Roark

The truck in question is an '89 4x4 V6 5 speed.


Last September, I replaced timing belt, water pump, crank/cam seals, both timing pulleys, and thermostat to both refresh the front end and remedy the quart every two weeks oil leak.. Before the breakdown, the truck was getting 17-18 mpg consistently, but after, it was getting 14-15 mpg consistently. My initial reaction was that I wrongly installed the belt, but I was told from multiple toyota buds that were the belt not correctly installed, there would be much bigger issues than a few mpg, so I let it be. Then this January I pulled the transmission and replaced the clutch and hydraulics and in March I installed the Downey headers I bought a while back. IIRC, I also checked the timing while installing headers and it showed at about 10* and I adjusted to 12* per suggestions from aforementioned toyota buds. Now, the truck gets 17 mpg again as if it returned to normal.

My question is, does the change from 10-12* in timing plus the Downey headers affect mileage that substantially, effectively curing whatever problem I created by possibly knocking timing out of whack when I replaced the front components? Or, does that change increase mileage to 17 from 14 when it could increase it from 17-19 but cannot due to whatever issue still causing the initial decrease in mileage?

I have until June 28th when I head out for a long road trip in the truck, so if I can squeeze out a few more mpg, I'm all for it. But I also don't have the luxury of tinkering with the truck as it's my sole vehicle.

Any and all advice is welcome!

Thanks guys.

MudHippy

The change from 10° to 12° wouldn't likely do anything for your mpg(good or bad). The headers, in all likelyhood, would though. More HP = More MPG. No getting around that.

Whether or not there's some kind of underlying "problem" keeping you from getting better gas mileage than you should be, I don't know. Maybe, maybe not. I can think of a lot of things you might want to take a quick look at, before concluding that you messed up the timing belt install(which I kinda doubt you did). Mostly simple stuff like, plugs, wires, cap and rotor, air filter, check for vaccuum leaks, run some seafoam through it, make sure your tires are properly inflated, etc., etc..

And if you want a little bit more mpg, without having to do any kind of tinkering whatsoever, you could just run premium fuel(if you aren't already). That'll net you an automatic mpg/hp boost. Not for free of course, but definitely worth the extra 20¢ a gallon...IMO.

Scrussanation

one thing that messed up my mpg was when I realized it wasnt running right after doin plug swap,,, never use import plugs mine failed after 2 weeks... also off subject but mudhippy I love love love your signature... wish more people did it lol

Roark

I will be sure to try out/calculate premium fuel/mpg for the next few fill ups and hope for overall gain. Thank you for the information, MudHippy. I've got a few areas to start checking!

Roark

I am running cheap Autozone plugs.. Hmm

Thanks, Scruss!

Scrussanation

First and foremost i want to give a big thank you to mudhippy. Ive been on this site for quite a while but not near as much as some and learned alot concerning fuel injection. Most the time i search for a issue like minei can usually find someone else who had that problem and give me an idea where to start looking.. I tried finding a thread that mudhippy had stated regarding timing... I remember hisexact words in regards to knowing where your timing on your enginerunsbest.. Those words of wisdom are as follows... "You Just Know!!!" Again thank you mudhippy as most the time im looking for a suggestion or good answer he always has one.. I would love to shoot the ˟˟˟˟ with this guy regarding my 89 V6 3vze as he too is in tune with his truck. Ive advanced to roughly 20-22 on the timing and like he said you'll know if its where it should be.. Ive been sitting at 12 but still seemed itneeded something.. Mudhippy hit it with a nail on good advance on timing.. I always love finding a post he chimned in on because most of what ive seen he knows his ˟˟˟˟... I just wish i knew as much as he did lol...maybe i teach you rv and you teach me what you know lol. Thx mud!

Scrussanation

Oh and i do the ngk plugs..whichever one that cost the most.. I will sqy the ngk wires are phenomenal. I love feeling and hearing the click on the boot for the plug. I know those imports didntfeel right to me and hence why they failed lol.