2F perfect idle to crap idle in one second. (1 Viewer)

[island45]

Solenoid clicks like it should, will get some more carb spray tomorrow. Still a bit confused by Mark's terms, 'victim' and 'culprit'. The bottom has certainly dropped out of my early vacuum numbers.

 

[77mustard40]

I went through this and it was the intake / exhaust manifolds, are you running headers by chance? If not it could be as simple as a hose or as disappointing as a crack in the intake manifold. Pics might help us help you.

 

[island45]

Stock manifold, no headers. I have a lot of experience with F/2F manifolds. I bet I have pulled, repaired, replaced landcruiser manifolds 15 times. Usually for exhaust leaks, often for problems with the connection between intake and exhaust. As a precautionary measure in 2021 (1000 miles ago) I pulled this current set, surfaced and inspected and re-installed with the remflex while the old FJ 55 body was completely removed from the chassis. I have owned and maintained this 55 since 1986. I know what's involved in pulling these manifolds, and I will if necessary. I also understand that stuff happens, and after 44 years of service anything is possible. I have searched for a hose off or visible sign to no avail. I also have oxy-atcetylene if that would work for an intake test. Otherwise I'll drive into town at lunch for some carb spray. Thank you all very much for the help so far.

 

[45Dougal]

Stock manifold, no headers. I have a lot of experience with F/2F manifolds. I bet I have pulled, repaired, replaced landcruiser manifolds 15 times. Usually for exhaust leaks, often for problems with the connection between intake and exhaust. As a precautionary measure in 2021 (1000 miles ago) I pulled this current set, surfaced and inspected and re-installed with the remflex while the old FJ 55 body was completely removed from the chassis. I have owned and maintained this 55 since 1986. I know what's involved in pulling these manifolds, and I will if necessary. I also understand that stuff happens, and after 44 years of service anything is possible. I have searched for a hose off or visible sign to no avail. I also have oxy-atcetylene if that would work for an intake test. Otherwise I'll drive into town at lunch for some carb spray. Thank you all very much for the help so far.

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You could try spraying water at it - it's a lot bigger than air and a lot less bangy than ether.
If its your manifold then it will help, if its your ignition then it will make it worse!

 

[fjwagon]

The first thing that comes to mind is a carb vacuum leak mainifold/intake related leak. Sometimes it's obvious, but what comes to mind is it if has a EGR vavle, it idle ok and after you Rev up the engine or what not it will get stuck and will not idle correctly. It's a possibility. Sometimes you can clean the carbon build up. Most will replace them. Since it's a 79...and if it has one you may end up modifying to accept one from FJ60. At the time i could not source an OEM one. Anyhow, thats what I ended doing to one I worked on.

 

[island45]

Water in a windex spray bottle does nothing anywhere except maybe slow the rough idle a bit. But OIL of various types sprayed or poured into the primary at rough idle races the engine and smooths out the idle. I know it's weird and most likely has no meaning in my search for the problem but pb blaster down the throat makes it smooth out. Marvel mystery oil even better, and what it likes best is 2 stroke oil, straight from the bottle. Vacuum goes from about 13-14 to 17 and stays there for about ten seconds after I stop pouring. I have been doing this treatment as I wanted to eliminate sticking intake valve as a source. Still inconclusive. Gonna race to napa for some carb spray , closes soon on this rock. I'm thinking manifold more and more. But ????

 

[middlecalf]

Oil in combustion chamber helps idle? Have you checked compression again since your first post?

 

[island45]

Haven't checked compression , but did pull plug wires one by one and got a similar drop at each one. The compression numbers from last year are written in sharpie on the inner fender. #2 was the lowest at 159. The other 5 were 168 and 170. I have my carb spray so will try to pinpoint any manifold leak tonight and will do a new compression check tomorrow. Still the mysterious part to me is how suddenly it went from perfect to crap. And it is indeed crap.

