2003 90HP 4stroke TPS issue

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Vwsandcar

Cadet
Joined
Jun 5, 2019
Messages
11
I have a 2003 Mercury 90HP 4stroke model number 1F90412AD. I’ve been having some intermittent lack of power issues/rough idle issues. The boat has never idled quite right since I’ve had it.This weekend I cleaned all 4 carbs, sync them up and set the throttle linkage to spec. I own a FSM so I did all this per the procedures in the manual. It still seemed to have a rough idle so I decided to check the TPS reference voltage and found at idle (850 rpm) it was reading 3.12 volts. By adjusting it I could only adjust it down to about 2.12 volts. Spec per the FSM is 0.68-0.82 volts. When I remove the TPS and turn the voltage down to spec by hand the engine idles much better. Another thing I found odd is that when I increase throttle the voltage goes down. Is that normal? What can I do to fix my TPS voltage? Could I just have a faulty sensor?
Thanks in advance.
 
dingbat

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
16,150
Vwsandcar said:
I have a 2003 Mercury 90HP 4stroke model number 1F90412AD. I’ve been having some intermittent lack of power issues/rough idle issues. The boat has never idled quite right since I’ve had it.This weekend I cleaned all 4 carbs, sync them up and set the throttle linkage to spec. I own a FSM so I did all this per the procedures in the manual. It still seemed to have a rough idle so I decided to check the TPS reference voltage and found at idle (850 rpm) it was reading 3.12 volts. By adjusting it I could only adjust it down to about 2.12 volts. Spec per the FSM is 0.68-0.82 volts. When I remove the TPS and turn the voltage down to spec by hand the engine idles much better. Another thing I found odd is that when I increase throttle the voltage goes down. Is that normal? What can I do to fix my TPS voltage? Could I just have a faulty sensor?
Thanks in advance.
Click to expand...
A TPS is a simple rheostat.

If the output voltage isn’t correct, the input voltage is incorrect or the rheostat is damaged.
 
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