you did the compression test with the throttle wide open right?

 

OK so I am back with an update, and I am not sure whether it is good news or bad news. There has been an increase in my mileage, but not as much as I was hoping for. I now have a new exhaust, and have checked everything that was remaining on my list.

As far as I can tell, all of the sensors are working properly. The one of the tests on the VAFM was barely on the low side of resistance for spec but not enough to call for a new part. The ECT sensor is an absolute b*tch to get to to check resistances so I have no idea of what I got was accurate.

I am now averaging about 6.5 kpl (15.2mpg) which in my opinion is still quite low, but from what I hear can be pretty normal. I am going to keep trying to find something that is causing my low gas mileage but im starting to think that 15.2mpg is about as good as I am going to get out of her.

 

As for new possible issues, I have two and I am wondering if you guys think this may be connected to my mileage woes:

My idle seems to like to bounce around very slowly. Its not a rapid thing where I can watch the tach bounce, but over the course of driving somewhere, the idle will wander anywhere from 1100rpm to 200rpm. Most of the time it will sit around the 800rpm that I set it at, but the wandering idle has my concerned that a sensor is still out of whack. Any ideas what sensor to look at? (the tps for sure checks out cause I took it off the truck to check it. ECT i thought tested fine but now I am not so sure.)

I am also pretty sure that I have an exhaust leak higher up in the exhaust system, most likely by the manifolds or the downpipe. I need to get in there and check for it but the tell tale signs of a fairly loud tick and exhaust fumes in the cabin sometimes when driving are there, so now I just need to find it. Could this have an effect on my gas mileage?

 

Yes those tests were done with the throttle wide open. thanks for asking

 

Do the resistence check at the ECM it's a little easier to get to.

Is that a typo maybe? It definately shouldn't be droping to 200! How consistent is that issue, can you probe some sensors when it's happening check the timing, maybe pull the vacuum on the fuel pressure regulator, toss a water sensor inline with the idle control lines.

Exhaust leaking before the oxygen sensor will cause you to run rich. (Bad for MPG's)

I'd run some injector cleaner thru it, can't hurt much can help alot. Perhaps it's sticky injectors.

And finally consult the big MPG thread with your tire size and gear ratio handy and see how you compare. Of course these are kind of subjective due to driving habits and terrain but should help you figure out where you should be in the ballpark.

 

I hadnt thought of checking it at the ecm, I will give that a try.

Unfortunately not that is not a typo. It will wander all the way to around 200rpm and will often stay there till I shut the engine off and come back later to drive it again.

I am going to try and figure out where my exhaust leak is so I can get that fixed, and then maybe my mileage will improve a little more.

I ran some seafoam through the gas tank when I did the rest of the seafoam treatment, but I am thinking it may be best to run an injector specific cleaner through them as well.

Thanks for the help Co_94!!

 

hope this might help. I was getting horrible gas mileage and hesitation on acceleration until fully warm. come to find out, I replaced my fuel return hose at the fuel pressure regulator which is on the fuel rail awhile back and it had a slight kink in it which caused me to get horrible gas mileage. fixed the kink. problem solved...