seem to be losing power 05 cc1500 5.3

michigan2500hd · December 21, 2005

Anybody know what might make my truck lose power ? Its a 2005 1500 crew cab,5.3l,3.73 gears. I bought it new with only 10 miles on it. Test drove it and loved the power it had. Felt stronger than my 03 2500hd 6.0. The 05 would roast the tires on dry pavement better then my buddies new ext.cab with the H.O. 5.3. I put in a westers 87-89 tuned pcm,magnaflow 3" in 3" out muffler, K&N drop in filter and synthetic oil. Truck seems to run fine but when you floor the petal even on damp pavement it doesnt roast the tires like it did when new. I think there is 3000 miles on it now. I wonder if the tune is not as good as the factory. I asked westers to firm the shifts ( they feel the same to me ),remove tq. management, and tune for max off the line power. Any ideas?

michigan2500hd · December 23, 2005

Anybody know what might make my truck lose power ? Its a 2005 1500 crew cab,5.3l,3.73 gears. I bought it new with only 10 miles on it. Test drove it and loved the power it had. Felt stronger than my 03 2500hd 6.0. The 05 would roast the tires on dry pavement better then my buddies new ext.cab with the H.O. 5.3. I put in a westers 87-89 tuned pcm,magnaflow 3" in 3" out muffler, K&N drop in filter and synthetic oil. Truck seems to run fine but when you floor the petal even on damp pavement it doesnt roast the tires like it did when new. I think there is 3000 miles on it now. I wonder if the tune is not as good as the factory. I asked westers to firm the shifts ( they feel the same to me ),remove tq. management, and tune for max off the line power. Any ideas?

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Took the K&N drop in filter out tonight and put the factory one back in also cleaned the maf sensor with fuel inj. sensor cleaner. The truck dogged even worse then it did before which leads me to believe the after market filter helps a little. Once the rpm's get above 3000 it seems to go like a raped ape. Just dogs bad off the line. Would winter fuel affect it this bad? There is nocheck engine light on and no drivability problems that i have noticed. Would the magnaflow muffler cause this? Two tanks of gas ago this thing would burn the tires pretty good out where i build houses in Grand Blanc. We have new streets with very few houses on them so its hard to pass up that kind of oppertunity to goof off with out watching out for the cops. I have never liked shell gas and i think that is what i filled up with last. Any help would be great. Thanks.

Shaners · December 23, 2005

Winter blend fuel could be the problem... Also the larger exhaust will reduce back pressure (something these Vortec engines need for low end torque).

lrymal · December 23, 2005

Winter blend fuel could be the problem... Also the larger exhaust will reduce back pressure (something these Vortec engines need for low end torque).

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YEP, the larger exhaust. I think the 3" exhaust is too big for the low-end.

michigan2500hd · December 23, 2005

Winter blend fuel could be the problem... Also the larger exhaust will reduce back pressure (something these Vortec engines need for low end torque).

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YEP, the larger exhaust. I think the 3" exhaust is too big for the low-end.

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Thats what i was leaning towards but all i did was chang the muffler. I kept the stock tail pipe, just cut the old muffler out which i was told the stock pipe size is 2 3/4"

Does the stock muffler have that much more restriction than the magnaflow?

I looked into the stock muffler after it was removed and could see light through it so i thought maybe these newer stock systems might not be as restrictive as they used to be. Are they tuned for each application?

lrymal · December 23, 2005

...I looked into the stock muffler after it was removed and could see light through it so i thought maybe these newer stock systems might not be as restrictive as they used to be. Are they tuned for each application?

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On the newer trucks, I don't think the stock system is at all restrictive, at least for a daily commuting driving truck. Just no hot roddy sound that we all crave. The SS exhaust is another story. That exhaust muffler is a bit weird. Go to the SS truck site and dig around for the details on that.

michigan2500hd · January 2, 2006

Truck seems to be running better now. Burned most of the Shell 87 octane out of it and put in some octane boost and 10 gallons of sunoco 93. Will now roast the tires better but not like it did when i test drove it new. My next question is should it run better on 93 octane with my 87-89 westers tune?

killerZ-71 · January 2, 2006

it could be that the truck is depressed from all the michigan losses to

OHIO STATE!!!

redvett · January 2, 2006

Truck seems to be running better now. Burned most of the Shell 87 octane out of it and put in some octane boost and 10 gallons of sunoco 93. Will now roast the tires better but not like it did when i test drove it new. My next question is should it run better on 93 octane with my 87-89 westers tune?

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If it was tuned for 87-89 your wasteing you money on 93 as long as there is no spark knock. 87 burns faster than 93 and the faster the burn the better it runs. Preamum only difference is slower burn to stop spark knock.

pm26 · January 3, 2006

Well, one of main benfits of using high octane gas is that if you have electronic ignition advance tied to a knock sensor, the computer will be able to advance the timing much more with higher octane fuel without causing engine knock than with lower octane fuel. Greater ignition advance will produce more power.

michigan2500hd · January 4, 2006

Well, one of main benfits of using high octane gas is that if you have electronic ignition advance tied to a knock sensor, the computer will be able to advance the timing much more with higher octane fuel without causing engine knock than with lower octane fuel. Greater ignition advance will produce more power.

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With the westers 87-89 tune will there be any advantages to using an octane higher then 89? It seems to run best on 93 from sunoco.

Butch 02 Denali · January 4, 2006

Well, one of main benfits of using high octane gas is that if you have electronic ignition advance tied to a knock sensor, the computer will be able to advance the timing much more with higher octane fuel without causing engine knock than with lower octane fuel. Greater ignition advance will produce more power.

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With the westers 87-89 tune will there be any advantages to using an octane higher then 89? It seems to run best on 93 from sunoco.

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Thats a 87/91 dual tune Mark, not a 87/89. We do that and 89/93 dual tunes. Then we have the dual hot tunes available in 89/91 and 91/93.

With crappy winter gas I bet you do run allot better on 93 octane! I'd estimate winter gas is about 2 octane points lower that the best summer gas. Even in the summer I bet you'll notice a good gain with the 93 too, and i bet you'll get a little better gas mileage too, hopefully enough to offset the additional cost!

2005 Z71 · March 14, 2006

magnaflow 3" in 3" out muffler

3 inch pipe on a 1500? Seems like that is the problem! Anyone else agree?

DanMan_S · March 14, 2006

I don't know if the 3inch pipe is that big of a problem. I've got a full 3 inch exhaust on my truck and I've no acceleration issues or problems lighting up the tires whenever I need. As well, the stock pipe is only around 2.75 inches. Any of the catbacks that I've seen for these trucks are all 3 inch systems; all of magnaflow's sure are.