Hello,
I was recently working on a friend's 1985 22R-powered Toyota pickup which had been sitting for 3+ years. A few routine checks and a new fuel pump later, it fired right up - gotta love the 22R. This didn't surprise me, as the entire engine was replaced 10,000 miles and less than 10 years ago. It is overall in good shape. After a week or two of using the truck with no issues, it began to act up. While it was driving, the engine suddenly began to sputter, misfire, and periodically stall. My friend limped the truck home and then contacted me, so I took another look at it a couple days later. I wanted to hear what the issue sounded like, so I attempted to start the truck. It sputtered all right, but after 20 sec of giving it some gas, it smoothed right out. I looked at some common issue causers (AAP Diaphragm, idle circuit/anti diesel solenoid, etc). The only problem I found was that the vacuum operated side of the choke had a non-functioning vacuum diaphragm. All else seemed well, though, so I dismissed the issue as a bit of blockage in a jet that got cleared out by revving. My friend went back to using the truck...
And a few days later, it crapped out on him completely. He had parked it to do a few errands in town, and when he came back to it, it would not start. There was a guy in the parking lot who offered to help, and the guy was able to get the engine to run enough for my friend to limp the truck home "after doing something to the choke to hold it open". The weird thing is that nothing had changed since my friend had parked the truck 20 minutes before. He contacted me again, and this time I determined that the truck was running extremely rich. It was blowing black smoke out the tailpipe. But again, after giving it some gas for about 30 seconds, the smoke cleared out and it started running great again. So, a bit confused, I went on to repair the vacuum choke opener diaphragm and tested the accelerator pump, AAP (again), vacuum leaks (none I could find), BVSV, throttle operation, EGR vacuum modulator, idle mix, some of the fast-idle cam confusion, choke heater, etc. Everything was fine, and the truck was running GREAT. So now, 2 days later, my friend uses the truck for a couple more trips to town, and again it begins to sputter and stall while he is using it. Again he limps it home. I am at a loss for what could be causing this periodic issue. It can't be timing, because timing isn't a periodic issue. It can't be lack of fuel supply or blockage in a jet, because that couldn't cause rich running. Could it be an EGR valve that periodically sticks and unsticks itself? Ideas?
Lastly, thank you for your patience with this overly wordy description.
Noah

 

From Factory Service Manual...



The last bit got cut off. The troubleshooting goes on to include...

EGR valve faulty
MC valve faulty
Incorrect valve clearance
Low compression

 

Fixed the issue! The truck started doing it again, and that time I was there and was able to observe what was going on. The carburetor was dumping fuel into the intake manifold, resulting in extremely rich running. Upon disassembly, the needle valve had a piece of junk on it which was holding it open. I replaced the fuel filter and adjusted the float level a bit and so far the problem hasn't come back! Fingers Crossed!
Thanks to all who posted suggestions, and perhaps this will be able to help someone else having the same issue!
Noah

 

Your very first post said "which had been sitting for 3+ years." But there was no mention of flushing out and inspecting the inside of the gas tank, checking all the rubber lines for deterioration/cracks/damage, or whether any of the rubber fuel lines were replaced.
I ask this because I've learned the hard way. With any older vehicle that may have older rubber fuel lines, that have been exposed to today's Ethanol-laced gasoline (up to 10% Ethanol), those older rubber fuel lines were not formulated to handle that level of Ethanol.
What happens is that the Ethanol degrades the inside diameter of those lines, and then they start shedding off rubber particles, which can very easily clog up those very small idle passages and jets, as well as cause that needle valve problem
Either way it causes a rich condition. If idle passage or jet is blocked, the engine will try to pull fuel from the main jet only at idle speed (rich condition, rough running). Junk holding open the needle valve, flooding, also a rich condition.
You can clear such blockages and the thing will run fine, until more particles find there way back to the same places, and cause the issue all over again.

Getting a new fuel filter on it was a good thing, but if the truck has those older rubber fuel lines, get ALL of those replaced ASAP with new lines, and new clamps, if the old clamps are any kind of suspect.
Almost any modern rubber fuel line you're going to buy at a parts store today is formulated to handle the Ethanol without deteriorating from the inside. Common rubber fuel line size for the 22R is 5/16"/8mm inside diameter.

I know all this because I went throught he exact same symptoms and problems on my '78 20R longbed. 3 times. Before I learned about the effects of Ethanol on older rubber fuel line.

 

I am having a similar problem with my 1985 22R truck, with it running very rough and apparently very rich. A little history:

Started doing this a few months ago, where it seems to hesitate and then surge, or "buck" as accelerating. The last time I had this type of a problem, it turned out to the Auxiliary Acceleration Pump (AAP). Thinking that it might be that again, I took out the diaphram to inspect and it seemed OK (flexible, no holes). Re-installed the AAP, but after no improvement (and maybe worse), wondered if had installed the AAP diaphram backwards, so went to take it out again. Due to my own stupid error, instead of taking the cover off of the AAP, I took the cover off of the choke breaker and didn't realize my mistake until after I had damaged the choke breaker. So, I sent carb off to be rebuilt.

