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BOBBYSS
BOBBYSS, Master Technician
Category: Chevy
Satisfied Customers: 17144
Experience:  ASE MASTER CERTIFIED, AA DEGREE AUTO/DIESEL TECH
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Just bought a 97 chevy 1500 that had engine replaced. Was

Customer Question

Just bought a 97 chevy 1500 that had engine replaced. Was just having problem with error code 507, then started getting error 340 and truck started running rough. Notice battery terminals were dirty, so disconnected, cleaned and applied dielectric grease.
JA: Have you metered out the ignition system?
Customer: When started truck again, idle went and stayed at around 1,800. When checked codes again, got 507, 102, and P1351.
JA: What is the model of your '97 Chevy?
Customer: 1500 Z71 with 5.7 Liter
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes, would like to fix it, as I somehow did something disconnecting the battery.
JA: Anything else you think the mechanic should know?
Customer: Truck was running fine, just high idle for last 200 miles. High idle around 750 with a/c running. That is all
Submitted: 3 months ago.
Category: Chevy
Expert:  BOBBYSS replied 3 months ago.

Hello, my name is***** would like to clarify, was the vehicle running fine prior to cleaning the battery cables?

Customer: replied 3 months ago.
Was getting 507 (high idle error) because idle was around 750 with a/c on. Yes, other than that it was running fine. Engine is a new crate engine with only around 300 miles it. Only change made before disconnecting battery was saw that passenger valve cover tube to air intake was loose at valve cover grommet. Thought this might be source of air leak and high idle, so used tape to increase tube width for tight fit in grommet.
Looking around engine..did not see any other loose wires or open tubes. Did see dirty battery terminal. So disconnected terminals, ground 1st, cleaned and applied dielectric grease.
1st start up was rough, with little back fire....then started, but at high idle. Let it idle for around 5 minutes to see in idle slowed down when coolant warmed up. It did not.
Turned off truck once, sat few minutes, started again. No back fire, started fine...however still high idle. 1875 on timing light readout.
Have not driven truck yet.
After disconnecting battery(less than one hour),
Customer: replied 3 months ago.
Was getting 507 (high idle error) because idle was around 750 with a/c on. Yes, other than that it was running fine. Engine is a new crate engine with only around 300 miles it. Only change made before disconnecting battery was saw that passenger valve cover tube to air intake was loose at valve cover grommet. Thought this might be source of air leak and high idle, so used tape to increase tube width for tight fit in grommet.
Looking around engine..did not see any other loose wires or open tubes. Did see dirty battery terminal. So disconnected terminals, ground 1st, cleaned and applied dielectric grease.
1st start up was rough, with little back fire....then started, but at high idle. Let it idle for around 5 minutes to see in idle slowed down when coolant warmed up. It did not.
Turned off truck once, sat few minutes, started again. No back fire, started fine...however still high idle. 1875 on timing light readout.
Have not driven truck yet.After disconnecting battery(less than one hour),
Customer: replied 3 months ago.
Customer: replied 3 months ago.
sorry, had ad blocker on and it was not letting see our conversation.
Expert:  BOBBYSS replied 3 months ago.

Thanks for getting back with me. When the vehicle lost power it is possible that when it recovered the computer tried to maintain and idle by actuating the idle control valve. If the valve was already worn out then it may have failed completely. I have also seen the mass air flow sensor fail and cause this. Double check that it is installed correctly and that the air intake tube is tight. If it is then check the idle control valve and possibly replace it a it is hard to test.

Customer: replied 3 months ago.
Oh, yes it does have 102 error ( low mass air flow) now. Will double check that nothing is loose. It should not have failed by me just disconnecting the battery, should it?
While waiting for response did find some procedures for relearning idle.
Tomorrow will do full battery disconnect for over an hour, and try idle relearn. Some people recommend disconnecting both battery terminals and shorting for a few seconds to drain all power out of system.
Do you recommend that, or will it cause problems?
Expert:  BOBBYSS replied 3 months ago.

I would do that also to start with a clean slate. As for the sensor, unless the cables were connected backwards it should not have caused any issues. I would check the fuses under the hood just to make sure that noting popped. Let me know what you find tomorrow.

Customer: replied 3 months ago.
Okay...controller reset did not help. Did allot of online research. Traced problem down to. 1. No 12 vdc at MAF. 2. blown fuse that controlls MAF and Camshaft sensor. Replaced fuse, brought idle rpm way down. However when drive...the fuse keeps blowing. This one fuse powers MAF, Camshaft sensor, EGR valves, Oxygen sensors....basically most of emissions stuff.
So just now have to climb in inspect wiring and unplug sections to find short.
Expert:  BOBBYSS replied 3 months ago.
Now you need to isolate it. I would drive it with each of the sensors unplugged one at a time. Most of the time the short is in the MAF sensor.

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