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Yamaha 2004 f150 running rich

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Sjacob

New member
2004 Yamaha f150 running rich plugs black . Leak down almost 0 on all 4 all 4 plugs black , no water in fuel . Have verified timing marks are perfect , injectors replaced , Vst cleaned and all filter replaced , t stat new , 40psi fuel 125deg at idle do have a code 29 intake pressure not sure why runs so rich , IAC iworking fine it seems . No other codes
 
If the fuel pressure is 40 psi after it's been warmed up and idling, I think that's a little high. Maybe the pressure regulator is faulty, or the vacuum sense line (which connects the pressure regulator to the air intake) is disconnected. At key-on, the fuel pressure should be slightly higher than it is at idle after warmup.
 
rejesterd said:
If the fuel pressure is 40 psi after it's been warmed up and idling, I think that's a little high. Maybe the pressure regulator is faulty, or the vacuum sense line (which connects the pressure regulator to the air intake) is disconnected. At key-on, the fuel pressure should be slightly higher than it is at idle after warmup.
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"at idle do have a code 29 intake pressure"
 
The code 29 is certainly not something to ignore, but the temp/pressure sensor isn't a cheap enough part to just go and replace based on that one code imo. The service manual tells you to test it first. For reference, I did actually have a bad temp/pressure sensor a couple years ago, and I had code 29 issued before AND after I replaced the sensor. The code was due to a small air leak in the intake manifold. I did actually need to replace the sensor because the temp readings were way off and causing it to stall on the first morning startup (if the weather was cold enough). But the code 29 didn't go away until I replaced the intake manifold gasket.
 
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