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problems

trccccy

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I have read the posts on the 173 code on the 94 explorer 4.0. I have replaced both the O2 sensor on the rt (passenger) side and the FPR. Left the battery disconnected for almost an hour after replacing the parts. Drove it for 10 minutes and the CEL came on. To my surprise the code 173 came back. The FPR vacuum line has vacuum. Any suggestions?
 


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FR-425

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Could be a miss-fire.

Check the spark plugs and wires. (an ignition fault after the coil can not be detected by the ICM)

A good way the check for a "leaky" plug wire is to get the truck in a dark garage and look for sparks.

I would also recommend doing a compression check.
 




trccccy

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Thank you. We just replaced the plugs (last weekend) and I have rechecked the wires they seem to be ok.
I left the battery disconnected over night (should clear the codes) when I got in and started it this morning it went through the self check? and the 173 was still there? do I need to put some miles on it? to clear it I am at a loss now. seemed all the other posts with this problem were fixed with the FPR and or O2 sensor.
with the key on it has 40# fuel pressure.
 




FR-425

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Ok, the most likely cause for uncontrollable "rich" situation would be a leaking fuel injector, bad compression, FPR, or ignition problem.

"Looking" at the wires is not going to tell much, Before you go spending a bunch of money and time chasing ghosts I would just replace the wires to eliminate that.

Check the bleed down time at the fuel rail. Fuel pressure should remain above 30 psi for 5 minutes after shutdown. If it falls fast it is usually due to a bad FPR or a leaking injector.

Pull the plugs back out; the cylinder that is running rich will have black carbon build-up, nice and obvious on new plugs, this will help to narrow it down to a single cylinder.

If it turns out to be a bad injector you will then know which one.

Disconnecting the battery will clear the code, so you do have a persistent problem.
 




trccccy

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is the vehicle supposed to go through the motions of self test every time you start it without the jumper wire?
 




trccccy

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fuel rail stays over 30 for more than 5 min.
FPR was replaced yesterday. it has vacuum.
MAF has .7v @ idle and 2v @ 4000RPM
DPFE has .5v. are the hoses attached to it supposed to have vacuum? neither of these have vacuum @ idle.
 




FR-425

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No vacuum, the DPFE is connected to the exhaust manifold.
 




FR-425

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Jumper wire?

Oh, you are doing the paper clip method?

Ummmm, I've never heard of a PCM being stuck in test mode.

However, my scan tool does have a warning both in the instructions and on the hand held display not to disconnect until after the test is complete and the key is off. Maybe this is why.

I do know that the command to test is not stored in temp memory; so disconnecting the battery will not reset it. It will need to be powered up to receive the command to end test mode. i.e. pulling the jumper off. And yes the PCM has power at all times even when the key is off.

So my guess would be to reconnect the jumper, turn the key on, let it finish the test, then turn the key off and last remove the jumper.
 




FR-425

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If that doesn't work; you may have to connect it to a scan tool to get it out of test mode.

No wonder you still have the same code, you probably fixed the problem but the PCM is still in test mode.
 




trccccy

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I hope it's fixed. I ran the test to completion and then shut it off then removed the wire.
Did not fix it. still goes into test mode on start up. I will look for a scan tool tomorrow.
Thank You for the help. I will keep you informed.
 




FR-425

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:thumbsup:

Weird problem; Please do let us know for future trouble shooting of this.
 




FR-425

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Hey,

Check this thread out. Guy had the exact same problem after doing the paper clip method. Same persistent 173 code.

Turns out the PCM was bad.

Coincidence?

Since this would be two confirmed cases of PCM failure after using the paper clip method, I'm beginning to think there is a real potential here to kill the PCM by using this method.

http://www.explorerforum.com/forums/showthread.php?t=292319
 




FR-425

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I'm eager to see if you are able to recover with a scan tool or if replacement is the only option.
 




trccccy

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Could not find someone with a scan tool.
I saw the other post and called a dismantler today and found one for $50. he was even good enough to let us plug it in and try it. WAIT FOR IT and it did not flash a light. drove to the smog center passed smog problem solved in my book.
Thanks for all your help.
 




FR-425

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Beautiful !

Just to be sure; does it no longer run self test when you turn the key on?
 




trccccy

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Correct. the PCM was the Final problem. The other stuff was also bad so I may have been the one who broke the PCM. PROBLEM SOLVED.
 




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