Power Valve?

russkiypenguin1 · Post by **russkiypenguin1** » Tue Nov 09, 2004 7:06 pm

My mechanic says I need to replace the power valve in my carburetor. The car won't idle anymore, it keeps dying, even after I put in new plugs, wires, cap and rotor.

icE · Post by **icE** » Tue Nov 09, 2004 9:28 pm

maybe you need to rebuild the carb? wish these cars were fuel injected

takza · Post by **takza** » Wed Nov 10, 2004 5:26 am

"A neat trick for fantastic mileage came from an old-time manufacturer of carburetors. It was to <span style='color:blue'>solder the power value shut </span>in my carburetors for great mileage and better efficiency. The power valve causes a huge waste of gasoline. This trick produced 26 MPG in my 1964 Ford van with no bad effects.

Furthermore no flooding occurred in V-8 engines, even with three, four or six carburetors. This trick solved a serious fire hazard with old carbs on performance engines. Leaky carbs and hot exhaust headers do not mix. My burn scars prove it. "

<a href='http://www.lubedev.com/articles/mileage.htm' target='_blank'>http://www.lubedev.com/articles/mileage.htm</a>

You could be the first to try this.........

Lateer · Post by **Lateer** » Wed Nov 10, 2004 5:53 pm

I wouldn't do that, myself.
Soldering that valve shut causes brief periods of seriously lean mixture, which will attack plugs, pistons and cylinder walls.
It's there for a reason. Leave it alone.

And I wouldn't mind seeing what Louis LaPointe (the author of the article) does for a living. Engineer/chemist/mechanic, cool. Chartered accountant, not so cool.
Some of the stuff he writes is bollocks, though. A lower octane rating is bad for our engines. Tercel 3A engines were designed to run on leaded fuel. Tetraethyl lead was added to decrease engine knock, decrease valve recession and increase the octane rating of the fuel. In this era of LRP, get some decent upper cylinder lubricant and use the highest octane rating you can find.

The bit about hot air is crap, too. Only do that in winter, as the air will be damn cold.. All combustion processes run better when there's nice, dense air around them. More oxygen that way, see? So running the air filter intake near the radiator will make sure that you get hot, less dense air and the engine won't run anywhere near as efficiently. Why else do we have intercoolers for turbocharged engines? To decrease the temperature and increase the density of the incoming air.
Oh and putting acetone in your tank is a great way to dissolve the rubber fuel hoses you have under your bonnet. Please, don't do this, even for a little while. <_<

Yes, leaky carbs and hot exhaust headers don't mix. So, most people actually let the engine cool down for a good hour before removing the carb to fix it.
Hell, I'm a dumb chemist and I even know that

And disassembly of a standard Tercel carb can't be anywhere as bad as pulling the Weber to bits.
Download the Tercel manual from here and have a read of the section on pulling the carb to bits. That's how you're going to have to change the power valve.

One thing, though. How come your mechanic told you to do it? It'll take him about half an hour to get the carb off, strip, rebuild and put it back on.
Why doesn't he do it?

russkiypenguin1 · Post by **russkiypenguin1** » Wed Nov 10, 2004 8:52 pm

icE: I think that's probably what needs to happen. But I trust my mechanic. This guy diagnosed a problem I was having with my 89 F250. He then installed a new timing chain, gears, starter, and a new battery for $750. Just this week the ground on my F250 fell off the back of the engine. $25 charge for that. One time they worked for 4 hours to change a heater blower motor, but only charged me the hour that it was supposed to take to replace it. So I might just try the power valve and leave it at that.

takza: I'm going to get my tercel running good and stock first. Then I'll start looking at an engine swap and other upgrades.

Lateer: Well, seeing as one of my plug electrodes was blown off when I swapped in new plugs it certainly sounds like air/fuel ratio and this power valve may be related to the problem. My mechanic said that it's a Toyota only part. He said if I pick it up from the dealership he would install it for me. I did check with Oreilly's and their carb rebuild kit didn't have this power valve. I don't really know why.

I've got to do something, because driving my f250 with the huge 460 in it is expensive as hell. In two weeks of driving the toyota vs. the truck it would pay for having someone rebuild it for me. And I have no time to work on the vehicles myself right now.

Logbear · Post by **Logbear** » Wed Nov 10, 2004 8:54 pm

How did the mechanic come up with the power valve diagnosis anyway? The manual lists relates power valve with hesitation or loss of acceleration. I would think fuel cut-off solenoid valve instead. Or something really simple like a plugged up fuel cap vent. I always like to look for the easy fix.

