No Power!!!

JCedar · October 22, 2005

Hey everyone,

My dad has an 03' Chevy Avalanche with the 5.3. He came home from camp today and started telling me how crappy it was running. So I jumped in and took it for a ride, and man the thing was just GUTLESS. You can put it to the floor and the motor just revs and a god awful rattling occurs. if you let off or drive really slow you don't notice it, but when you want to pass someone it has NO power at all. So I pulled back into the driveway and put it in park and listened. As I revved it up a loud rattle started to come from under the truck. So I had my dad give it gas as I went under the truck to see if I could pin point it. It SOUNDED like it was comming from the cats but I'm not 100% sure. The truck has 38,000 miles on it, so that's making me lean away from the cats, but what else could it be? It's LOUD, I mean you don't have to listen for it, it's loud and clear. Also he said the engine light came on but went off about a minute later. I'm clueless as what it could be.... any ideas?????

pacodiablo · October 22, 2005

The rattle and poor performance may or may not have anything to do with each other.

Check for codes stored in the computer before replacing anything. Most car parts stores will do this for free. This won't tell you what to replace or fix, but it will give you an idea of what you need to look at.

The rattle could just be a heat shield.

Supercop8100 · October 22, 2005

Easy fix, 90% sure your either your crank position sensor or MAF sensor malfunction. If I had to bet, I would go with the crank position sensor. They can go bad at any mileage and will cause this symptom.

JCedar · October 22, 2005

Easy fix, 90% sure your either your crank position sensor or MAF sensor malfunction. If I had to bet, I would go with the crank position sensor. They can go bad at any mileage and will cause this symptom.

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So how would the rattling and the crank position sensor be related? I'm 100% sure they are associated with eachother! It never made this noise before and as soon as it did the truck started running like crap. Any tips on replacing the crank position sensor if that's what it is or is it pretty straight forward. I'm pretty mechanically inclined so I'm not too worried about it but any tips would be apprciated. Thanks

Have a good one!

Salmon Stalker · October 23, 2005

After the recent events with my own truck, I would make sure that everything is in working order with the distributer and rotor before I went to far... Wingman has some pictures of my messed up rotor that he is going to post soon....

My suggestion... Rule out the cap and rotor and then go from there....

Good Luck...

GM-Tech · October 23, 2005

The truck has 38,000 miles on it, so that's making me lean away from the cats

Mileage means nothing. We put cats on vehicles with way less mileage than that. If a misfire or other similar condition occurs, it can take out a cat in a short time. Doesn't matter if the vehicle has 1,000 miles or 100,000 miles.

We put a new cat. conv. on an Astro van a week or so ago that developed a severe misfire afterwards and it destroyed the new cat. The new cat had exactly 80 miles on it!

GM-Tech · October 23, 2005

My suggestion... Rule out the cap and rotor and then go from there....

An '03 Avalanche with a 5.3 doesn't have a cap and rotor because it doesn't have a distributor. It has an individual coil for each cylinder.

Salmon Stalker · October 23, 2005

An '03 Avalanche with a 5.3 doesn't have a cap and rotor because it doesn't have a distributor. It has an individual coil for each cylinder.

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That doesn't change anything... I'd still be out there looking for it...Maybe I wouldn't find it, but I'd be looking for it...

So what tells the coil when to fire? Is it all computer contolled?

JCedar · October 23, 2005

Thanks for the replies, the Avalanche is at the dealer now. My dad got a brand new Trailblazer as a replacement for now. Hopefully it is the cats because that would be covered under the warranty. Any how thanks for the replies and I will post again once the issue has been resolved.

Texas disaster · October 23, 2005

My last truck was an 04 silverado regular cab v6 and the cats went out on it at 16,000 miles. When they did it sounded like a mariatchi band under my truck.