quick misifire question!!
01-13-2010, 03:26 PM
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quick misifire question!! well guys just installed a set of headers on my ole ladys car... (2000 z28) got it going, went and sprayed the engine bay out to clean it up with a pressure washer (not the firtst time ive cleaned it) but when i left it was really really weak and wouldnt really go anywere... then after abt 5 minutes or so it clears up and seems to run ok... but it does it about everytime i shut the car off, runs like crap for about the first 5-10 minutes... then seems to clear up, but if i mat down on it it will clear up somewhat... hooked up my snap on scanner and the only code i beleive related to the problem is a p0300 engine misfire... so i looked and misfired data, 2,4,6,8 is misfiring... so i check the conection to that side of the coils and it seemed ok... anyone else have any input... btw i washed it about 3hrs ago....
01-13-2010, 08:04 PM
#5
You are getting a 300 code which is random miss fire. So that is what the computer is telling you. We very rarely wash an electronic engine for that reason. We work on tuns of ford engines with COP and watter is always a problem with ford engines. With that being said watter is not good for the O2 sensors. O2 sensors use outside air to work properly. I always get tuns of honda engines that run like crap and set O2 codes because guys install O2 sensors facing down and they pick up watter and dirt. Look at the O2 sensor with your scan tool and see if they are responding. Normally an O2 will not cause a missfire. But stranger things have happened. Peace Tom
01-13-2010, 08:13 PM
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thanks alot guys ill get scanner on it tomm. and let you all know... i know its throwing a bank2 o2 code of some sort didnt look into it much figured its bc the header install... but what would bank 2 circuit 2 be???
01-13-2010, 11:56 PM
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bank 2 circut 2 would be the passenger side rear o2, i believe... which unless you are running cats then it doesnt matter... are you running an ORY... i would bet my money on the bank 2 sensor 1 gone bad and causing the misfire...
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01-14-2010, 03:25 AM
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not the cam sensor chris or it would start like mine and the tach wouldnt work...call me in the morning and ill bring my key up to the shop and we can pull my coil pack and put them on there if you still think its the coil packs...if you woulodnt have bailed on me tonight i would have done it tonight dick head lol
01-14-2010, 04:47 PM
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Can you watch the O2 readings with your scanner? If so let it completly cool down and then start it up. The sensor readings should start cycling from 40ish to 800ish and back down very rapidly once it goes from Open Loop (it will be in OL at startup) to Closed Loop (it will be in CL all other times except WOT once the engine JWT comes up to temp) you can see which mode the PCM is in by watching the commanded AFR, if it is not commanding 14.7ish then it is in OL (unless you are at WOT). If the O2 sensor readings are not cycling back and forth rapidly, then I bet the sensor is the issue. Also there might have been some kind of coating inside of the headers that once burned off might have poisoned the O2 sensor and killed it. I would think if the cam sensor was bad the car would not run and you would have that code as well. Usually with your symptoms I find the issue is the O2 sensor. Check for water in any and all conectors before you go and buy new sensors, they are over $100 each for the Bosh 13111 sensor. The Bosh 13111 sensor has a better heating element in it and will come up to operating temp quicker then the stock sensors, wich is why they work better in LT headers were the sensor is in the collector.
02B1-S1= STAYING ABOVE 800
02B2-S1= right at 1107
02B1-S1= MID 400's
02B2-S2=Mid 400's
SO.........................
01-14-2010, 07:01 PM
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The sensor 2 on each bank you can ignore. Did sensors 1 ever start to cycle back and forth or did they just stay pretty much flatlined? Once the engine comes up to temp and the PCM goes from Open Loop to Closed they should start cycling. If they do not cycle then you might have a sensor issue. I would also take a good timing light and place it on each plug wire one at a time and watch the light pulse. If you have a missfire at idle caused by a coil you might be able to see it with the light. Keep in mind that if the O2 sensor is not working right, the PCM will not know this and it will add fuel to that bank trying to get the sensor to respond. It will do this until it floods that bank out. Once that bank floods out your timing light will not light up as well as the PCM might report a missfire error. What I am getting at is if by looking at the timing light you find a few cylinders not setting the light off, it could be do to the cylinder is flooded or the ignition system. So do not automaticaly think if the light does not flash the problem is in the ignition.
The problem in diagnosing this is a missfire can also make the O2 report wrong. So before you go out and spend $ on new O2 sensors, double check the entire ignition system and double check for any air leaks in the headers. Do you have the rest of the exhaust on the car yet? From the headers out the rear of the car? Make sure you do not have a leak were the collectors and the Y pipe is. A leak there or even no exhaust on the car yet will also do this. An open header collector or a leak at the end of the collector can/will draw air back into the exhaust up to the sensor, and that too can cause the sensor to report lean.
The problem in diagnosing this is a missfire can also make the O2 report wrong. So before you go out and spend $ on new O2 sensors, double check the entire ignition system and double check for any air leaks in the headers. Do you have the rest of the exhaust on the car yet? From the headers out the rear of the car? Make sure you do not have a leak were the collectors and the Y pipe is. A leak there or even no exhaust on the car yet will also do this. An open header collector or a leak at the end of the collector can/will draw air back into the exhaust up to the sensor, and that too can cause the sensor to report lean.
so Im stumbled!!!
