Do I need a new CPU
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Do I need a new CPU
1990 F150, 4.9, auto. Truck has been running good, but recently after disconnecting battery cables (new cables, new ends, new battery) then Reconnecting, truck doesn’t want to run properly. Will barely idle, then smothers out and dies. Will restart with ease, but it just won’t idle correctly. Help! And thanks!
Fleet Owner
Joined: Oct 2005
Posts: 20,783
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From: Kentucky
Run the Key On Engine Off (KOEO) tests and Stored Code display. List any codes you may see and when they were displayed. Your model year may display two or three digit codes. It's a toss up. Highly suggest to invest in an Equus/Inova 3145 code reader. Eliminates counting flashes. Or if the budget is tight use a paper clip....
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
One thing to keep in mind, 1980 was a long time ago, any engine control or "computer" device that contains electrolytic capacitors on the board need replacing. Any replacement board you find may have the same issue. These capacitors are not expensive.
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No codes
Run the Key On Engine Off (KOEO) tests and Stored Code display. List any codes you may see and when they were displayed. Your model year may display two or three digit codes. It's a toss up. Highly suggest to invest in an Equus/Inova 3145 code reader. Eliminates counting flashes. Or if the budget is tight use a paper clip....
filter, wires, etc...all the obvious things. Guess that’s why I was wondering if it was all coming down to the CPU.
Fleet Owner
Joined: Oct 2005
Posts: 20,783
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From: Kentucky
At the very least you should have gotten the System Pass Code 11 or 111 for the KOEO tests and Stored Code display. What did you use to initiate the tests and display?
I assume you are referring to the Throttle Position Sensor (TPS)?
I have no idea what you are referring to on this one.
The obvious thing to me is checking fuel pressure at idle, idle with vacuum hose removed, and under load. You can rent a fuel pressure tester at many auto parts stores.
I assume you are referring to the Throttle Position Sensor (TPS)?
I have no idea what you are referring to on this one.
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