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1999 Z71 P0300 P0102 P0157

chris001979

By chris001979
in Ask A GM Technician

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chris001979 Enthusiast

chris001979

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Hello i have a 1999 chevy z71 159k miles started missing took it to t he chevy garage all they could tell me was it was throwing a P0300 code they couldn't tell what was causing it they said it was an injector or an o2 sensor and for me to take my pic but they couldn't guarantee this would fix it so i just don't drive it but now i need it so i dusted it off fired it up and drove it for a day and it runs fine as long as you floor it the faster you go the better it runs took it to advanced hooked it up and it through these codes P0102 mass airflow sensor low input P0157 o2 sensor #2 bank#2 and P0300 but didn't state what cylinders were missing so my question is can a bad a bad mass airflow sensor make a car run like this and if it was bad wouldn't the truck run different if i unplugged it. The truck idles low when warmed up like 500 range and you can feel the miss the most at idle and moderate acceleration if you just nail it the truck will run like a beast any ideas would be great

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scooby5121 Enthusiast

scooby5121

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Posted

Read about the MAF sensor....If it is not operating properly it can screw up your air/fuel mixture. Lean or rich and noticeable fuel milage depreciation.

Go to the wreckers and try a used one (cheap). New ones are expensive so this could be a troubleshoot way. Since you have a 99 should be able to pick one up.

 

Scooby (don't throw good money for something that the mechanic is guessing at when he diagnosed your codes)

 

Hey Govtec4 , at least he tried a chevy garage !!

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

ya he did ,to bad its a shit garage ,,,,

 

anywho ,buy a spray cleaner for sensors ,use an ear q-tip and clean the sensor CAREFULLY ,,both sides by bending the q-tip ,,,,be carefull ,that should raise the idle ,,,it worked for me at work ,,,,

 

what about the 02 sensor code? ,is it a perf code ?,the position of the sensor is not the full code title ,please elaborate as i dont want to look it up lol

 

misfire is not pointing at a cylinder yet ,,,,throw a fuel filter at it for giggles and measure pressure also to start ....

 

14 yr old truck out of moth balls ,,,,sure we can fix it ,,,,

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

anywho ,buy a spray cleaner for sensors ,use an ear q-tip and clean the sensor CAREFULLY ,,both sides by bending the q-tip ,,,,be carefull ,that should raise the idle ,,,it worked for me at work ,,,,

 

what about the 02 sensor code? ,is it a perf code ?,the position of the sensor is not the full code title ,please elaborate as i dont want to look it up lol

 

misfire is not pointing at a cylinder yet ,,,,throw a fuel filter at it for giggles and measure pressure also to start ....

 

14 yr old truck out of moth balls ,,,,sure we can fix it ,,,,

 

omg ,what happened with the 2 posts ????? ,it did refresh lmao !!!!

chris001979 Enthusiast

chris001979

Posted
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Yeah i can't remember what all it said about the o2 sensor just think it said it was bad but a buddy told me that o2 sensor 2 bank 2 was after the cat and should not make it run bad when i changed the water pump i was not friendly with the air filter lid and hose the mass airflow sensor was left hooked up and im sure it was banged around a bit none the less i had the problem before it every threw the code for the mass airflow sensor i don't

 

Yeah i can't remember what all it said about the o2 sensor just think it said it was bad but a buddy told me that o2 sensor 2 bank 2 was after the cat and should not make it run bad when i changed the water pump i was not friendly with the air filter lid and hose the mass airflow sensor was left hooked up and im sure it was banged around a bit none the less i had the problem before it every threw the code for the mass airflow sensor i don't want to just dump money at random problems

scooby5121 Enthusiast

scooby5121

Posted
Posted

I had it un hooked when i changed the water pump and clutch fan last weekend and it didn't make a difference with it or with out it truck ran the same

Well, now you know why the Engine light is on and you are having codes.

 

The sensors are not needed to drive your truck, Just as long as the Radio Works eh!!!

chris001979 Enthusiast

chris001979

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I had them.reset and they come back horrible misfire unless you have it floored then it runs great idles at 500 and feels like the motor is caming out shakes the whole truck

chris001979 Enthusiast

chris001979

Posted
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i did the listen to the injector trick with a screw driver and injector number 8 is hardly working at all sounds way differnt than the rest and number 4 didnt sound to healthy im thinking with 2 bad or weak injectors and a bad mass airflow sensor this could be why the truck isnt running very good any more info would be great and thanks for all your guys input

chris001979 Enthusiast

chris001979

Posted
  • Author
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New fuel filter fuel preasure is good or with in specs right at the 60 lbs mark just was thinking that the cheap scaner tool at advanced wouldn't pin point what cylinders were missing and since the chevy garage did say it was an injector or o2 oh and i replaced the MAF No help

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