01 chevy z71 air to fuel raito problems
#1
09-09-2013, 04:08 PM
01 chevy z71 air to fuel raito problems
One of my buddies and i just installed a set of header, i purchased new o2 sensors for the truck and i had removed the cats but now my truck is rollin coal( blowing black smoke) which is not normal for a gas engine. do any of you know what is wrong and also it gave me a p0300 code which means random misfiring.
#2
09-10-2013, 02:17 PM
Double check all the wiring to the plugs etc., something may have broken or did not get connected. Pull the plugs to check which cyclinder(s) are not firing right. Maybe one or more O2 sensor is bad. Replace them with the original ones and see what happens. However I would think if it was an O2 sensor you would get a code for the sensor.
#4
09-11-2013, 09:38 AM
The O2 sensor in front of the cat is the one that is used by the computer for adjustments. The one behind the cat is only a reference but not used for adjustments, however it will through a code and cause the check eng light to come on.
#5
09-11-2013, 04:06 PM
the code reader told me it was bank 1 sensor 1 and bank 2 sensor 1. ive been looking at a lot of things ive seen where it says I need to tune my truck after header installation because this all started after I installed the headers
#6
09-12-2013, 03:54 PM
Those are the front sensors used by the computer. If you did not find any wiring issues I suggest you disconnect the battery for 10 minutes and let everything reset. Maybe you did this with the header install but try it again and short the - and + battery cables together when they are disconnected. Re-connect it and start it and drive it. I think it takes about 20 minutes for the computer to re-adjust everything. The O2 sensors need to heat up to give a reliable reading.
#7
09-12-2013, 08:42 PM
I did that and then yesterday I drove it and it drove good for about 5 minutes an then went straight back to smoking
#8
09-13-2013, 12:59 PM
Hmmm, sounds like a side affect of removing the catalytic converters. A problem I experienced once may be applicable...
A buddy of mine removed the cat on his 01 Impala, along with the second O2 sensor (as it is not used for A/F trims), buthis caused a severe drop in fuel economy. After some research, we discovered that this is actually a result of bad programming with the computer.
The post-cat O2 sensor is used as a reference to see if the catalytic converter is operating. Upon start up, the engine compares the readings from the two O2 sensors. Even though the cat won't be up to operating temp, there will be a difference between the sensors. If a bad signal is being read from the second O2 sensor, the engine will enter a diagnostic mode, dumping fuel into the cylinders to attempt to get any reading from the second O2 sensor. Unfortunately for my friend, the engine won't exit this state and will continue to dump fuel.
Sometimes, if you are stubborn about not putting the catalytic converter back on, you can get around this issue. My friend completely removed the second O2 sensor, but as long as it is still on your vehicle you can try it. The first O2 sensor signal will fluctuate as the engine switches back and forth from rich to lean mixture. With a functioning cat, the second O2 sensor will read a similar but extremely damped waveform of the first, which is how the computer knows the cat is working. With the cat removed, this effect can sometimes be achieved by installing one or two spark plug non-foulers between the second O2 sensor and the threads it is supposed to enter. The threading is all the same, so they should slide right in.
It should look like this:
| |
| (female threading) (non-fouler) (non fouler) (O2 sensor)
| |
This backs the business end of the O2 sensor out the the exhaust stream enough to trick the engine into reading a functioning cat signal. Doesn't always work, but non-foulers are cheap and you aren't modifying anything, so worth the risk.
Hope it helps.
EDIT: Reading over this, I am realizing I may not have been super cear about the root cause of this problem. If you want something explained, or more information about how ctalytic converters work/are monitored, let me know.
A buddy of mine removed the cat on his 01 Impala, along with the second O2 sensor (as it is not used for A/F trims), buthis caused a severe drop in fuel economy. After some research, we discovered that this is actually a result of bad programming with the computer.
The post-cat O2 sensor is used as a reference to see if the catalytic converter is operating. Upon start up, the engine compares the readings from the two O2 sensors. Even though the cat won't be up to operating temp, there will be a difference between the sensors. If a bad signal is being read from the second O2 sensor, the engine will enter a diagnostic mode, dumping fuel into the cylinders to attempt to get any reading from the second O2 sensor. Unfortunately for my friend, the engine won't exit this state and will continue to dump fuel.
Sometimes, if you are stubborn about not putting the catalytic converter back on, you can get around this issue. My friend completely removed the second O2 sensor, but as long as it is still on your vehicle you can try it. The first O2 sensor signal will fluctuate as the engine switches back and forth from rich to lean mixture. With a functioning cat, the second O2 sensor will read a similar but extremely damped waveform of the first, which is how the computer knows the cat is working. With the cat removed, this effect can sometimes be achieved by installing one or two spark plug non-foulers between the second O2 sensor and the threads it is supposed to enter. The threading is all the same, so they should slide right in.
It should look like this:
| |
| (female threading) (non-fouler) (non fouler) (O2 sensor)
| |
This backs the business end of the O2 sensor out the the exhaust stream enough to trick the engine into reading a functioning cat signal. Doesn't always work, but non-foulers are cheap and you aren't modifying anything, so worth the risk.
Hope it helps.
EDIT: Reading over this, I am realizing I may not have been super cear about the root cause of this problem. If you want something explained, or more information about how ctalytic converters work/are monitored, let me know.
Last edited by Prometheus2508; 09-13-2013 at 03:41 PM.
#10
09-13-2013, 09:12 PM
Really, you'd have to look at the sensor data with a scan tool to know for sure what the computer is doing. Could be the coolant temp sensor in combination with the pre-cat 02 sensors (bank 1 sensor 1, bank 2 sensor 1). If those are inside a primary for a single cylinder, that can cause some pretty big issues. Do you "NEED" a tune for headers? I'd say most likely not, because if the 02s are in the collectors, no big deal. The truck will run, but could "use" a tune.
Now yes, the computer will add fuel to warm up the catalytic converters faster, but I doubt it would go into "smoke screen" mode. Personaly, I'd try your old 02 sensors, and then maybe try putting the second sensors back into the exhaust stream, even though they will rear incorrectly and be redundant and only tell the computer you have no cat.
If you're absolutely sure you need your computer tuned, then get it tuned and go from there. But to me, it sounds like the computer wants to see 02 sensors, even if they're reading values that would indicate a catalytic converter or not.
Now yes, the computer will add fuel to warm up the catalytic converters faster, but I doubt it would go into "smoke screen" mode. Personaly, I'd try your old 02 sensors, and then maybe try putting the second sensors back into the exhaust stream, even though they will rear incorrectly and be redundant and only tell the computer you have no cat.
If you're absolutely sure you need your computer tuned, then get it tuned and go from there. But to me, it sounds like the computer wants to see 02 sensors, even if they're reading values that would indicate a catalytic converter or not.
