i semi-recently came into possession of a 91 s-10 blazer, v6, 4.3tbi, etc etc. it seems to have passed through the hands of a lot of backyard mechanics and while some things seem well maintained, it's scattershot. anyway.

i was aware my truck needed a new intake manifold gasket so i took it to a friend, an independent mechanic since despite being comfortable with basic maintenance stuff so far, i didn't want to take a chance botching or going over my time limitation since this is my primary work vehicle.

after the work it was running very poorly in short order, like full blown missing, flooding at times, we even got it backfiring up through the throttle body once or twice when trying to get it started/running. my friend was convinced it had to be the temp sensor and after some finagling narrowed it down to the temp sensor wiring and redid that, and threw in a little tune up for the trouble. spark plugs, rotor button, checked the timing. i was grateful for it since spark plugs on these trucks are such a pain as i'm sure everyone here is aware and i wasn't really looking forward to doing it myself.

it's been running solid ever since, so i decided to track the mileage for a week. it comes in at 18mpg. i measured it when i first got the vehicle, it was about 17. so i'm going to chalk this up under "no difference whatsoever" which is pretty disappointing (especially considering one of those old spark plugs wasn't even firing initially, the wire was apparently not connected as he told me? who knows.)

i do take into account this is a 20 year old engine, but this is my first truck, and also my first vehicle of this age, so i'm curious if 18mpg is to be expected at this stage of it's life or if i should be looking for more issues?

i ask because while the truck has run solid since all the aforementioned (about a week), the last two days it's been popping the check engine light at me on and off, with no pattern i could yet call concrete (though i have my suspicions). when i hit the aldl with my incredibly advanced scanning tool (paperclip) it gave me a code 15 which my factory service manual lists as, yet again, a coolant temp sensor issue (abnormally low temp). i guess my concern here is it may be running in open loop or limp home mode or something that's killing the gas mileage. is that a possibility or am i just overthinking what is probably a simple issue?

oh, this is probably important information: the on-dash temp gauge doesn't work. havn't been able to find a replacement instrument cluster anywhere locally so i'm probably going to just bite the bullet and mount something discretely to the dash soon here. so unfortunately i can't actually say what the engine is running at when it pops the check engine light.

thanks to anyone who can provide any insight who struggled through my book here. i've been trying to read this forum regularly since i got the truck, be they issues i've had myself or not and found it quite the informative place.

 

I miight have a temp gauge, or a cluster that I could give you if you'd be willing to cover shipping. And fwiw, my truck's getting 15 hwy, with 4.11 gears and the same engine as you. If yours is 2wd, you're probably getting good mileage. if it's 4wd, you're getting pretty great mileage.

 

Couldnt tell you what it is in milage (we dont use that up here) but my 93 4x4 gets 410km or so to a take of gas (65litres) in town, and around 500km on the highway. In the winter when its -30 I can almost cut that in half due to warm up times and using 4x4 alot.

Does your on dash temp gauge not read anything, or peg all the way? And your coolant temp sensor for the dash, and the one that has some kind of fault for runability are two different sersons if you didnt know already.

 

ohso: according to google convert, you're getting 14.8MPG. or 6.3 Km/L. in town, anyway. Highway that's... 18! Crap, my fuel economy sucks! my 15 figure is almost completely highway.

 

I get between 19 and 23, almost all interstate highway driving, and always in overdrive.

 

My 92 S10 2 door 4X4 automatic 4.3 W engine whihc I bought new in 92 gets about 21-23. Yet I understand 18 is about right for the 4.3 TBI.

I know that the parts store owner has a 94 S10 pickup 2 wheel drive automatic 4.3 TBI, he says the best he has ever got is 18 MPH.

So it seems your getting about what your suppose to.

 

the other thing is that the PO swapped the gearing in the diffs to a higher ratio, and my engine has to rev higher on the highway.

 

i'm starting to learn not to take what other people say about cars at face value. the guy i bought this truck from just dismissed it as "oh, the temp gauge doesn't work." so i never thought more of it.

i actually paid closer attention today and saw that it does in fact move, simply very little. from totally zero at start up to a level i'd call about 130 on the analog gauge when running. so the needle does actually seem to move. i can't believe i never really looked at it for half a year. that's what i get for trusting someone else's word over my own eyes.

i was also unaware there are two different sensors, the one i'm aware and which i refer to when i say "temp sensor" is the one that's mounted to the engine block near the thermostat housing. is this the fault sensor or the gauge sensor?

do you have any thoughts on this? could it still be a physically bad gauge, or just the sensor? or even a wiring issue?

it's not something i've looked into at all because.. i just believed what i was told. i was never what i'd call a car person before owning this vehicle, i need to break myself of the habit of implicitly trusting what other people tell me about vehicles, especially mine. in particular when i know this douchebag has misled me about other things related to ze truck.

also good to know the mileage is pretty much where it should be, thanks to everyone who chimed in with their experience.


and theonetruetom, i'd definitely say i'm interested, pending determining if there really is a problem with the gauge itself or what. if you or anyone else here has any knowledge regarding this issue, please feel free to let me know. there is a bulb out in the instrument cluster anyway which makes it difficult to read at night, so i've found myself thinking of replacing it anyway if i'm going to the trouble of cracking it open to replace a bulb.. and then i read things like this and start wondering just how ambitious i'm feeling.. god, i love how 90s that digital dash looks. i can practically hear the theme from total recall playing just looking at it. it's the future! led's are THE FUTURE!

 

Oh man, I didnt know you havent checked it out much yet. Here, this is the one that runs your gauge. Its got a crappy little connector on it check and see if its loose of whatnot.

This is looking at the passenger side head.


And the sensor is that little gold thing. If you change it, make sure you do it fast, like have the new on ready to go in with teflon tape on the threads already. Its going to leak when you take it out, so get the new on in fast so you dont spill much.


It seems you know where the one that will affect runability is - by the thermostat.

And for changing your dash bulbs... They come in boxes of 25 - I dont have a part number. But it was like $8 for the box and they are all easy to change if the dash cluster is out, they have little plugs that twist out. Theres probably about 20 in the dash. The cluster is not that easy to get out, you will find the cables on the heater controls are a nightmare, just leave them hooked up and try to wiggle the cluster out from under everything. I wouldnt even know how the heater control cables are unhooked.

 

Oh, mine had 3.42 gears from the factory.