 

[island45]

I found a spot where the spray raises the idle quite a bit. It is on the manifold facing out, just below the carb. There was a fixture there, long ago removed, with a diamond shape clamped by a stud at each end. The studs remain and there are two holes through the manifold. Plugging these holes are two bolts with gaskets inside and outside. Perhaps 7/16 bolt on top and 5/16 below it. The bolts were introduced from inside with carb off and double nutted on the outside. This is my work from the late '80s or early '90s. I remember doing this as I did not have pipe taps. Perhaps an inside gasket was deteriorating and finally sucked away. Light wrenching on the double nuts shows no wiggle or looseness though. The carb spray reveals no leaks at the remflex gasket. With the carb off tomorrow after work I will address this and go for another re-do. It won't have to last 35 years this time as I turned 70 last week. What should I clean or check on the carb while it's off? Idle circuit? Keep in mind I drove it again today and other than the idle it performs as new in all manner of driving and starting etc. It's very hilly here and truck has 3.73 gears and 33" tires and it pulls like a goat. Thanks all!

 

[igotta40]

Here’s another approach. I have seen this happen twice. you may have a air leak at the brake booster. Listen for a air hissing sound up under the dash while working the brake pedal.

 

[fjwagon]

I'm not surprised the manifold/intake has a leak. They are so long and it has two types of material and then they cool at different rates especially and if water gets on its when hot it which may increase the odds of warparge. On a 78 you can remove the entire assembly minus the carburetor and have a machine shop resurface it. Easey-peasy. But this happens to be a 79 which the ends on the manifold move independently. You can spot weld it before removal and do the above. Just cut the welds at the joints before installing it. Others have installed two manifold gaskets. This is just a band aid in my opinion that will eventually fail or make the warpage worse. But if you indeed have an EGR, remove it and plug it with a small plate just to make sure it's not part of the problem. You could have multiple problems. I say this because it's a lot work to have the manifold reworked.

 

[AussieHJCruza]

Solenoid clicks like it should, will get some more carb spray tomorrow. Still a bit confused by Mark's terms, 'victim' and 'culprit'. The bottom has certainly dropped out of my early vacuum numbers.

If the engine has lousy vacuum, the carburettor can't/won't work properly, it therefore is the victim of engine troubles, rather than the cause of the poor idle.
At 13 inches of vacuum, the carby will struggle to function correctly
If she was pulling good vacuum, the carby could be the culprit.

 

[45Dougal]

I found a spot where the spray raises the idle quite a bit. It is on the manifold facing out, just below the carb. There was a fixture there, long ago removed, with a diamond shape clamped by a stud at each end. The studs remain and there are two holes through the manifold. Plugging these holes are two bolts with gaskets inside and outside. Perhaps 7/16 bolt on top and 5/16 below it. The bolts were introduced from inside with carb off and double nutted on the outside. This is my work from the late '80s or early '90s. I remember doing this as I did not have pipe taps. Perhaps an inside gasket was deteriorating and finally sucked away. Light wrenching on the double nuts shows no wiggle or looseness though. The carb spray reveals no leaks at the remflex gasket. With the carb off tomorrow after work I will address this and go for another re-do. It won't have to last 35 years this time as I turned 70 last week. What should I clean or check on the carb while it's off? Idle circuit? Keep in mind I drove it again today and other than the idle it performs as new in all manner of driving and starting etc. It's very hilly here and truck has 3.73 gears and 33" tires and it pulls like a goat. Thanks all!

Sounds like it's time for a close up photo

 

[island45]

Great help from all! Sadly, I no longer have boosted brakes. When going from FJ 55 firewall to '47 ford PU firewall, there was no room for a booster. I am running a mustang MC from a period where the system was front disc, rear drum and manual brakes (unboosted). So that eliminates booster leak. No racing of idle all along the manifolds to head joint. The remflex style gasket is a good one. I have a 6x48 belt sander with which I have surfaced many manifolds and other parts. And yes the seperate horns at the ends provided a challenge so I made a jig for that. All leakage is at base of carb area and I intend to slowly go around the whole base at the insulator where I made the new gaskets from Interface RN 8011. These gaskets are becoming suspect as I see no mention of using the material in intake gaskets. Every year Sandy Olsen from Olsen's Gaskets gives me a box of gasket material scraps, all types of fun stuff, all different thickness and corprene along with many others. After research I find the 8011 is for low pressure oil and water joints, and is a cellulose with two types of rubber involved. Automotive uses are oil pan gaskets for engines and trannys. Turns out I can draw air right through it.....Maybe, just maybe I 'Fixed' the initial problem by repairing the loose carb stud, then cleaned all surfaces, made new gaskets from a porous material and clamped it all back together nice and tight with two 1/16" sponges for gaskets.
In the interest of honesty, (which mattressking insisted on right from the start). I decided to include this chapter on the use of potentially porous carb base gaskets. I will Of course attend to the two bolts being used as hole plugs and do another compression test. I will get some engine bay pics too. Starting 14 big sliding interior doors today in the shop and have a retired friend who's 75 coming to help rough out the parts, so will check back after work. And Aussie cruza, thanks for the clarification, reading it loud and clear.

