2003 Chevy Silverado 1500 Runs Horrible

[Mr. Z71]

My '03 Sierra 5.3L acted similar to your problem. Ran like crap until warmed up, don't remember exact codes thrown but were lean codes. Turned out to be intake manifold leak. Once warmed up the intake would seal off and run great with no codes thrown after clearing existing ones. But while cold it ran like crap.

 

I'm with txab, check the intake.

[Colossus]

3 hours ago, Jacob11531 said:

I am going to replace the fuel filter tomorrow and ill check the plugs. I was going to buy an obd2 scanner eventually but not now because of the holidays. Can i have a parts store also check my sensors? I know it wont be when its completely cold but maybe it will show something.

No.  A parts store won't be able to see anything.  You need to get a Tech-2 tool on there to read the sensor readings. 

[Colossus]

Throttle position sensor perhaps?  Also you were right to replace the O2 sensors, they would be tired at that kind of millage.  Fuel filter might be clogged as well, but I believe by 2003, the fuel filters were in the tank and not in-line.  I'm also going to suggest you remove the battery cables for about 30 min, touch the battery cables together to discharge any additional power in the system, then re-connect.  Then start and let's see how it behaves at that point. 

The Cat might also be plugged..

 

Instead of throwing money at it, it just might be worth taking it into a good reputable shop to have it diagnosed properly. 

[Jacob11531]

Thanks for the response Mr. Z71, mine runs the same as yours but it seems to get worse when it warms up. Im quite mechanically inclined but do you think taking off the intake will take a decent chunk of time and alot of work? O2 sensors were replaced and did not fix problem if that is what you were asking. I will take the cables off tomorrow and see how it runs. Does taking the cables off for 30 mins also reset codes? Thanks!

[davester]

2 hours ago, Colossus said:

No.  A parts store won't be able to see anything.  You need to get a Tech-2 tool on there to read the sensor readings. 

lots of hand-held odbii readers (albiet more expensive ones, not necessarily the dirt-cheap ones) can display and/or record live data, not only a techii.

 

However, if you plan on keeping this truck for a long time, and do repairs on it yourself, I recommend getting something like Autogenuity w GM Enhancement.  It's windows software that uses a usb cable to connect to your truck, and it can read codes from all the computers in your truck, not just 1 or 2 (there's between 10 and 15 in your truck), as well as display live sensor data and also perform a variety of diagnostic and repair operations.

[Jacob11531]

Cool, will definetly look into that. Thanks! 

[Jacob11531]

Ok so I got the codes checked out and it is still lean in bank 1 and bank 2 with misfired so this time I bought a new mass air flow sensor and it still does not work. Also, the manofolds are ok and clamps, etc are tight. So far it has new o2 sensors, coil packs, spark plug wires, and an maf. I'm $400 into this and it's hard to even want to fix this thing. What else could it be? 

[txab]

How did you test for leaking intake gaskets?

[Jacob11531]

I did not test for leaking intake gaskets. I was confirming that the exhaust manifolds were proporly seated which the were. Sorry bout that. Not sure how I would test the intake gasket. What equipment would I need for that? I'm only 16 and I'm somewhat mechanically inclined with some good resources for help, would get it professionally fixed but don't have the $$$. Thought I could fix this myself but it seems more severe than I thought. Thanks!

[dewfpo]

You can test a leaking head gasket by spraying carb cleaner or throttle body cleaner around the mating surfaces while the engine is running.  If it speeds up, you have an external leak.  You can also use propane (un-lit of course).

 

DEWFPO

[Jacob11531]

Did you mean intake manifold? Will try that tho. Thanks!

[Adrian17]

I dont know how much sense this makes but here it goes. Try your fuel pump. My truck not to long ago started to die while stoped at a red light made it to a parking lot and it started to shake badly like you described. Then after that it eould not even turn on. I hit the fuel take were the pump is and the truck came back like if nothing was wrong. A few weeks went by and it was a cold morning mabey like 35-40 degrees. Turn the truck on and I notice a harsher shake then regular and then the engine light came on and started to blink hit the fuel tank again and its been fine ever since. I have yet to replace it yet but its just a thought

[Jacob11531]

I'll probably get one if it's cheap. Thanks for the info. Had to get to Wisconsin for a vacation and I was forced to take this truck. It is -10 when I got here and it runs pretty rough and drinks through a lot of fuel. 

[Jacob11531]

How do I go about testing fuel injector resistance. What should the resistance on the fuel injector and the plug connector be? Thanks.

[Jacob11531]

I got the time to spray around the gasket today and it did not rev up but it did die. Maybe it got so much of it it killed it. Do you guys think the problem is bad gaskets then? Thanks!