Setting timing is the second to last step.
Do the above then:
1. Set timing
2. Adjust idle speed one last time
3. Done
Do the above then:
1. Set timing
2. Adjust idle speed one last time
3. Done
Carb tuning and frustration...
- Thread starter gregnash
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gregnash
Anal Retentive Analyst
- Thread starter
- #62
Ok so to go on another thread post by @LAMBCRUSHER (I believe).
I should....
While truck is OFF...
- set idle mix screw to desired mixture (3 turns out to start say)
- set idle speed screw so that the screw is just touching the plate
While truck is ON..
- set idle speed to desired idle speed
- set timing to new spot (so doing this based on the FSM, this includes disconnecting BOTH vac advance ports) at 7* (the bb)
- THEN adjust the idle speed one last time?
CuCruiser
SILVER Star
Well the truck needs to be at temp, so I would warm it up good first.
Then I don't know if you are meaning 'desired mixture' as a choice, but really it needs to be adjusted 'on the fly' in other words you don't just pick a number, you tweak until it's right.
The lean drop method goes like this:
Set idle speed to 690
Adjust idle mixture in or out to achieve highest idle speed or vacuum (you are looking for the sweet spot)
reset speed to 690
adjust idle mixture again till highest speed/vacuum
...and over and over until you feel you have a happy engine (maybe 3 times total, let's not get crazy)
set idle to 650
set fast idle to 1800
Getting to the idle mix screw with the air cleaner on is the major hurdle. I put on a thin cotton glove and use a stubby screwdriver. I put the tach/dwell meter on the air cleaner right in front of me and turn the mix screw without taking my eye off the tach and listen to the quality of the idle and take my time. With the glove it's not so bulky that you can't feel or fit (it's tight don't get me wrong) and you don't get singed everytime you twitch and loose the slot in the screw.
Don't get hung up on where the screws are. It doesn't matter turns etc. What matters is the idle quality. Forget how many turns you are in or out. I'm kinda new at this but this has worked perfectly for me every time I've done it.
I would guess that if you do this and you still have a rough idle at 650-690 there must be a vacuum leak.
Hope I'm not telling you stuff you already know. HTH! Good luck!
Then I don't know if you are meaning 'desired mixture' as a choice, but really it needs to be adjusted 'on the fly' in other words you don't just pick a number, you tweak until it's right.
The lean drop method goes like this:
Set idle speed to 690
Adjust idle mixture in or out to achieve highest idle speed or vacuum (you are looking for the sweet spot)
reset speed to 690
adjust idle mixture again till highest speed/vacuum
...and over and over until you feel you have a happy engine (maybe 3 times total, let's not get crazy)
set idle to 650
set fast idle to 1800
Getting to the idle mix screw with the air cleaner on is the major hurdle. I put on a thin cotton glove and use a stubby screwdriver. I put the tach/dwell meter on the air cleaner right in front of me and turn the mix screw without taking my eye off the tach and listen to the quality of the idle and take my time. With the glove it's not so bulky that you can't feel or fit (it's tight don't get me wrong) and you don't get singed everytime you twitch and loose the slot in the screw.
Don't get hung up on where the screws are. It doesn't matter turns etc. What matters is the idle quality. Forget how many turns you are in or out. I'm kinda new at this but this has worked perfectly for me every time I've done it.
I would guess that if you do this and you still have a rough idle at 650-690 there must be a vacuum leak.
Hope I'm not telling you stuff you already know. HTH! Good luck!
I poked a hole in a big fluffy car wash sponge (dry of course) and pushed it over the carb top to replicate the air cleaner during tuning. That worked well.
gregnash
Anal Retentive Analyst
- Thread starter
- #65
You talking a sponge like this??? Chemical Guys MIC_495 - Ultimate Chenille Microfiber Two Sided Wash Sponge, Blue
That's actually not a bad idea.
And @CuCruiser that is all stuff that I have been doing and cant seem to get her to STAY idling at 650rpm. Like right now, the last set of adjustments that I did last week I was able to stay down at 650rpm after multiple adjustments and what not. Then I go for a ride to see how she is doing, making sure that there is no backfire on loaded deceleration (coming down a hill in third while the engine does the braking vs. the brake) and when I get to a spot where I am idling at a stop sign or light then the idle sticks at 1k.
Now I can pump the gas one quick pump and it will bring it back down under 1k (new development over last couple days) and occasionally come down to 650rpm (where the screw is on the tach is about 650rpm from my previous measurements).
And also, I thought from previous readings that JimC had said with a desmogged vehicle that 3 turns out on the mix screw is a good starting point. The problem that I seem to be running into is that when I do attempt to get the idle down to 650rpm the idle is not healthy because it has become that fuel mix screw has been turned in far enough that it seems to be not supplying enough fuel. So the idle becomes rough. Truck is always up to operating temp, usually go for a run right before I start the adjustments or I have just gotten home from work so it has been warmed up with my normal 15ish minute commute home.
CuCruiser
SILVER Star
I figured you had all that covered but you don't know till you get it out there. But you def want something to replicate the resistance of the air filter.
If you can get a good idle at 650 but can't get it to 'reset' to 650 reliably then that points to a hangup in the linkages, agree?