 

[island45]

Upon reading the thread 'fuel cut solenoid' that is currently up here, I decided to start up my engine, get it up to temp and with idle speed inceased a bit, choke knob in, I disconnected the wire to the solenoid. No change whatsoever. Same idle, same crappy running , but no sign of stopping. I pulled it out and cleaned it with carb cleaner, then pb blaster, installed a new copper washer and the O-ring from my chinacarb, and hooked it back up. Runs better for sure... Now when I disconnect wire every time it stops dead. Coulda been part of the problem all along and I 'fixed it' with the SpongeBob xtra-porous carb gaskets. I have also had more time to spray the carb cleaner around the base of carb and yes, new gaskets are my plan of attack next. My current vac reading is edging up on 16.....

 

[island45]

Upon reading the thread 'fuel cut solenoid' that is currently up here, I decided to start up my engine, get it up to temp and with idle speed inceased a bit, choke knob in, I disconnected the wire to the solenoid. No change whatsoever. Same idle, same crappy running , but no sign of stopping. I pulled it out and cleaned it with carb cleaner, then pb blaster, installed a new copper washer and the O-ring from my chinacarb, and hooked it back up. Runs better for sure... Now when I disconnect wire every time it stops dead. Coulda been part of the problem all along and I 'fixed it' with the SpongeBob xtra-porous carb gaskets. I have also had more time to spray the carb cleaner around the base of carb and yes, new gaskets are my plan of attack next. My current vac reading is edging up on 16.....

My lowest compression number is now 160 and the others continue to climb with the truck's new life after mostly sitting for 20 years. #1 and #6 are now 175. I have the carb off, and have lightly surfaced it's base flange on my diamond whetstone. This took very little effort to get an even shine. Upon close inspection the thin factory gaskets adhered to my insulator block appear intact and in good condition. Anything that was flaking previously was most likely some thin permatex smear that came off easily. I may scuff them lightly in the morning on a piece of adhesive sandpaper on my cast iron table saw top. Should I put anything like perhaps grease as a sealant on these surfaces? With everything so wide open access and all clean I'm thinking I will run in to napa in the morning and get a tap and run my one long homemade carb stud in a little deeper for good measure. I need to know what size and pitch tap I need. I know it's the same at both ends. Will be revisiting the two mainfold holes where I used bolts as plugs in the past. I will close this evening with a tip of the hat to the engineer that came up with the carb studs with the unthreaded tip. It's genius. After 52 years as a full time woodworker, most of my fingertips have been 'compromised' and that rear inside corner nut would be nearly impossible for me to start without that shoulder on top. Need I mention the perfect fitting nut allowing an easy spin to bottom out the nut? OK, enough gushing about my favorite engine.

 

[island45]

Here's my take on this as of Sunday morning. I'm thinking Mark was right about the idle circuit being the culprit. Before I posted this thread I had fixed the loose carb stud and added the two semi permeable base gaskets, thus creating a vacuum leak that did not exist previously. I am hoping I have addressed my vacuum leak with proper gaskets and surfacing along with tapping proper holes for pipe plugs and any repairs where needed. I am now getting ready to reinstall the carb but unfortunately there is no longer an O ring on the solenoid. Hoping it will still let the engine idle correctly until I can get a new o ring. I understand it will no longer shut off the fuel to the idle circuit upon shut down. Here's a pic showing why I have a hard time starting a nut around a blind corner. This was just one of my trips to the hand surgeon.....

 

[island45]

This is running with no o ring on the solenoid. Engine shuts off instantly at hot idle. Wish I could say it was easy....