fadeface

I would love some feedback on the issue I'm having.

At full throttle the truck stumbles almost like it's getting flooded/not enough fuel. I have been through the entire ignitions system as a result of a separate issue so the distributor has been replaced along with plugs, wires, cap, and button. The coil tests perfectly and I'm guessing it's not the igniter as I am still getting spark. On the fuel side I've replaced the fuel filter, all vacuum lines, and carb. The carb idle mixture is set according to FSM. I spent a few hours today setting my float because in the new carb is was not filling the glass halfway. I now have it just a little over halfway up the glass but still within spec according to the FSM. My choke works fantastically and tests perfect. The stumbling is most apparent under a load, as in trying to accelerate, although sometimes while not under a load if I give it full throttle it will pretty much sit at 700-800 rpm while sounding like it's trying to die. I've checked and rechecked for vacuum leaks hoping that I was just a failure at finding them on my previous attemps. I've been over it with a very good diagram checking to make sure that everything is connected. If I can think of any other info that I forgot I'll bump it later.

oh btw the truck is

87 22r carbed
4spd manual

Any input would be greatly appreciated as I've been searching this forum and trekkar for days to no avail.

swampfox

Is the carb that you installed new,used or rebuilt? Did the other carb do the same thing?

fadeface

the carb I installed was new and no the old one did not do the same thing but something similar which I actually found was a problem with the drivers side choke. And the choke on the new one works perfectly.

swampfox

It sounds like the power valve may not be working right or the fuel pump might be weak.The power valve is suppose to add fuel on wot.

fadeface

alrighty well I can test the fuel pump I'll just get an in line gauge for that but is there any way to test the power valve or do I just throw another one in and would that be in the rebuild kit that I have.

swampfox

If you have a carb kit it should have a diagram to show the location of the pv. About all you can do is check it for binding or trash in the passages. If the fuel pump has been replaced make sure the spacer was installed between the pump and head.

fadeface

well unfortunately it's dark here and I don't have a garage to work on it in but tomorrow I'ma check that out and see if either is at fault I do have a good diagram for the carb, so it shouldn't be hard to find. I appreciate all the input I just pray that my problem is one of these as I've replaced/tuned/cleaned almost everything I can think of under that hood lol.

86bedlesstoy

Any luck fadeface?

xxxtreme22r

am I understanding you in that it stumbles if you give it full throttle with the engine at 700-800 rpm?

swampfox

If it has trouble starting with the choke open, it might have accelerator pump problem. which would make more sense on the idle to wot part of the problem. But i don't know if it could cause a problem driving on the top in.

fadeface

xxxtreme22r- at any rpm range it stumbles at WOT, and swampfox it does not have trouble starting at all while choke is on or off. I've checked the fuel pump and PV fuel pump is puting out constant 6 psi and when my engine is reving hits 7 so I'm guessing it's good. the power valve appears to be functioning correctly and has no trash in it, I'm almost thinking that I may have to go back to the timing. also I've been messing with the idle mixture I tried factory spec and I haven't been able to feel a whole lot of difference between 2.5 turns to 3.5 turns but anything outside that range and the truck runs like total crap. also in the book it says to adjust until you achieve max rpm and I'm not getting any rpm change when adjusting it so I'm not really sure if I'm even close on that. but that's where I'm at today lol thanks a lot for all the advice so far keep it coming

swampfox

Was the spark blue or yellow ? You can have spark but it could be weak.

fadeface

spark is blue thank god lol

swampfox

Have put a timing light on it ,to see if it is getting a timing advance on acceleration? I'm running out of bright ideas. Also might check to see if the secondaries are opening smoothly. They could be sticking or binding.

fadeface

ok so a quick update the timing was off just a touch and the carb was out of adjustment but again just a touch I'm pretty sure I've got all that kickin good now though as my fuel milage is through the roof. it still stumbles at full throttle. I am getting 30-32 mpg city right now though lol. Haven't been out on the highway for an extended period of time to test that mileage but I would love to fix the stumble gonna check my valve tolerances this weekend and hope that the last time I adjusted them I messed one or two up lol. wish me luck guys.

xxxtreme22r

if your not getting any type of rpm change when adjusting the idle mixture screw, then it ususally means you have a vacuum leak somewhere.