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Discussion Starter #1
Good afternoon, everyone, Im Kevin and I'm new to this forum, so i apologize in advance if I'm posting this in the wrong place. Anyway, Im the proud owner of a 2008 GTCS 5 speed, and recently I've started noticing that I'm losing a ton of power in the mid/high rpm range at wot. My current mods are just a cmcv delete. i left the module connected to not set a cel but i haven't had it tuned yet. anyway, it only seems to do it with its warmed up, at wot, and over 3500-4k, sometimes its so bad it feels like i just completely let off the gas, and again sometimes its not very noticeable. One thing i learned while trying to pin point what it was, was turn the kay off while moving than back on. Ran like a champ for about 30 secs than it goes back to losing power. No cel other than cmcv bank stuck open. So far I've already cleaned the mad and tested the tps, but no luck. and with every passing day i notice more white hair on my head lol, any help would be very much appreciated. Thanks in advance!

Kevin.
 

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You really need a tune for a CMCV delete. I'd give Brenspeed a call and discuss what's going on with them. Even if you don't give them business, they're usually fantastic at helping out with this type of thing.
 

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Discussion Starter #3 (Edited)
Ill give them a call to help find out what the problem could be, is there anything else that may cause this? I checked my cel again and it is also throwing a code for cmcv position sensor, not sure if this could affect it. I think im going to get a handheild tuner with the 3 tunes. Im going to put cams, headers, and cai on next. Assuming i can fix whatever this is. What could cause something like this to happen and go away if i turn the key off than back on? Closed loop problem maybe...thanks tho, ill give brenspeed tomorrow
 

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Ill give them a call to help find out what the problem could be, is there anything else that may cause this? I checked my cel again and it is also throwing a code for cmcv position sensor, not sure if this could affect it. I think im going to get a handheild tuner with the 3 tunes. Im going to put cams, headers, and cai on next. Assuming i can fix whatever this is. What could cause something like this to happen and go away if i turn the key off than back on? Closed loop problem maybe...thanks tho, ill give brenspeed tomorrow
Kevin,

You should really do one of two things before moving forward. Either remove the delete plates and see if the car goes back to normal, or get a calibration for the delete plates and see if the issue goes away. Because you are running something on the car with the incorrect calibration you could spend countless hours trouble shooting. So the answer is pretty easy, do one of the two things listed above, then move forward. That is exactly what we would do if your car was at our facility. A lot of times the car will not run proper spark tables when it thinks something is up with the IMRC's so you need to start with the correct parts or calibration first. Good luck.
 

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When you turn your key off and on, the oxygen sensors don't kick in for about 15 to 20 seconds. Also, you should try doing the proper reset procedure for the car. Unplug the battery for a while, then plug it back in, make sure the handbrake is pulled up, and turn the car on. Let it idle by itself until it is at operating temperature, then let it idle for one more minute after that. Then, turn on your A/C and let the car run for one more minute so the car can relearn it's idling strategy. Then you'll have to take the car for a drive and it will relearn it's driving strategy over the course of 10 miles.

Doing the above helped me fix a bunch if problems when my car would act weird sometimes. You're supposed to do that anytime you unplug the battery to work on the car. Other than that, I'm a noob lol. I also did just trade my 2007 v6 automatic for an 08 manual GT and it's great. I hope you can fix the car!
 

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You really need a tune for a CMCV delete.
What he said. You've deleted the CMCVs without tuning for the mod so the engine's running too lean.
Kevin, I'd advise you to get an SCT X4 tuner from Brenspeed and upload the canned CMCV delete tune to your ECU. Then when you add more mods, you can get a Brenspeed custom tune.
I've had excellent service from them so you can't go wrong.
 

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Discussion Starter #7
What he said. You've deleted the CMCVs without tuning for the mod so the engine's running too lean.
Kevin, I'd advise you to get an SCT X4 tuner from Brenspeed and upload the canned CMCV delete tune to your ECU. Then when you add more mods, you can get a Brenspeed custom tune.
I've had excellent service from them so you can't go wrong.

