Hi all,

So I was getting my 86 Toyota 22R (carbureted) ready to sell this past week. Wanting it to be right for the new owner, the only thing I had noticed requiring attention were the emissions hoses, likely original, looking brittle and needing replacement (especially the small ones). The truck ran fine prior to this....just wanted to do the "right thing!"

Upon starting it up after replacing all emissions hoses, large and small but for the shaped one from the valve cover to under the air cleaner, it backfired a bit. After a few minutes, I thought that somehow I might have routed one of the small emissions hoses incorrectly. I referenced my other 86, original and very low mileage truck, and found I had in fact somehow swapped 2 hoses around. The truck then ran well, but for a small backfire on deceleration (cold engine). I took it for a drive into town, and it ran perfectly (starts first time, accelerates well, etc...). The backfire also seemed to disappear when it was warm.

This morning, starting from cold (again, started immediately), the backfire issue was still there. So, it appears that when the engine is cold, until it goes for a run, is when I notice the problem. Also, the idle is slightly less smooth than it was prior to doing all of this work.

Any ideas? I can tell you that one of the small emissions hoses, directly under the air cleaner on the right side of the carb (looking at it from the front of the truck), was found to have a screw plugging it....and another opposite it was not connected. When replacing all of the hoses, I assumed (and verified assumed correctly by looking at my low mileage truck) that these two hoses should have been one continuous piece. Other than that, nothing else changed.

I'd appreciate any input.

Thanks,
Julian

 

When you say emissions hoses, are you talking about the vacuum lines? Did you use aftermarket or Toyota? If aftermarket did the hose fit really really snug or are they easy to pull off? If easy then vacuum leak may be the problem.

You can download a copy of FSM from this link.
https://web.archive.org/web/20110102...ttora.com/FSM/

From FSM for 22R...

 

Thanks for the reply! Aftermarket hoses (took an old one to the auto parts store to match)....but, yes, they are not quite as tight as the original (granted, they've probably shrunk with 40 years of heat on the fittings!). Might be an issue. Oh, yes, I am referring to the vacuum hoses (some larger diameter, but mostly very small ones on the carb and nearby components).

The FSM is helpful. I did notice a small break in the top plastic barb of the VSV valve I circled in the pic. That valve is apparently part of the "AI" system that can be related to a backfire on deceleration.

What do you think?

Thanks again,
Julian

 

The Toyota vacuum lines fit very tight even new, as they should. I replaced all of mine with aftermarket years ago. After a year if you just bumped one of the aftermarket ones they would fall off. I then replaced all of those with Toyota vacuum hose. There should be something in the FSM showing how to test the VSV. If all you changed is the vacuum hoses, then had the problem, my money is on a vacuum leak. Good luck!

 

Thanks....well the crack is worse than I thought....the barb is falling off that piece circled! I must have damaged the plastic barb pulling off the tight hose. Anyway, I guess I will try that first, and then go with your plan of the new hoses.

Just thinking about it, I can take the good valve off my low mileage truck and fit it temporarily to see if that cures the problem.....

Any thoughts on why the PO might have plugged a line with a screw? What would that achieve??

Julian

 

Hi all,

So I swapped my good VSV valve into the truck. Less backfiring (minimal), but still not a smooth idle as before. I noticed the circled area of the carb was icy cold to the touch, with condensation dripping off of it!

Any idea why this would be? Any idea what this area is called (could not locate a name on diagrams I found online or the FSM). Still leaning towards redoing the vacuum hoses, but thought I'd mention this finding.



Thanks
Julian

 

Just to clarify, I'm not an expert. From my time on yotatech I've learned there are few carb people to answer questions so I do what I can to help.

The part circled is called a "Union". It's my understanding that it's attached to the intake manifold and that's where the vacuum is initiated. It's interesting that the parts diagram calls it a Union for the Gas Filter which is the device that screws in to the union and has vacuum lines attached. There is no gas running through that area. Weird. Check out the vacuum piping diagram. Click on a 5 digit number to get a popup with part name and 10 digit part #.

https://japan-parts.eu/toyota/us/198...piping/2#23269

Check out page EC-34 Mixture Control (MC) system in the FSM. Pull the big hose off the union after you've driven the truck, the hose that connects to the air filter box/MC. I'm curious if the condensation is from gas getting down in the union. Again I'm fairly certain there should be no gas.

I don't know why the union would have condensation coming off of it. I'll check mine tomorrow after I've driven some to see if mine is the same.

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The previous owner may have used the screw to block the vacuum to whatever the line ran to cuz the part wasn't working. Have you plugged that line to see if the problem goes away?

 

Thanks very much!! I suppose I could do the same with my other truck, but its VSV valve is on the patient truck right now LOL!

I was thinking about your comments about the tightness of the vacuum hoses. This indeed could be the issue. Although I still wonder why the PO had capped that vacuum hose with a screw. If I remembered which one it was, I would replicate that to eliminate it from the equation (but unfortunately I don't remember which!).

I had also forgotten about a smoke machine I bought a couple of years ago to use on a British car I was chasing a leak on. Instead of buying and replacing every hose again, perhaps I should run a smoke test? Any recommendations on where to connect it in the Toyota's system?

Just thoughts, as I only have a few minutes after work to look at it until a day off over the weekend!

Thanks again,
Julian

 

I'd run the smoke test before replacing all the vacuum lines. I've never used a smoke machine to find vacuum leaks. I've thought about buying one just to have on hand. There are probably some youtube videos on how to hook it up to test for leaks.

