98 K1500 Power loss?

[greenhead05]

I drive a 1998 K1500 with 100,000 miles. I have noticed lately that my truck has absolutely no power. It almost seems to bogg down. Every now and then when I put high octance fuel in my truck it runs great and has very good power. Then when I go back to the cheap stuff the power is lost. Could this be that my computer is reading the fuel measurements wrong, or the air to fuel ratios aren't right, timing problem, or what? I have replaced the fuel pump, fuel filter, air filter, change oil regularly, fuel relay, plugs, distributor, and rotor. I also ran a diagnostics test on the truck to see if it was throwing any codes and it wasn't. There should be more power to my 350 V8 than what I am experiencing. What other reasons could it be that I don't have the power that I should have?

[chevytrucks92]

I think you pretty well answered your own question there buddy. Naturally you're gonna make more power on high octane gas. Maybe your truck has always before been run on nothing buy 93 (that's all mine has ever had, and its a 1992 model, so I'm positive it probably wouldnt run on 87). That and the fact you are over the 100,000 mile mark. that's not ALOT of miles, but it is enough to make parts wear and to loose horsepower.

[Faze2183]

try running a med. grade that to me all the chevys (96-00 vortec 5.7s) run really good though u throw that cheap stuff in there and it doesnt run right, i maybe wrong but thats what ive noticed, good luck man

[Thunderbolt]

I don't buy the mileage or the 87 octane gas bit. I have a 98 1500 with a 5.7 and I have owned it since new. It now has 180,000 miles on it and the only fuel that it has run on is 87 octane. When you changed the distibutor did you have a scanner to reset the timing ?? Could be clogged injectors, Does it actually bog down or just feel like there is no power. It could also be a catalytic converter, But usually the SES light will come on because the O2 sensor will read goofy.

[Faze2183]

Originally Posted by Thunderbolt

I don't buy the mileage or the 87 octane gas bit. I have a 98 1500 with a 5.7 and I have owned it since new. It now has 180,000 miles on it and the only fuel that it has run on is 87 octane. When you changed the distibutor did you have a scanner to reset the timing ?? Could be clogged injectors, Does it actually bog down or just feel like there is no power. It could also be a catalytic converter, But usually the SES light will come on because the O2 sensor will read goofy.

can u reset the timing on 96k1500s? because i knw mine is off, and how would u reset the timing?

[chevytrucks92]

Originally Posted by Thunderbolt

I don't buy the mileage or the 87 octane gas bit. I have a 98 1500 with a 5.7 and I have owned it since new. It now has 180,000 miles on it and the only fuel that it has run on is 87 octane. When you changed the distibutor did you have a scanner to reset the timing ?? Could be clogged injectors, Does it actually bog down or just feel like there is no power. It could also be a catalytic converter, But usually the SES light will come on because the O2 sensor will read goofy.

You could be right, but he said it has good power on 93 octane, but not on 87. You have always run 87 in your vehicle, maybe his was usually run on 93 and the switch causes it to loose power. I garuntee my truck would'nt run good on 87, becuase its never had nothing but 93 (120,000 miles now).

[Faze2183]

the med grade is ok, i dont get that good feel that i do with then with the 93.... ive wanted to throw just a tank of vp in there to see if the truck runs any better and if i get any better milage or not cuz right now i get any where from 375 to 400 miles per tank, and thats with all the mods and etc btw anyone knw if u where to buy that 32 gallon tank from the dealer will it work on a half ton?

[Thunderbolt]

Faze2183. The only way to set the timing on the 96 and up is with a scanner that has the timing feature. It has to be 0 degrees plus or minus 2 degrees so it can be from -2 to + 2 degrees. Un fortunately you need to find someone with a scanner. You can get it close or maybe even get lucky by removing the distributor cap, bringing the #1 cylinder to the top making sure it is on the compression stroke and turn the distributor until the rotor exactly lines up wher the #1 terminal is in the cap. When you are removing the cap mark the distrbutor housing where #1 is and when you are setting it turn counterclockwise on the rotor because any play in the gear need to be taken up to be accurate.While doing this turn the distributor until the rotor lines up with your mark. This will get you close and maybe even right on, But it is best to find someone with a scanner.

[Thunderbolt]

Chevytrucks92, You could be right also because my neighbor has a 99 Yukon and the SES light keeps coming on and the code is always saying bank one , bank two or both are lean and to check fuel pressure and fuel filter. The fuel pump has been replaced the fuel filter is new and the regulator is new and it still does it. We finally had her take it to the dealer and they said fuel filter, When we said we have to keep replacing it they asked what gas she burns. She said premium and they told here to run 87 because the computer is set to run on 87 and some vehicles don't respond well when anything else is used or if you change back and forth. If you fill up one time with 87 and the next with 93 it confuses the computer. Maybe he does need to stay with premium.

[Faze2183]

thanks thunder bolt

[chevytrucks92]

Thunderbolt: I would almost bet that is what his problem is. And I have another example as well (this one just the opposite of his, lol)

My dad bought a 1991 Chevrolet K1500, 350, auto trans, 4WD, just like my truck only a 91 instead of a 92, and started using 93 octane and it suffered from long starts (it would grind/turn over for nearly twice as long as my truck). He switched to 89, and it helped somewhat, then went to 87 and now the truck starts almost as fast as mine! So we figure the truck had always been run on 87 (had 108,000 miles at time of purchase, roughly 115,000 or so now, but we've had it for alittle over a year), and that's why it would'nt start as fast when switched to 93.