Fuel mileage issue!

[Chris6060]

Hey guys, so, I have a 1994 Chevrolet ECSB K1500 Silverado with the TBI 350 in it. I've done the ultimate TBI mods except the quarter mod/fuel pressure regulator. It has shorty pacesetter headers and true dual exhaust with dual high flow cats and dual flowmaster 40s.

I'm getting around 330kms to 85-90L of fuel... So average of around 22L/100km or 10MPG.

I've tried driving he truck nicely, hard, everything, fuel mileage barely differs.

Timing is advanced, according to a timing light, past 12 degrees, but its the only way the motor runs right, if you retard it down to 12 degrees or 0 degrees, it can barely pull itself forward. Maybe its a crappy timing light... I dunno. I don't have another timing light to try right now. All I know is the line is long past 12 degrees and it runs like a top... Pulls 2000-2013 5.3s all day through first gear.

So I don't understand why my fuel mileage is a steady 10 MPG regardless of driving habits, and its starting to get hard to afford!

Thanks in advance for any help/ideas you guys can give!

 

[skylark]

2 things. Are you disconnecting the est wire when setting the timing? Has the outer ring of the ballancer slipped causing the marks to be off?

 

[Chris6060]

I didn't disconnect the est wire, what is it?

and maybe the outer ring has slipped, I really don't know. When I went to advance the timing in the first place, the timing was already way past the 12 degree mark.

Point is, the engine runs like an absolute top as it is, I just wanna figure out why my fuel mileage is so crappy.

 

[Scrufdog]

if you want to properly set the timing, google up how to set timing on these engines. If I remember correctly a 94 has the wire behind the glovebox taped to a large harness. Should be a tan wire with white stripe... maybe an orange wire on this truck. It will be a 1 wire harness that you unplug, start the engine, and set the timing. Shut down the engine, plug back in, reset computer by disconnecting battery.

Edit

Set timing from somewhere 0-6 is generally acceptable for a stockish engine and stock chip.

 

[Chris6060]

if you want to properly set the timing, google up how to set timing on these engines. If I remember correctly a 94 has the wire behind the glovebox taped to a large harness. Should be a tan wire with white stripe... maybe an orange wire on this truck. It will be a 1 wire harness that you unplug, start the engine, and set the timing. Shut down the engine, plug back in, reset computer by disconnecting battery.

Edit

Set timing from somewhere 0-6 is generally acceptable for a stockish engine and stock chip.

I'll look it up and set the timing the correct way this weekend.

Thing is, I've felt the truck run when the timing isn't set correctly and I've driven it the way it is now. And I know that I can't find a spot where it runs better than it does right now.

One of my buddies had a '91 that he advanced the timing to 12 degrees on, 90% stock, and it ran like a dream... I dunno, I find that each truck is different in certain ways.

I still don't think my timing as it sits right now is the cause of my poor fuel mileage though. I just want more ideas.

I've been thinking about getting a tune for the truck, but I don't know where would be the best place to get one done... No where local does that kind of stuff, and finding anywhere to do an OBD1 tune is probably hard.