not much help from the expedition forum maybe you guys can help
#1
02-16-2011, 08:24 PM
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not much help from the expedition forum maybe you guys can help
1998 expedition starts but stops immediately
problem started after truck sit for 3 days battery disconnected while repairing a blowed out #8 plug... tapped helicoiled and installed spark plug
fuel system has been checked and all is good
vacuum and IAC have been checked= IAC had a light dusting nothing that should impede its operation and ohm checked good
no battery voltage to ckp and cmp with key in on position
have battery voltage to IAC MAF with key in on position
theft light is not flashing
forgot to mention it is a 5.4l
no codes stored in pcm using code scanner
using a mechanics diagnostic computer = no key code fault and something similar, pointing to anti-theft system
will start and run applying accelerator = runs terrible under 1500 rpm sounds fine over but the exhaust is so rich that it will burn your eyes
any info would be greatly appreciated as i'm about to pull my hair out
truck was running before fixing the plug
problem started after truck sit for 3 days battery disconnected while repairing a blowed out #8 plug... tapped helicoiled and installed spark plug
fuel system has been checked and all is good
vacuum and IAC have been checked= IAC had a light dusting nothing that should impede its operation and ohm checked good
no battery voltage to ckp and cmp with key in on position
have battery voltage to IAC MAF with key in on position
theft light is not flashing
forgot to mention it is a 5.4l
no codes stored in pcm using code scanner
using a mechanics diagnostic computer = no key code fault and something similar, pointing to anti-theft system
will start and run applying accelerator = runs terrible under 1500 rpm sounds fine over but the exhaust is so rich that it will burn your eyes
any info would be greatly appreciated as i'm about to pull my hair out
truck was running before fixing the plug
#2
02-16-2011, 11:19 PM
My '99 repeatedly passed the ohm's test for the IAC, but, when reconnected to the harness, and tested while cranking, with straight pins pushed into the connectors it failed. A new Motorcraft fixed it.
Other than that, it seems to be calling for more fuel than the engine speed needs. Have You checked the TPS for voltage and voltage increase as the throttle is opened ? I see you have no codes, but the problem just started, and without 2-3 driving cycles, at least, you may not see one. Other than that, all you can really do is check sensors one by one, and clean them where called for ( like the MAF). You might have voltage there, within spec's, but if it is pretty dirty, it still won't work accurately, and may never pop a code. Make sure the EGR isn't stuck in the open position.
Dave
Other than that, it seems to be calling for more fuel than the engine speed needs. Have You checked the TPS for voltage and voltage increase as the throttle is opened ? I see you have no codes, but the problem just started, and without 2-3 driving cycles, at least, you may not see one. Other than that, all you can really do is check sensors one by one, and clean them where called for ( like the MAF). You might have voltage there, within spec's, but if it is pretty dirty, it still won't work accurately, and may never pop a code. Make sure the EGR isn't stuck in the open position.
Dave
#3
02-17-2011, 04:57 AM
Here is a thought.
Since plug 8 was worked on it is right there at the fuel regulator.
Look for a fault with the regulator leaking into the intake or the regulator not limiting the fuel; pressure to the area of 35 to 45 psi by checking the fuel rail pressure. If it is very high it will drown an elephant.
Good luck.
Since plug 8 was worked on it is right there at the fuel regulator.
Look for a fault with the regulator leaking into the intake or the regulator not limiting the fuel; pressure to the area of 35 to 45 psi by checking the fuel rail pressure. If it is very high it will drown an elephant.
Good luck.
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