Sometimes I hate these engines.. they are humbly low on power production and thirsty SOB's.. I mean, we didn't even get a choice.. Usually, it's one or the other.. THEN, they made the bastardos tank tough.. meaning you may have issues under your hood you don't even know about- until you do.. Most imports will let you know quick like when even the smallest thing goes wrong, and you gotta fix it.. Not these.. They'll try to bang on five cylinders a week before you turn your radio down and figure something is amiss..

but then there is the gas prices.. and keeping these rascals humming becomes crucial..


So- I read all the time about MPG's and much of it is lost on me.. I run an '02 5.9, 4.56 gears through that gawd awful 46RE and it's sitting on 35"x12.5" rubbers.. I've got several bolt on mods, but still no real power.. I'm damn happy with what power I do have, as this is a truck and not a go-fast.. But still, I'm going to squeeze it for every MPG I can get.. Several weeks ago I was getting 14.5MMPG overall mileage- based on math, not drive computer.. I was happy based on everything I've been reading..

Lately, it has dropped to around 12MPG overall.. for no real reason (I thought, though this goes back to these things being built like tanks, and the reason I mentioned it).. Today, I decided to put off the tranny cooler/remote filter/deep pan project to figure out what was going on.. Well, I found it..

Seafoam is my friend.. It cleans out an engine yadda Blah Blah, but I'll tell you what else it does.. It will pin-point an exhaust leak quick like.

I had a leak at the collector plate, just north of my cat on drivers side (cali-emission truck).. the upwind o2 is about four or five inches behind it.. pff pff pff pff... I had to take the wheel shroud out to get to it, or to even hear it clearly.. I always thought that was a sound my belts were making...

what difference does it make asks you?

My PCM is dumping more fuel than it needed to is my guess.. It was running rich.. I've been trying to figure out why I was running rich after it has been running a while, and now I know..

I discovered this last night.. this morning, on a totally cold engine- I tightened up the header bolts, the collector plates, and every other bolt that I could see that doesn't have a required torque, and fired her up with the shroud still out.. No pff pff pff pff..

Then I took her for a long drive on a full tank of gas.. about 150 miles round trip.. and finished with a top off.. Math says I got close to 14MPG...

A small thing really, that makes a difference..

I thought I'd share..

Next week, I'm going to do the cooler/remote filter and pan.. and I'm going to re-torque the exhaust all over again..

 

whats a collector plate....

 

where the header tubes come together as one and bolt into the exhaust piping. it's a flange with two bolts holding it together.. I have a aluminum donut between them, and one side was much tighter than the other, which was allowing a leak on the engine side of the connection because a) it was in there at a weird angle, and b) I couldn't see it until I saw the seafoam smoke puffing out of it there..

 

Where the Y pipe bolts to the manifold, I think.

 

exhaust flange? is that better?

I don't have a Y pipe.. a matter of fact, had I discovered how jacked up the factory Y is, I wouldn't have headers either- I'd have manifolds and a aftermarket Y or X.. as it is I have shorty headers and true duals out to a magnaflow true X muffler.. as far as I'm concerned, THAT was a waste of money.. I'm willing to bet I would have dang near the same gains I got from exhaust work had I just cut out the Y and replaced it..

exhaust flange.. collector plate.. I think we're talking about the same critter here.

 

It's always something, eh?

Most guys would have seen that smoke there and thought, "No big deal". Stick a gold star to your toolbox, man.