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Please Help, Before I Shoot Myself


January 10, 2010
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I'm trying to help out a buddy get his explorer fixed and I think I'm going insane. Its a long story as to what is going on with this thing but I'll try and give it the 30 second version. Its an '02 XLS 4x4 with the 4.0L

There was a really bad timing chain rattle and the tensioner guide was pretty much gone in the rear. So I pulled the engine did the timing with the special ford tool, put the thing back in the car and it ran like crap, but it ran enough to get me to the gas station, but not back. So I pulled it apart again and found the timing was off on one of the banks by about 5 to 10 degrees. So I fixed the timing and then the car would idle for about 10 seconds and then die out from being flooded and wouldn't start again unless it sat. I found out that the third cat was somehow plugged so I "declogged" it and then it idled nicely and ran just fine on low throttle. When I got it up to about 5k rpm the power went away and it didn't want to go past 50mph. If I keep it at 1/4 throttle it will accelerate up to 70mph no problem, it just takes a while. The only other symptom that I can think of is that the engine shakes sometimes when its idling. And it gets some popping in the exhaust, probably from the removed cat.

This thing has been in my garage for a long time now and I really want to get it out. Please give help me figure this out. I'm open to looking at anything, I just need some ideas.

Thanks in advance.

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the V6's have always had a slightly rough idle... is it running any codes? a problem this bad HAD to have thrown some codes.

There are no codes being set and no SES light.

After thinking about it I'm going to go for a drive tonight with the fuel pressure gauge hooked up. If I'm loosing fuel pressure then I might get this symptom, but would think I would be getting some pinging as well, but I couldn't pick up on that.

I was also going to disconnect the cat back exhaust. Perhaps I blew some of the declogged cat into the muffler or something like that.

If anybody has any other ideas I would love to hear them.


only thing that comes to mind for no codes, poor running, no power have been fuel filters.

Well, I took it for a ride and the same thing happened, except it made it to a little over 5000 rpm this time and then just hung there.

The fuel pressure was at 62psi so it doesn't seem like that's a problem.

I guess can tear the thing down again and double check the timing, again.

There has to be something I'm missing.

Oh and the backfiring has gotten better, until I put my foot into it and then its back again.

Im with jr, check the filters. I see you say the pressure is ok, but is that a static reading, or made while the vehicle is in motion? It may show 62 at idle, but when you jam on it, the pump might not be able to keep up.

What are you doing to make sure the PCM is programmed correctly? If it for whatever reason is dicking with the timing, nothing mechanical you do will help it. Trust me, it is about 90 percent computer, 10 percent mechanical on these things now. Seriously, look into doing some datalogging, or just watch what its' doing in real time.


he said he went for a drive.

62psi was at WOT going down the road at 5000rpm. I'm sure that the CPU is a big part of it, but I have no way of doing any data logging.

The stock computer should be setup to run a stock engine without any type of issues. There should be some kind of code if something is going bad enough to cause it to kill power that much if the CPU was doing something to make it happen.

Do these things have knock sensors?

SOHC has a knock sensor

If the 2002 is the same as my 2000 then there is a knock sensor on top of the block near the intersection with the right head. The only way I know to test it is with a scan tool that can read the knock retard value. I was getting more than 8 degrees of retard due to the knock sensor responding to my chain rattle.

I assume that you have tried cleaning the MAF sensor. If not, I suggest that you do.

Your fuel pressure sounds like its completely normal. If the engine were running lean the PCM should detect and set a DTC.

Do you happen to have Bosch platinum plugs installed?

If you run the RPM up in park from idle.

Does the engine start to sound like it's misfiring above 3500 RPM?


Do you happen to have Bosch platinum plugs installed?

I'm running Motorcraft Platinum AGSF22FM plugs. Brand new.

Well, I played a bit more around with it today and the middle drivers side plug is coated in carbon except for the very tip where the spark would come out at. The other two plugs on that bank looked ok.

I thought an injector might be bad so I swapped it with another one and the problem remained on the same middle cylinder.

I also pulled the exhaust all the way off and took it for a ride with open headers again. I just went to the end of the driveway, but it was definately getting extra pops in the header from too much fuel when I hit the gas.

And the car seems to be having issues dieing when I put it into gear from idle when its warmed up.

EGR valve hung open? Just spit-balling, but it could cause most of this.

EGR Stuff

If it rattles is it still OK?

I dont know that it should rattle. System is easy enough to bypass on the explorer, this simple bypass will trick the ECU into thinking the EGR system is working, while the valve is disconnected.

I only know how do to this with the 2 port DPFE Sensor, so if you have something different this wont work.

1) Locate the DPFE Sensor (typically mounted on the drivers side valve cover).
2) Disconnect the two lines from the exhaust system and plug them.
3) Locate the EGR valve and disconnect the vacuum line from it.
4) Now take that vacuum line that was on the EGR valve and connect it to the "REF" port on the DPFE.( I think its the left port, but its marked REF)

Thats it. You are finished.

If your DPFE sensor is shot, this wont work and you will get a EGR related code. So its a good way to check that part.

This is how this works, when the ECU sends vacuum to the EGR valve to open it, the DPFE measures the differential pressure change in the exhaust and reports back to the ECU that the EGR did open and flow was detected.
By moving the vacuum line from the EGR to the REF port, the DPFE thinks that vacuum is the differential pressure in the exhaust and all is well.

So if you think your EGR is not closing correctly and allowing unregulated exhaust gas to enter the intake, try the above bypass along with this little procedure.

Remove the two bolts that connect the EGR to the intake tube. Now make yourself a homemade gasket (high temp material) that does not have the center hole. Bolt it all back up and your finished.

Some people say that not running the EGR system is a bad thing for various reasons buy I have never had it connected for 116K miles and my intakes are nice and clean (no exhaust carbon buildup).


End of EGR Hijack. No more EGR questions, this is not my thread.

I have checked the EGR valve and I know its closing. I'm still stumped as to why one cylinder is running extra rich.

I pulled it all apart and double checked the cam timing and its where it should be.

injector cleaner, my money is on a bad injector... the fuel rail is always presurized, and the injectors just open for a predetermined amout of time, if one is dirty or bad, it can cause a cylender to run rich or lean. test and clean your injectors.

Burning Rich

I wonder if that one injector is getting a bad signal (pulse width). I dont know if a noid light would help to test that or not. I think the little light will just blink for each pulse just to show signal. Im not sure how you would test this. Is there anyway the intake could be clogged? Is the cam good? You may want to take a look at the travel of that intake valve, make sure its opening up enough. Look close at the cam lobes, pay close attention to the chamfer for signs of wear. Here are a couple pictures, good cam, and bad cam.

Good Cam

Bad Cam

Could be a weak spring or a bad valve too.
Have you done a compression test on it? Did I miss that in a post?

Let us know what you find.


Wow that's a bad lobe!


I swapped injectors with a different cylinder so its not that. And I have run a compression check on it and its at 180psi. This is without the intake manifold on there so very similar to WOT.

This compression is close to what I'm seeing on the two cylinders on the same bank. If there's enough wear on the lobe to cause a large difference in the valve timing I would think it would show up on the compression check.

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Im running out of ideas for you, could be a weak or broken spring. Could be the valve is a little sticky. Those may not show up in a compression test.

If the injector is getting a bad signal from the ECU that would do it. I have no idea how to test the signal, only thing I could think of is to swap the ECU with a known good one.

You seam to have it narrowed down to one cylinder and the compression is good so, not that many more things it could be.