Next steps to address bad idle / surging power (1 Viewer)

[iCruiser]

Recently picked up a completely stock 1983 FJ60 with 134k original miles. This was a Dallas truck for most of the service life and had been mostly in storage here in KC for the last 10 years.

Had a heck of a time driving the rig home. Would not hold an idle and stalled at every intersection. Essentially had to ride the choke to get it home. After reading and searching here, learned quickly this is a somewhat common issue related to most likely a vacuum leak.

So far I have addressed the following:

• Replaced 3.5 and 5mm tubing except the few tubes clustered that sit below and in front of the carb.
• New OEM plugs and wires
• New OEM air filter
• New OEM fuel filter
• New OEM PCV
• Confirmed ignition coil resistance (primary and secondary coil) within spec
• Adjusted timing though not sure it is perfect as holding a constant idle while twisting the dizzy has been a challenge.

After making these adjustments, the truck runs much better. For the most part, the surging and stumbling under power has greatly diminished. Truck runs well when on the gas through all gears. The idle has improved as well until the engine gets to operating temps. Then it begins to idle rough and stall. When spray carb cleaner liberally, I'm not really seeing an increase in RPMs.

Now I'm zeroing in on the carb, valves and intake manifold. Since the truck sat for 10 years, sure the carb is in need of a rebuild. Plan to pull the carb and see what's going on. The site window is not clear so I can't tell how much fuel is in the bowl. Also plan to check and adjust the valve clearance. Not sure if that could be causing some of the idle issues. Once I get the carb off, can then inspect the inside top of the intake manifold for the typical crack in the aluminum.

I do plan to eventually de-smog the 2F. Would I be better off addressing this idle / performance issue first then de-smog or get rid of all that smog stuff that could also be contributing to this current issue? Apart from de-smog, would have Jim or someone rebuild the carb to be compatible with this setup.

Any suggestions of other things I should consider are greatly appreciated. Looking forward to getting this sorted so I can concentrate on restoration projects to bring this beauty back to life.

 

[mwebfj60]

Sounds like you're going about it pretty methodically. I would suggest getting a copy of the Emissions FSM, they are available on here for a hell of a price. It goes through each system and gives you the steps to check all of the vacuum valves....there are many.
A mighty vac and vacuum gauge are kind of essential tools for these tractor motors.

If you are going to desmog, that will get rid of quite a few things but add some other minor issues at the same time, plenty of threads on the subject and a bunch of different ways to skin that cat.

A manifold vacuum reading will be good to see.

When you start messing with the carb, run some checks on the FCS (fuel cut solenoid aka Idle cut solenoid). In my posts there are some detailed checks on it.

Good luck and keep us posted, most on here enjoy working through these things with you just make sure to throw some pics up frequently....

 

[OSS]

Everything @mwebfj60 said.
The number ONE cause of chronic stalling at idle is vacuum leaks. Highest vacuum is at idle but fuel delivery is naturally lowest at idle. The higher the vacuum (idle) the faster the leaks (if there are any). That equation computes to too lean of a mixture (aka fuel starvation) and engine conk out.

 

[iCruiser]

Thanks for the feedback. Forgot to mention the vacuum gauge was reading 15 in-Hg and steady. Makes me think there is a leak. Do have all the manuals thanks to this great resource site. Will use the Emissions manual to go through each system. Just so I can appreciate true baseline, would like to get this sorted before de-smoging. Still think the carb itself could be an issue since I can't even see through the site window. Is that usually an indication things are gunked up inside the carb? The truck has had minimal use the last 10 years.

 

[mwebfj60]

15 is pretty low for 1000' elevation. Is that warmed up or cold?

With my desmogged 2F, I pull about 18.5" right after a cold start and 21" when motor is up to temp.

OSS imparted a lot of knowledge in this vacuum thread..
Chasing a vacuum leak

The carb could be an issue if it sat for extended periods of time. The main thing I have found in sedentary carbs is check balls being kind of glued into place and cylindrical sliding mechanisms such as the power valve assembly being resistant to moving smoothly. The accelerator plunger dries and shrinks a little but still functions ok when it gets soaked in gas again. It wouldn't hurt to go through it. At least you could blow all the passages out and inspect everything.

I might be a bad source of encouragement though, I have had a need to disassemble every thing I've ever owned to see how it worked....and carbs are at the top of my favorites list.