HP Production Low in 3.5k+ RPM - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 08-27-2010, 04:52 PM Thread Starter
 
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HP Production Low in 3.5k+ RPM

EDIT: Resolved (hopefully)--the dealer today determined nearly complete blockage of the drivers side Cat. Fully covered under the emissions warranty. He had a new stock Cat overnighted (being in uniform at a dealer who caters to military has its perks) and promised my car back to me within 24 hours. I will post again once I have test-driven it.


A couple days ago I started noticing what I thought was an overall lack of power in my 2005 GTO with 63k miles.

Torque and power under 3k RPM seem to be normal but anything over that seems to be "wasting gas" (i.e. the RPMs are sitting 3k-6k but no extra power or acceleration is being produced).

My first thought was the clutch was slipping at the higher RPM/torque load, but the clutch looks brand new (in fact it turns out it was installed with 50k on the car after talks with the previous owner).

If I attempt any type of "non-standard" acceleration I have a flashing engine light by the time I get to third gear. Even in 5th or 6th gear on the highway if you hit the gas you can hear a sort of click-stop under the hood as if something is attempting to open.

Any suggestions for what to look at? Thanks for your help!

Last edited by davidbutzin; 08-31-2010 at 05:42 PM.
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post #2 of 7 (permalink) Old 08-27-2010, 06:56 PM
 
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Any codes on the ECM? A flashing CEL means a more serious problem.
Probably an 02 sensor or other sensor going bad. A scan should get some
info.

Larry

2005 GTO Quick - 1984 Honda V65 Magna Quicker - 2004 Z06 Quickest
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post #3 of 7 (permalink) Old 08-27-2010, 07:26 PM
 
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Have it scanned and don't drive it. Flashing = potential serious damanage.
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post #4 of 7 (permalink) Old 08-28-2010, 07:59 AM Thread Starter
 
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Just got back from Autozone--a random misfire is apparently the trouble code. No cylinder associated with the code. I guess I'm pulling coilpacks and plugs 1 by 1 to see if there's any corrosion, etc.

If anyone else has had this issue please let me know!
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post #5 of 7 (permalink) Old 08-28-2010, 11:16 AM Thread Starter
 
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Update: Replaced all the plugs--found one (second from the front, drivers side) had a peg worn down to a nub.

Test drove it and while there is definitely more power it is still not right. Thinking the bad plug I found is a symptom rather than the cause.

I got it to code again in 1st around 4.5k RPM, random misfire. There is a fairly loud snapping/clicking coming from what sounds like under the vehicle when this code pops.

Any ideas before I have to go fork over way too much money to someone else to do it?
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post #6 of 7 (permalink) Old 09-02-2010, 07:02 AM
 
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Check your injector, plug wire and coil on that cylinder first.

<-- Guess which ones quicker?.....Nope! Not even close.
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post #7 of 7 (permalink) Old 09-09-2010, 06:58 AM
 
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I'd be a little concerned at what caused the cat to plug up in the first place. Maybe too much fuel being exhausted because of a cylinder not firing correctly? I hope I'm wrong, but I don't think your car is fixed. My guess is that the plugged cat is a symptom as well. Keep an eye on that cylinder you found the messed up plug in and keep us posted.

Thank you for your service.
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