Sanity check before adjusting idle & mixture (1 Viewer)

[albert110]

Hi all, been a while since I posted. Moved overseas for a few years and didn't want to risk putting my TLC on boat. The wagon sat in a climate controlled warehouse, and I drove it all last spring and put it away for the summer (Texas heat + no AC). I'm having an issue with idle and mixture but I wanted to poll the group before I try to adjust the carb because there's a chance it's something else.
I took the car out last week, changed the oil, put some fuel treatment in the tank along with fresh fuel. I started the car and quickly ran into the familiar hesitation/stumbling issue so many of us have had. The engine would run fine when cold but the hesitation would start once it got warm, which ultimately led to the car not being able to idle.
To rule out the low hanging fruit I replaced the fuel filter, and then put in a new ignition coil. Those two things fixed about 80-90% of the problem, no more hesitation, and the idle is 'mostly' back to normal. I have noticed that the idle is pretty low, I'd guess a little above 400rpm, and it smells like it's running rich. It will cut out every once in a while, I'm guessing due to idle speed.
Another detail I have to admit is that I have the EGR installed but am bypassing with the golf tee trick, and I have not recurved the dizzy, which I really ought to do...

My question is whether there's anything else I should check before I adjust the carb? What I don't want to do is adjust the mixture and idle speed settings as a way of fixing the symptom of a different issue. The idle speed and mixture did not seem to be a problem before I swapped out the coil (maybe it ran a little bit rich, but not enough to concern me). Or should I bite the bullet and get the dizzy sorted before I try to mess with anything else? I've never had an issue with detonation or pinging as far as I can tell, if that helps.
Thanks.

 

[CruiserTrash]

Lots to do before twiddling the carb screws:

Put a vac gauge on the 3x nipple coming off the intake manifold (between the carb and power steering pump). In Texas you should see 20-22inHg. If not start hunting down vacuum leaks. Replacing every single vac hose in a smogged engine only costs about $40 and is cheap insurance - cheaper if you're "desmogged" (which could also be a reason for issues).

Set the timing.

Set the valve lash.

The truck running ok when cold and then stumbling when warm really makes me think the issue is related to one of the vacuum widgets that responds to temperature - there's two of them stuck into the thermostat housing. One controls the EGR and keeps it OFF when the engine is cold. So when the engine warms up and that widget enables the EGR to function ... perhaps that's worth looking into. The other temp-controlled systems are kind of a pair: HAI and HIC. Aside from the vac valve in the thermostat housing for those, there's a other valves going on for those systems and they're usually bad. PArticularly the HAI valve, I' have yet to find one that works properly, so most 2Fs out there are running around sucking in hot air. Get the Emissions FSM from the Resources section here on Mud and test all of it.

How's the PCV valve? If you pull it out and give it a shake can you hear the stopper? The amount of crankcase pressure would vary with temp and the PCV system can have vac leaks.

The manifold bolts could be a bit loose when cold, and fine when warm. Adjust them to 35ft-lb when cold (the smaller 14mm bolts get less torque, check the manual). I can be done without removing the carb if you get tricky with it, use lots of various sized socket extensions and wobbles. This would probably cause the opposite issue - running rough when cold, but fine when warm - but heck, check it anyway.

Once you know all of that is dialed in, do the lean drop method of carb tuning. It's in the manual. If you try to adjust the carb without having confidence that everything else is ok, you'll be trying to hit a fuzzy moving target. FWIW I run with the EGR system removed and am still using the original dizzy. I know I should have it recurved but it's not causing a stumbling issue. Also do a search here on Mud for "classic stumbling issue", there's quite a few good threads that have found different causes. Ok, after all that I'll say it's pretty safe to adjust that idle speed screw to bring the idle rpm up to the 600-750 range IF you're going to ferret out the issue and lean drop the carb later. The idle screw can get you by for now.

 

[albert110]

This is tremendously helpful @CruiserTrash I'll follow this sequence and see what I uncover. I appreciate the thoughtful list. I did search around for stumbling/idle/hesitation issues but since I haven't ever tried to sort an issue like this I don't have a great sense of how to approach something like this sequentially... And I don't want to throw new parts at the issue until it goes away. I did replace all the vacuum lines with silicone hose a few years ago, but did it without actually testing for functionality, will definitely start there and report back.

 

[OSS]

The factory unmolested carburetor has a press fit cap sealing off the idle mixture screw. It’s there to prevent tampering. The idle mixture is not something that Toyota recommended adjusting.

