Frank Leal

Hello all,
First off, I want to thank any one who contributes with help. Thank you.

-I finally got a code reader to pull the codes on my 2007 Chevy Tahoe / 5.3 L / V8. I need to pass smog in the next few weeks.
I bought a OBDLink SX that connects to my laptop.
so here are the codes I first pulled:
Code Type Status Description
---- ---- ------ -----------
P0053 PowerTrain Stored HO2S Heater Resistance
P0134 PowerTrain Stored O2 Sensor Circuit No Activity Detected
P0135 PowerTrain Stored O2 Sensor Heater Circuit
P0303 PowerTrain Stored Cylinder 3 Misfire Detected
P0053 PowerTrain Pending HO2S Heater Resistance
P0135 PowerTrain Pending O2 Sensor Heater Circuit
P0303 PowerTrain Pending Cylinder 3 Misfire Detected

-i resolved all the O2 sensor codes. i replaced the bank 1 up stream sensor as the fuses were ok and i had heater voltage at cold start.
so then i replaced all spark plugs and wires thinking that might resolve the misfire issue. they had never been replaced and i'm at 95k miles.
then i cleared the codes and the O2 codes have not returned and on the scanner program i see the voltage readings fluctuation as conditions change so it is now communicating.

the only code i have now is P0300 which is a general code meaning more than one cylinders are misfiring. this is the area i need help with.
-the on board monitoring report shows that cylinders 1 & 3 are the ones misfiring.
-i'm also concerned with the long term fuel % trim bank 1 ---- take a look at the image i'm adding. i don't know much about fuel trims nor how to interpret that
data i'm seeing just that there is a different between the bank 1 and 2 and my guess is that is should much closer between the two banks.
-does this help anyone to narrow the trouble possibilities?? could it be an intake leak, burnt valves, or injector issues??
My gut tells me it's an injector issue but i'm not sure how to go about checking.
the symptom is slight rough idle but the vehicle drives fine and doesn't die at idle.

Again any help resolving this issue would be great.
thanks all.

Frank Leal

Anyone have any advice???????????????????

kevinkpk

Well, if you feel it's injector, replace them. Or swap them around to a different cylinder, if the problem follows it, you got it.

Frank Leal

Update: So I removed the fuel injectors in bank 1 and cleaned them with Carb cleaner. I replaced the old O-rings with new ones. I moved the injectors from cylinder 1 and 3 to cylinders 5 and 7 to see if the misfire issue would follow the injectors moved or continue misfiring on 1 and 3. after connecting my scan tool i found that cylinders 1 and 3 continued misfiring. i reved the engine to 2000 rpm and held it there while checking for misfiring and it stopped. i refreshed the codes and had a new code: P0107 PowerTrain Stored Manifold Absolute Pressure/Barometric Pressure Circuit Low Input.
now with this new code i unplugged the MAP sensor and the Rpm's went up from approx. 660 to 750 rpm and stayed steadier than when the sensor was plugged in. i checked for misfiring and it stopped. when i plug the map sensor back in it lowered the rpm back down to 660 and the misfiring began again. any one know how i test the MAP sensor as to weather it is defective or not? Are those able to be cleaned? any help would be appreciated.
thanks

Frank3

I found a good source of information on this error and the sensor at....

https://www.obd-codes.com/p0107

Frank Leal

Update: I have been watching the short/long term fuel trim numbers and began checking for a vacuum leak with propane. Sure enough when I place the hose from the propane bottle near where the intake and engine meet, the long term fuel trim goes really negative to -18,indicating to me that there's a minor leak. And the computer is trying to lean out bank 1.
Many thoughts or help would be appreciated.
Thanks