Topic: Bad Gas Mileage

[83MT]

Sorry if this is asked a lot but I feel like I've put some work into finding the cause, so...I'm working my way through the FSM trying to rule things out, but...if I'm getting 10mpg in town, 15 highway, in an '83 22R recently rebuilt (about 8,000 miles), rebuilt tranny, new clutch, clean air filter, replaced all but about 6 vacuum hoses, just cleaned the egr valve, stock gears 30x9.50 tires.

What I know-my egr vacuum advance module is plugged up
                 -I have a lot of black crap in my tailpipe that could be unburnt fuel

How do I adjust the carb if I've got unburnt fuel, and does anyone have a method of cleaning the vacuum module since they want $88?

And does anyone have carb rebuild kit recommendations? Toyota is asking $79 for JUST a gasket kit, not all the other stuff that would normally come with a rebuild kit, and NAPA doesn't have one specifically for my truck, just for the "most common" Toyota carb, whatever that means..any advice?

And I still have to check to make sure the brakes aren't dragging..

[Duffil]

what's the number on your carb?

[83MT [OP]]

I'll get that for you, I looked yesterday and just saw an A 13 or something, but no long number like NAPA was looking for. Somebody pointed me towards Advanced Auto and I do see some kits on their site, but I guess until I find my carb number I won't know.


And I should have mentioned yesterday, I just did my timing a couple weeks ago, too, so it should be fine.

[Duffil]

there should be a small silver tag with a 5 digit number on it.

[83MT [OP]]

And is that tag towards the base, on the drivers side? Because I see a spot with two empty screw holes...and I cannot find any numbers other than a sideways 13 next to an A. Anyways, how likely is it that if I get the number off someone elses '83 carb, that it'll be good enough?

While we're on it, my carb was either rebuilt or messed with, because the plug over the idle mixture screw is gone.

I was looking at a site on aisin carbs, and it outlined the way to set idle mixture if it's been messed with. It says (at operating temp) to turn the mixture screw until you get the fastest idle possible, then set the idle speed screw where you want it, and continue this process until turning the idle mixture screw does nothing to the idle speed. My problem is, I turned the mixture screw until my idle wasn't getting any higher, then turned the speed screw, and it dropped the idle a bit, but not much. So now, no matter how far I turn the idle speed screw, my idle will not drop any more. Am I missing something in the instructions? Anybody have a better way of setting it? It's idling fine now, just a bit high, but not bad.

Also, does idle mixture just affect idle, or overall mixture? So if my idle mixture's off, could that be why I've got a bunch of black crap in my tailpipe?

[83MT [OP]]

Ok now what about this...I had a mechanic look at my engine because after the rebuild I've noticed some oil buildup on the front (timing cover etc). He said yes there's some seepage but nothing to worry about, no drips, but the reason for the oil on the intake, and on the fuel pump and hoses, and even up onto the bottom of that side of the air filter housing is because the mechanical fuel pump has a leak and it's coming out the seep hole. Is there any way that if oil's leaking out of the head, fuel could be leaking in? Might not be my mileage issue, but it won't help, nor will it help my oil if there's gas dumping in there...
Still doesn't tell me why my tailpipe has a lot of black crap in it, but anyways, it got me thinking.

Now, back to my carb....

[Highwayman]

Interesting as your engine sounds a little like mine. Leaks in the same place after buying a remanufactured Jasper engine. My rebuilt carb runs rich I have been told which could be the reason behind my lack of fuel mileage. The manuals I have haynes and chilton don't cover enough for me to have the faith to mess with it (need more pictures). I was able to adjust the idle though.

[83MT [OP]]

Yeah, I was able to ajust the idle, until I messed with the mixture. I'm checking for sticking choke parts now, but I've got everything really lubed with white lithium grease right now, so it shouldn't be sticking unless there's something bigger going wrong. I'll just make sure nothing it sticking, screw the mixture screw in all the way and start again from there. If nothing else, it seems to be running (and idling) just fine right now, so maybe it's ok. I also just bought a fuel pump, which may solve more problems than I expect (I hope ).

I'm going to advance my timing a bit and try some seafoam and see if that helps, and if I get around to it, clean & adjust my rear brakes, make sure the e-brake isn't grabbing etc. I know my ebrake doesn't work right now, but I figure it could be slightly stuck on.

Get an FSM, and visit this site http://www.bluebassdesign.com/boonin/carb_faq/
Gave me a lot more confidence to mess around.

[83MT [OP]]

Well, I put in the new fuel pump last night. Hopefully that will have some effect...
Still can't find what carb I have but it's very different from another guys '83 so I'm wondering where I'll find a good vacuum diagram for it.