# '97 Silverado - Bogging down past half trottle



## inkedmn

I have a 1997 chevy 1500 siverado with a 5.7 vortec that has been having a problem for about 6 months now. The truck starts, idles, and revs normally and when accellarating slowly everything works just fine, but once you get past half throttle it falls on its face and acts like it has a clogged fuel filter or bad fuel pump. It actually goes slower than below half throttle. The bogging gets consistently worse the more throttle you give it. I have replaced everything that I could think of, as well as everything many chevy guys have suggested. here is a detailed list of everything replaced in the last 6 months. (Distributor cap, rotor, plugs(twice), plug wires(twice), fuel filter(twice), fuel pump, fuel pressure regulator, both O2 sensors, fuel injectors cleaned).I have also checked the fuel lines for kinks, crimps, and leaks and found none. I have also unbolted the exhaust and run the truck to check the Cat for clogs, but it ran the same. The most confusing part of the whole thing is there is no check engine light on, so i have no way to check it on a computer. My friend looked at the spark plugs and noticed a little brown on them which he said might be caused by it running lean. Any ideas you could give me of what to change or check would be greatly appreciated. 

If I can offer any other information that might give you guys more insight into what my problem might be, let me know.

Thanks in advance!


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## sonjaab

Sounds like the cat is clogged to me....Most good muffler shops will test for free...........geo


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## crashz

Bad injectors? - but that would trip the check engine light. I'm with geo, Its probably a clogged cat or muffler.


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## Crash935

going out on a limb here, but check the egr valve for vacuum and movement at the diaphragm. Sounds crazy but had one stick on my truck where it wouldnt idle but would run great with my foot mashed to the floor.


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## lawnmedic

EGR or fuel restriction. Check to see if carbon canister has been flooded with fuel. This will keep gas tank from breathing properly...

I just had the exact same problem after replacing gas tank and fuel lines on the 89 2 weeks ago. turned out to be twist in braided fuel line running from fuel filter up to engine...Chuck


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## SWC

*Bogging past half throttle*

Check the ignition timing.

Change the fuel filter.

Change the plugs, plug wires, disributor and rotor button.

Do a system analisis to see if one or more of the half dozen or so sensors is bad.

Put some injector cleaner in the fuel tank.

Check for vacum leaks.

Check the valve clearance.

It's more than likely a clogged fuel system, bad sensor, or faulty ignition compontent/ignition timing.


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## arosewag

*solution?*

I have the same problem in my '98 2500 silverado. Have you found a solution?


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## SWC

*Bogging down*

It could be the watered down fuel we're paying close to $2.00 a gallon for as well.

Put some octane boost in the tank and see if it helps.


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## Dig-it Landscap

my friends dads truck had the same problem he took it to the dealer and got a new computer chip and hasn't had a problem again.


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## SWC

*Bogging down*



Dig-it Landscap said:


> my friends dads truck had the same problem he took it to the dealer and got a new computer chip and hasn't had a problem again.


Did he know the chip was bad?

I read somewhere that those chips can store error codes in them, I'm not sure if a stored error code will imulate the problem as far as performance goes, but I've heard that disconnecting the battery will reset the chip to factory settings and clear the error codes.

Does anyone know if a stored code will produce the problem on the performance end.

It seems that it would, since changing the settings in the chip can improve performance.


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## arosewag

*fixed?*

Have you been able to fix it? I'm dying to know. I'm having the same problem and it's really bugging me. I can't accelerate unless i'm half throttle, not too fun when trying to merge on the highway. I'd like to try to fix it myself.


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## ggwash21

I had the same thing rigth before plowing season started... changed fuel filter, IAC, EGR, plugs wires, cap rotor, Now its off like a prom dress.......... thing runs better then when i first got it......... The big one that made a difference was EGR.......


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## arosewag

Thanks GG, I'll do the same. What is IAC?


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## ggwash21

Idle Air Control motor.. not expensive at all


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## NJBuickRacer

Dig-it Landscap said:


> my friends dads truck had the same problem he took it to the dealer and got a new computer chip and hasn't had a problem again.


There is no removable chip on a '97 PCM. The computer can be reflashed(reprogrammed) with updated software if you have the equipment. Generally, a reflash will not rectify a situation that arose so late in the truck's life. I would drive the truck with a fuel pressure gauge attached in a position viewable from the driver's seat, if the pressure is not dropping off while you experience the problem then look elsewhere. I have had similar symptoms arise on these trucks, many were bad catalytic converters(tested ok, partially blocked internally), but I have also had several bad coils and a few with poor grounds at the engine-trans bolts and near the t-stat housing.


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## scottL

I just recently went through the issue of it ideling fine. Light acceleration was fine but, near half pedal and above there were issues like you described. I filpped out the MAP sensor - about 5 minutes. Everything ran like new again. power like I had back when the truck was new in '97.


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## 572bowtie

*5.7 tbi*

i have a 95 k1500 5.7 tbi and i was wondering if there was a 02 sensor in my cat b/c if there is not i would like to take that off and run true duals out my back end. Also can i take out my cat without anything going wrong with my engine and i would hope for better performance.


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## scottL

I'm not sure if you have a Co2 sensor back in your exhaust. On a '97 I have 4 Co2 sensors - ugh. So, if you do you would need to re-add them or the compter will go nuts. Unless some smart person knows how to render the sensor as working properly to the computer. Otherwise dropping the cat's should have hurt your engine. It will increase your flow, maybe a tad louder.


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## ggwash21

I have a 94 350 and i believe theres 2 o2'.. one on the cat and one on the exhaust manifolds, i could be wrong but just take a look..


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## arosewag

*fixed!*

About a month and a half ago I replaced spark plugs, wires, rotors, caps, and throttle position sensor. None of which seemed to help. About two weeks later I changed the fuel filter, now everything is fine. Well, fine for 240,000 miles of engine wear. She doesn't accelerate like she used to, but doing a lot better.


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## PLM-1

My grandmother's Lincoln Towncar does this. It's fine for a couple of days after you change the fuel filter and then it falls on it's face. It does it when you come around a corner and start to accelerate and then again at full throttle. It's sorta scary trying to pull out into traffic


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## Timothy Logan

scottL said:


> I just recently went through the issue of it ideling fine. Light acceleration was fine but, near half pedal and above there were issues like you described. I filpped out the MAP sensor - about 5 minutes. Everything ran like new again. power like I had back when the truck was new in '97.


What did you do to map sensor?


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## Timothy Logan

scottL said:


> I just recently went through the issue of it ideling fine. Light acceleration was fine but, near half pedal and above there were issues like you described. I filpped out the MAP sensor - about 5 minutes. Everything ran like new again. power like I had back when the truck was new in '97.


Hey man please get back with me as soon as you can I think it has something to do with map sensor want to make sure before buying new one


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## the Suburbanite

Timothy Logan said:


> Hey man please get back with me as soon as you can I think it has something to do with map sensor want to make sure before buying new one


You are replying to a 14 year old post buddy.


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## Mr.Markus




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## Timothy Logan

the Suburbanite said:


> You are replying to a 14 year old post buddy.


Yes but hopefully someone figured it out I need to figure it out


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