Wavering hot idle problems
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Mountain Pass
Joined: Mar 2007
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Wavering hot idle problems
1989 E150, converted to 351W and MAF injection.
Cold, the motor runs fine. Lots of power, smooth idle. As the motor heats up, the idle gradually gets noticeably rougher, but not too bad. When idling while hot, the motor "hunts" for idle RPM. The idle speed bounces up and down between 550 and 800 RPM. Also, when I put the A/C on, the idle gets rougher and the idle speed drops.
I am not throwing any codes, idle vacuum is 15-17 inches, base timing is verified to be 10 BTDC.
What the heck? I though the computer was supposed to keep the idle smooth and constant and compensate for things like the A/C load on the motor?
Bad TPS? The TPS output is about .85 at idle.
Bad IAC?
Cold, the motor runs fine. Lots of power, smooth idle. As the motor heats up, the idle gradually gets noticeably rougher, but not too bad. When idling while hot, the motor "hunts" for idle RPM. The idle speed bounces up and down between 550 and 800 RPM. Also, when I put the A/C on, the idle gets rougher and the idle speed drops.
I am not throwing any codes, idle vacuum is 15-17 inches, base timing is verified to be 10 BTDC.
What the heck? I though the computer was supposed to keep the idle smooth and constant and compensate for things like the A/C load on the motor?
Bad TPS? The TPS output is about .85 at idle.
Bad IAC?
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