My truck is misfiring..help!

[Cue-Ball]

Sorry if my previous message came across as harsh. That was not the intent. My point is that you should make sure all of the basics are taken care of before you start messing with the carb. Tuning carburetors can be very difficult even if you know what you're doing and have all the right equipment. If you don't know what you're doing and don't have the right equipment, tuning one correctly is nearly impossible.

Not sure where in SD you are, but hopefully there's another board member close enough that can help you set your timing and check some other stuff. It's hard to teach someone how to do these things via message board, and you still need tools like a timing light.

[ivorton74]

its kool man..i know ur tryn to help. i did have my mechanic look at it and what he did was adjust my dwell angle and the carb. but it got worse. i would take it back to him but he is kinda far way and my truck doesnt have the best gas mileage. plus the way its running now i probably wont make it to his shop. I have been calling him and telling him whats going on and he told what to check. My uncles also know alot about these trucks and they're tryin to help me too. but I am checking everything that i think would cause it. hopefully i'll find the culprit soon.

[ivorton74]

heres a vid i shot today of it driving. notice how it stumbles when i accelerate...link is below

http://youtu.be/HfhttVTf-ec

[ivorton74]

so today i tried starting my truck...it fired up at first but died out and now it wont start again. now im thinking it is my fuel pump.

[terryj]

You said your running a Q-jet, there really tricky to adjust if your not sure of what your doing. You can create more problems than you fix. My engine was giving me problems like this a while back and it was the Q-jet causing it. Instead of rebuilding the carb I replaced it with an Edelbrock 1406, man what a difference, it idles better, better throttle response and better fuel mileage.

[beamn7]

Sounds fuel related to me but might be worth plugging or pinching off the vaccum line to the brake booster to verify that is not the culprit of a large vaccum leak. Seen that more than once........

[terryj]

Originally Posted by beamn7

Sounds fuel related to me but might be worth plugging or pinching off the vaccum line to the brake booster to verify that is not the culprit of a large vaccum leak. Seen that more than once........

I was thinking that same thing also, and I would suggest looking at the vacuum line connecting the PCV, the way there installed under the front of the carb you can have a problem and never see it. It may be worth looking at.

[ivorton74]

update...i had my uncle look at it and turns out one of the spray nozzles in the carb was spraying out way too much gas into the carb.it was almost like turning on a water faucet at full blast. so he adjusted the carb and it ran much better but still misfires at higher speeds(from 45 mph and up). my uncle insists that its my vacuum advance cuz he said he had an old mercury that did the same thing my truck's doing and he changed his vac advance and it stopped misfiring. so im gonna try changing it out and see what happens. im still gonna get my carb rebuilt.

[rs72z]

Originally Posted by ivorton74

update...i had my uncle look at it and turns out one of the spray nozzles in the carb was spraying out way too much gas into the carb.it was almost like turning on a water faucet at full blast. so he adjusted the carb and it ran much better but still misfires at higher speeds(from 45 mph and up). my uncle insists that its my vacuum advance cuz he said he had an old mercury that did the same thing my truck's doing and he changed his vac advance and it stopped misfiring. so im gonna try changing it out and see what happens. im still gonna get my carb rebuilt.

You can replace the advance but i seriously doubt it will stop your missing. Sounds like a good starting place would be to have someone that KNOW'S how to rebuild your qjet.

[Goldfinger]

First off get a loaner timing gun and get the timing correct. If you haven't already try a fuel pump. I've had vacuum leaks almost everywhere. check the egr, carb mounting, and lines for cracked or damaged lines. adjust the carb to about 13:1 fuel ratio. replace foul plugs and gap them correctly.

[ivorton74]

today i decided to take it for a run to town which is about 8-10 miles away from my house. i drove at 45mph all the way and drove thru town. it ran really nice and smooth. but on the way back its strted bogging out again. i turned on the street to my house and stopped then i punched the gas about half way. it sputtered for about 5 secs then it ran down the rest of the way really smooth. im just stumped..its runs good when it wants to...other times its just straight up buggin. im on my way to my uncles house to check the gas flow from the fuel pump.
@goldfinger...i changed the plugs, carb base gasket along with fuel filter,points and condenser. cap and rotor are good. ill try and get a timing light and vacuum tester and check that stuff out.

[Oilbrnr]

my .02 - coil

[ivorton74]

well i ruled out the fuel pump...turns out it pumping fuel to the carb as it should..has good pressure. my other uncle showed and suggested i hook up the egr hose to the carb(egr was disconnected) and it started running a little better. ill have to give it another test drive and see how she drives.

[irishman999]

Do you have your PCV valve hooked up?

[ivorton74]

yep the pcv lines are all hooked up. i took it for a test drive and its drives pretty good for now. maybe it was the egr the whole time. ill drive it some more and see if it continues to run good. i floored it earlier and it didnt misfire or nothing at all.

[irishman999]

Someone will probably argue this but I time my truck by ear. I have a timing but the last time I adjusted the timing it was by ear. You can get it well in the ballpark of where it needs to be without a timing light.

As far as the carb... I like my Q-jet but ended up with a eddy 1406 and its proving to be a great unit so far. In a 26 year old full size 4x4 I am getting 16mpg out of the truck and still have a little room to lean it out.

[ivorton74]

i wanna get a holley street avenger 570 carb. i heard they work pretty good.

[motornut]

i'd say check the vac advance but your not using it
if mine sticks,makes it stumble sometimes
but clearing out rusty crud between the pump and the carb made a difference too
(remove and clean out the gas line)
figured the crud pushed up to the carb and wasn't getting caught in the filter
but i'm sure it was blocking it up

hows the choke working

[ivorton74]

i've had enough man. im taking it to the shop to have it checked out. i tried everything i could. if i had more tools like a timing light etc. i would check more stuff. im taking it tomorrow evening. im gonna have it converted to hei while its there. hopefully everything will go well.

[ivorton74]

update...trucks been converted to hei. timing and carb was adjusted and the truck runs way better than ever b4. i quite pleased with how its running. has lots of power now. cant wait to get headers.oh and i cleaned up the carb today. looks much more presentable.