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2000 Silverado 5.3

charlesbwright

By charlesbwright
in Ask A GM Technician

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charlesbwright Enthusiast

charlesbwright

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I drive 2000 silverado 1500 5.3 vortec. Well here for last month or 2 notice decrease in power etc. Requires more throttle going up hill,rough idle or inconsistent idle, and also on it occasionally will hesitate or the best description is it will start like cutting back like a train (chuga,chuga) with almost no power it just cruises the speed I'm going mostly in lower rpm from a stop.Ive changed fuel filter,oil, oil filter (just because why not) today i got my cats replaced and exhaust system installed. Problems still occurring, so that only leaves a vacum leak or maybe a bad sensor (mass air flow)?? Idk please help or point me in right direction!! Thanks in advance

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Are there any codes set?  Check engine light on?  As with any vehicle made since the first internal combustion engine chugged off the line at the factory, they all need three things in order to run, fuel, compression and spark.  Always start troubleshooting with your eyes, not your wallet. 

 

As already suggested, check fuel pressure.  If you reproduce the issue at will, see if you can monitor fuel pressure at the same time. Try tapping the MAF sensor and move the wiring around slowly.  By tapping I mean take a normal size Phillips screw driver, hold it by shaft and tap with the screw driver handle. 

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted
9 hours ago, charlesbwright said:

I drive 2000 silverado 1500 5.3 vortec. Well here for last month or 2 notice decrease in power etc. Requires more throttle going up hill,rough idle or inconsistent idle, and also on it occasionally will hesitate or the best description is it will start like cutting back like a train (chuga,chuga) with almost no power it just cruises the speed I'm going mostly in lower rpm from a stop.Ive changed fuel filter,oil, oil filter (just because why not) today i got my cats replaced and exhaust system installed. Problems still occurring, so that only leaves a vacum leak or maybe a bad sensor (mass air flow)?? Idk please help or point me in right direction!! Thanks in advance

Well, there's ALOT more to it than that! 

 

I agree with txab - fuel pressure.

charlesbwright Enthusiast

charlesbwright

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Only error code I've had was p0420 I beleive it was low efficiency bank 1 can't exactly remember. not able to make it cut back manual. It did it twice yesterday once going up hill then again later that night. If i give it more throttle it stops. It seems to happen right after I take off and I'm just cruising when I say that I mean not giving extra throttle just maintaining speed. Gonna try tapping MAF today.  

charlesbwright Enthusiast

charlesbwright

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Also should of mentioned sooner I have a Bluetooth obd 2 scanner in truck with realtime readings. Pictures from scanner tool, first picture just started driving second picture went about 2 milesScreenshot_20190317-113934.thumb.png.b9e6ddeb1065dad08c4403199272cc73.pngScreenshot_20190317-114125.thumb.png.c8b09882cdf68edcef23148c47329f16.png

charlesbwright Enthusiast

charlesbwright

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Sitting at oreillys right now check fuel pressure 50psi so I beleive that is good, have not change plug,wires,coil packs, I honestly don't think they are problem, could it be map sensor being the vacum pressure fluctuate so much. Plugs and wires next step I guess.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Stop throwing parts at the thing! From what you described - missing at cruise, but not at full throttle, suggests an intake vacuum leak. Need to do some testing to find out for sure.

 

None of the parameters you posted from your reader are of any good. You need to post short and long term fuel trims, and upstream and downstream o2s on both banks, and MAF just in case - should be able to spot a problem within just those. 

charlesbwright Enthusiast

charlesbwright

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Told myself today I was done throwing money at it. Well in my original post when I said got cats fixed I mean i don't have any but that's the only code I've ever had since owning the truck nearly 2 yrs,  low efficiency  below threshold bank 1 about 5 mins ago got bank 2 code.had exhaust put own yesterday around lunch.  I cleaned MAF sensory about 2 or 3 weeks ago, If I unplugged MAF while truck is running should it continue to run. BEST way to check for vacum leaks? I'm NO mechanic  (Obviously)

charlesbwright Enthusiast

charlesbwright

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8 hours ago, Jsdirt said:

Stop throwing parts at the thing! From what you described - missing at cruise, but not at full throttle, suggests an intake vacuum leak. Need to do some testing to find out for sure.

 

None of the parameters you posted from your reader are of any good. You need to post short and long term fuel trims, and upstream and downstream o2s on both banks, and MAF just in case - should be able to spot a problem within just those. 

Screen shot idle before cats were removed, friday, idk if this helps, Screenshot_20190315-003956.thumb.png.203079742bb25ecdef5b97b9714e87a2.png

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

If it's an intake leak, it'll be the worst when the engine is cold. I use water - just poke a hole in a plastic water or soda bottle, and squirt it along the intake manifold gasket area. Best to be watching long and short term fuel trims, and look for any quick changes in the short term trims. If the leak is bad enough, you'll hear it getting sucked in. It won't pull enough in to do any damage.

 

Your fuel pressure is a bit on the low side, though - I would focus on that first. Full throttle run (without crashing or killing anyone of course!! 1st gear ONLY is plenty) with scan tool connected, o2 sensors should peg RICH (.800 volts or higher) and stay there. If they don't, you have a fuel delivery problem. Watch the MAF too - should see a triple digit grams per second reading, and roughly the displacement of the engine in grams per second at idle.

Jsdirt Senior Enthusiast

Jsdirt

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Posted

What are the long term trims reading?

 

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