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I have a 2000 Suburban with a 5.3l engine and have been

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getting a P0303 obd code...
I have a 2000 Suburban with a 5.3l engine and have been getting a P0303 obd code with erratic acceleration. The problem crops up after the engine reaches 185 degrees engine temp . I develop unven engine acceleration with engine codes P0303, P0300, P0306. One run the engine starts stumbling with uneven idle speed, the next run the engine will run normally. I have replaced egr,iacv, coil, sparkplug, intake air gasket, spark plug wire and associated fuel injector but to no avail. had diagnostic done by two Chevrolet dealerships and no one can solve the problem. The engine has 287,000 miles with nominal oil consumption and has run great until this problem started. Can you help me?
Submitted: 2 years ago.Category: Chevy
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Answered in 7 minutes by:
9/3/2015
Chevy Mechanic: Gary, Chevy Technician replied 2 years ago
Gary
Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 17,512
Experience: 15 years GM master tech
Verified

I am sorry for the long wait

can you confirm the ground on the front of the right cylinder head are clean and tight ? if the ground is not on the front of that right head then the ground is on the back of the cylinder head G103 as seen here in this picture

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Customer reply replied 2 years ago
Gary,
I just got home and I'm going to look at it tonite. My plan is to remove the G103, clean the terminal thoroughly , apply a lite coating of dilectric grease and re install. I assume the other end of that lead is secured at the firewall. I'll let you know what happens as soon as I can.
I apologize for the delay, but it's coming up on Labor day and I had a lot to do.Thanks
Scott
Chevy Mechanic: Gary, Chevy Technician replied 2 years ago

no rush at all

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Customer reply replied 2 years ago
Gary, I can now confirm I have a solid ground on G103. I just put 2 runs on the engine . The first run the engine started fine (as it always has) and after 2 minutes of idle the engine started running rough. As soon as I took the vehicle out on the road
I got a P0303 code. I ran the engine at 65 mph and got two more P0303 codes. As I pulled into a parking lot and put the trans into park, I got a P0300 code. The next run of 15 minutes the engine ran smooth as silk. I pulled into my driveway, put the car in
park and let it idle for two minutes and it started running rough again. It didn't run rough enough to produce another engine code though. I have a scanguageII OBD. Do you need any of the data such as the hexadecimal codes? I can give you other parameters
such as intake air temp, LOD, Ignition, volts etc. if that will help. Please let me know. Thanks, Scott
Chevy Mechanic: Gary, Chevy Technician replied 2 years ago

can you monitor like computer data especially current cylinder misfires and when it is acting up does the live misfire show just # ***** cylinder misfiring ?

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Customer reply replied 2 years ago
Gary,
For the most part it shows P0303. However, occasionally I will produce a P0306 and the engine will really have erratic acceleration and misfires at cruise speeds. Yesterday, in addition to the P0303 I got the random misfire code P0300. If you want, I can send the fuel trim parameters associated with the P0303code.
Chevy Mechanic: Gary, Chevy Technician replied 2 years ago

with this being it seems 2 specific cylinders when it acts up we need to go after those cylinders

this had a brand new fuel injector on # ***** and or # ***** cylinder ?

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Customer reply replied 2 years ago
Gary,
I haven't had a P0306 in a week. I replaced the #3 fuel injector. Upon inspection of the fuel injector, it looked good. I replaced it, the spark plug, coil pack, and wire. I guess I could pull the #3 coil and swap it with #5 coil and try that again. What do you think?
Chevy Mechanic: Gary, Chevy Technician replied 2 years ago

that's where i was going with this

swap # ***** coil with # ***** coil

if it still does this with the 303 code with a new injector and coil and or coil swap the only thing left and is somewhat common is a bad crank sensor located behind the starter acting up and firing # ***** cylinder at the wrong time which will cause this issue

replace the crank sensor and perform the crank sensor relearn with the scan tool and see how it drives

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Customer reply replied 2 years ago
I have noticed that on the OBD the IGN values change dramatically during cruise operation. it will vary greatly between 25 to 48. However, you are taxing me beyond my shop capabilities. This will require me to take the vehicle to a Chevy dealership or a Pep Boys repair facility. What is the approximate shop time to effect this repair? If we are in agreement on this repair, I will take the car in on Tuesday, when the shops are open. I'm inclined to agree with you because of the changes in the ignition timing. I thought the ignition timing was supposed to be pretty stable but I guess the PCM controls all of that.
Please let me know and we'll get it done.Thanks
Scott
Chevy Mechanic: Gary, Chevy Technician replied 2 years ago

a shop to change the crank sensor and relearn the new crank sensor would be 1.0 hours of labor X's the shops labor rate and the crank sensors can vary for $ 50 to $ 75 give or take

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Gary
Gary
Gary, Chevy Technician
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