Low power

[Purplestaff]

I have a 1994 k1500 with the 5.7 TBI, a lot of other gmt400 trucks I have driven have quite a bit of git up n go, mine does not. I've replaced the plugs and wires, headers and 3" pipe through dual cherry bombs. Could it be the O2 sensor? TBI injectors maybe? How would I go about testing those?

 

[PlayingWithTBI]

Are you getting any SES codes? On these TBIs you may have a stored code with the light out. You can do the "paperclip trick" or, better yet put a scanner on it to see codes and what's going on with your sensors and fuel trims.

 

[Purplestaff]

Are you getting any SES codes? On these TBIs you may have a stored code with the light out. You can do the "paperclip trick" or, better yet put a scanner on it to see codes and what's going on with your sensors and fuel trims.

What is the paperclip truck?

 

[PlayingWithTBI]

What is the paperclip truck?

This may help, you can Google "Paperclip trick on OBDI ECMs" for more info but, this site has a lot of good info.

Chevy Check Engine light Codes without a Scan Tool - FreeAutoMechanic

Pull GM Engine Diagnostic Trouble Code Charts | OBD I.

freeautomechanic.com

 

[1998_K1500_Sub]

I have a 1994 k1500 with the 5.7 TBI, a lot of other gmt400 trucks I have driven have quite a bit of git up n go.

Are you running the original-sized tire or something other?

Does your speedometer indicate an accurate speed?

Are you aware of any changes to the rear end gearing? What gear ratio is in it now?

One method of determining your rear end ratio is to check the RPO codes on the glovebox sticker, assuming your rear end is unchanged since built. The relevant codes are:

GT4: Rear Axle: 3.73 Ratio
GT5: Rear Axle: 4.10 Ratio
GU4: Rear Axle: 3.08 Ratio
GU6: Rear Axle: 3.42 Ratio

 

[Purplestaff]

This may help, you can Google "Paperclip trick on OBDI ECMs" for more info but, this site has a lot of good info.

Chevy Check Engine light Codes without a Scan Tool - FreeAutoMechanic

Pull GM Engine Diagnostic Trouble Code Charts | OBD I.

freeautomechanic.com

My check engine light does come on if I sit in one spot at idle for a couple minutes

 

[Purplestaff]

Are you running the original-sized tire or something other?

Are you aware of any changes to the rear end gearing? What gear ratio's in it now? Does your speedometer indicate an accurate speed?

I'm running 265/75/16, just a tad bigger than stock. It's 3.73 gears, speedo is about 3-4 mph fast (if it says I'm going 25 I'm going ~22)

 

[PlayingWithTBI]

My check engine light does come on if I sit in one spot at idle for a couple minutes

That needs to be addressed before you throw any more parts at it. It's paperclip or scanner time. You can take it to an auto parts store and have them check for codes too. A real scanner can tell you what's going on and log it so you can more easily find your issue when it happens.

 

[Purplestaff]

That needs to be addressed before you throw any more parts at it. It's paperclip or scanner time. You can take it to an auto parts store and have them check for codes too. A real scanner can tell you what's going on and log it so you can more easily find your issue when it happens.

I'll do that

 

[1998_K1500_Sub]

I'm running 265/75/16, just a tad bigger than stock. It's 3.73 gears, speedo is about 3-4 mph fast (if it says I'm going 25 I'm going ~22)

Ok, makes sense, I would guess the tire's about 10% bigger than stock (check me on this) so the indicated speed is correspondingly about 10% lower than actual.

Have you checked the ECU for trouble codes? Do it even if the SES light is off, there may be stored codes.

My father had a 1995 5.7L TBI K1500 with 3.73 gears on OEM tires and it drove very nicely, never felt like a dog.

Those larger tires aren't your friend tho, 10% change, if that's truly the difference (I'm just assuming it is from what you've said) will be noticeable in the acceleration.