Hi all,

I'm looking for help for my mom's truck. She has a 1997 C1500, 5.7 Vortec. It usually runs great, but has recently started bucking under load (I believe that's the right term...cuts out for a fraction of a second, comes back hard, repeats). It doesn't seem to follow any pattern... sometimes it does it until it warms up sometimes never, sometimes all the time. It didn't start until the heater core inlet hose began leaking, and I figured that all that coolant was grounding out the cylinder or two on the passenger side and it would go away once I replaced the hose. No such luck. On the advice of one of the O'Reilly's men I replaced the fuel filter which resulted in no improvement. There is no Check Engine Light or code.
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I'm handy with a wrench and not afraid to get my hands dirty, I'm just not experienced enough to know where to begin. Any thoughts?

Thanks,
Jack

 

My opinon, crappy gas. I know you replaced the fuel filter, but that won't cure if you have water in your gas, and I go with that, possible water in the gas. Either try some HEET in the tank, or drain the gas tank, and go from there.

 

I hadn't thought of that, but mainly because it has been doing it through two tanks of gas, from different stations. It won't hurt to try the HEET, though...

 

How were the codes checked? Using a basic code reader or at the parts store or....? Even without a check engine light or active codes (which is all a basic reader can pull), there might be pending or history codes that are useful here.

More advanced code readers (meaning between the cheapest and most expensive) off the shelf can usually pull them. You might also find an independent shop nearby willing to check them for free or a minimal charge.

That said, bad gas is one potential cause, but it could also be one of the speed sensors for the transmission or related wiring.