Injector Circuit Malfuntion

[boom boom]

I'm having an intermittent issue with injector #4 throwing a P0204 code which eventually triggers a P0304. I put a noid light on it during the issue and it indicated wide open throttle while the engine was idling. Then the injector will simply go back to normal operation without any changes. Driving down the highway I can smell it dumping fuel during the malfunction. Take it up to wide open throttle and the engine runs normally. Just super fat during low throttle and intermittently.


Couple background details. I've only owned the car a few months and it has 111000 miles. 06 Jun-02 production date. Ford replaced the engine October 2007 at 53308 miles after loss of oil pressure wiped out the rod bearings. Engine assembly was 3W3Z-6006-ABRM. which I think tells me it was a long block and they reused the intake.


Also not sure if related, but the speedometer needle will occasionally and randomly drop/fluctuate and then return to normal operation. The two have not coincided and the speedo issue is much more rare.


Has anyone experienced this before? Thinking maybe mechanic damaged the wiring harness when they replaced the engine. Looking for some input before I start cutting the harness apart to find a chafed wire.


My understanding is that the injector fires when the computer grounds the circuit. If so, I'm thinking that an intermittent ground short could cause the issue. Problem is I haven't found it by moving and wiggling the harness.


Thanks in advance.

[justbob]

Wiggle the main harness right behind the drivers side head where it chafes on the wiper cowl bracket. Do this as you monitor your noid light. Very very common issue of rubbing at that location.


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[Turbov6Bryan]

If you cant find the issue, remove the injector harness and give it a good look.

Maybe the 2 valve crown vic and MGM injector harness is the same?

[musclemerc]

Not the same.....

[boom boom]

Pulled it into the garage after throwing the code on the drive. Spent an hour poking, prodding, twisting, wiggling, and jiggling- not even a hiccup.


Afterward, I drove it for fifteen miles and it never did it once....wth


I have some spare injector harness plugs from a junkyard aviator. If I make a harness extension with two female and one male connector, can I put the noid in series so that I can drive it on all 8 cylinders and watch? Not sure if that would screw up the injector operation?


Really want to get this figured out before I take the cowl out and cut the tape and cover off the harness.

[boom boom]

Welp, I bit the bullet and pulled the wiper cowl to revealed this.....


It looks like Ford left the harness on the EGR tube when they replaced the engine under warranty. It is melted into the EGR shield bad enough that I'll have to take the harness out to splice or repair it. Anyone have a spare harness to sell cheap, haha?


Was the harness routed improperly after the engine change or is this where its supposed to go?

[BUCKWHEAT]

going from memory, the harness should be farther back toward the firewall. I will look at mine in the am....

[BLACKMARAUDER04]

I'd take it back to ford and make them fix it again under warranty for their mistake.

[boom boom]

I'd take it back to ford and make them fix it again under warranty for their mistake.


Haha, yep. A new owner 6 states away and 11 years later, I'm sure they will bend over backwards.

[Zack]

That harness can be repaired with ease

[justbob]

^Exactly^

The drivers side is quite easy to disconnect. Flip it over to the passenger side and fix it. When you are done, route it on the other side of the EGR tube and clipped to that hole on the lower intake where it belongs.


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[boom boom]

2.5 hours to R&R the harness with the wiper cowl already out. Insulated, friction taped, and shielded. I wish my hands were about half size to get to all those connectors but it was relatively easy to remove once the wiper cowl and vacuum/evap were out of the way.