 

[ToyotaMatt]

This is tremendously helpful @CruiserTrash I'll follow this sequence and see what I uncover. I appreciate the thoughtful list. I did search around for stumbling/idle/hesitation issues but since I haven't ever tried to sort an issue like this I don't have a great sense of how to approach something like this sequentially... And I don't want to throw new parts at the issue until it goes away. I did replace all the vacuum lines with silicone hose a few years ago, but did it without actually testing for functionality, will definitely start there and report back.

what year and modle Land Cruiser do you have by chance ?

 

[albert110]

what year and modle Land Cruiser do you have by chance ?

It's an '86 FJ60 with only 330k miles on it. I'll find some pics and post them later.

 

[ToyotaMatt]

It's an '86 FJ60 with only 330k miles on it. I'll find some pics and post them later.

do you ?

or ..........

do you not have the aluminum factory service plug / cap still originally installed that @CruiserTrash & @OSS speak about above ?


i know who can make short work of this 2F 21100-6 # # # # .....

21271A	PLUG, IDLE LIMIT
21673-61140

@Spike Strip

​

.

​

 

[4runner2FJ60]

Otramm lean drop method. THIS may help you?

 

[albert110]

Whelp, looks like I have some hunting to do. I verified the cap is still on the mixture screw, but before I worry about anything relating to the mixture I'll need to figure out why I'm only getting about 7 mmHg at the intake manifold. I'm hoping that given how big this leak must be that it'll be easy to track down, will report back when I find something.

 

[Pighead]

Have you tried just advancing your timing? Might bring your idle and vacuum up

 

[albert110]

Have you tried just advancing your timing? Might bring your idle and vacuum up

Haven't tried that just yet, I just want to do a quick once over and make sure there aren't any glaring vacuum leaks and whatnot and then I'll go to timing. I have a gun and the FSM so I should be good to go. Not sure how I should test the dwell angle or if that's something I need to consider at this point. This has already been a really good opportunity to methodically rule things out instead of throwing random parts at the problem. maybe an old dog can learn a trick or two after all

 

[Pighead]

Not sure how I should test the dwell angle or if that's something I need to consider at this point.

Let's not worry about dwell angles. A timing light is good though. The FSM might say to set timing at 7* but your engine might like a little more. Give it a try, don't be shy. Turn the dizzy body just a tad Counterclockwise and listen and see what happens .

 

[albert110]

Closing this thread out hoping it might help someone in the future. @Pighead thank you for your sage advice, a small timing adjustment was all I needed to get her running like a top. So, one more data point for the persistent lurching/hesitation/idle issue, check the coil, fuel filter, and timing before digging much deeper. Thanks everyone!

 

[albert110]

Ok, opening this thread back up. The wagon ran for a while and then started developing very similar issues again, it's been sitting for a while but I'm ready to dg back in. I believe I have 2 separate issues at this point based on the following measurements with a vacuum gauge:
1) When I hook up the gauge and fire up the engine cold and read fast idle with the choke out, the best I can get is 12-13mm Hg. I tried adjusting the timing through the entire range and it doesn't go above that value. I cannot push the choke in completely without it dying, but I can get it to run at 1/2 choke in this state. At this point I could probably drive around with the choke out half way.
2) after a minute or two, there's an 'event' I won't call it a click because the engine is so loud I can't really tell , but all of a sudden it will drop from 12mm Hg to around 9, and at that point the engine is really struggling and I'll usually just kill it at that point.

I'm thinking I must have two things going on, maybe something like a cracked manifold and another vacuum leak in the lines that opens at a certain temp, but I haven't started hunting yet. I have one question, because I have a fully smogged setup (that is currently bypassed) and I want to try ruling that out first:

Could I block off 2 of the three vacuum ports off the manifold, just leaving the feed to the vacuum advance for the distributor, just to rule out any and all leaks in the vacuum lines? I figure if I can do that, and the vacuum doesn't go back to where it should be, then I know I need to pull the manifold, but if I read 20mm Hg, then I can celebrate not having to tear down the intake and just focus on the 40 feet of vacuum line.

 

[Mark W]

The factory unmolested carburetor has a press fit cap sealing off the idle mixture screw. It’s there to prevent tampering. The idle mixture is not something that Toyota recommended adjusting.

Toyota did that because of all the silly federally mandated emissions stuff going on back then. If you actually have a carb from back in the day that still has that cover over the mixture screw. Then you have a carb that needs to have it removed so that the mixture can be adjusted correctly.


Mark.

