Lost 22 HP!
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
Lost 22 HP!
My '02 heads/cam vert seemed to be running a but weak lately, went to the track and was off by nearly 3/10! So changed or checked the usual plugs, wires, filters, all recent good and fresh, went to the dyno and am down 22 HP, no codes historic or otherwise, the left side bank seems to be running rich about 100 degrees cooler than the passenger side, but the plugs look good. No loose wires or connections anywhere that we can find...compression is good and pretty even all around as well.... Any thoughts/suggestions? Hate to start randomly throwing a bunch of parts at it, I have no access to HP tuners but buddy has the latest Snap On diagnostics....thanks!
Advanced
Joined: Jan 2007
Posts: 69
Likes: 0
I'd do a leakdown test on it. That's going to tell you if what you don't want to hear is true. If that comes back fine, pull off the valve covers and check to see if you have any broken rocker arms or valve springs. If not, I'd throw a set of springs on it and see where your at after that. How many miles are on the setup?
Melting Slicks
Joined: Dec 2012
Posts: 2,312
Likes: 8
From: Frisco Texas
I'd do a leakdown test on it. That's going to tell you if what you don't want to hear is true. If that comes back fine, pull off the valve covers and check to see if you have any broken rocker arms or valve springs. If not, I'd throw a set of springs on it and see where your at after that. How many miles are on the setup?
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
compression test is all good, fresh plugs, recent GMPP wires, fresh BT Racing dual springs only about 2,000 miles....all looks good under the valve covers....
feels like a bit of a miss from time to time, usually under light throttle, but can't seem to determine if it's fuel or ignition, shows no codes at all...
feels like a bit of a miss from time to time, usually under light throttle, but can't seem to determine if it's fuel or ignition, shows no codes at all...
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
after checking all the electrical, fuel, etc systems and wiring, injectors, coils, etc, can't find any issues, went to a GM tech to get the whole system scanned, the only thing out of the normal is my AFR at 15.8 at idle, and 14.7 at higher rpm... didn't check it under load or on the road though, but he's sayin it should be around 14.7 at idle, and never over 12.8 at rpm regardless if under load or reving in neutral....i no longer have access to HP tuners or EFI live mind you, he's using GM program Snap On scanners/diagnostics, so right now neither of us can make any changes or go into the tune....we're just able to read and trouble shoot...
what AFR in the same condititions are you tuners seeing for heads/cam cars? nothing's ever been changed on my tune except some trans and TC things....
what AFR in the same condititions are you tuners seeing for heads/cam cars? nothing's ever been changed on my tune except some trans and TC things....
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Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
That was my 1st thought, but they're LG 3" high flows, was told they couldn't plug up like standard cats..(?)....kinda acts like it though, right side cyls hotter than the left side, down 22hp, bit of a bobble type almost stutter under certain throttle conditions etc.....maybe I'll throw some "off road test pipes" on and try it....tried everything else...
Racer
Joined: Aug 2010
Posts: 472
Likes: 9
From: San Diego CA
How did you test your injectors? Under load? Did you check/clean the harnesses too? Bad coil under load? Bad spark plug under load?
What size injectors?
Condition/mileage of your 02 sensors?
For problems like this, you need to log...especially both banks and afrs...need to see fuel trims. I know you don't have access to a logger, but it sure comes in handy for these cases.
Could be clogged cat, failing injector, failing coil, failing spark plug. Maybe try switching coils to the other side...
What size injectors?
Condition/mileage of your 02 sensors?
For problems like this, you need to log...especially both banks and afrs...need to see fuel trims. I know you don't have access to a logger, but it sure comes in handy for these cases.
Could be clogged cat, failing injector, failing coil, failing spark plug. Maybe try switching coils to the other side...
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
everything was tested andscanned with GM software.... couldn't make anything break down...fresh plugs/wires didn't make any difference....
running stock injectors, had no issues so far with them, coils all fire good according to the scanner, cats are 3" high flow metal matrix, and 02 sensors check out fine.....my tune was good, shouldn't/couldn't have changed for no reason with no input...
it's getting worse, should be easier to find now.... hopefully I'll be able to get it fixed next day or so...hooked up with a new tech with HP Tuners and EFI Live...otherwise I'll have to hoojk u8p my wideband and drive it around and do some logging...
running stock injectors, had no issues so far with them, coils all fire good according to the scanner, cats are 3" high flow metal matrix, and 02 sensors check out fine.....my tune was good, shouldn't/couldn't have changed for no reason with no input...
it's getting worse, should be easier to find now.... hopefully I'll be able to get it fixed next day or so...hooked up with a new tech with HP Tuners and EFI Live...otherwise I'll have to hoojk u8p my wideband and drive it around and do some logging...
Racer
Joined: Aug 2010
Posts: 472
Likes: 9
From: San Diego CA
everything was tested andscanned with GM software.... couldn't make anything break down...fresh plugs/wires didn't make any difference....
running stock injectors, had no issues so far with them, coils all fire good according to the scanner, cats are 3" high flow metal matrix, and 02 sensors check out fine.....my tune was good, shouldn't/couldn't have changed for no reason with no input...
it's getting worse, should be easier to find now.... hopefully I'll be able to get it fixed next day or so...hooked up with a new tech with HP Tuners and EFI Live...otherwise I'll have to hoojk u8p my wideband and drive it around and do some logging...
running stock injectors, had no issues so far with them, coils all fire good according to the scanner, cats are 3" high flow metal matrix, and 02 sensors check out fine.....my tune was good, shouldn't/couldn't have changed for no reason with no input...
it's getting worse, should be easier to find now.... hopefully I'll be able to get it fixed next day or so...hooked up with a new tech with HP Tuners and EFI Live...otherwise I'll have to hoojk u8p my wideband and drive it around and do some logging...
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
Burning Brakes
Joined: Feb 2012
Posts: 1,047
Likes: 43
From: Longview Texas
Glad you found the issue. Regarding the cats my tuner told me that aftermarket cats need replaced every year or two and will "clog" up over time; especially when you run high RPMs like many of us do. I went with an off-road x-pipe to not have to deal with this. Not sure if it's true or not but I wasn't going to mess with it ever and can get inspections without them seeing it.
