Hi all,
Recently purchased a 92 4x4 pickup and had the valves adjusted, exhaust manifold gasket replaced, new AC compressor, and oil pan leak fixed (I will never do that again). I noticed after having the AC fixed and valves adjusted that I had a slight loss of power when warm. The motor will start jumping a bit when the idle lowers. Today, I changed the plugs and wires with no avail; it is still doing the same thing...any thoughts.

 

Jumping a bit when warm, loss of power?

I assume you're talking about a miss at idle and not the idle surging up and down.
The idle surge is very common if there is any air trapped in the coolant system.

Some idle and power problems can be caused by missing or bad grounds and or power cables. It's something waaay too many of these trucks suffer from. Alot of people don't pay attention to them until they have white stuff growing on them or they fall off.

Have a look at yours and make sure they are all there. https://www.yotatech.com/forums/f116...-guide-194413/
But remember just seeing they are still there isn't enough. They must be drop tested to find out if they're still good or not.

Sometimes even though they look good they simply don't transfer enough current to make things operate like they were supposed to.
Age and usage do take their toll!

https://www.yotatech.com/forums/f127...charge-287463/

 

I will definitely check out the grounds tomorrow. Not sure how to check for air in the coolant system. I did notice that when it's cold, and I removed the radiator cap, it seemed as though the coolant was under pressure

 

Excessive information about it but you get the picture. It might not need to be done at all but you'll never know until you do it and purging the system of air has helped many with idle issues.

Check leaking or bulging hoses.
Are you using Toyota Red PT#002721LLAC01 antifreeze? I've found the red color helps locate the smallest of leaks.
Once I got rid of two small leaks I thought I was good. Wrong

Check the radiator cap.
If it doesn't hold pressure and open at the correct point the system will never function correctly.
I had purchased a new radiator cap shortly after I purchased the truck so I assumed it was good.
Once the small leaks were fixed and the system was building good pressure the NEW cap started leaking because one of the rubber gaskets was faulty from the start.

Check the hose that connects the radiator to the recovery tank. Think of it as a vacuum hose!
If that hose doesn't hold vacuum the radiator will be drawing in air through the leak instead of coolant from the recovery tank when it cools down.
Remove the hose and see if it holds vacuum. Make sure it seals at both connection points and doesn't have any leaks.


Check the heater control valve position. #3 in the picture below
If it's only partially open it will trap air in the heater core.
Like mine, a few people have reported their's wasn't adjusted to allow it to fully open.
I just disconnected the cable from underneath the valve and pushed the valve fully open/hot position when I bled the system.
I like to leave the cable disconnected and the valve wide open for a few days until the system remains at the same level all the time.

Some people disconnect the heater hose and fill the heater core from there.




I haven't done it but I've read about a couple of people who have removed the thermostat and filled the block with coolant to avoid air pockets in the block.


Because air travels upward you want the fill point to be the highest point in the system
Two other things I do to drive air up and out is;
1. Jack the front end up as high as I can get it when filling and purging air from the system.
2. I use the Lisle no spill funnel that places the fill point higher than the heater hoses. I also use the 4-5 inch extension tube that comes with the 24680 kit to get it WAY higher than it needs to be.


The next morning before I start the engine I place some masking tape on the tank and mark the level.
I always look at the level first thing in the morning before I start the engine. The height may lower a little the first day or two but if after a few days the level hasn't stabilized I know there's a leak somewhere.

If you do all that and have no leaks you should be good to go.



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Make sure the engine is very cool to dead cold so you won't get injured by coolant if there's any pressure in the system when removing the radiator cap.

1. Turn the heaters blower fan to off!
Slide the heaters temperature control to full hot
(only step one so you won't forget)



2. Fill the coolant overflow bottle to the full mark.



3. Jack up the front end as high as you can get it and place it on jack stands.
The reason for this is that air always wants to travel upwards and by placing the radiator up as high as you can it allows the air to escape easier.
No jack or jack stands, drive to the steepest incline or hill and proceed.



4. Remove the radiator cap and start the engine.
4a. Check coolant level.
If coolant is low fill it to about 1/2 inch below the start of the filler neck.
You'll be adding more so having it right up at the top isn't important and can keep the splashing down and conserve coolant.



5. From inside the truck wait till the engine temperature is allowed to get off of the cold mark on the gauge.
5a. Have someone hold the throttle open for you at 2500-3000 while you observe what the coolant is doing.
If you're alone go back under the hood and hold the throttle open by hand until the engine is about 2500-3000 rpm.
Hold the throttle open until you finally see water start rushing about in the radiator a few times.
That's the thermostat opening and allowing the flow of coolant.



6. When the thermostat opens you'll likely see the coolant level drop because air is being purged from the system.
Refill the radiator as described in step 4a. (1/2 inch below bla bla bla)



7. Staying clear of the fan squeeze the upper radiator hose at it's tight bends while holding the throttle open.
It will help to get any trapped air moving along to the radiator where it will be purged from the system.



8. Repeat steps 5a-7 for roughly 20+ minutes always refilling if it needs it.
Keep an eye on the temperature gauge and don't let the engine go into the danger zone.



9. While the engine is running fill the coolant to the top of the filler neck and screw the radiator cap back on.



10. The next few times you go for drives always pop the hood and check for leaking hoses, leaking radiator, and make sure the overflow bottle is still at the full mark.
If any leaks are found fix them ASAP.
Try to find dry spots to park over after a drive. When you're about to get back in look at the ground under your truck for leaks.
It's important not to have any leaks in the cooling system so it can regulate the temperatures correctly and if enough air gets into the system you'll be back to having a surging idle.

 

Thanks, I will definitely try it

 

Ok, checked the grounds, which looked good...looks like new grounds. I haven't been able to purge the coolant system but did notice that when I open the radiator cap, water spews out like it's under pressure. I checked the codes and I'm getting a 21 because it doesn't have a Cat, and I'm getting a 41, 43, and a 52. I know what the codes mean so I guess I have to adjust my TPS but not sure about code 43 and the one for the knock sensor.

 

Code 21 has nothing to do with the Catalytic converter; you have an open in O2 sensor heater circuit. Code 41 is an "open" in the TPS; it can be caused by mis-adjustment, but more likely a "wore-out" TPS (there's an open spot in the rheostat). Code 43 is a missing STA signal; if the truck runs I would first try resetting the codes and reading them again (pull the EFI fuse for about 30 seconds). The most likely cause of code 52 is a bad "pigtail" from the knock sensor to the other side of the intake manifold (though AZSpeed on this forum claims to have fixed his by replacing all the capacitors in the ECU).

 

Forgive me but what is an open in the O2 sensor heater circuit and the capacitors in the ECU...I know where the ECU is but not sure about the capacitors

 

Ok, I pulled the EFI fuse for 30 sec, checked for codes again and now the eng light just flashes

 

The codes won't re-appear until you drive it a bit.

A circuit is a closed loop (like, from the + through the O2 sensor heater back to the -, via ground). If the circuit isn't closed (broken wire, burned out heater, loose connector), it's ... open. That's what code 21 is. http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf

If you don't know what a capacitor is, you're not going to be able to tackle that. The good news: ECUs VERY rarely fail. You'd address the pigtail first.

 

Ok, scared me for a min

 

Best place online to purchase electrical components and/or sensors?