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Discussion Starter · #1 ·
Hi Everyone-
I have a 2008 Explorer 4.0 176K miles. Some back story first that might be helpful. Originally I was getting codes P0401, P0451, P0642. The only real issues I noticed was that it would rev really high on cold start ups and then drop back to normal after a few seconds. Not a big deal, so I dealt with it for over a year. Finally I took in to Ford last week to check them out as well as some transmission issues I'm starting to have (won't get into that now, but i'm thinking it's the servos- dealer said it's dropping 3rd & 4th and I need to replace tranny). They said most likely that the EGR valve needed to be replaced. If not that, then it's probably the vapor canister. I could have guessed that myself based on the codes I got. I thought they would actually test the EGR or other components to find the actual issue and not throw parts at it.

Anyway, I replaced the EGR valve myself and cleaned the throttle body in the process. I unplugged the smaller plug from the throttle body that faces the front of the engine and forgot to disconnect the TPS plug before cleaning it (not sure if this is useful to you later on or not). I did disconnect the battery before I cleaned it, but not sure if I moved the plate at all before then.

After I plugged everything back in, I reset the PCM. When I started the car up the SERVICE RSC light came on and car was running really poor. It threw out codes P0122, P0222, P060B, P2104, P2110 as well as 2 that it already had P0451 and P0642. I found that the TPS wires were all touching. The insulation had fried. I'm guessing they msut have been brittle and moving it around finished them off. I taped each wire up and put it back together. Now, all those new codes are gone and no more RSC light, but I it's still running rough and new codes showed up P0191, P2196, P2198 and the 2 original codes P0451 and P0642 and black liquid/smoke coming out of the exhaust.

After some searching on the site and online it looks like it could be the fuel rail pressure sensor, fuel pump, spark plugs, TPS and/or fuel filter. Before I dive into replacing these, could the burned up wires have caused the P0191 to come on by messing up one of these parts? Or any suggestions on what to replace first? I just find it weird that one of those parts are now bad when they worked fine before. Any help would be appreciated.

I've had this truck since 48k miles and the only issues I've had to do is to the upper thermostat housing and the ignition starter switch. It's treated me well.

Thanks,
Robby



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It sounds to me like you have some faulty wiring. Low voltage on a circuit, possibly the fuel injector harness causing the engine to run in limp mode and spray excessive fuel. A $10 USB OBD2 adapter and a laptop to log live data would help determine which sensor or circuit is having issues communicating with the PCM. Sensors, injectors, etc typically communicate with either a 5v signal and resistance readings (ohms). Crossing the wires would open up the 5v completely or give a low resistance signal to the PCM.

A number of sensors can cause the engine to run rich if crossed or grounded. Engine coolant temp sensor can cause the PCM to add too much fuel if the resistance is too low from a faulty wire. The Mass air flow sensor can cause the transmission to appear to have problems and strange engine problems. This sensor can be cleaned with MAF cleaner and the resistors inside should look shiny bright. Live data will show if it is reading properly. The engines PCM is too dumb to tell you if particular sensors or wires are problematic.

Welcome to Ford Explorer ownership. I'm not sure if Ford used the 5R55E transmission in that year model but these have valve body issues. It could be as simple as a solenoid change. These shops always put in a different tranny rather than replace a $30 solenoid. I'm dealing with the plastic bull crap intake manifold and thermostat housings at the moment.

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Discussion Starter · #3 ·
Thanks for the info! I actually tried wiggling the wires with the engine on this morning and didn't notice a chance. I then unplugged the egr valve and it started running fine. Plugged it back in and after a few restarts it's running fine now. Very strange.

I do still have the P0191 code though. Possibly bad pcm? Any suggestions on how to test? I do have a scanner, just not sure how to read any of the values. I just use it for pulling the codes.

Also, after a test drive, I had code P0172 and P0175 pending. So I took out the maf and cleaned it. Now I'm only getting P0172 and not the other one. Should I clean it some more in case I missed some spots?

It uses the 5R55S, probably similar to the E. I'm probably going to try the modified servos from AJ1E as well as new valve body and reverse solenoid first and hope for the best.

Good luck with the housing! The aftermarket I bought started leaking after a year. Of course warranty was only for a year. I'm probably going to upgrade to the metal housing if all goes well with the tranny.


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Test your main battery ground resistance. It should be .06 ohms from engine to batt, batt to firewall, firewall to eng. Than, remove the (what I recall being the PCM) harness connector behind the intake manifold. D/C battery and check that it looks okay.

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Discussion Starter · #5 ·
Test your main battery ground resistance. It should be .06 ohms from engine to batt, batt to firewall, firewall to eng. Than, remove the (what I recall being the PCM) harness connector behind the intake manifold. D/C battery and check that it looks okay.

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Tried the test you suggested. With black cable to battery negative and red to car ground or engine the reading keeps fluctuating. If I do red to battery and black to the others then it's 0.00.

Same with ground to engine. It fluctuates and if I swap them, it's 0.00.

Not sure if it's relevant, but on cold start it cranks a few seconds longer than usual before it turns on.

All PCM connectors look fine unless the issue is on the other ends, like I had with the TPS connector wires. Are there any other connectors I could check for burnt up wires aside from MAF, TPS, fue pressure sensor?

I'm also now getting P0451 again and there is some grumbling from the exhaust when reving in idle. Haven't driven it yet, since I currently have the rear right caliper off due to some grinding. Looks like one of the sliding pins needs grease. 3 lug nuts broke in the process so now I'm dealing with replacing those. Tried pressing them on with lug nut and wrench but didn't work. I'm going to get me an air hammer and hit them from the back.




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I'd be careful using an air hammer on the hub assembly. This can damage it.

The resistance reading should be stabile on black to black. You do not need to test red to black. Just probe each end of the main cables for a reading of near .06. It could be the meter. Try to clean up the ground connections. The hot battery connector can also have a poor connection and cause problems.

Rumbling exhaust can be a loose muffler or small hole - I have that issue and it becomes more noticeable when there's a misfire.

I'd continue on the path of checking each harness connector. Google the basic method of testing each one with a meter. Most of the harness sensors/connectors have the same generic testing method as any other OBD2 vehicle.

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Discussion Starter · #7 ·
I'd be careful using an air hammer on the hub assembly. This can damage it.

The resistance reading should be stabile on black to black. You do not need to test red to black. Just probe each end of the main cables for a reading of near .06. It could be the meter. Try to clean up the ground connections. The hot battery connector can also have a poor connection and cause problems.

Rumbling exhaust can be a loose muffler or small hole - I have that issue and it becomes more noticeable when there's a misfire.

I'd continue on the path of checking each harness connector. Google the basic method of testing each one with a meter. Most of the harness sensors/connectors have the same generic testing method as any other OBD2 vehicle.

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I was able to press them on. My issue was that the washer wasn't wide enough and when the wider groove was getting pressed in it was getting caught. I put the rotor on to finish the last few turns.

If I disconnect the egr plug the P0642 code doesn't come up and car runs with no issues. I guess there must still be something messed up with the wiring further than where I fixed the burnt up wired before. I'll check it tonight. Is it ok to drive with egr plug disconnected?



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