04 f150 idle problems

[driver27]

I have a 04 yamaha f150 outboard that is giving me trouble. It will not idle properly, idles around 600 rpm and surges up and down constantly to the point it routinely cuts off. I have cleaned all of the filters, the one in the vst, the one on top of the vst and the main filter on the front of the motor. It also has a new fuel water seperator filter. Has new plugs, removed injectors and they look externally clean, and have tried fuel injector cleaner as well. Finally the motor has been run on an external fuel tank with known fresh gas, all with no impovement. One thing I have noticed is that plugs 3 and 4 are fuel damp and dark tan when I remove them, while 1 and 2 look perfectly dry and dull white. I thought it was a bad coil, but 3 fires off one coil and 4 the other coil. I put a couple of the old plugs back in to rule out bad plugs, and the new/old ones also come out fuel damp.

Also, is there a way to reset the computer on this engine? Just curious.

I am at a loss and was wondering if anyone could help.

 

[rodbolt]

Re: 04 f150 idle problems

check the TPS output voltage and the ISC valve for proper operation.
ISC check will require the diagnostic software and a laptop.

 

[driver27]

Re: 04 f150 idle problems

Will check tps voltage tonight, actually hope to find a problem there, becasue the sensor is way cheaper....

Does anyone have the YB 06795 diagnostic harness they would like to sell, loan or rent so that I can see if any codes are stored? I would gladly pay a deposit for use.

Thanks

 

[driver27]

Re: 04 f150 idle problems

check the TPS and got .69 volts a throttle closed, 4.03 at wot and 4.94 volts for reference. It alwasy returned to .69 volts, so I think all is good there. Any ideas at all on a test for the ISC valve?

One other point I did not mention on my motor is that it does not idle up or even attempt to idle higher when first starting. My friends motor idles slightly high cold then quickly settles down to normal idle. Is it possible that one of the temp sensors is bad, causing this idle problem?

Thanks for your help.

 

[rodbolt]

Re: 04 f150 idle problems

possibly, but I doubt it. if its an inrange failure the diagnostic test lamp wont display it.

 

[driver27]

Re: 04 f150 idle problems

The motor is defintely in limp home mode. Took it to the lake, and it will not go over about 2800 rpm and runs rough at that. Checked high pressure fuel pump and I am getting 38 -41 psi and checked the low pressure pumps and got 13 psi. The sevice manual I have says over 2 psi is good, Is 13 PSI too high for the low pressure pumps?

I have been able to check all of my sensors for resistance readings and all look good, but not able to check the Idle speed sensor or the inlet air pressure sensor. The rest look good based on the testing I have done.

Trying to fix this problem on my own since there is a 3 week wait for service work here.

I really appreciate everyones help, and I mean that.

 

[rodbolt]

Re: 04 f150 idle problems

limp in mode should lock you to 2000 RPM.
only thing now would be to have the injectors cleaned,a leakdown test done, make sure the tech knows what a balancer failure sounds like and use the laptop to test the ISC while watching it.