Why only 13-14 mpg, still?

[Michelangelo]

Engine (4 cyl) has 30 k on a new crate engine w/ new clutch too.
Brand new stock spec carb, w/ new fuel filter.
New dist/rotor.
31 inch tires
Valves are quiet (timing has not been checked yet).
Thorly header w/ new 2.5 inch pipe w/ high flow muffler.

The thing will only get 12-13 mpg on the freeway or in town!
It will not pull past 70 mph on a flat stretch of road!

Ideas? Perhaps the fuel pump could be putting out more fuel than it's supposed to be?
I was told the throttle plate might be sticking, but I doubt this could be it, since it was getting the same mileage before and after I put the new carb on. I'm out of ideas and fed up.

Another guy with a similiar ride but 33 inch wheels can at least do up to 90 mph on the freeway, heck I can't get past 65 mph!!!!
It has a very sooty exhaust pipe and I can smell the overrich fuel mixture through the exhaust.

[toy4x4]

gears?

[bbagwell]

I would check the timing first.

[Michelangelo]

I will check the timing but assuming it's correct?
I'm at 4k ft above seal level. Should I advance 4 degrees then?

What is stock timing for a 22R, 1984 4Runner?

[Michelangelo]

I think I found the problem; having to do with the float level. The level in the window on the front of my carb is at the very, tip, top. My master mechanic friend seems to think this is the problem. We shall soon see and I hope this is it. I'll still check the timing, or at least have the mechanic who put it in check it.

[Kyron]

You realize that with the 31's your spedo is off..... and you need to factor that into your MPG

If your friend has regeared with his 33 thats why it'll go that much faster........

[Michelangelo]

Yeah well I've been told the speedo is off but that is not true. As I've said, I've compared it to the mile markers on the freeway and I'm within .5/10s of a mile every time. Even when I put my speedo at 60mph and time myself between mile markers I am at 1 mile or within .5/10s. So..I think the notion that people throwing around of 31 inch tires putting your stupid off, are way out, as in not very accurate.

[Kyron]

Originally posted by Michelangelo
I think the notion that people throwing around of 31 inch tires putting your stupid off, are way out, as in not very accurate.

HUH ....... have you ever looked at a 28inch tire next to a 31inch tire?? What do you think it would take for the gearing and spedo to become wrong?

3 inches DOES make a diffrence ......... ask a girl :Angel:




so your saying if you drove past 20 mile markers your odometer would say you drove 19 miles?

[Michelangelo]

Yes I'm saying if I drove past 20 mile markers, my odometer would read 19 miles. That is hardly enough to account for 13-14 mpg. Don't you think?

What about the accelerator pump? What does that do adn where is it located? I'm still thinking the float level might be a cause too.

[Oatmeal]

Did you try pulling a spark plug and looking at it? It sounds as if it's running way rich. Are you sure you have the correct plugs in there? Spark nice and strong? Pull the coil, cable, hold it slightly away from a ground source, have someone crank it and you should have a fairly healthy spark. Correctly setting the timing makes a big difference too. Going from a 28" to 31" tire is about a 10% error (speedometer reads about 90% of what it would with a 28" tire) If your buddy's truck is running 4.88s and 33" tires, his speedo is reading just a hair faster than actual speed, then again I have yet to see a 33" tire that actually measures a true 33" so, it may be off more than you think. All things considered, though, it should get better mileage than that............Hans

[Michelangelo]

Where in the sight glass (float level), should the level be at? The glass is shaped like a sideways hourglass. Assume the skinny part of that is the range? Should be at the lower portion instead o ftop right?

[84toy]

Originally posted by Michelangelo
Where in the sight glass (float level), should the level be at? The glass is shaped like a sideways hourglass. Assume the skinny part of that is the range? Should be at the lower portion instead o ftop right?

When I ran the stock carb my fuel was set just a hair above 1/4 way in the glass not half.Half way is where it should be set at though.
I ran mine lower because it helped alot when wheelin,climbin etc... also when I would pull a grade or floorboarded down the highway it would starve for fuel,but just cruisin not pushing it,it ran fine.

