installed headers now stumble at idle
03-17-2004, 09:47 AM
#1
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installed headers now stumble at idle i installed a set of uncoated jba headers have checked for exhaust leaks and found none. changed all my plugs. still original wires 69k miles on car. i have double checked the plugs and they look alright. relearned idle procedure and even reset pcm. there is a small stumble at idle it is worse when the a/c is off it seems to happen when the car reaches operating temperature i am guessing it is going into a closed loop. no check engine light except for one set off b/c of !air and !egr. besides that no other problems are evident. is it possible a o2 sensor went bad during the installation or the heat has fried the wires?
btw checked the plug wires and were giving me about 330-340 in resistance.
any ideas would be greatly appreciated.
thanks
98 z28 a4
69k miles
!air, !egr
btw checked the plug wires and were giving me about 330-340 in resistance.
any ideas would be greatly appreciated.
thanks
98 z28 a4
69k miles
!air, !egr
03-17-2004, 09:51 AM
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atap/efilive/tech2 log your o2's.
If your extensions are buggered then it would run like **** (and throw a code) im guessing.
Headers by nature change the dynamics of air flow around the o2 sensors, thus the reading you used to get, you will not get with headers, now your car may adjust its trims in response and if it runs too lean/rich it will stumble a little.
put a big cam on, you won't notice it one bit
If your extensions are buggered then it would run like **** (and throw a code) im guessing.
Headers by nature change the dynamics of air flow around the o2 sensors, thus the reading you used to get, you will not get with headers, now your car may adjust its trims in response and if it runs too lean/rich it will stumble a little.
put a big cam on, you won't notice it one bit
03-17-2004, 10:33 AM
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lol big cam! thats the thing i dont know anyone with atap or any of the above programs. is there any other way to read or check if the o2s are good/bad
03-17-2004, 04:58 PM
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find someone in the local forums. If you were in atlanta, you'd be more than welcome to use mine. however if the ECU doesn't like what it sees (many o2 checks) it will throw codes left and right. there's a ton of o2 codes/checks and you'll see them real quick when in closed loop if shiz aint kosher with your o2's. I think i got a dying o2 (70K miles) i randomly (cold days) get P0135 and only p0135. Pre-headers = no codes at all. Could be a loose/moisture issue with the extensions. Since it warmed up no codes at all.
Honestly on all my cars i stick to 60K miles replace O2's. It's not like they are hard (when doing headers) they won't be krusted on, and its just good sense.
Btw if you tune your car, i strongly suggest new o2's. It seems the trims that it learns are based on o2's. so if your o2's are weak, im not sure but it may be possible your tune have some compensation for the trims of your current o2's, and new ones might throw off the tune a little. This is just my theory. I've got two widebands so i guess i can drill some taps in and see whats really going on when it gets a little warmer.
O2 sensors are highly egt sensitive as i said, so when you ditch the cats, jet coat the headers, and increase flow, the air is passing by the o2 faster than if say a cat was there and there was more flow restriction. This itself i believe might cause your car to run richer than it commands. If the air passes by the o2 faster it might not think its so rich, and add fuel. Does that make sense?
please feel free to argue, i'm new to gm, but have a bit of experience tuning other cars, and assume some things are the same (may not be).
Honestly on all my cars i stick to 60K miles replace O2's. It's not like they are hard (when doing headers) they won't be krusted on, and its just good sense.
Btw if you tune your car, i strongly suggest new o2's. It seems the trims that it learns are based on o2's. so if your o2's are weak, im not sure but it may be possible your tune have some compensation for the trims of your current o2's, and new ones might throw off the tune a little. This is just my theory. I've got two widebands so i guess i can drill some taps in and see whats really going on when it gets a little warmer.
O2 sensors are highly egt sensitive as i said, so when you ditch the cats, jet coat the headers, and increase flow, the air is passing by the o2 faster than if say a cat was there and there was more flow restriction. This itself i believe might cause your car to run richer than it commands. If the air passes by the o2 faster it might not think its so rich, and add fuel. Does that make sense?
please feel free to argue, i'm new to gm, but have a bit of experience tuning other cars, and assume some things are the same (may not be).