1986 22r pu getting 12mpg

[Maz]

Greetings all and my first post here. I hope I am in the right place.

I bought a 1986 2wd pu with 22R (carb), auto tranny, 137K miles, bone stock. She was in a terrible shape. I was getting 11 mpg, but she passed California smog inspection with flying colors.

To give the pu new life and to remedy poor gas mileage, work done so far includes changing, PCV valve, plugs, plug wires, cap, rotor, air filter, fuel filter, fuel pump, intake manifold gasket, decarbed EGR, EGR pipe, carb and internals. Had the ignition timing checked by mechanic and it was to spec. The problem is I'm now getting 12 mpg. I am not sure on how to check carb further and adjust idle (no tach). The idle is not smooth. I am planning to have the dealer check/adjust the carb, but shutter on the idea of the dealer telling me I have to change half the engine.

I suspect a bit of exhaust leak at the manifold. Could that cause poor gas mileage? How about Ox sensor? It looks ancient. Would out of spec valves be the cause? I doubt the valves have been adjusted in a long time.

I am looking for advice on what else to check/change.

BTW, FWIW, the truck is underpowered (takes a long time to get up to 65 mph), and also the tranny won't shift down without some wiggling of the gas pedal, in case any of these are related to poor mpg.

A big TIA ... Maz

[Bakemono]

Its possible that you need to get the carb rebuilt. Perhaps the valves need to be adjusted. All of those could be hurting your fuel economy.
The fact that it is an automatic hurts it as well. Older Toyota automatics were known for poor performance and fuel economy compared to their manual tranny'd siblings. The newer automatics are much better and can even rival the manuals in terms of performance and fuel economy.
The fact that you have to really stomp on the gas pedal to make the truck downshift hurts the milage. Perhaps you could try manually downshifting the truck rathar than using the gas pedal to make it downshift.
Im not sure how the shifter on an older automatic like that is set up (if its mounted on the steering column or if its floor-mounted) but it should have a button the prevents the tranny from shifting into overdrive.
If not, there shoul be some other way. Perhaps it has P, N, 1, 2, 3, D. If so, try downshifting it manually into 3rd.
You also might have to accept the fact that this truck is past it's prime and wont pull 20 mpg. I had an '85 4Runner and all it was good for was 14 mpg (22R-E with a 5-speed manual). I would think that your's would get better than 12 mpg just because its a 4-banger and a 4x2 but then again its an automatic so who knows.
Best of luck...
Cap'n

[Maz]

Thanks Captain-Toyota for the reply.

I do understand that the older automatic trannys rob power.
The tranny shifter is on the steering column with OD button.
I don't have to rev up for the tranny to downshift. Actually, I have to let up the gas for it to downshift. Odd!

-Maz

[Rycam]

One of the most common causes of a fuel hungry truck with a 22r carb is a leaky "auxilliary accelerator diaphram" in the "auxilliary accelerator pump system". this part can be accessed from the outside. The danger comes from a diaphram with hole. This lets gasoline get sucked through the vacuum line attached to it. This extra gasoline can cause "fuel washdown" when so much raw gas get sucked into the engine that it removes the protective oil film from cylinder walls from the running engine. This can ruin an engine.

Most people who experience a broken diaphram can see raw gas inside the the thin vacuum line attached to aux. accelerator pump...and most say they smell raw gasoline from the tailpipe.

A new catylitic converter can cover a lot bad engine dynamics by burning the exaust clean.

I wish I could be more specific where the "auxilliary fuel pump" is but there available manuals available. I do know that it has 3 screws covering it, and a bent metal vacuum nipple with a small diameter vacuum line coming out of the center. I believe it is located at the top...front driver's side... corner.

I will see if I can find a web pic!

[Maz]

Thanks Rycam;


I know where the auxilliary auxiliary pump is (on the side of carb, close to intake) and it checked out OK when I followed a procedure to verify that it's working. I forget the procedure now. It's about a $40 item, so since you mentioned it, I might as well go ahead and replace that too. You could be right about AAP being the cause of my bad mpg. It can't hurt.

BTW, if you want a pic of the AAP, I can send that to you as well since I've taken a few pics of the repairs.

-Maz

[Maz]

Got a new AAP diaphragm from the dealer. $50, ouch.


Took the old one out and it was good. When I took the housing off, a spring flew out and disappeared in the engine bay. I'm mad as hell. No matter what I did, I couldn't find it and the truck is sitting un-drivable. Anybody know if that spring can be ordered separately?

FWIW, I priced a new carb at the dealer. $1200+ !!! More than the truck is worth, LoL. Just for kicks I asked how much to diagnose my truck's problems. They said that they don't (or seldom do) work on carbed Toyota's anymore, and, probably can't help me.

Thanks for reading (just venting a little) ... Maz

[coargonaut]

Perhaps a replacement carb, in the form of a Weber or Holley would be more friendly, pricewise.


Ed

[Maz]

Update. Found the spring and the AAP is back together. No difference at all. Drinks gas and has little power. Scary to drive on frreways as the best she'll do is 65 mph.

Anybody have any other suggestion?

Are Webers Califormia smog legal?

TIA ... Maz

[Bakemono]

Performance Products used to list Weber carbs that are Cali smog legal.
It still sounds to me like that truck is running waaaay rich.
Im not all that familar with automotive carburators, is it possible that the choke is sticking and resulting in a very rich air/fuel mixture?
Whens the last time the air filter was replaced? If the filter is very, very dirty it might not be letting as much air in as it should, and that could be causing it.
Cap'n

[Rycam]

Maybe the float valve's needle seal is worn out. If the carb cannot control the flow, all kinds of probs can arise.

[Maz]

Took her to a shop. Ignition timing was right on with strong vacuum. Idle speed was on 1200 rpm! We couldn't get it below 950, without the engine dying with tranny in gear. At 950, it barely idles. The fuel level in the sight glass was about 1-2 mm above the medium line. Ran an emission test. The result without load was:

HC ppm: 39
CO%: 0
O2%: 4.55
CO2%: 11.3
NO ppm: 62

I don't understand all these numbers, but the conclusion was that the engine was running too lean and starving for gas. She needs to have the carb rebuilt. The price quoted me was $145 if I take the carb to them, or $195, if they take the carb out; with a 3 month warranty. Does that sound reasonable?

I guess I understand that a lean running motor will be under-powered, but does lean explain the 12 mpg? I don't get it. Can someone explain please?

[Bakemono]

It is possible that because you were running lean the engine was running hot. When the fuel entered the combustion chamber, as soon as it touched the top of the piston it was instantly vaporized because of the heat and just blew right past the valves.
Thats the best guess I can come up with, perhaps other who have more technical knowledge than I can give you a more detailed explanation.
Cap'n

[Mr Tode]

Maz:

There is a CA smog-legal version of the Weber 32/36 carb, which is a decent stock replacement on a 22R motor. I've had good luck with Jam Engineering (www.jameng.com) as a source, though a quick visit to their website didn't reveal anything about smog legal kits. They are knowledgable guys, a phone call is probably the best idea.

Whether or not a new weber is a better bet than a rebuilt stock carb, I dunno.