Got a problem with the rex here, if I let off the gas above 4000rpm then hit the gas again, it will have like no power, feels like the engine is suffocating. Its really annoying when I shift and then when i hit the next gear and hit the gas, i have no power until it goes below 4000 rpm, then i can hit the gas and have normal power until redline. What causes this and how do i fix it? I was thinking maybe it was the secondaries on the carburator not opening or something. Any ideas?

 

the secondaries open according to pressure they aint set at a certain rpm.

so just taking a big guess here, maybe you have some vacume lines that are cracked that run to the the thingy that opens the secondaries? and its releasing the pressure to fast and makeing em close b4 their time..

just a guess

 

the car is one annoying mass of vacuum lines, hehe, I'll see what i can figure out.

 

Could it be your accelerator pump isn't keeping up, or how about the gas level in the carb is too low??(float setting) Or just not enough gas flow (pump, filter,)??
The vacumn for the secondaries is all internal to the carb.

 

Yeah, but the mechanisim could still be sticking...Hence having to let off and re-apply throttle to break them loose. You could try spraying all the linkages with carb cleaner or some kinda lubricant to try and loosen it all up. The secondary vacuum linkage is on the "front" of the carb. As you stand at the front of the car facing the engine, the secondary vacuum linkage will be on the side closest to you. If your standing on the passenger side of the car looking at the engine, you will see a square housing with 4 screws. Thats the vaccum diaphram. Coming out the bottom of that is the linkage that mives the secondary butterflies. Try lubing/cleaning that. If that makes sense...

~T.J.

 

Nah, aint secondaries. If you had a vacuum leak, youd have a rough or no idle. The fact that after you let off the gas and wait, then hammer it, then it pulls fine to redline tells me you have a fuel starvation problem. Possbly clogged fuel filter, weak pump, something like that.

 

Ok, heres another option. Just convert the carb to mechanical secondaries if you think that them sticking may be part of your problem. Sean (82Transam) and I came up with this little write up a while ago. Its fairly easy to do, and doesnt take that long. Heres a link: http://slegers.com/sites/sean/mechsec.htm

Or, if you dont want to do that, as I said earlier, you could simply just clean and lube the linkages. I came up with a few pictures that may help describe what Im talking about...Oh, and while youre in there, spray some carb cleaner down into the carb, but aim it at where the butterly shafts pivot at down in there, just in case some nasty stuff has built up in there too.

Heres the vacuum box I was talking about.


Heres the side view of the box and the secondary linkage thats more than likely just as nasty and gummed up as mine was (the cover for my secondary vacuum box was off in this picture).


Before you can get to that, you have to remove a little switch do-dad so you can more easily get in there. Well, I guess you dont have to, but its only two bolts and makes it easier. Be sure to get it back in right though .


So there you have it. Thats all the information I have to give about your problem concerning the secondaries. Another thought I have is to check your fuel filter. Better yet, just replace it. They need to be replaced fairly frequently anyway, might as well do it now while youre "checking it". Personally, I think its too hard to tell if its good or not by just looking at it and trying to judge the color. Hell, youre already in there and it only cost like $3 for a new one, just change it . And last but not least, it could be that your vacuum diaphram is leaking. This could explain why it will open them revving up past 4K, but if you let off and then hit it again above 4K, it cant hold enough vacuum to open them again? I dont really know, thats just kinda out there. Anyway, I hope all this helps ya out .

~T.J.

 

a little switch do-dad = TPS (Throttle Position Sensor)

 

Really? Cool . I wonder if I could use something like that to trigger a Zex N20 computer as long as I had the right kinda fuel pump and stuff...Those Zex kits look snazy as hell, and Ive heard good things about them too . I wouldnt mind trying one of those if I had a FI car.

~T.J.

 

If I convert the carb to mechanical secondaries the choke will still working properly...........

 

MEch secondaries wont affect the choke.

 

Thanks........new on this.

 

If something was just sticking, why would it always have the problem at exactly 4000 rpm every single time?

 

Cause thats approxomatly when they try to move because of the vacuum control...At 4K RPMs the engine builds enough vacuum to open the secondaries. Otherwise, they would never open. So unless the car is over 4K RPMs, the secondaries will never open, regardless of how far you press the pedal. So like at 2K RPMs in 4th gear and you just all out floor it, the secondaries wont open until the engine "needs" the extra help around 4K RPMs .

~T.J.