Major engine power loss has me baffled

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kfisher777

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My 03 ls v8 has been needing a coil replaced for about a month, month and a half now which will cause a minor to moderate engine power loss but all of a sudden now I seemed to have lost 50 to 60% engine power. During acceleration it WILL NOT exceed 3500 rpm as it accelerates through the gears. WOT does not seem to make much difference to increace power.

The most unusual thing about all this is how much louder the engine is coming from the intake(intake modified with KKM kit). It's as least twice as loud.

I tried unpluging the mass air flow sensor to see what happens and it expectedly went into ETC Failsafe mode and the engine sound returned to normal and had an increase of power and able to exceed 3500 rpm.

Does anyone have any idea what this may be? I'm at a loss and desperate. Thanks in advance!:)
 
kfisher777 said:
My 03 ls v8 has been needing a coil replaced for about a month, month and a half now which will cause a minor to moderate engine power loss but all of a sudden now I seemed to have lost 50 to 60% engine power. During acceleration it WILL NOT exceed 3500 rpm as it accelerates through the gears. WOT does not seem to make much difference to increace power.

The most unusual thing about all this is how much louder the engine is coming from the intake(intake modified with KKM kit). It's as least twice as loud.

I tried unpluging the mass air flow sensor to see what happens and it expectedly went into ETC Failsafe mode and the engine sound returned to normal and had an increase of power and able to exceed 3500 rpm.

Does anyone have any idea what this may be? I'm at a loss and desperate. Thanks in advance!:)
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Had the same sh1t happen to me and found out 4 of my coils were DEAD and the spark plugs were failing. My car as well wouldn't exceed 3500RPM and when I try to floor it...the engine would shut off completely....loudness came with the problem too :p
 
Just get it over with and fix it all. Coils and plugs...probably out valve cover gaskets right away too. Plus you can cause damage to your catalytic converters if you keep driving it like that, if you haven't already.
 
Wow and I thought my coils were bad. Gettin mine installed finally on Tuesday.
 
You need to fix this asap. If you continue to run with the bad coils you're going to have to replace cats and o2's as well, if it hasn't happened already. If the cats went bad it would be the reason for your power loss. Believe me I know from personal experience.
 
Thats what really concerns me....the cats going bad. I know i need to replace the proper coils and plugs and plan on it asap. These new symtoms of the intake being really loud and what seems to be a computer controlled power loss and 3500rpm limit have me wondering, but its not in failsafe mose and actually runs better when it is. I unplugged the mass air flow sensor to force into failsafe mode this morning because I had to run a quick errand so it would run well enough to do so...thanks for all the info!:)
 
nickandersonLS01 said:
Coils are around $40 shipped from teamford..... why have you been driving for over a month?
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Stupidity? :confused: :confused:

Get the coils fixed already! 2003's are covered under warranty for 10 years, 100K miles. You really have no excuse!
 
I got laid off from my job and broke. I cant afford to buy new one s until I get paid from my new job.
 
To me it sounds like you already did damage to 1 or more cats. I think you melted(clogged) one or more. The added intake noise is from the motor not being able to pump exhaust out of the motor. Remember motor is just an air pump, air in then air out. It runs better on fail safe because the comp is alternating power cycles and that will let enough exh out to somewhat breathe at low rpm. I had this happen on my F-350. Truck would not rev or go over 10mph. And had crazy intake noise.To test for clogged cats all i did was loosen exh manifold bolts to let breathe. This is before the cats so lets motor breathe and it went normal again just loud lol. You could also pull front O2's that would let it breathe too. Frank
 
Oh P.S. You don't have a computer limit on power at 3500. The cats being clogged won't let air in motor so no power to be made. Its 100% like the old saying "you have a banana in your tailpipe" Now these are just my guess's but your problems fit.
 
I have 119k miles on it so I cant get it fixed under the warrany deal....man that sucks bad. Last I checked, the limit was 10y 100k miles
 
Right on the Mark said:
To me it sounds like you already did damage to 1 or more cats. I think you melted(clogged) one or more. The added intake noise is from the motor not being able to pump exhaust out of the motor. Remember motor is just an air pump, air in then air out. It runs better on fail safe because the comp is alternating power cycles and that will let enough exh out to somewhat breathe at low rpm. I had this happen on my F-350. Truck would not rev or go over 10mph. And had crazy intake noise.To test for clogged cats all i did was loosen exh manifold bolts to let breathe. This is before the cats so lets motor breathe and it went normal again just loud lol. You could also pull front O2's that would let it breathe too. Frank
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Your diagnosis is correct. I removed the upstream o2's and wa-la! POWER! And lots of exhaust noise LOL. Need new cats.
 
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