I think you're right, Thats the same info i got from brenspeed. The main reason i deleted them in the first place was because the module stopped working, But i left it plugged in, so it could be telling the computer its closed when their open, this would explain why it only does it sometimes. Im also gonna check the o2s just for the heck of it, but I'm giving brenspeed a call back and getting the sctx4 like you said and see where it goes from there. Thank you all VERY much for all of your help!! Next up, some livernois cams 5830.gif
 

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your halfway on the right track to cmcv delete plates. look on your local CL for a unmarried sxt tuner for around 200$ or so. you want the 3015 if you can find it, or if you have the money, get the sx4. they come with a menu of options and one is the cmcv delete your looking for. you can also change gears and turn of rear o2 sensors ect. the stock cmcv's open at around 3000 rpm and that's probably why your having throttle trouble around that rpm range. if your looking to fix on the cheap, you can gut your current ones and use the tuner to turn them off, its really easy. I got a used intake and gutted them so I still have an oem setup incase I decide to sell in the future. good luck
 

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Discussion Starter #9
UPDATE-------

Got the cmcv problems tuned thanks to brenspeed, but my problem now is..it still does it :( Ive cleaned the maf, checked the o2s, checked the tps, fuel psi is good, still the same problem, wot at about 4k falls flat on its face but if i cycle the key it makes power again for about 5 seconds than falls again. no backfiring, jerking, just goes from planting me in the seat to getting passed by a station wagon. no cel codes thrown, Im guessing its a sensor, Could the fuel pressure sensor do this, or maybe the iat sensor? If i give it 3/4 throttle it pulls harder than wot unless i cycled the key. I thought it could have been the cats too, but you wouldn't think that could change with a key cycle. Im truly stumped now question.gif

EDIT: Also when it happens, sometimes it pulls hard up to 4k than drops, other times it hits at around 3 and slowly chugs up to 4+ and as soon as it hits the exhaust sounds muffled slightly. When it happens at lower rpm, it doesn't fall on its face like at 4k, more like a smooth loss of power that i don't even notice until i hear the rpm coming up way too slow
 

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since you have a handheld, now it would be best to download live link and do some logging.

look at the o2 voltages, short term trims ,cam position, maf voltage, spark.
 

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UPDATE-------

Got the cmcv problems tuned thanks to brenspeed, but my problem now is..it still does it :( Ive cleaned the maf, checked the o2s, checked the tps, fuel psi is good, still the same problem, wot at about 4k falls flat on its face but if i cycle the key it makes power again for about 5 seconds than falls again. no backfiring, jerking, just goes from planting me in the seat to getting passed by a station wagon. no cel codes thrown, Im guessing its a sensor, Could the fuel pressure sensor do this, or maybe the iat sensor? If i give it 3/4 throttle it pulls harder than wot unless i cycled the key. I thought it could have been the cats too, but you wouldn't think that could change with a key cycle. Im truly stumped now question.gif

EDIT: Also when it happens, sometimes it pulls hard up to 4k than drops, other times it hits at around 3 and slowly chugs up to 4+ and as soon as it hits the exhaust sounds muffled slightly. When it happens at lower rpm, it doesn't fall on its face like at 4k, more like a smooth loss of power that i don't even notice until i hear the rpm coming up way too slow
KWA302,
The good news is you are on the right path to getting the mystery solved. Since the car did not used to have a problem, and you now have the correct cal on the car now, you can look at sensors. I suggest sending an e-mail to [email protected] with the description you listed above and we will e-mail you over some ideas on where to go from here. Hopefully before you know it your car will be back to tearing up the streets. thanks!
 

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Whens the last time you did the fuel filter? Its often the simplest things. It may flow enough up to 4k but after that it cant keep up. Pressure would be fine still but the volume isnt there to feed the engine. One bad tank of gas can wreck a filter.
 
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