Oxygen sensor ?

[Phatcat]

Hello,

So I’ve spent the past few months fixing up this 84 T4WD I purchased in the end of March. Cleaned and went through replacing a bunch of clogged and old carb parts, replaced the vacuum advance on the dizzy, went through the vacuum line’s replacing all of them while also checking routing and the function of all the vsv’s, TVSV, evap system, all the emissions components, setting the fast idle speed, idle speed etc etc etc.. The car runs and does so okay. Fires right up cold and has a solid high idle, and idles down accordingly after heating up a few and popping the gas a few times (depending on how warm it is and how long we let it run to warm etc). However, there seems to be a slight hiccup at idle and I know it can run better. Oh, and I’ve set the timing at about 10 btdc with the vacuum advance vacuum removed and lines plugged. I’ve basically been running through the FSM a few times checking everything with the multimeter and battery power jumpers to activate switches, and applying vacuum etc. Everything checks out good, but the O2 sensor. This is a California vehicle btw, but being in WA and a collector, it will not have to pass any inspections ever again, hopefully. Anyway, when I probe the O2 diagnostic plug at the passenger fender under the wiper motor, I get absolutely nothing, even after warm to standard operating temperature and running the motor at 2500 rpm for a good few I get nothing.. Now, this assumes I’ve probed the correct plug and done things correctly, but im leaning toward tossing an O2 sensor in there. The sensor does look original with a yellow plug and lots of life lived, and there are a few very rough spots on the sensor wire where it’s damn near broken (almost looks like mice got to it), but I’m wondering what folks think, replace it or not? It just seems like an O2 sensor in a vehicle this old and simple shouldn’t effect the motor much, but rather be in place for emissions health and function purposes. Lastly, I have no check engine light or codes either, if these cars have a place to store them etc. I’m still learning this older car and would appreciate some knowledge and experience from those who have more. Let me know what you think. Thanks

[SirFoxx]

Hello,

So I’ve spent the past few months fixing up this 84 T4WD I purchased in the end of March. Cleaned and went through replacing a bunch of clogged and old carb parts, replaced the vacuum advance on the dizzy, went through the vacuum line’s replacing all of them while also checking routing and the function of all the vsv’s, TVSV, evap system, all the emissions components, setting the fast idle speed, idle speed etc etc etc.. The car runs and does so okay. Fires right up cold and has a solid high idle, and idles down accordingly after heating up a few and popping the gas a few times (depending on how warm it is and how long we let it run to warm etc). However, there seems to be a slight hiccup at idle and I know it can run better. Oh, and I’ve set the timing at about 10 btdc with the vacuum advance vacuum removed and lines plugged. I’ve basically been running through the FSM a few times checking everything with the multimeter and battery power jumpers to activate switches, and applying vacuum etc. Everything checks out good, but the O2 sensor. This is a California vehicle btw, but being in WA and a collector, it will not have to pass any inspections ever again, hopefully. Anyway, when I probe the O2 diagnostic plug at the passenger fender under the wiper motor, I get absolutely nothing, even after warm to standard operating temperature and running the motor at 2500 rpm for a good few I get nothing.. Now, this assumes I’ve probed the correct plug and done things correctly, but im leaning toward tossing an O2 sensor in there. The sensor does look original with a yellow plug and lots of life lived, and there are a few very rough spots on the sensor wire where it’s damn near broken (almost looks like mice got to it), but I’m wondering what folks think, replace it or not? It just seems like an O2 sensor in a vehicle this old and simple shouldn’t effect the motor much, but rather be in place for emissions health and function purposes. Lastly, I have no check engine light or codes either, if these cars have a place to store them etc. I’m still learning this older car and would appreciate some knowledge and experience from those who have more. Let me know what you think. Thanks

if you get nothing at the service plug, disconnect the o2 sensor and check it directly. they are a 1 wire narrow band sensor, so they dont need to be plugged in to operate. red lead on the yellow plug, black lead to ground.

if you have everything else connected and functional, and the o2 sensor isnt outputting the correct voltage, id replace the o2 sensor. these are a feedback carb and every little thing can affect how they run.

without hearing yours idling, i cant say if its normal or not, but ive never had a 3a that idled nicely like an efi car. just isnt going to happen with a 40 year old carb.

there is no check engine light or codes...or even an ecu for that matter. there is a emissions "ecu" but calling it an ecu is like calling the computer that sent the first space ship to the moon powerful.

[dlb]

What is the "slight hiccup" at idle, can you be more specific?

I definitely agree with SirFoxx re: tempering expectations of an old carb'd engine. So if by hiccup you mean sometimes it idles at 600 instead of 800 rpm, I'd say that's just fine. But if you mean it sometimes runs rough or almost dies at idle, then for sure that's something that should be addressed.

Have you disassembled and cleaned/rebuilt the carb?

[Phatcat]

What is the "slight hiccup" at idle, can you be more specific?

I definitely agree with SirFoxx re: tempering expectations of an old carb'd engine. So if by hiccup you mean sometimes it idles at 600 instead of 800 rpm, I'd say that's just fine. But if you mean it sometimes runs rough or almost dies at idle, then for sure that's something that should be addressed.

