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Whoaru99

1994 Chevy k1500 5.7L running rough and no power

8 posts in this topic

Wouldn't you know, Friday afternoon before Memorial weekend, old trusty decides to act up, nearly causing the camping trip to be called off. Luckily the GF's minivan had a towing package on it adequate for pulling the pop-up to save the weekend .

Had been running fine as I pulled it around to the side of the garage and shut it off. Then, after I threw in the last few items and started it up, it started fine then just like you flipped a switch, started running rough...like it was missing on several cylinders.

Figured maybe it just needed to be driven around the block to clear it out, but it barely would drive and idled very low. Barely enough power to move itself.

Through it all, the "Check Engine" light has not come on (except startup lamp test), and it starts fine.

Any thoughts about where to start?

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My guess, and I am no mechanic at all, is that your plug wires are shot. Getting poor or no spark. just a guess...

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Start it up, let it idle, and see what happens when you spray a little carb spray in the throttle body. Does the idle smooth out?

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OK, so I got geared up to try the carb spray suggestion, but before I even sprayed any in, I noticed that one injector (of the pair) wasn't spraying fuel into the throttle body.

Did a cursory inspection of the wires right around the TBI and didn't see anything unusual so I wiggled the wires going to the TBI and to that specific injector. Watched for another minute or two but no change, still was running rough and same injector not spraying.

No more than got around the side of the truck to the driver's door to shut off the engine and it smoothed out and the injector was now spraying.

Hmmm....?

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You got ahead of the direction I was going but there you go. Next time it flakes out ohm the injectors they should have almost exactly the same resistance. If the one that is not working has lower or open resistance than replace it.

These also have issues right where the wires bend around the throttle body under the air cleaner.

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Checked the injectors with the ohmmeter and sure enough, the curb side (RH from driver's seat) injector was giving a flakey reading.

It was initially higher than the LH injector so I gently wiggled the pins right on the injector and the reading fluctuated from around 5 ohms to open circuit. The LH injector reads a steady 1.4 ohms.

Darn...those little buggers aren't cheap.

Wonder if I should replace both just for good measure since the truck has >200K miles?

EDIT: Yeah baby!!!

On a whim I checked with a guy I know and he had a partially parted out TBI from another 5.7L, but it still had the complete fuel meter body with injectors. Checked the resistance of the injectors, both 1.5 ohms, swapped it out (REALLY easy) and she's back to purring like a kitten!!

Total cost? $10 and a hours time.

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Plus the consultation fees! Just make the check payable to........ grin

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I certainly do appreciate your advice that got me headed in the right direction from the get-go!!

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