 

[Mark W]

Ok, opening this thread back up. The wagon ran for a while and then started developing very similar issues again, it's been sitting for a while but I'm ready to dg back in. I believe I have 2 separate issues at this point based on the following measurements with a vacuum gauge:
1) When I hook up the gauge and fire up the engine cold and read fast idle with the choke out, the best I can get is 12-13mm Hg. I tried adjusting the timing through the entire range and it doesn't go above that value. I cannot push the choke in completely without it dying, but I can get it to run at 1/2 choke in this state. At this point I could probably drive around with the choke out half way.
2) after a minute or two, there's an 'event' I won't call it a click because the engine is so loud I can't really tell , but all of a sudden it will drop from 12mm Hg to around 9, and at that point the engine is really struggling and I'll usually just kill it at that point.

I'm thinking I must have two things going on, maybe something like a cracked manifold and another vacuum leak in the lines that opens at a certain temp, but I haven't started hunting yet. I have one question, because I have a fully smogged setup (that is currently bypassed) and I want to try ruling that out first:

Could I block off 2 of the three vacuum ports off the manifold, just leaving the feed to the vacuum advance for the distributor, just to rule out any and all leaks in the vacuum lines? I figure if I can do that, and the vacuum doesn't go back to where it should be, then I know I need to pull the manifold, but if I read 20mm Hg, then I can celebrate not having to tear down the intake and just focus on the 40 feet of vacuum line.

This may not be the problem... But before i bothered doing anything else, I would check tpo make sure that the idle circuit cutoff solenoid is functioning correctly. Common problem in the FJ60s is for the grounding circuit to fail or become intermitent.

Also... there is not a lot of adjustment to be done on the carb and it is pretty basic chit. Not anything to hesitate over. Hell, I don't even change spark plugs on a rig without checking the carb adjustments to see how far off they may be from optimum. (well, if it has a carb anyway. )

Mark...

 

[albert110]

This may not be the problem... But before i bothered doing anything else, I would check tpo make sure that the idle circuit cutoff solenoid is functioning correctly. Common problem in the FJ60s is for the grounding circuit to fail or become intermitent.

Also... there is not a lot of adjustment to be done on the carb and it is pretty basic chit. Not anything to hesitate over. Hell, I don't even change spark plugs on a rig without checking the carb adjustments to see how far off they may be from optimum. (well, if it has a carb anyway. )

Mark.

Solid advice, thank you. I've got a smoke machine on order since they're cheap and I've always wanted one, but I'll inspect that solenoid ASAP as well. I have a strong feeling this issue is made up of a number of smaller problems that are adding up, which is why I'm trying to be methodical and look at as many things in order as I can...
I want to save twiddling with the carb until dead last because I don't want to be in a situation where I try 'fixing' X when the actual problem is Y and end up making my situation even worse (wouldn't be the first time).

 

[Beehanger]

Lots to do before twiddling the carb screws:

Put a vac gauge on the 3x nipple coming off the intake manifold (between the carb and power steering pump). In Texas you should see 20-22inHg. If not start hunting down vacuum leaks. Replacing every single vac hose in a smogged engine only costs about $40 and is cheap insurance - cheaper if you're "desmogged" (which could also be a reason for issues).

Set the timing.

Set the valve lash.

The truck running ok when cold and then stumbling when warm really makes me think the issue is related to one of the vacuum widgets that responds to temperature - there's two of them stuck into the thermostat housing. One controls the EGR and keeps it OFF when the engine is cold. So when the engine warms up and that widget enables the EGR to function ... perhaps that's worth looking into. The other temp-controlled systems are kind of a pair: HAI and HIC. Aside from the vac valve in the thermostat housing for those, there's a other valves going on for those systems and they're usually bad. PArticularly the HAI valve, I' have yet to find one that works properly, so most 2Fs out there are running around sucking in hot air. Get the Emissions FSM from the Resources section here on Mud and test all of it.

How's the PCV valve? If you pull it out and give it a shake can you hear the stopper? The amount of crankcase pressure would vary with temp and the PCV system can have vac leaks.

The manifold bolts could be a bit loose when cold, and fine when warm. Adjust them to 35ft-lb when cold (the smaller 14mm bolts get less torque, check the manual). I can be done without removing the carb if you get tricky with it, use lots of various sized socket extensions and wobbles. This would probably cause the opposite issue - running rough when cold, but fine when warm - but heck, check it anyway.

Once you know all of that is dialed in, do the lean drop method of carb tuning. It's in the manual. If you try to adjust the carb without having confidence that everything else is ok, you'll be trying to hit a fuzzy moving target. FWIW I run with the EGR system removed and am still using the original dizzy. I know I should have it recurved but it's not causing a stumbling issue. Also do a search here on Mud for "classic stumbling issue", there's quite a few good threads that have found different causes. Ok, after all that I'll say it's pretty safe to adjust that idle speed screw to bring the idle rpm up to the 600-750 range IF you're going to ferret out the issue and lean drop the carb later. The idle screw can get you by for now.

