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Bought a mistake I think, need help!!!

BowtieTillIDie1995

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BowtieTillIDie1995 Enthusiast

BowtieTillIDie1995

Posted
Posted

Hey guys I'm new to this forum and really need the help. I can turn wrenches but I am new to the v8 and chevy world. Anyway I bought a 1997 k1500 4x4 5.7 vortec with 153,000 miles on it. I bought the truck with the ses light on and knew it was a bad o2 sensor (bank 1 sensor 1). Anyway I replaced it by 154,000 and not even 100 miles later the ses light came on again. I scanned and retrieved a code for the other o2 sensor on the passanger side manifold befor the cat. Before I could get around to fixing it the light went out so I figured all was good. Within the span of 3 weeks the ses light has come and gone maybe 2-3 times. But today on way to work (30 miles) the light blinked and then stayed on.....Also (I've learned its a commen problem) the 5.7 seems to "knock" when I start in morning, or after my 10 hr shift. Doesn't do it if I run to Walmart or anything just after it sits. Is there a way to fix the noise without going "balls deep" into the engine. I love the truck and payed too much so I'm stuck with it. Anyway I don't know what I've gotten myself into, and I'm afraid I may be screwed.

2010LTZ4x4 Enthusiast

2010LTZ4x4

Posted
Posted

Welcome to the forum, that sucks about your truck. I know the later 5.7 Vortecs were bad for intake manifold coolant leaks. How's the coolant level in your rad. If there's coolant leaking into to your oil that could contribute to the knocking. Or if the coolant is being burnt some how and coating the O2 sensors that maybe why there throwing codes. Just a thought.

darkfox1 Senior Enthusiast

darkfox1

Posted
Posted

from my experience a transient CEL/SES is fairly common among older vehicles, even with low miles. My 2000 camaro had the same problem and it was entirely determined, it seemed, by the temperature outside.

 

It really makes your heart sink when that light comes back on when you've fought to get it to go off, moreso when you have to have it off to keep your car on the road because of inspections.

 

I'm wondering if the knock you're describing is piston slap? I know this was VERY common in late 90s/ early 2000s vehicles and would occur pretty much any time the vehicle was cold. It sounds very bad, but its not as bad as you might think on the engine. Basically in the case of piston slap its because of the different metal types and expansion rates used in the engines. They compensated by making the pistons "too small" iirc.. which made them "knock" in the cylinders until everything warmed up and they all became the same temp. I could be wrong here tho.. I know this for a fact on LSx engines, but a 97 still had that TBI iirc.

BowtieTillIDie1995 Enthusiast

BowtieTillIDie1995

Posted
  • Author
Posted

My buddy said something about lifter noise because hydraulic lifters idk haha. Anyway the truck is now miss firing bad and the check engine light blinks 8 times every now and then. I'm gonna take it to the shop and just pay to have someone knowledgeable to figure it out, don't have the money but i figure I need it so.....oh and my mpg sucks haha

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Yeah a blinking light means a cat-melting misfire - basically fuel going right out the tailpipe instead of making power. That's why your mileage sucks. Could be any number of things on OBD-II ...

 

TBI's last year was '95 - no OBD-II vehicles were TBI, just FYI. If it was TBI it would still be running without a problem ... and if there was a problem it would be a simple, & cheap fix. OBD-II ended all that in the name of emissions ... :sick:

SteveBBB Senior Enthusiast

SteveBBB

Posted
Posted

Like someone has already posted, piston slap was a well know problem back then. It actually sounds worse than it is. That might be your knock.

darkfox1 Senior Enthusiast

darkfox1

Posted
Posted

Well if he's got a rough idle and hes burning up o2 sensors from dumping too much fuel..

 

TPS? MAF? The knock may still be piston slap but that goes away when the engine warms up. What DOESN'T go away is valvetrain noise. But that's not really a knock. More like a "rattle."

 

There's several kinds of "knocks" in motors, it could even be as simple as a pulley thats out of round. Ya know early LSx motors (and even more recent ones) had an issue with the crank pulley being press fitted together and as the rubber broke down the pulley would wobble. Could be something like that?

 

I'd say you should do some simple maintenance yourself on the truck, won't cost ya much.

 

clean the tps, clean the maf, clean the IAC change the air filter if it's not fairly new, clean the TB (I dont know how the pre lsb post tbi throttle bodies work, but on lsx TBs you get a lot of grime on em that can make them stick and mess with your tps and IAC) Pull your plugs and check their condition/gap, have your fuel filter changed. I HIGHLY doubt any of this will fix your issues, but its good to do, especially if you dont know how the previous owner took care of the truck and/or the last time this was done.

SILVER SLED Senior Enthusiast

SILVER SLED

Posted
Posted

They didn't have piston slap problems in the old 5.0 and 5.7 small blocks like in your 97. Piston slap didn't come around until the LS motors like the 5.3 and 6.0's...from 99 and up. You may have a bearing noise. That may sound serious, but my current 97 5.7 has it a few seconds, less than a minute on cold start ups, and so did a previous 5.7 truck. Those motors are still going strong, and will probably outlast the trucks they are in.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Yep - the 5.7 is legendary. Reliable as a stone ax when you factor out all the '96-up electronic emission crap. Same with the Ford 5.0/5.8. I've got the 5.0 in our '86 Grand Marquis with 220k miles on it. Boy does it RAP LOUD on the first fire of the spring after sitting all winter long draining oil back to the sump. After 11 springtime start-ups it's amazing it still has bearings left! THAT'S how you build an engine. :thumbs:

The more I think about this, the more deja-vu I'm getting after working on my buddy's '96 Tahoe. I ended up throwing in the towel after my buddy threw THOUSANDS of dollars into trying to make this thing run right, and it still insists on being a 6 cylinder instead of a V8.

Here's a vid of when I first got it running after it sat with the oil pan and timing cover off in my buddy's barn for 5+ years ...

 

(searching for the vid - thought I had it ... I'll update when/if I find it. You can clearly hear the spark knock as it idles like a diesel ...)

scooby5121 Enthusiast

scooby5121

Posted
Posted

Replace both of the sensors before the cat. Heating element is probably gone

It's telling the computer wrong info for fuel/gas on cold temperatures

Replace both of the sensors before the cat. Heating element is probably gone

It's telling the computer wrong info for fuel/gas on cold temperatures

Replace both of the sensors before the cat. Heating element is probably gone

It's telling the computer wrong info for fuel/gas on cold temperatures

Replace both of the sensors before the cat. Heating element is probably gone

It's telling the computer wrong info for fuel/gas on cold temperatures.

Replace both of the sensors before the cat. Heating element is probably gone

It's telling the computer wrong info for fuel/gas on cold temperatures.

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