because when iwould rev the car it would drop to really low rpms. When i was listening for a whistle on the hoses my hand touched the throttle (like barely poked it) and the idle dropped low. I noticed that and then lightly touched it (as if to try to open the throttle) and idle got higher. The car stumbles when the throttle is opened to quick but when its opened slowly it will rev just fine... Could the cable be loose/ not adjusted right? Throttles sticking? any help would be greatly appreciated thanks everyone.

 

Any cels? What ecu? You can check for vacuum leaks by spraying brake cleaner around hoses and intake manifold . Doesn't really sound like a throttle cable problem

 

Does the throttle move smoothly when you twist it by hand? When was the last time you changed the fuel filter?

 

i would look at fuel flow/pressure. get your helm manual and run the fuel pump flow test to make sure you are getting enough fuel to the rail.

 

Sounds like you might be getting to much air at full throttle. ^^^^^ check te above. Fuel pressure and such

 

the throttle stuck when i first got it but i sprayed wd- 40 and cleaned up the gunk it had so now its not as bad.. I did notice the little nut that holds the assembly together was loose tho... The fuel filter has yet to be replaced im going to replace it once i get my breaker bar back from my buddy. (the filters bolts are on really tight so might have been a while since it was changed before i got the car) i'll probably get a new gas cap too the seal looks worn. Hopefully i can do both this weekend and then check fuel pressure

 

oh forgot to mention the throttle doesnt feel that smooth when i open it by hand. Its not too bad but doesnt feel as smooth as it should

 

How does the mechanical timing look?

 

Lube the crap out of it. I would still change the fuel filter- for piece of mind if nothing else.

 

DOHC ZC's aren't the easiest to set the mechanical timing, and what's right doesn't look 'right' unless you're following a manual.

I'd also check the voltages at your TPS (on the back of the throttle body), see if you have any flat spots.