Cruisertrash:
On a rebuilt engine, having similar issues here. Curious about what you meant by ("PCV SYSTEM can have vac leaks". Do you mean around the PCV valve to the intake connection?
the reason ask is I did a smoke test via the brake booster connection and the only leaks I could find were at the carb throttle shaft, and a small leak coming from out of the timing cover. This would create a crankcase ventilation leak, technically, correct? Wondering if I need to smear some more RTV down there or reinstall the timing cover if this would create an issue.

for the longest time (the last 4 months) I thought I had a massive intake leak. The smoke test showed nothing of the sort, but am wondering if im getting an intermittent leak because I didn't torque the 14mm bolts lower torque spec. I'm using a remflex gasket and a tri mil header and set everything to 20. Hypothetically how much higher should the larger bolts be torqued to, like 23? and leave the 14's at 20?

I believe you're familiar with my general situation and have commented on this thread before. Here it is for context: Advice on whether I should buy a Land Cruiser - https://forum.ih8mud.com/threads/advice-on-whether-i-should-buy-a-land-cruiser.1227794/

This thread is very helpful.. I have had stumbling issues for 3 months now and can't seem to get ahead. Testing things out but your take on the above would be infinitely helpful. AS of now, I can't tune and idle mix screw adjusts nothing.

Here's a video of it running with a vacuum gauge (im at 5200 ft):

Tonight I'm tackling the ICS topic. I'm getting 12v at the black and yellow wire and not the green wire. I am also switching to a 1 pronged connection. On the old one it did click, and the stumbling persisted, but can it still click and have a bad ground per @Mark W 's comment?

@Spike Strip CCing you here as well

Thanks,
Dan

 

[Beehanger]

Cruisertrash:
On a rebuilt engine, having similar issues here. Curious about what you meant by ("PCV SYSTEM can have vac leaks". Do you mean around the PCV valve to the intake connection?
the reason ask is I did a smoke test via the brake booster connection and the only leaks I could find were at the carb throttle shaft, and a small leak coming from out of the timing cover. This would create a crankcase ventilation leak, technically, correct? Wondering if I need to smear some more RTV down there or reinstall the timing cover if this would create an issue.

for the longest time (the last 4 months) I thought I had a massive intake leak. The smoke test showed nothing of the sort, but am wondering if im getting an intermittent leak because I didn't torque the 14mm bolts lower torque spec. I'm using a remflex gasket and a tri mil header and set everything to 20. Hypothetically how much higher should the larger bolts be torqued to, like 23? and leave the 14's at 20?

I believe you're familiar with my general situation and have commented on this thread before. Here it is for context: Advice on whether I should buy a Land Cruiser - https://forum.ih8mud.com/threads/advice-on-whether-i-should-buy-a-land-cruiser.1227794/

This thread is very helpful.. I have had stumbling issues for 3 months now and can't seem to get ahead. Testing things out but your take on the above would be infinitely helpful. AS of now, I can't tune and idle mix screw adjusts nothing.

Here's a video of it running with a vacuum gauge (im at 5200 ft):

Tonight I'm tackling the ICS topic. I'm getting 12v at the black and yellow wire and not the green wire. I am also switching to a 1 pronged connection. On the old one it did click, and the stumbling persisted, but can it still click and have a bad ground per @Mark W 's comment?

@Spike Strip CCing you here as well

Thanks,
Dan

On the topic of ICS since im starting with that on the long list of ptoential issues, where does the wire ground? This is aftermarket connector as I broke the original. I have a little brass clip thing on the wire but that can't be it right? Just one clip and only getting 12 v from the black and gray wire on the green plug side. Trying to figure out how to ground it and if it can still audibly click when connected to the green plug yet still be faulty (hasn't done this yet, I have yet to hook it up. but the old solenoid did audibly click when connected to the female end.

Much appreicated and apologies for the hijack!

 

[Mark W]

On the topic of ICS since im starting with that on the long list of ptoential issues, where does the wire ground? This is aftermarket connector as I broke the original. I have a little brass clip thing on the wire but that can't be it right? Just one clip and only getting 12 v from the black and gray wire on the green plug side. Trying to figure out how to ground it and if it can still audibly click when connected to the green plug yet still be faulty (hasn't done this yet, I have yet to hook it up. but the old solenoid did audibly click when connected to the female end.

The single wire ICS is simply connected to ignition switched 12V. It grounds through the carb body. If it clicks, it is functioning. The passages that the fuel flows through to and beyond the ICS might be clogged too. A quick shot of air will clear them if you remove the ICS and introduce the air there. Worth removing the idle mixture control screw and applying a quick shot of air at that end too.

Mark...