2003 5.0L MPI - Loss of RPMs

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pmp1986

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EricP-NH, based on what we did in another topic, check:
1. fuel pressure at line (done as i see).
2. test and clean injectors.
3. tps! (by digital meter easily, couple times for sure)
4. spark plugs
5. spark wires
6. distributor cap and rotor
7. engine compression
 
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EricP-NH

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I am actually wondering if something is going on with the throttle cable. I hooked up the Rinda software and watched as I moved the throttle. It takes quite a bit of movement before it changes the throttle %. I moved it back and forth and watched. Then compared what I see in the software to what happens when I am out on the boat. It looks like once I get to about ~70% that's where I don't get any more power. When out on the boat I estimate that from 70% to 100% I am not getting any more RPMs. Is it possible the cable has stretched? Or maybe the TPS? Seems like the likely candidate. I did replace the distributor cap and rotor, they were corroded pretty badly, but that didn't make much, if any, noticeable difference. Everything seems fine, and even with the loss of RPMs the engine runs great, smooth and no other issues.

Thanks,
-Eric
 
alldodge

alldodge

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The TPS normally displays counts (normal 70 to 250). If your TPS is not getting above 70 % then there is an issue. If you take a volt meter you should be able to read the voltage with the engine off. It should be close to 4.8V at WOT
 
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EricP-NH

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My TPS will show up to 100% when I am on the trailer moving the throttle. I haven't checked it when running the boat in the water. I'll work on checking it with a volt meter, thanks for the info.

-Eric
 
Fun Times

Fun Times

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EricP-NH

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TPS wiring looks good. I connected the Rinda software and recorded throttle movements. Typically I can get to 99.87% (hit 100% once) and voltage for the TPS is 4.44 VDC.
 
alldodge

alldodge

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You sure have a puzzler, when mine did what yours is doing there was the code showing up. You have the software and there are no codes, not even a 44.
 
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EricP-NH

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I have the following codes I pulled today. I connected the software and recorded a ride of about 20 minutes. All were active during the recorded run.
PITOT CKT LO
FUEL LVL CKT HI
STEER CKT LO
TRIM CKT HI

I couldn't find much about them.

Thanks,
-Eric
 
alldodge

alldodge

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Don't think you have any of those sensors so they are of no concern. The Pitot is the Pito tube for speedometer, Steering and Trim are for smartcraft and mostly seen with digital controls. Fuel lvl is smartcraft
 
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EricP-NH

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That's pretty much what I was able to find searching around. I have changed the plugs and tomorrow will go out and try turning off the injectors one at a time using the Rinda software if changing the plugs doesn't change anything. Just learning that software, looks like it has some good tests that I can try. Also found a good mechanic who will come take a look after I do my tests.

Thanks,
-Eric
 
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EricP-NH

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So it turns out this was a combination of a corroded distributor cap & rotor which caused 2 plugs to foul. I changed the distributor cap & rotor Friday and the plugs on Sunday and went out yesterday and all is well. Full power restored.

Thanks all for your advice.

-Eric
 
alldodge

alldodge

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Glad you got it worked out. You mentioned in post one that you were going to check out those parts. Sometimes its the easy parts
 
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