Poor gas Mileage on 350 Vortec and a Miss Still

[davbell22602]

Why do I have crapy gas mileage on my 97 K1500 137k 4x4 ext cab 6ft bed? I replaced starter, alternator, engine belt and fuel filter back 2010. I'm only getting 330 miles on a 26 gallon tank.

Here's what I replaced since Sept. 2011

Brake pads, brake rotors, brake calipers, brake shoes, brake shoe hardware, resurfaced rear drums, rear main seal, oil pan gasket, ball joints, pitman arm, idler arm, CFI to multi port injection conversion, Gibson performance shorty stainless steel headers, direct fit cats by magnaflow, universal joints-rear driveshaft, new pioneer cd player, pioneer speakers front and rear, spark plugs, spark plug wires, dizzy cap, rotor button, PCV valve, amsoil air filter and power brake booster.

 

[davbell22602]

I did a compression check back in January.

Here's results:

#1 - 200 then dropped to 195 within 2-3 seconds
#3 - 200 then dropped to 195 within 2-3 seconds
#5 - 200 then dropped to 195 within 2-3 seconds
#7 - 195 no bleed off
#2 - 195 no bleed off
#4 - 200 then dropped to 195 within 5 seconds
#6 - 195 no bleed off
#8 - 195 then dropped to 190 within 2-3 seconds

 

[JollyGreen]

So I'm guessing no codes? The best I've gotten with mine ('97 w/ 140k on it) is 350-360 miles out of a tank. Those #'s are about what I've gotten on mine too.

 

[davbell22602]

So I'm guessing no codes? The best I've gotten with mine ('97 w/ 140k on it) is 350-360 miles out of a tank. Those #'s are about what I've gotten on mine too.

No codes. I replaced plugs with acdelco plugs and napa plug wire back in october 2011 @130K. I was only getting 300 miles to a 26 gallon tank on the CFI spider fuel system before converting it too ac delco multiport spider injection

 

[JollyGreen]

Sort of off topic, but how difficult was it to change the factory spider with the multiport?

 

[davbell22602]

Sort of off topic, but how difficult was it to change the factory spider with the multiport?

Not hard at all if the old tabs dont break on the spiders when removing them. I had 2 where the tabs broke off and ended up getting them with piliers. The one was actually stuck in the hole and took some to get it out.

 

[am92]

Sorry to be the bearer of bad news, but 330 miles to the tank sounds about right for one of these trucks. Right now I get about 11-12 mpg city/ 15 hwy ... As for the miss, you said it isn't throwing any codes? One of the only things you haven't replaced is the distributor itself. I've heard that the gear can get worn though and that will throw off the ignition timing causing a miss. You can pull it and check to see if the gear has knife-like edges to tell if its worn out

 

[bluex]

How many gals are you putting in it when you fill up?

I usually go between 350-375 miles on 23-24 gals....

 

[am92]

Me? I go about 300 on 23 gals, pure city driving though...Driving out to the river last week and back I got 345 out of 23 gals when I filled up today

 

[bluex]

Well ya, but the op too. Empty really isnt empty if ya know what I mean. Mine will be at E an its all I can do to get 24 gals in it