13.0 - 13.5 MPG, stock drive train

[Nailzs]

new plugs, wires, injectors, radiator(it was leaking), rad hoses, thermostat, intake gaskets, rebuilt tranny(yeah, that was a nightmare), clutch, slave cylinder, rear main, pads, rotors, calipers, fuel filter
engine has been decarbed 3 times, blue devil coolant sealer has been ran through twice(head gaskets leak on cold starts, blows white smoke), tb is clean, maf and iat is clean, intake has been cleaned out and so have intake ports on heads(as best as i could)
the headgaskets were leaking when it was warm also, but now only when cold
some of this stuff has nothing to do with gas milage, but i wanted you all to know everything that ive done to it(that i could remember atm)
the drive train is stock, i took my 33's off and my "cold air" intake and put on a stock intake hose and breather box and put 235/75/15's on to see if that would help my mpg(thinking that the extra load of turning the bigger tires was what was killing me)
my mpg actually got worse. with my 33's i ussaully got 13.5 - 14
at this point im at my wits end. i know that my little head gasket leak would cause a loss of mpg and power, but not this much i would think
any idea's/suggestions? im at my wits end here


oh, and MAKG, i owe you an apoligy. in a previous thread of mine you told me something was wrong with my truck and i didnt believe you. then i discovered the leaking head gaskets. well, you were right, and i apoligize

 

[MAKG]

Apology accepted (actually, it was forgotton...).

Even a modest head gasket (or head crack) leak allowing coolant into the cylinders can "poison" the oxygen sensors and cause it to run pig rich. Often, if any complaints at all come from the PCM, they will complain it's lean. This is because ethylene glycol contains oxygen.

There is little point in replacing the oxygen sensors prior to fixing the head/head gasket, as the new ones will get poisoned as well.

Stop-leak or block sealer is a bad idea. It doesn't often work, and some types may require you to resurface the block (if you can't carefully sand off the residue), normally not necessary on a head R/R.

 

[Nailzs]

oh, i replaced the o2 sensors also. all 3
one of them was bad(the driver side bank), so i just replaced all 3
it made my then code go away and i got my mpg back so that i thought it was normal. the rest of the mpg problem i thought was the tires(thisi s before the discovery of the head gasket)
i didn't think that the 02 sensors could go bad this fast? this was olny this summer when they got replaced, closer to fall

this small leak could cause this? im pretty sure it doesn't leak once its warm, because with a coolant funnel on it i dont see any bubles coming up the radiator
and i have no blow-by(i thought i would throw that in. i forgot to say that earlier)

 

[Jspafford]

My opinion on the matter would be have the leaking gasket replaced and then troubleshoot. Your only causing yourself more trouble by not fixing it properly.

 

[pillen140]

you can test to see if there is oil in the coolant to make sure that is the problem(if its an internal leak). if it is leaking, all your work is like throwing a bandaid on a severed arm. i would do the head gaskets, while your at it get them planed flat and checked for cracks.

 

[Nailzs]

aint got the money for head gaskets right now
and if one of the heads is cracked, i really dont want to know

but if i do do them, what should i get done? any head modifications? are these engines interfernce engines? i can do the work myself, its just getting the machine shopto do the heads and making sure i tell them the right things

 

[MAKG]

Yes, a head R/R is a good major DIY job. It's not hard, but it does have quite a lot of steps and will take a bit of time. No expensive or large tools are required. The worst is a T-55 torx socket. Get a good one; you do NOT want to shear one of these off in the head. Make sure you have a reasonably accurate 1/2 inch torque wrench. Once you get it removed, take the completely assembled head to a machine shop for cleaning and inspection. Inspecting it yourself requires a valve spring compressor, good quality caliper, combination square, dial indicator, and Prussian Blue. None of these are expensive, but you may not have anything but the square lying around. Haynes and Chilton's books are quite good at describing head removal and inspection.

The engine does not need to come out of the vehicle if you only go as deep as the heads.

While the heads are removed, check the deck for flatness. All you need for that is a steel straightedge and a feeler gauge.

Modifying a head will only make it more difficult to figure out what's going on. And there aren't any modifications you can do by eyeball that will make any difference. You might have a good machinist with performance experience AND a flow bench and pitot tube do that, but you're unlikely to see significant benefit without also changing the cam, valve springs, rockers, etc. It gets real expensive real fast; not a good thing to do if you're starved for cash.

I don't believe it's an interference engine, but it's a good idea to pretend it is. But it doesn't make a difference on an OHV engine unless you have removed the timing chain (for OHCs, you have to have separated the cam from the crank, so you have to set them up before installing the head).

 

[Nailzs]

wasn't really concerned about the performance, as just fixing this would probably be a huge gain. i was more concerned with the oil flow problems that the lifter had and stuff like that