Rebuilt carb was re-installed and for first test drive it ran great; acceleration was smooth, idle was smooth, no sputtering sounds from exhaust pipe. Since then, it has been running poorly, except once when I started my return trip from an errand it ran fine. Soon afterwards on same trip home it started running poorly again.

Thinking deteriorting fuel lines might be the problem as suggested by 13Swords, I replaced the short rubber hose going to the fuel pump, from the fuel pump to the carburetor, the fuel filter, and the short rubber hose on outlet side of fuel filter. Need to check to see if there is any more rubber fuel line between the filter and the fuel pump that can be replaced. Tend to think the problem is not with the carb itself, since it ran so well right after it was rebuilt and reinstalled. Hopefully if something has fouled the carb, it will be possible to spray clean it out without having to remove from engine.

Any suggestions on most likely thing(s) to check next? Does this seem like something wrong with the emmisions controls system?

 

There are 3 more short rubber hoses at the fuel tank itself that you might consider replacing if they are originals. One is for the feed line to the fuel filter, one is a return line to the tank from the fuel pump, the 3rd one is for the charcoal canister. Here a diagram of where they are:
https://toyota-usa.epc-data.com/pick...ody/7751/?full
Numbers on diagram are (in order mentioned above) 77241B, 77254B & 77277B.

I don't think any originals are still offered today but any quality modern 5/16"/8mm I.D. fuel line will work. You will need to drop the tank to do these, and you may want to consider replacing the in-tank fuel filter while you can get access to it. Toyota part # 77023-12050. You could also make sure you don't have any excessive "trash" in the tank, since if you drop it, this will be a good opportunity to check it out.

You didn't mention anything about the condition of your vacuum lines or if you had replaced them or not. Sometimes a degraded vacuum line can cause the intermittent symptoms you describe. If it were me and those lines hadn't been replaced in a while, I'd just redo them with all new line. Vac lines can also be subject to Ethanol degradation, as well as just heat-aging & developing hairline cracks that allow too much air to go into the system, throwing off the air/fuel ratio.

Since the run issue comes and goes it could be particle blockages on the idle side, and then "clearing itself" under increased vacuum at higher engine speeds, 'sucking' the particle(s) loose & unblocking the idle circuit, or the vacuum problem I described, or both. I think the carb itself is fine mechanically, since it did run properly to begin with. Only other thing I can think of is a fuel float sticking and holding the needle valve open, causing a bit of flooding, or a sticking needle vale, but both of these things are rare on a recently and properly rebuilt carb. Next time it starts running poorly and rich, check the sight glass on the front of the carb. If the fuel level is normal then it's not the float or needle valve. Normal fuel bowl level should look like this:



I know it may sound like a lot but if I've learned anything about working on these old trucks, it's that if you are complete and do it right, it tends to stay fixed for a long time, so it's worth doing.

 

I have been able to replace the soft fuel lines at the tank without dropping the tank on my '87. It's a little tricky but doable. I totally agree with 12Swords about vacuum lines. I highly recommend you go with the Toyota vacuum lines, not aftermarket. I went aftermarket once and had to replace those about a year later.

 

Time for an update and request for more expertise.

I haven't replaced any more of the fuel line(s), but did replace all of the 1/8" vacuum tubing with Toyota brand tubing. (FYI, the fuel line on my model is 1/4" I.D.) No change in how it runs. When engine cold, it runs a lttle rough, but not too bad. Within driving a few miles and as engine warms up, the "bucking" will begin. The fuel level at the sight glass is correct.

I have the service manual and am trying to systematically go thru it and find possible cause/culprit, but this is where my lack of general automotive knowledge comes into play.

Steps so far:
1. Inspection of Mixture Control (MC) System. Truck has manual transmission. I feel no vacuum when I disconnect the vacuum hose and place finger over air inlet of the MC valve. I also don't feel any vacuum momentarily when the vacuum hose is reconnected. Engine does not die, but same rough idle as when started with everything connected.

2. Inspection of EGR System. I bought a Harbor Freight Vacuum Gage and using a 3-way connector placed the vacuum gage between the EGR valve and the vacuum pipe. The engine started and ran at idle (therefore EGR Valve was seated OK?) With engine just started and while still "cold", revved engine to 3,000 rpm (+/-) and vacuum gage read "0". With engine warmed up, vacuum gage read low ("3") at 3,000 rpm.

The next step is where I need help. Service Manual says to "Disconnect the vacuum hose from port R of the EGR vacuum modulator and connect port R directly to the intake manifold with another hose." The small picture of the Intake Manifold is virtually useless to me. How and where is this connection point to the intake manifold?

 

Issue fixed! A friend who is very knowledgeable about all types of cars and things mechanical or electrical came over and helped me complete the testing of the EGR system. No problem was found with that system. Then, his experience kicked in. He noted that the engine was sputtering / misfiring when idling by listening to the exhaust from the tailpipe. While the engine was running, he pulled the spark plugs wires off of the spark plugs (one at a time), and noticed that pulling one of the wires had no effect on how the engine ran or sounded. He checked the continuity of that spark plug wire and found it was bad. Temporarily replaced that wire with a wire from his car and the truck ran great! Will be replacing all spark plug wires today.