1996 4.3L Vor

Just took it in because I was having problems with it stalling out when I was giving it gas. Was told it was the fuel pump, so I had it replaced (along with the starter cause that was giving me problems as well)

Well now my gas milage is bad
When I first got the truck about 2 years ago, i would be getting about 310 miles to the tank, roughly 16mpg (mixed city and hwy)
Then it went down to 280, 15.5mpg
Now after having the fuel pump replaced, I am lucky if I can get 230, 12.8mpg.

I had the fuel filter changed while they were at it, only cause I didnt feel like dickin around with it on a wet and cold garage floor (chicago winter).

The engine light isnt comming on....but I have no clue where to start to get my gas milage back. Any ideas?

Time to do a tuneup.

well what would I have to change out for the tuneup?

I replaced the spark plugs not 5 months ago with some Rapidfires. Cap should still be fine, but I will check again.

Tune-up? When was the last time you did a complete tune-up? Plugs, wires, cap, rotor, air filter, pcv valve. A bottle of injector cleaner wouldn't hurt either. Does it run okay? Do you smell gas? Where does your temperature gauge stay? (stuck thermostats are a common problem with these things and if the temp. doesn't get high enough the computer won't go in closed loop and this will hurt your fuel economy...mine used to stay a little below a 1/4 and I didn't know it was a problem til I came here, I changed the thermostat and got another 1.5 mpg)

Unrelated:
If you haven't done so you are also due for an antifreeze change too. You need to change your radiator cap with one not made by AC Delco too.

That took a long time to type there were no replies when I started.

Hehehe....

Follow what Blazee said.

What Rapidfires did you use?

What model #?

Also, you "think" the cap and rotor is ok after close to 10 friggin years?

Well about 5 months ago. Changed the spark plugs, the wires, cap, rotor, and cleaned the airfilter (KN box filter).
PCV valve I havnt changed

Injector cleaner I use once in awhile ( once a month) when I fill up.

THe temp needle stays at about the 1/4 mark.

And why do I need to change the radiator cap?

Had the coolant flushed last week as well.....and thats got problems I was gonna take care of eventually. When I got the blazer, Ive had it flushed maybe a total of 8 times, and there is still this crap in the system. It looks like a brown sludge almost.

model for the rapidfires was #12 I believe

And why do I need to change the radiator cap?

Had the coolant flushed last week as well.....and thats got problems I was gonna take care of eventually. When I got the blazer, Ive had it flushed maybe a total of 8 times, and there is still this crap in the system. It looks like a brown sludge almost.

The radiator caps are defective and cause the dexcool to turn into a brown sludge. You should buy a 16psi Stant from Advance Auto. Since you just had it flushed you may be okay by just replacing the cap but if the sludge comes back... you will need to do a complete system flush (including a back flush and chemical flush) to remove all the sludge and open any clogged passages. After that you should have no more problems, just keep the system full and flush and replace the antifreeze every three years.

Yea, replace the rad cap.

We have found your problem.

your thermostat is stuck open.

Temperature gauge should be reading just to the left of the 1/2 mark.

And there is your problem, replace the stat with a 192f, replace the rad cap, reset the computer by pulling the negative battery cable for 30 minutes and you will be good.

Yea, replace the rad cap.

We have found your problem.

your thermostat is stuck open.

Temperature gauge should be reading just to the left of the 1/2 mark.

And there is your problem, replace the stat with a 192f, replace the rad cap, reset the computer by pulling the negative battery cable for 30 minutes and you will be good.

ok, so for the rad cap, you are talking about this one (http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=STB&MfrPartNumber=11230&PartType=116&PTSet=A) ?

And forgive my "newness" to this, but what is that 192f you speak of? And how difficult will it be to replace? Where is it done in my truck?

and the thermostat could vastly affect the gas milage? I wouldve never guessed that. Thought they were somewhat independant of each other.

THe temp needle stays at about the 1/4 mark.



This one I am a little unsure about. The normal is one click left of 210. You have a border line temp. probably suggesting a partially stuck open thermostat (which wouldn't be a surprise with all the sludge you've had in your system). This could be causing some of your fuel economy problems I would recommend replacing the thermostat.

yet another slow reply :)

Yes that is the right cap, The 192 he is refering to is the temperature rating of the thermostat...I believe most places list them as 192/195 thermostat

ahh ok. So any suggested brand for that as well? I see that advance auto site listing 6 different thermostats, 2 from Stant, 1 from acdelco, and 3 from prestone. 2 from Stant, one is a superstat, other is a reverse poppet. The superstat would be the one I want, correct?

I hope BlazerLT isn't answering this and I am wasting my time, but.... The thermostat is in the housing where the upper radiator hose enters the top of the motor it is fairly easy to replace. make sure when you buy the new one that it comes with the seal.

How a thermostat effects fuel economy:

A stuck thermostat doesn't allow the engine to reach operating temperature, when the computer sees that the engine isn't warm enough, it adjusts the air/fuel mixture to try to warm the engine, this causes incresed fuel consumption.

Get a AC Delco thermostat and a Stant Rad cap.

ahhh ok...


and another off topic question. Could there be scannable codes if the check engine light isnt on? or do ALL codes trip the engine light?

ahh ok. So any suggested brand for that as well? I see that advance auto site listing 6 different thermostats, 2 from Stant, 1 from acdelco, and 3 from prestone. 2 from Stant, one is a superstat, other is a reverse poppet. The superstat would be the one I want, correct?

As far as the brand of the thermostat.... I really haven't heard of any problems that would suggest any one brand is better than another. I replaced mine with one from NAPA (I don't even know what brand it was).

When you replace the thermostat will first need to drain some of the coolant out so the level is below the thermostat housing. (about a gallon) Drain it into a jug so you can put it back in when you're done. It may not all go back in, so you will need to save it and keep the system topped off as the air is worked out. (it may take a day or two)

Guess I need typing classes.

lol....nah

it all comes with practice, like all things.

When the computer senses a problem it trips the light and the code is stored, even when the light goes out the code will be stored for awhile. ( a certain number starts or disconnecting the battery will clear it)