Two questions...
 

Yea, I'm a recent Ford Ranger owner. I've been going over my truck with a fine tooth comb - I've replaced the PCV valve, air filter, fuel filter, spark plugs, plug wires, fresh oil change, transmission service. So far so good.

I've noticed that the DPFE sensor is disconnected... I can't find the connector anywhere... And the computer thinks everything is fine! (?) It did pass a smog test, but I am a bit concerned. Is this something I should be worried about (esp given I live where they love to do e-tests)?

http://img.photobucket.com/albums/v4...r/IMG_1534.jpg

The other thing I discovered is that I have a small coolant leak on the drivers side of the truck. I traced it as far as I could go, but I'm not overly familiar with the 4.0L motor at all... Uhh, too many GM car's over the years. But as far as I can tell, it's running down the back of the motor from under the head, onto the trans bell housing, and then onto the ground. It's a small leak, but I'm wondering if there's a coolant passage in the intake manifold in that area...if so, then maybe it's time I renew the manifold gaskets.

Did you check to see if your thermostat housing is cracked? Im not sure if it'd drip that way but its worth a try to check!

you should replace the upper intake gasket yes as they are known for trouble in the 4.0 ohv if that is what you have. unless your motor has no egr then make sure that is connected it has somethin big to do with it. (cant remember)

i have a ranger 3.0 v6 and i had a similar leak and it was the timing chain cover seal. that particular seal is underneath the water pump. option a) pull the engine to fix or option b) drop the transmission

Yup, it's a 4.0L OHV. I'll replace the manifold gasket's... That will give me a chance to inspect everything. The truck does have an EGR and it is hooked up, but the DPFE electrical clearly isn't. Hopefully when I pull the manifold I'll be able to locate the plug and get it plugged in, though I'm still confused why that hasn't set off an EGR code in the computer.

Yeah, that's an EGR pressure sensor. I just replaced the one on my truck along with the EGR valve and solenoid. That's strange the plug in should be right there unless it's been moved or cut.

that stuff can be shut off in the pcm to keep it from throwing codes, is the pcm stock? do you know if it has been tuned? several tuners shut off the egr in even some of the most base tunes.

Hmmm...Well, I don't have the history of the truck...But if the EGR system was disabled in the PCM, that would explain why I'm not seeing any codes. I was figureing if someone simply unplugged it, they would simply get a P1408 code.

check your freeze plugs in the back to see if those are leaking

Yea, I just got a complete intake gasket set - Victor Reinz. And in there was some notes that the rear water jackets for the manifold are plugged internally on the heads (1997 through 2000)... So, I won't be digging into this yet - I'll get the exhaust manifold and head gaskets because now it's looking like I'm pulling the heads. I really *HOPE* it's just a freeze plug or head gasket and not a cracked head...

i must ask why does you iac have a big fat vac hose coming off of it???

Dunno - those hose is hooked up to the EGR.

i believe thats how it is, i believe my iac has a vac hose too.

At this point, I must assume I have two cans of worms here... One major, and one minor. The major one I must address this weekend is that coolant leak. Then I must have a good look at the EGR system in it's entirety just so that I'm am sure of what's going on with it.

Okay, the coolant problem was just the lower intake gaskets. I can't belive how toast the seals where around the cooling jackets. I've installed good Victor Reinz gaskets - no more leaks now, and hopefully it stay's like that for a good long time.

As for the EGR system, it has been totally bypassed. The connector for the DPFE was cut out of the wiring harness. Unless it becomes a problem, I'm just going to leave the EGR system as it is.