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

 

bump... anybody??

 

#8 may be due to the cps. Do you have a spare?

 

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?

 

It could be. Do you have the service manual for your truck?

 

the little book? or like the actual book?

 

I'll post a link to the service manual for you. Not the "little" book, that is the owners manual.

 

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)

 

Here it is Steve. It will give you some pinpoint tests for the Map

1999 F-Super Duty 250-550 Workshop Manual

 

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.

 

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.

 

Nice work Jim, but the pinpoint tests, as well as the DTC listing and tests are in the 1999 PC/ED Manual

 

Thanks Chris. I've never seen the one that you posted. I'm going to see ifI can find the 01 link.

 

this one

oops wrong one now I lost it

oo

 

How about I save you the trouble

https://www.ford-trucks.com/forums/7...ml#post6238526