Maybe if you can replicate that, i.e. get it to hang up, then feel the linkages for the link where it's tight on one side and loose on the other? Or get someone in the cab to run the throttle and watch the linkages for 'catches' or places where the motion is not smooth. IDK if that would actually work. The more experienced members would probably have a better idea of where in the throttle linkages tends to hang up commonly.
That would be frustrating. Grr... and bad weather doesn't help.
But just think of the feeling you'll get when you win.
If you can get a good idle at 650 but can't get it to 'reset' to 650 reliably then that points to a hangup in the linkages, agree?
Maybe if you can replicate that, i.e. get it to hang up, then feel the linkages for the link where it's tight on one side and loose on the other? Or get someone in the cab to run the throttle and watch the linkages for 'catches' or places where the motion is not smooth. IDK if that would actually work. The more experienced members would probably have a better idea of where in the throttle linkages tends to hang up commonly.
That would be frustrating. Grr... and bad weather doesn't help.
But just think of the feeling you'll get when you win.
gregnash
Anal Retentive Analyst
- Thread starter
- #68
LOL no doubt... Yeah that is part of the reason that I am thinking I need to pull the carb to ensure that nothing is binding that I can see.
And the ability to pump the gas to get the idle to somewhat "reset" may be pointing to what @NookShneer was talking about with needing the helper spring.
And the ability to pump the gas to get the idle to somewhat "reset" may be pointing to what @NookShneer was talking about with needing the helper spring.
DFXR
SILVER Star
My PO drilled a 1/2" hole straight through the top and bottom of the aircleaner housing, directly above the idle mix screw. Then put a short piece of 1/2" OD rubber hose through it to "seal" the hole, but allow pass thru for a long screwdriver to access the mix screw. It took me a while to figure out that's what it was for.
I wouldn't recommend it over the sponge method or contortions with a short stubby... but it kinda works.
I wouldn't recommend it over the sponge method or contortions with a short stubby... but it kinda works.
CuCruiser
SILVER Star
Springs are cheaper than a trollhole, for sure. Sounds like a plan.
Funny about the hole thru the air cleaner. Clever I guess in a redneck engineering kinda way!
Funny about the hole thru the air cleaner. Clever I guess in a redneck engineering kinda way!
Next time is hangs at 1000 rpm, instead of pumping the gas pedal to try to get the idle to drop, hook your toe under the gas pedal and lift it. If the idle drops, that seems like a linkage issue
This is the, "That's not an answer to the fxxxing question, a******", answer.
Get the PFISYS FI without the HEI dizzy and use the Toyota dizzy and an external module and coil. No speed sensor or anything special, and my truck runs so good I'm pissed off as hell. Deep down I needed cornered into a 5.3 swap to overcome my old age laziness, but the gutless brick is doing fine past 4000 and it wont blow. I had it out yesterday, broke thru some ice into a mud hole, and hammered on it relentlessly, and it never ran so smooth. 35's with 4.88's and I'm getting 13mpg combined and it starts on the fist tap of the key no matter how cold.
God damn FI.
Get the PFISYS FI without the HEI dizzy and use the Toyota dizzy and an external module and coil. No speed sensor or anything special, and my truck runs so good I'm pissed off as hell. Deep down I needed cornered into a 5.3 swap to overcome my old age laziness, but the gutless brick is doing fine past 4000 and it wont blow. I had it out yesterday, broke thru some ice into a mud hole, and hammered on it relentlessly, and it never ran so smooth. 35's with 4.88's and I'm getting 13mpg combined and it starts on the fist tap of the key no matter how cold.
God damn FI.
gregnash
Anal Retentive Analyst
- Thread starter
- #73
Pics or it didn't happen!!
Done that and I am not having that issue anymore.. I was originally having that issue WAAAAYYYY back when I first replaced everything but now I have found that the screw was adjusted far enough out that it was not actually contacting the idle plate for the linkage.
How I am finding that it is "just touching" is that I adjust the screw in until I see it physically start moving the linkage AND hear and idle change then back it out about 1 full turn.
It is supposed to warm up at the end of this week so I think I am going to grab my old gopro and strap it to my head and go through all this making a little video to see what happens. Would love to have this resolved soon as we have a club run on Saturday.
I'll be rivited, to the screen like I was waiting for the "Dallas" Who Shot JR, season opener.
This is the tool I use so I can do lean drop with the air filter housing on. Flat head bit with a vacuum cap for grip.
Where's that damn vid!
NeverGiveUpYota
Dare me.
Brilliant. I was pondering a right angle bent thing... some reason a paint can opener always comes to mind but I have one and it def doesn't fit the bill. That looks perfect. Thanks for the share!
NeverGiveUpYota
Dare me.
he said 'end of week.'
gregnash
Anal Retentive Analyst
- Thread starter
- #80
There was someone on here that had a similar situation. Their air cleaner had two plugs in it that they couldn't figure out why. Then one day it randomly occurred to them that the plugs were lined up with the fuel mix screw. Basically you remove the plugs and the screwdriver goes through. Replace the plugs and all is good.
Gonna have to hit harborfreight for some new toys soon.
