1969 FJ40 Idles High and Misfires

SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
Hello again everyone!

I finally bolted on the Aisan carb that I got rebuilt and after a lot of tinkering with it trying to get it to run right, I am not sure what I am missing. I can't get it to idle without misfiring pretty regularly and it has some issues starting sometimes. I have tried following threads about adjusting the idle mixture screw until the RPMs no longer increase, and then backing off of the idle, but I cannot move the idle speed adjustment screw out anymore to adjust the idle. The timing is set to factory specs and I have not found any vacuum leaks and tried the cardboard over the mouth of the carb trick and it just put a good suction on the cardboard and died. Any suggestions?

Thanks in advance!
 
P

pithicus

Joined
Nov 25, 2014
Messages
898
Location
Western victoria Australia
Sometimes the butterfly's don't close fully. You can try pushing the linkage towards closed with your fingers to see if it slows the idle.
 
1MOA

1MOA

SILVER Star
Joined
Nov 7, 2017
Messages
1,808
Location
Warrenton VA
Check for leaks as well at the base and intake manifold and vacuum lines. As the posted above said check for free operation as well if that's not it see if whoever rebuilt it can check their work
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
who rebuilt the carb
Mark rebuilt the carb for me. I put it on a few weeks ago and discovered some old gaskets I had for the spacer were causing a vacuum leak so after I got those replaced, it behaves better but is still doing this.
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
Sometimes the butterfly's don't close fully. You can try pushing the linkage towards closed with your fingers to see if it slows the idle.
I noticed sometimes it’s a bit sticky, but the problem persists even when I push it towards closed, the idle just won’t go lower.
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
Check for leaks as well at the base and intake manifold and vacuum lines. As the posted above said check for free operation as well if that's not it see if whoever rebuilt it can check their work
I’ve checked around the base and all the vacuum lines and did discover a small leak, it definitely behaves a bit better now that I have fresher gaskets there, but it still idles high and misfires. I was thinking about setting the timing to 10-13 BTDC in the morning and seeing what happens. I shoulda mentioned I replaced my stock dizzy with a vacuum advance petronix one.
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
A missfire at idle is more likely to be caused by too far advanced. You could try and retard it a bit too.
I’ll give it a shot tomorrow! Whenever I open the throttle it’s sounds great so maybe that’s it
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
I’ll give it a shot tomorrow! Whenever I open the throttle it’s sounds great so maybe that’s it
So after adjusting the timing all over the place, still no luck. The vacuum gauge is just about glued somewhere between 18 and 19 in Hg until it has a misfire.
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
So after giving it some thought, I decided to mess with the choke while it was running to see what would happen. When I close the choke almost all the way, it runs almost perfectly (although the RPMs, the misfire goes away). I then tried to adjust the idle mixture screw some more to see if maybe that was super out of adjustment, but it did not seem to change anything similar to how the choke being closed does. I am guessing that this means that I am getting too way much air and not enough gas, so maybe I have the wrong jets in it? I am at sea level and the carb itself came from Norcal, maybe that's contributing? I'm going to wait for it to cool down and look into that. I also tested the idle solenoid and I heard a good click when I hooked it up with the key in, the truck also died when I disconnected it when it was idling.
 
P

pithicus

Joined
Nov 25, 2014
Messages
898
Location
Western victoria Australia
The fast idle seems strange. It has to be getting air somehow? It should die or at least idle slow when both butterfly's are fully closed. Brake booster leak? PCV valve problem? Butterfly shafts really badly worn?
 
Last edited:
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
The fast idle seems strange. It has to be getting air somehow? It should die or at least idle slow when both butterfly's are fully closed. Brake booster leak? PCV valve problem? Butterfly shafts really badly worn?
My truck doesn't have a brake booster (yet), the body is from 64 while the motor is from 69. I can also forget about the jets idea, the sizes were correct. it running better with the choke on is weird, especially since when I covered the air intake with cardboard it just immediately died. Maybe somehow it's sucking through the secondary?
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
E5BDC01F 2683 4387 BFAA 4420CA374AB5
3FA67AC6 6FC7 44B8 98D6 B1FA5F31947A
6EA67737 DBC1 41C4 BE57 69FDBBABFD94
79EC77DF C06A 4BD9 98CE F244034C45BF
15A461E3 4817 4D5B BBC2 D015F76AC737
 
MDH33

MDH33

Joined
Jul 5, 2005
Messages
1,547
Location
Ames, IA
In the pics, your throttle cable is disconnected, and it's the wrong kind for this carb. The pcv hose is loose, big air leak. What is the big manifold vacuum line connected to (the SAE made in Thailand hose)? I don't see any fuel in the sight glass either. Is this how it's currently set up, or just when you first installed?
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
In the pics, your throttle cable is disconnected, and it's the wrong kind for this carb. The pcv hose is loose, big air leak. What is the big manifold vacuum line connected to (the SAE made in Thailand hose)? I don't see any fuel in the sight glass either. Is this how it's currently set up, or just when you first installed?
It’s just how it’s sitting there at the moment after I’ve been messing with it. The throttle cable isn’t connected because I’ve been trying to mess with the idle and didn’t want it in the way. The bowl is empty because I just checked the jets sizes. The SAE hose is just manifold vacuum that goes to a vacuum gauge inside the cab. I tried to get the right pcv hose from SOR, but the one I was sent was too small so I have this for now. I was pretty sure this is the right linkage for the carb since it’s a July of 71, it looks the same as the one on the SOR carb identification page?

Edit: Sorry, I thought you said linkage, what would the right cable look like?
 
Last edited:
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
So a bit of an update. I guess it is the PCV valve? After taking the PCV hose off the valve and plugging it, it runs much better. I ordered a PCV valve off SOR earlier because it was cheap enough but forgot my motor is an 8/69, so the PCV valve was not compatible. Where I could find the earlier one or how I could possibly clean this one up? Edit: We are going to try putting a reducer in the neck of the metal part of the spacer that the PCV valve hose attaches to and see if that helps. I am also probably going to soak the PCV valve in carb cleaner for a bit later, I'll let y'all know if the reducer thing works.

A42CBCEA B379 42DE ABC3 F32232693C87


B059E900 606B 4ABD BD25 9F3C9DCC3EF8


B8EAE4CF 5123 4AA4 9A4C B128E071F606


CA3B5DBF 5211 4414 92ED 4D8BC3104375
 
Last edited:
graham5david

graham5david

Joined
May 3, 2016
Messages
1,258
Location
odessa, tx
Just suck on that valve. You should hear or feel a valve open and let air through. It's a 1 way valve. It lets air run to the vacuum off the carb plate or intake but not the other way. If you plugged the other side of the hose coming from the engine then get ready for side plate and oil pan leaks. Put the new valve on with new hose and good clamps and see if it fixes your problem. I
 
SlimerP98

SlimerP98

Joined
Jul 2, 2021
Messages
53
Location
California, USA
Just suck on that valve. You should hear or feel a valve open and let air through. It's a 1 way valve. It lets air run to the vacuum off the carb plate or intake but not the other way. If you plugged the other side of the hose coming from the engine then get ready for side plate and oil pan leaks. Put the new valve on with new hose and good clamps and see if it fixes your problem. I
Unfortunately, the valve I have is the wrong style, maybe there’s a way I could get it to work until I find the right one?
 

Similar threads

P
Replies
8
Views
426
Peddyk
P
Shyrock
Replies
4
Views
257
MDH33
MDH33
turbodrabbit
Replies
11
Views
598
cbmontgo
cbmontgo

Users who are viewing this thread

Top Bottom