Drivability Issues on 5.3L CANT FIGURE IT OUT!!!
07-30-2011, 03:38 PM
#1
Drivability Issues on 5.3L CANT FIGURE IT OUT!!! My daily driver...03 GMC Sierra Z71 with the T-code 5.3(non Flex Fuel). It first threw a code that said Injector circuit malfunction, So I replaced the Injectors, after checking the fuses and Putting a noid-light on the injector plugs to make sure hey are pulsing. That made it run a little better, however it still had a bad miss. So I plugged my code reader in again and it shot up the code for mass/air circuit bellow performance standards...so I put a mass air on it. It is still throwing up a random/multiple cylinder miss-fire...I have changed the plugs, thew the coils off of my camaro on there the MSD ones and it changed nothing and pulled boots while it was running and they all arced. I cant figure it out...so far I have replaced and or have tested these parts to make sure they are working...
Changed Mass/Air sensor
Changed Spark Plugs
Tested Coils
Tested Fuel Pressure idles at 50psi and goes to about 70-75psi by 4000rpm in park.
Changed Fuel Filter
Changed Air Filter
It is hesitating to rev up when I give it gas and it slowly and roughly climbes its way up...it has been throwing codes about the cats being below threshold. Is there some thing I'm missing? or haven't checked?
Changed Mass/Air sensor
Changed Spark Plugs
Tested Coils
Tested Fuel Pressure idles at 50psi and goes to about 70-75psi by 4000rpm in park.
Changed Fuel Filter
Changed Air Filter
It is hesitating to rev up when I give it gas and it slowly and roughly climbes its way up...it has been throwing codes about the cats being below threshold. Is there some thing I'm missing? or haven't checked?
07-30-2011, 03:58 PM
#2
Staging Lane
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You have pretty much covered all the bases. I'd cut the cats out and straight pipe it just to see if its the cats. If so buy new ones before your next smog check if you have them.
07-30-2011, 04:01 PM
#3
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My daily driver...03 GMC Sierra Z71 with the T-code 5.3(non Flex Fuel). It first threw a code that said Injector circuit malfunction, So I replaced the Injectors, after checking the fuses and Putting a noid-light on the injector plugs to make sure hey are pulsing. That made it run a little better, however it still had a bad miss. So I plugged my code reader in again and it shot up the code for mass/air circuit bellow performance standards...so I put a mass air on it. It is still throwing up a random/multiple cylinder miss-fire...I have changed the plugs, thew the coils off of my camaro on there the MSD ones and it changed nothing and pulled boots while it was running and they all arced. I cant figure it out...so far I have replaced and or have tested these parts to make sure they are working...
Changed Mass/Air sensor
Changed Spark Plugs
Tested Coils
Tested Fuel Pressure idles at 50psi and goes to about 70-75psi by 4000rpm in park.
Changed Fuel Filter
Changed Air Filter
It is hesitating to rev up when I give it gas and it slowly and roughly climbes its way up...it has been throwing codes about the cats being below threshold. Is there some thing I'm missing? or haven't checked?
Changed Mass/Air sensor
Changed Spark Plugs
Tested Coils
Tested Fuel Pressure idles at 50psi and goes to about 70-75psi by 4000rpm in park.
Changed Fuel Filter
Changed Air Filter
It is hesitating to rev up when I give it gas and it slowly and roughly climbes its way up...it has been throwing codes about the cats being below threshold. Is there some thing I'm missing? or haven't checked?
run for crap. Just remove them O2's and see if it revs up better. You may even have to break the exhaust loose a little before the cats and try it. You'll probably find your problem.
Last edited by Chicken Coupe; 07-30-2011 at 04:07 PM.
07-30-2011, 04:30 PM
#5
The last time I had a 5.3 drive me nuts I had all fueling data within paramaters and still could not get it to run right, it ended up being bad gas, I hadn't seen someone get bad gas in so many years that I ended up chasing my *** for 2 days on that truck.
If you think you have a vaccum leak that will be real easy to tell by watching the STFT. Does your scanner have data stream capability?
And I am completely pulling this out of my ***, but have you checked the crank sensor? If it is freaking out then so will your spark/fuel. I would give the wiring a good look over. You may even pick up a crank sensor and try it, if it doesn't help, clean it and take it back. Try disconnecting the cam sensor and see if it will run without signal, it can also cause ignition and fueling events to go haywire. I used to diag MAF sensors by seeing if the engine ran better with them disconnected. If the sensor is sending a incorrect signal it will cause the engine to run worse than no signal, this is because if the signal is missing the PCM will substitute a value in its place based off of other data.
If you think you have a vaccum leak that will be real easy to tell by watching the STFT. Does your scanner have data stream capability?
And I am completely pulling this out of my ***, but have you checked the crank sensor? If it is freaking out then so will your spark/fuel. I would give the wiring a good look over. You may even pick up a crank sensor and try it, if it doesn't help, clean it and take it back. Try disconnecting the cam sensor and see if it will run without signal, it can also cause ignition and fueling events to go haywire. I used to diag MAF sensors by seeing if the engine ran better with them disconnected. If the sensor is sending a incorrect signal it will cause the engine to run worse than no signal, this is because if the signal is missing the PCM will substitute a value in its place based off of other data.
Last edited by 00pooterSS; 07-30-2011 at 04:37 PM.
