I have a 98 CrownVic with the 4.6 DOC, V8 that is blowing hot air from the A/C vents at all times, regardless of position (IE floor, defrost, etc), as well as having a dead miss on the number 5 cylinder according to a scanner code 0535 I believe. HOWEVER, the a/c compressor is running the whole time, feel cold air coming out of the line access ports on the engine compartment air box, but blowing hot air from the vents. Though if I disconnect the battery, resetting the computer and temporarily delete the MIL trouble code from the ECU, the A/C works correctly, the engine is no longer sluggish and the MIL lamp stays off for a short period of time. It then comes back on, engines starts missing on number 5 again, and A/C blows hot. I have checked the coil to plug boot for cracks, splits, compromised areas, to no avail. The plug is firing blue and hot, and on time. The spark plug appears in good condition and gapped correctly. Cylinder compression is good, and all cylinder chambers are less than a 1 lbs difference between them all. Using a pulse lamp I also checked for injector pulse commands, all appears well. I have to admit at this point, after standing in the hot texas sun cookin my brains, I am at a loss.
Any and all help would be greatly appreciated.
The air problem is caused by the miss.It will delete unnessessary options one by one to keep the engine running. Find your miss and cure all problems.Change your plug and wire along with the coil.If this don't fix your problem ,then it is in the ECU.
Also- do you have the plastic intake manifold? If your thermostat housing is plastic, replace the manifold with the updated design. You can get them at a parts store for $250. The plastic design is famous for cracking, causing a #5 misfire.
my problem was the miss was caused by a bad injector and it was not noticable at all until i turned the a/c on then the engines miss was very noticable, i popped out the injector and sprayed to well with kemtool spray. stopped the miss and never did it again. for some reason #5 is the one cylinder that everyone has problems with in the 4.6 my neighbor had prob with his tbird and it was the plastic air intake . don
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