01-15-2010, 11:07 PM
#16
The sensor 2 on each bank you can ignore. Did sensors 1 ever start to cycle back and forth or did they just stay pretty much flatlined? Once the engine comes up to temp and the PCM goes from Open Loop to Closed they should start cycling. If they do not cycle then you might have a sensor issue. I would also take a good timing light and place it on each plug wire one at a time and watch the light pulse. If you have a missfire at idle caused by a coil you might be able to see it with the light. Keep in mind that if the O2 sensor is not working right, the PCM will not know this and it will add fuel to that bank trying to get the sensor to respond. It will do this until it floods that bank out. Once that bank floods out your timing light will not light up as well as the PCM might report a missfire error. What I am getting at is if by looking at the timing light you find a few cylinders not setting the light off, it could be do to the cylinder is flooded or the ignition system. So do not automaticaly think if the light does not flash the problem is in the ignition.
The problem in diagnosing this is a missfire can also make the O2 report wrong. So before you go out and spend $ on new O2 sensors, double check the entire ignition system and double check for any air leaks in the headers. Do you have the rest of the exhaust on the car yet? From the headers out the rear of the car? Make sure you do not have a leak were the collectors and the Y pipe is. A leak there or even no exhaust on the car yet will also do this. An open header collector or a leak at the end of the collector can/will draw air back into the exhaust up to the sensor, and that too can cause the sensor to report lean.
The problem in diagnosing this is a missfire can also make the O2 report wrong. So before you go out and spend $ on new O2 sensors, double check the entire ignition system and double check for any air leaks in the headers. Do you have the rest of the exhaust on the car yet? From the headers out the rear of the car? Make sure you do not have a leak were the collectors and the Y pipe is. A leak there or even no exhaust on the car yet will also do this. An open header collector or a leak at the end of the collector can/will draw air back into the exhaust up to the sensor, and that too can cause the sensor to report lean.
If the ECM does not see O2 input it sets a code. If the ECM sees a rich condition it will blink the SES light to caution the driver of excessive fuel contamination of the cats. Your statement that the O2 adds fuel to see a response is not correct. If O2 signal is not detected the ECM goes limp in mode. It will never add fuel that will overheat the cats. Flood out the BANK??????? That will also cause the cat to overheat and that is once again not what the ECM will do. The last thing the ECM will do is flood the cat with raw gas. That is really feeding the cat which can cause a fire in the car. That is why the SES light plinks when you have a dead cylinder that is still reseaving FUEL. The ECM will shut down the injector of that cylinder. If you have ever shot a miss fire problem you would know that once the trouble is cleared. The ecm codes must de cleared to reactivate the injector of that cylinder. The ECM does not add fuel to a cat that is already flooded because of a MISS FIRE. It does the OPPOSITE. Why would a working O2 add fuel if there is to much there to begin with ?????????????????????????
Last edited by tom falco; 01-15-2010 at 11:12 PM.
01-16-2010, 05:43 PM
#17
TEMPER TEMPER DUDE i really dont give a flip what you think. I was not trying to put anyone down. But now that you mentioned it . FLOOD the bank and that kills the spark. The ECM keeps adding fuel till the O2 respond. (that was a joke right) (what if the O2 sensors are BAD how much does the ECM richen it up )Also whether it has cats or not the computer still processes the info the same. The ECM is designed to protect the cats. It will not keep adding fuel to make an O2 respond. It will revert to limp in mode or BYPASS. Also i never said if an engine is rich the SES FLASHES. It flashes with a missfire input. Or excessive rich mixture To warn the driver the cat is in distress. Dont take it personally. I was just trying to digest your comments and correct them. You dont have to Blow a head gasket about it. I was polite and just chimed in. I really dont care either way. And i am not going to start a tit for tat. Over this.
Last edited by tom falco; 01-16-2010 at 06:05 PM.
01-16-2010, 06:27 PM
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Texas Ws6, id love to get some of the **** your smoking. So the gm engineers will flood the engine out when you get an 02 sensor problem?? Think again pal.
Maybe somebody should get you a service manual.
I love all these guys like texasws6
they widely spread false information and then flame people with correct information and then have the nerve to get mad at that guy, who has the right information and Imo wasnt a dick about it, its people like YOU who think you know everything and are mad when somebody that ACTUALLY know what their taking about chimes in are why people stray away from message boards 
Looks to me like tom falco has brushed up on factory service manuals because basically everything he says is written right in the manual.. but i guess you know more then gm..... then have the ***** to flame him for stating WHAT CLEARLY IS IN SERVICE MANUALS
Not sure what this "tech tool" you speak of is, But i do know that my TEC 2 gm scanner will show you everythign you need to know live feed, your best bet would be to ask a gm service guy for a hand for a few mins with the scanner
Maybe somebody should get you a service manual.
I love all these guys like texasws6
they widely spread false information and then flame people with correct information and then have the nerve to get mad at that guy, who has the right information and Imo wasnt a dick about it, its people like YOU who think you know everything and are mad when somebody that ACTUALLY know what their taking about chimes in are why people stray away from message boards Looks to me like tom falco has brushed up on factory service manuals because basically everything he says is written right in the manual.. but i guess you know more then gm.....
then have the ***** to flame him for stating WHAT CLEARLY IS IN SERVICE MANUALS Not sure what this "tech tool" you speak of is, But i do know that my TEC 2 gm scanner will show you everythign you need to know live feed, your best bet would be to ask a gm service guy for a hand for a few mins with the scanner
Last edited by glocklimited9; 01-16-2010 at 06:34 PM.
01-18-2010, 09:24 PM
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well guys i changed all plugs etc... car is no longer throwing a check engine light atm... i also had the downstream 02 sensor on passenger side in the upstream spot!!! But it still has a stumble the first time you take off in the car, still trying to find out what it could be....
