open headers made my service engine soon light come on
05-16-2009, 04:49 AM
#15
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
It's not really running lean, the O2 sensors just think it is...
By removing the exhaust system you have a big fat exhaust leak* that is making the O2 sensors think the engine is running lean--the adaptive fuel strategy is compensating by making the mix richer, when the short term fuel trims hit +25%.or better the DTCs are thrown.
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*-With no exhaust the negative pressure trailing end of the exhaust pulses are sucking air back into the header and making the O2 sensor read lean.
By removing the exhaust system you have a big fat exhaust leak* that is making the O2 sensors think the engine is running lean--the adaptive fuel strategy is compensating by making the mix richer, when the short term fuel trims hit +25%.or better the DTCs are thrown.
----------------------------------
*-With no exhaust the negative pressure trailing end of the exhaust pulses are sucking air back into the header and making the O2 sensor read lean.
Last edited by cliffyk; 05-16-2009 at 05:06 AM.
05-16-2009, 07:54 AM
#16
2nd Gear Member
Join Date: Dec 2005
Location: MO
Posts: 439
When I first got my car together I ran it for about an hour to break in the motor with no X-pipe or mufflers, just 30" of pipe on either side. It ran very rich - so rich it turned the oil dark in that time. After I put on the exhaust it ran fine.
It is likely that your O2 sensor THINKS you're running lean when it is really rich. Either it is getting a whif of fresh air at idle when it tends to 'pulse' the air or the O2 sensors need a little backpressure to work properly. Since it thinks it's lean, it richens the mixture.
Either you need to 1) run exhaust or get a 2) tune for open headers (and 3) maybe wideband O2 sensors to allow for some adjustment). #1 is cheap, 2 is more and 2 and 3 is not worth it unless it's a dedicated drag car with open headers all the time.
It is likely that your O2 sensor THINKS you're running lean when it is really rich. Either it is getting a whif of fresh air at idle when it tends to 'pulse' the air or the O2 sensors need a little backpressure to work properly. Since it thinks it's lean, it richens the mixture.
Either you need to 1) run exhaust or get a 2) tune for open headers (and 3) maybe wideband O2 sensors to allow for some adjustment). #1 is cheap, 2 is more and 2 and 3 is not worth it unless it's a dedicated drag car with open headers all the time.
Last edited by ozarks06; 05-16-2009 at 07:58 AM.
05-16-2009, 09:30 AM
#18
Banned
Join Date: Sep 2008
Location: tn
Posts: 0
It doesn't sound like the 02 sensors are turned off, check and be sure that you did. Bank 1 is the right (passenger) pipe and Bank 2 is the left (drivers) pipe. It is leaning out your engine because it isn't getting a reading back from the 02 sensors. You need to check your tune again and if it still doesn't fix it, then you will need MIL elims.
05-16-2009, 09:33 AM
#20
2nd Gear Member
Thread Starter
Join Date: Nov 2008
Location: tx
Posts: 329