Have you disassembled and cleaned/rebuilt the carb?

The hiccup I speak of is a poof at the tail pipe sorta thing. Also, just knowledge of feeling an engine run and how much shake or smoothness is felt. Yes, it’s a bit rough, and is so at various idle settings (higher/lower). It can run better. This isn’t my first carbureted vehicle, but I’ve also not had very many. Yes, the carb was removed cleaned and inspected. I’m confident every component and orifice is clean. I’ll try probing straight to the sensor and see if we get resistance.

[SirFoxx]

What is the "slight hiccup" at idle, can you be more specific?

I definitely agree with SirFoxx re: tempering expectations of an old carb'd engine. So if by hiccup you mean sometimes it idles at 600 instead of 800 rpm, I'd say that's just fine. But if you mean it sometimes runs rough or almost dies at idle, then for sure that's something that should be addressed.

Have you disassembled and cleaned/rebuilt the carb?

The hiccup I speak of is a poof at the tail pipe sorta thing. Also, just knowledge of feeling an engine run and how much shake or smoothness is felt. Yes, it’s a bit rough, and is so at various idle settings (higher/lower). It can run better. This isn’t my first carbureted vehicle, but I’ve also not had very many. Yes, the carb was removed cleaned and inspected. I’m confident every component and orifice is clean. I’ll try probing straight to the sensor and see if we get resistance.

the hiccup sounds normal for these cars. no, they dont get much better than this. cant really compare it to other carbd cars. the feedback carbs are very unique, and everyone did it differently.

[Phatcat]

I’m headed out to test the O2 directly, but I’m still leaning toward replacing it. Autozone has the sensor on hold at the moment.

The previous owner had this car since the late 80’s and had extensive detailed service records, that now I have. He wrote down every filter and fluid change.. I was fortunate to get such a gem. The car’s in fantastic condition and so very unmolested at every aspect, including the motor and components. PO had the cylinder head rebuilt about 8 years ago and had a shop do all of the work. Personally, I’m not a fan of doing this type of work at a shop, as I’ve seen and experienced more BS than success going that route. It’s the frustration and waste of time and money that propelled my wrenching abilities. We (my wife Alison and I) always wanted to drive older Toyota trucks and quickly learned that we’d have to fix things ourselves. This was over 16 years ago.. We did and over the years became very good at maintaining our old, getting older trucks. The wife drove her awesome 86 4 Runner for many years while I drove my 95 pickup, both 22RE powered. Prior to her 86 she had numerous 90’s 4Runners with the 3.0 3VZ-FE motor. I also had a fantastic blue 1981 longbed Pickup with a 22R (carb was swapped for the Weber 32/36 DGEV). We just recently sold off the 86 Runner and 81 pickup for a new Outback Wilderness. Time will tell on the Outback. I still drive the 95 pickup and T4WD we are discussing. We didn’t need another vehicle really, but I couldn’t pass on the Tercel from the PO and condition. Which is about the extent of my wrenching. So I’m familiar with the Weber system and archaic Toyota EFI systems, but have no real experience with the older emissions vacuum riddled factory Toyota carburetors (such as the feedback system we’re discussing). The FSM has been very helpful and as I said, every component passes the tests on this car, aside from the O2 sensor. Lastly, I may replace the throttle linkage return spring as I believe it could use a little more strength to get the idle more consistent back to home. That springs been on there for nearly my entire life… so it’s old and been worked to death. So here we are. Life story complete. I’ll post back to give my findings.

[Phatcat]

What is the "slight hiccup" at idle, can you be more specific?

I definitely agree with SirFoxx re: tempering expectations of an old carb'd engine. So if by hiccup you mean sometimes it idles at 600 instead of 800 rpm, I'd say that's just fine. But if you mean it sometimes runs rough or almost dies at idle, then for sure that's something that should be addressed.

Have you disassembled and cleaned/rebuilt the carb?

The hiccup I speak of is a poof at the tail pipe sorta thing. Also, just knowledge of feeling an engine run and how much shake or smoothness is felt. Yes, it’s a bit rough, and is so at various idle settings (higher/lower). It can run better. This isn’t my first carbureted vehicle, but I’ve also not had very many. Yes, the carb was removed cleaned and inspected. I’m confident every component and orifice is clean. I’ll try probing straight to the sensor and see if we get resistance.

the hiccup sounds normal for these cars. no, they dont get much better than this. cant really compare it to other carbd cars. the feedback carbs are very unique, and everyone did it differently.