Those VSVs aren't available new. If there's enough of the barb left on it maybe you can get a straight connector made for connecting vacuum lines to stick in it. Just a thought.

Keep us posted on what you find.

 

I did try what you suggested, but the barb was sheared off---and trying to drill it ever so slightly probably just resulted in a vacuum leak! The one from my other truck ,as noted, seemed to reduce almost completely most backfiring issues. I ordered a replacement VSV today from a breaker (tested and with a 30 day warranty!).

I am off work tomorrow. Might try a smoke test on it and see where I get.

I will definitely update you with what comes of this.....appreciate your time!

Julian

 

I ran a smoke test.

I ran smoke through the large vacuum pipe to the brake booster (but before the valve)......smoke just emitted from the carb top (air cleaner feed).

I then randomly selected small vacuum hoses to disconnect, one by one, to see if smoke was visible at other junctions/fittings. It was.

That said, this implies that a vacuum leak is the likely culprit. I went into town, and got the next hose size down, which was just under 3mm in diameter as it was standard (no place in town had 3mm hose, including Toyota who just said the truck is discontinued and they use wiper washer tubing when needed!).

Obviously, the new hose is a slightly tighter fit than what was on there, but I am going to try replacing all of it Sunday. Will see where that gets me. Assuming the very slight reduction in diameter is not an issue for the vacuum lines, and the fact that there should definitely be no leak at all as they will be tight on all fittings, hopefully it brings me back to where I started and the issues go away! Well, everything except for the unknown reason for the PO putting a screw in one of those small vacuum hoses, that has been eliminated by me since.

Julian

 

I checked my union after driving my truck. There was no condensation and it was warm to the touch.

I hope the problem is just a vacuum leak! When I have to unplug one of my vacuum lines, it takes a lot to pull one off, and that's the Toyota lines. So tighter is better!

 

Unfortunately, I achieved nothing today I replaced every vacuum hose with the smaller diameter hose, and there is no way that there can be any leak in any hose connection as a result!! Upon restarting the truck, the same held true....some backfiring and a questionable idle. Note that I referenced my other Toyota to ensure every line was in exactly the right place (twice!!).

At this point, banging my head, my thought was that the only thing that has changed during the process of me replacing the hoses was coming across the hose the PO had put a screw into to cap it off (and eliminating it). So, there was one vacuum hose connected to nothing, and one vacuum hose with a screw in it. These two originally would have been one hose. As mentioned before, in the process of replacing hoses, I made these two hoses into one (and, again, correctly connected them).

I wish I had taken a photo of the location of this screw hose prior to replacing it, but I did not. I do remember, however, that it was one of the vacuum hoses underneath the air cleaner on the driver's side of the carb (looking at the carb from the front of the truck). I thought I would, one by one, remove a hose in this area, cap it, test the truck, and on and on (testing capping either side of each hose also). After several tests, I capped one, which resulted in no backfire and a smooth idle. I hooked up my timing gun to use the tachometer feature, and the truck was idling pretty smoothly at around 700 rpm (per specs).

I took it for a drive.....no backfire, perfect acceleration, perfect idle. Thought I had solved it.

After sitting for 45 min or so, I went to move the truck on the driveway and back to the same problems!

Does anyone have any idea what might be the issue? To summarize this long post:

-Symptoms.....occasional backfire (on deceleration), rough idle....but, starts instantly and drives perfectly
-Other observations: the union circled in red in the attached pic is noticeably cold/icy to the touch after running for a short time (condensation noted the other day); I noticed a patch of carbon on the driveway from the exhaust also today
-Other thoughts: could the PO have been compensating for something else by putting a screw/cap in the vacuum hose in the area I described??
-One more idea I just thought of: I used my original very low mileage 86 Toyota as a reference for the vacuum hose connections. The area circled in red, to the right side, has some sort of a fitting to which 3 of these small vacuum hoses connect.....this fitting might be screwed into the union on the left.....therefore, is it possible that the orientation may be off by 1 (either clockwise or counterclockwise) as assuming this fitting screws in to the union then it might not "rest" in the same position as the one on my other Toyota (not sure if I am describing this well).....so this would result in the hose connections being off....

Thanks for any and all thoughts....

Julian

 

That sucks! Post a pic of the line that you plugged.

Start testing the items in the FSM for troubleshooting backfire on deceleration. Start with the MC since that's the line that runs from the cleaner to the union. Again my union is warm to the touch and no condensation after driving.

 

Thanks....I did pull the large hose from the air cleaner to the union....no fuel or fuel smell evident. Perhaps the "filter"....screwed into the side of the union now I look at the FSM...is faulty. Will see if there is a way to test that. Then the other part of the MC system in the air cleaner itself.

I am a bit out of my depth I think, but will try once again on my next day off.

Thanks for all your input!
Julian

 

I also noticed a lot of black carbon in a patch on my driveway under the exhaust (not sure if that is normal).
Any thoughts.......as of yesterday, in addition to plugging and unplugging lines, I have, per the FSM troubleshooting guide in Emissions:

-Checked the EGR vacuum modulator (and cleaned filter)
-Checked the EGR valve.....holds vacuum
-Checked the fuel solenoid cutoff valve
-Checked (and cleaned with 43PSI air) both charcoal canisters
-Put vacuum on the HAI diaphragm (and I can see it activating)
-Checked the Mixture Control valve under the air cleaner lid
-Checked the vacuum valve (round one on the pass fender) for continuity (with and without power)

Starting to run out of ideas!
Julian