Maybe 911 need some advice
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From: Tupelo,Ms
Maybe 911 need some advice
ohhk comin home from work today i had to get on it to get into traffic and i notice it didn't smoke like it used to with the diablo... anyway got home plugged it in to run diagnostics and guess what... i scroll down and notice that the map sensor has no volt readings? then i get down the the cyl. leak down i think and no 3 cyl. showed 3.4% and no 8 cyl. showed 5%... what now? i've noticed a mechanical knock latley still knocks when truck is in defuel coasting what am i lookin at guys? thanks
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From: Tupelo,Ms
nope no cps had'nt had time to get one yet... would adding a hpx cause this... and im still confused why the map aint showing nothing. i checked in the tube is hooked to the boost T... maybe bad map sensor causing it?
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From: Rochdale MA
I'll post a link to the service manual for you. Not the "little" book, that is the owners manual.
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Post Fiend
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From: Texas
A high reading on #3 & #8 is fairly common with the "new and improved" gray CPS. I've got high readings on those cylinders in my truck too with no performance issues.
A bad map sensor (or one that is unplugged) will cause the pcm to infer default boost values from. I don't really know how that would play in to a tuner on the PCM, but it could easily cause a noticeable difference in the stock mode, since it's designed to limit fuel quantity during acceleration for smoke control.
Do you know anyone with a 7.3 that you could maybe swap sensors with? Sounds like either a wiring or sensor issue. The odd thing is you're not getting a code for the MAP. Try unplugging the MAP sensor and taking it for a spin around the block. Then check codes again to see if you get a MAP code (there should be one with it unplugged)
A bad map sensor (or one that is unplugged) will cause the pcm to infer default boost values from. I don't really know how that would play in to a tuner on the PCM, but it could easily cause a noticeable difference in the stock mode, since it's designed to limit fuel quantity during acceleration for smoke control.
Do you know anyone with a 7.3 that you could maybe swap sensors with? Sounds like either a wiring or sensor issue. The odd thing is you're not getting a code for the MAP. Try unplugging the MAP sensor and taking it for a spin around the block. Then check codes again to see if you get a MAP code (there should be one with it unplugged)
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Hotshot
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From: Rochdale MA
Here it is Steve. It will give you some pinpoint tests for the Map
1999 F-Super Duty 250-550 Workshop Manual
1999 F-Super Duty 250-550 Workshop Manual
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From: Tupelo,Ms
jim and chris thanks.. i just hate this you know i automatically think there is something bad wrong because of these little things... now im a little more comfortable about it! its raining right now so i'll wait for it to clear up and check out the map and stuff.
Fleet Owner
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From: Rio Rico, AZ.
Check your fuel pressure, I noticed a huge power drop with the 80HP Diablo tune loaded and it turned out my fuel pressure was dropping to less than 20 psi if I floored it.
It would take off real good for about 2 seconds and then fall on it's face.
It would take off real good for about 2 seconds and then fall on it's face.
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From: Texas
Here it is Steve. It will give you some pinpoint tests for the Map
1999 F-Super Duty 250-550 Workshop Manual
1999 F-Super Duty 250-550 Workshop Manual
Hotshot
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From: Rochdale MA
Nice work Jim, but the pinpoint tests, as well as the DTC listing and tests are in the 1999 PC/ED Manual
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