[Michelangelo]

Well I checked the float level again and this time it appears ok. I think I must've had it on a slight incline the first time, giving me a bad reading.

I also just replaced today, the fuel pump. Wonder if that will make a diff?
I guess my real problem is why it won't go over 65 mph with the pedal to the metal on the freeway? I think if I can figure that out it might fix my fuel mpg problems.

Here are my ideas at this point:

Ignition coil
Timing way off.
Auxillary air pump.


This is about all I can think of at this point.

[84toy]

I would check the timing and maybe play with it alittle until your engine is at it peak perf. Is your choke operating right?I ran my timing at 8*that's what the sticker said on the hood.
You should be getting way better milage than what you are now....

[jvmin]

there are a lot of things that can cause your problems?

the sooty exaust is a big hint of running too rich but that could be during start up. and the choke taking too long to shut off. you may want to check the choke adjustment and see if when it is off that it is really all the way off. that would be my first guess my second guess would be the snorkle heat exchanger (if applicable) you know the little silver tube thing connecting your exaust to your snorkle to make the choke cut off faster.

thirdly the timing could be your problem or your ignition system coil could be weak

your plug gap settings

your plug wires will cause problems as well if they are old and cracked

distributor cap could be cracked even if it is new

you said: qoute"Engine (4 cyl) has 30 k on a new crate engine w/ new clutch too.
Brand new stock spec carb, w/ new fuel filter.
New dist/rotor. "unqoute

where did you purchase the engine from?
the carb is new did you check the choke settings?
are you sure you have all the vac lines hooked up correctly?
is the EGR and air pump connected? correctly? you said it was carbed so it's pre 86
make sure the engine you purchased is your year model and not an earlier year or later year for that matter 84 -85 carbed has different heads than an efi 86 and newer the ports are different from what I understand. (pear shaped compared to oval) the 83 had different pistons in them and different heads as well. to the best of my recollection anyways. 80-83 had low compression pistons and high compression heads. and the newer engines have a high compression piston and low compression head. if you happened to get an engine from a rebuilder that put a block from an 80-83 with a head from a 84-85 then the end result would be lower compression than stock.

go over your vac lines and check the choke settings make sure the timing is right. take it outside on a dark night and crank it up and look under the hood for arcing wires or distributor cap. check the snorkel valve. if you don't have a heat riser tube attached because of the header the choke will stay on longer than a stock set up. one last thing is the air filter new? if so you may want to replace it with a free flow or a new one just to be doubly sure. also make sure the intake snorkle system isn't blocked in anyway. example a crimped or smashed tube or a birds nest or rodent's nest.

a new engine will have a little blow by until the rings have worn in and seated. and this may have allowed more pressure on the positive cranckcase ventilation system causing it to oil the air filter making it flow less. if you find an oily filter replace the pcv valve and filter.

that's about all I can think of right now.

and by the way your speedo is off to some extent if it isn't your defying the laws of physics. or it was off to begin with in the stock set up or your tires aren't what you think they are.

my 33's made 7 mph diff at 55 with stock gears. best way to get it right is to ride along side someone that can signal you and run it at 35, 45, 55, 65, 75 to get the exact amounts. oh strike the last speed until you figure out what's wrong with your engine.

could be bent valves on the head too check the compression someone can tell you what it is supposed to be stock.

[jvmin]

oh yeah and my 33's were really 34's when measured

and my 35's are 34.5 when measured so tire type makes a diff too as well.

[Michelangelo]

Took truck back to my mechanic and told him to check a few things. First thing he found was timing was retarded 2 deg. Wonder if that will make a diff, getting that back to where it needs to be.

2nd thing is one of the choke valves was not opening at 1/2 to full throttle. He could not figure out why the linkage was not opening it. the only thing I can think is that there is an aftermarket linkage on it, probably the one that was running the Holley carb that was once on it. At any rate, he wired that choke valve open and we'll see what happens.