Gasoline Fumes · Post by **Gasoline Fumes** » Wed Nov 10, 2004 9:13 pm

Lateer wrote: Oh and putting acetone in your tank is a great way to dissolve the rubber fuel hoses you have under your bonnet. Please, don't do this, even for a little while. <_<

Is that the only problem with using acetone? What kind of tubing could handle the acetone? I need some cheap octane for my turbo Metro!

russkiypenguin1 · Post by **russkiypenguin1** » Wed Nov 10, 2004 9:37 pm

Logbear: I don't know what to tell you. He's done me right in the past. My real dilemna is do I have him rebuild the entire carb or just swap the power valve.

Lateer's description of how easy the carb rebuild is makes me want to just have him rebuild the whole thing. B)

Logbear · Post by **Logbear** » Wed Nov 10, 2004 9:57 pm

I imagine you will have to get a carb rebuild kit with all kinds of little parts.
I don't know if you can get just one small part. I would opt for the whole rebuild. That way no matter what the problem is in the carb, it will be taken care of.

Does the car run good at speed but just won't idle? Or is it not running good at all?

arbskynxnex · Post by **arbskynxnex** » Thu Nov 11, 2004 12:57 am

I rebuilt the carb myself when I was rebuilding my engine. It took me maybe five hours to rebuild it, but that was cleaning it with carb cleaner and steel wool and probably 60000 miles of oil blown back from badly adjusted valves. Just make sure you lay the parts out in the order you took them off, take a few (lots) of pics, and have a large area with a light colored paper or cloth so you can see all the parts ok. Oh yeah, it even started when I was done.

My kit only cost me $27 and it had all the gaskets to fit some of the carbs on the 4a too. Although it was generic enough to cause some headaches.

russkiypenguin1 · Post by **russkiypenguin1** » Thu Nov 11, 2004 4:24 pm

Logbear: Nah, you can buy the Power Valve. The parts person in Toyota pulled it up for me in under a minute. It's just that I've never rebuilt a carb. If I knew how deep the power valve was buried I would know better if I should rebuild the whole thing. But if it's easily accessible, I'll probably just throw on the power valve and call it a day. If I get time later today, I'm going to dig around in the PDF. Someone said that they have a carb diagram in there, so I'm hoping that will help me.

arbskynxnex: OK, that sounds more likely to me. 5 hours for a carb rebuild sounds believable. I'm sure a mechanic could probably do it in 3 hours or so.

russkiypenguin1 · Post by **russkiypenguin1** » Thu Nov 11, 2004 10:33 pm

OK, so I've looked over the PDF and the power valve is super buried in the carb. If I bother going that deep then might as well do an entire rebuild.

Now an interesting question. Do I pay my mechanic a few hundred to rebuild the carb? Or do I buy a rebuilt carb for $200 at O'reilly's? I probably have the time to swap out a carb one for one. I've got a week to figure it out as I don't get paid till next Friday.

arbskynxnex · Post by **arbskynxnex** » Thu Nov 11, 2004 10:47 pm

I would do the carb myself, or buy a Weber or Holley. The most frustrating part on the stock carb is getting the nuts back on to secure it to the manifold. I don't think I would pay a mechanic to do it, just because if you do it yourself and it doesn't work then you aren't out alot of money that you'd be spending on anothe carb. If you could find a mechanic to do it for under $100, and yes I've actually heard of one doing a carb for that cheap, just last year, then I'd pay him to do it.

chilibilly · Post by **chilibilly** » Fri Nov 12, 2004 12:23 am

Assuming your mechanic is right and all you need to do is replace the powervalve. You could buy one from toyota or get a rebuild kit for 25 to 30 dollars from a parts store with the power valve in it. Take off the Air Cleaner. Unscrew the top of the carb without removing it. Tilt the top piece of the carb out of the way. Replace the power valve, put the carb top back on, assuming you didn't screw up the main top carb gasket. If you did and you have the rebuild kit they usually contain two top carb gaskets. Replace Air Cleaner. Your done. This should take someone who's done it before about 15 minutes. Start the car. If the problem is solved, your mechanic is a genius. If not and you bought the carb rebuild kit. Proceed to remove the carb and totally clean and rebuild per instructions. Its not that hard, you just have to be meticulous.

tercel4wdrules · Post by **tercel4wdrules** » Fri Nov 12, 2004 11:11 pm

Some carb people over here rebuild carbs for $100. Some do a good job, some don't and I have gotten a good one and a bad one. I've even heard of some people rebuilding carbs from some of these people for as low as $50!