Okay, so unfortunately the O2 sensor didn’t fix my alleged issue. At least, not immediately. I’m sure it will help in the long run. The old one definitely had damage to the wire (I suppose I could’ve fixed), but the new one went in.. I will admit that my expectations are higher than most. I’m reasonable, but stubborn when it comes to my things (cars). Just trust me, this thing can run a bit better. So when I went through the carb after initially buying the car, I had to hurry a bit. I replaced the auxiliary pump diaphragm and the vacuum port on the auxiliary pump housing was completely clogged. I had to drill it out with a small bit. I also replaced the power valve and cleaned quite a lot of corrosion from the bowl and various other orifices. I used my carb cleaning brushes and jet cleaners with compressed air and carb clean. Everything seemed good top to bottom. And I rechecked the passages multiple times to be sure. My thought are that the throttle linkage isn’t returning as well as it should, and also, I did not set or test the primary and secondary butterfly operation per the FSM. I simply made sure they operated freely on the bench, lubed in the bushings/shafts with some spray lube, worked it in and moved on. At the time I hadn’t downloaded the manual yet, so didn’t know about the FSM checks that exist. So it’s possible pulling the carb again and going through the FSM procedures for checking the carb would be beneficial. Here’s an actual question, when you all are tinkering with your carbs, can you push the throttle linkage down with a finger, but not ripping on it, and cause the idle to drop? Even after setting the idle (which does adjust accordingly with a flat head) I can then blip the throttle, but then pushing the linkage will lower the idle more. This fact makes me think I don’t have something set or cleaned properly in there. Anyway, I’m thinking of replacing that throttle return spring AND removing the carb again to ensure everything is free and clean enough. Lastly, when bench testing and cleaning everything both idle cut solenoids worked perfectly. Both rattled freely and activated with voltage applied. I’m missing something here though..

I may just throw a Weber on and see how that does. I like the simplicity of the Weber systems, but wanted to give this factory carb a shot with a vehicle in such good condition and unbuggared.

[Petros]

I think if you can sort out the factory carburator, it is better than the weber. the daily driving is not so different, but the factory carb runs better at extreme temperatures: easier start and running when very cold, or very hot. the FSM has a series of simple tests for each system you should work through, it may be one of the extrenal componets not working correctly that causes it to not run well, not the carburator as well. More than a few times mine hicked up, or was hard to start, and I rebuilt the carb and found nothing terribly wrong with it, and after I re-installed it, it ran exactly the same. the problem was not the carb at all and I just wasted a lot of time rebuilding the carb. usually fixing or replacing any of the vac operated componets is quick and simple, finding the problem is more time consuming. And getting a replacement part may be troublesome since they have not made any of them for perhaps 30 years. You have to get them from the wrecking yard, same age as yours, and hope they are still working.

that is pehraps a good reason to switch to the costly weber, to clean up all of the auxilalary fuel and emission system connents vac lines out of the engine compartment. If you can not get replacement parts, and you can not by pass them, you will have to go to the weber.

A couple of observations: the car lists it has an ECU, but it is really just a relay box, several sensors will either turn on, or off various switches during certain driving conditions. the "feed back" carb controls the mixture ratio by allowing bleed air under the carburator during certain driving conditions to lean out the mixture. unfortunately when anything in this system malfunctions, it still runs okay, but the economy drops from perhaps 28-30 mpg, down to about 20 mpg. there are several parts to the feed back system you have to check/test to find why the economy suddenly dropped. Many of the emissions systems components can be deleted, or by-passed if they no longer work, but many are necessary so it runs and drives properly because the carb and fuel system was designed to run with them. This is one of them, unless you are okay with really poor econonmy (I am not). I may try to work out a way to bypass that system, and still get good economy. I but have not attempted that yet (and I have boxes of spare parts I collected over the years...so I am set for now). But the weber may be the only option if you can not get the parts needed to keep it running well.

Another is you can not buy the same kind of gasoline today that this car was designed to run on. Though a lot of questionable rationalization, and frankly dishonest politics, we have to buy gasoline formulations determined by lobbying from the oil companies, and most of it in the USA is blended with ethanol. This stuff runs like crap on our older cars, it can also cause a lot of corrosion in the carb and fuel system, it also has lower energy per gallon (and cost more to make, meaning it uses more resources) than pure gasoline. Here in WA there are a few places that will sell ethanol free gasoline, but it is half a dollar more a gallon, and hard to justify spending that much to 1 mgp better economy. So if you can find it, you might try running a tank or two of ethanol free gasoline through your car to see if it will idle better.

these are fun cars to own, and easy and cheap to fix usually, but you must be a DIY type because any car this old always has a lot of small annoying problems to fix, things that do not normally get replaced on cars that get junked in less than 20 years, switches, door locks, etc.. And depending on where you are, most mechanics are clueless about these cars (and if they are honest, which many are not, should tell you that), and will take your money, spend a lot of time not fixing it, and charging you for their education. Best learn about your own older car, and than work on it yourself. Most modern mechanics want to connect an analizer to tell them what to do, rather than tracking down any problems and fixing it. they do not really know how any of the systems work, but depend on the computer to tell them what to do (and they still get it wrong a lot). bring a car without these systems, they will not know what to do. besides, it will save you a lot of money to learn how to fix it yourself, and it will give you a lot of confidence that you can fix anything that might occur to your car, and not have to depend on others for the repairs.

Good luck.

[xirdneh]

The primary butterfly on stock carb will wear on forward side causing it to hang up sometimes not allowing return to low idle. i add extra spring for this.