3.8 Help!!

RP27G8G · #1 (**permalink**) 11-02-2008, 08:10 PM

I need to start off by saying the car is in Wichita KS and I'm in Cheyenne Wyoming and I don't have pics. With that said here we go. My son had a problem with his car and an adult friend of mine (very mechanically inclined FORD guy) looked at it. From his description the EGR sensor (hope I got that right) on top of the engine next to the EGR valve has a hole blown through it. He said it looked like it got VERY hot and popped. Story on the car - replaced the engine less than 3K ago. Previous owner lost head gasket and kept pouring water in it to keep it going. So we replaced the engine with a good one but I think the exhaust was full of water and may have toasted the cats.
With all that said, my first instinct is the cats are bad. My son said the car started "hissing" and lost power/wouldn't accelerate. I'm sure the hissing would be the hole in the sensor. We have another sensor off the old engine but don't want to ruin a good part.
Am I tracking to think one/both cats are bad, created too much heat and/or back pressure and blew out that sensor? I'll be back there this Thursday and will look at it. I'm just trying to have a plan in mind when I get to it. My first instinct is to pull the cats and check it out with "test" pipes then go from there. Any help will be greatly appreciated.

BrianA · #2 (**permalink**) 11-04-2008, 11:40 AM

I'd say given the info you have, and the fact that the vehicle is not where you can check it yourslef right now, you appear to have a resonably good plan.

Hey, you gotta' start somewhere!

You could remove all the plugs and check for any liquid prior to turning it over.
Maybe another bad gasket?

RP27G8G · #3 (**permalink**) 11-04-2008, 10:39 PM

I'm not thinking head gaskets. There isn't any smoke or reason to believe that is it. The replacement engine appears to have head gasket work done already. I'll see it in a couple days and let you know.

RP27G8G · #4 (**permalink**) 11-06-2008, 03:31 PM

I got to look at th damage today and here's what I saw. There is a sensor for the EGR system that is connected to the steel tube that goes into the EGR valve itself. The sensor is connected to the steel tube by a 3"-4" rubber hose and has a wiring connector on it. It appears that the pressure coming through the hose was so great and so hot it melted the sensor. Everything around it appears fine. When I traced the steel tube it appears it runs down into the passenger side exhaust manifold right next tot he O2 sensor. Mind you this car has separate exhaust pipes off each manifold then they run into a long "muffler" looking thing, possibly a resonator?, and come out of that as one pipe. So, any more advice? Thanks!!

BrianA · #5 (**permalink**) 11-06-2008, 09:57 PM

Sounds like a clogged cat convertor might be the problem.
You think that is likely?

RP27G8G · #6 (**permalink**) 11-06-2008, 11:41 PM

That's exactly where I'm headed. The cats are available plus I found a guy with a Cougar and a T Bird he wants to part. I'm hoping to get the exhauset from one of those cheap and go from there. CAn't do anythign until Monday so I'll post more then. Thanks!!

RP27G8G · #7 (**permalink**) 11-11-2008, 11:26 PM

Anyone know if there is a way to test a cat?? Aside from removing it from the car.

bokker · #8 (**permalink**) 11-12-2008, 08:07 AM

hi, the only way i know of testing for a blocked exaust is with a vacuum guage hooked-up to the inlet manifold. if at tick-over the vacuum falls right off that is the sign of a blockage.
i have a guage fitted pemanently on top of the engine and i use it to check for leaks within the pipe work system but i do not want it on full view in side the truck as it sent me in a spin watching it. good luck bokker.

RP27G8G · #9 (**permalink**) 11-12-2008, 08:38 AM

Thanks Bokker!! So where is the inlet manifold? Are you talking the intake? I would guess there is supposed to be some level of pressure coming back up to the EGR valve. Is there a way to test it there? I do have a manual so I should be able to find whatever ports are needed. I take a look and see what I can find. Thanks again!

bokker · #10 (**permalink**) 11-12-2008, 02:18 PM

hi, some times the translation ( i am british) gets mixed up. you are correct i am refering to the air intake manifold. if i remember rightly i tee,d of an existing pipe coming straight from the manifold. good luck bokker.

BrianA · #11 (**permalink**) 11-12-2008, 06:44 PM

Translation issues or not, bokker is a champ when it comes to helping out his fellow 4.2 owners.

Thanks for the help bokker.

RP27G8G · #12 (**permalink**) 11-13-2008, 12:32 AM

Here's what I found today. I started the car and put my finger over the outlet nipple (on the EGR valve hard line) that has the hose that runs to the sensor. Even with a cold engine I couldn't keep my finger on there but for a couple seconds. The pressure coming out and the heat were extreme. So, we pulled the exhaust off and I fired it up. runs like a champ and very little pressure coming out of that "nipple" and it wasn't hot. I do understand that there is no exhaust so there won't be as much back presure. I ran out of time but will be doing some more "tests" tomorrow with pieces of pipe and different parts of the exhuast. I'm more convinced now that it's a cat problem than I was before. I'll try to get some pics of the burnt sensor and post them tomorrow.

KD5NSS · #13 (**permalink**) 01-30-2009, 02:39 AM

Hey, I hope I am not too late to help.
The sensor you are referring to is called a DPFE sensor (auto zone calls it a EGR sensor.) its purpose is to tell the PCM how much exhaust is going through the EGR valve. In the small pipe that comes from the exhaust manifold to the EGR valve ( the one with the two rubber hoses going to the DPFE sensor) there is a very small orifice. this orifice is between where the two hoses connect. This orifice has a tendency to get plugged with carbon from the exhaust, and can cause the symptoms you are talking about. You can clean this orifice with some good strong carb cleaner (sprayed in the hose closest to the EGR valve) letting it soak. Check to make sure the orifice is clear by plugging the hose farthest from the EGR valve and blowing in the other one. you will also likely need to replace the DPFE sensor. with the engine running, if you get good flow from the tailpipe your cats are NOT pluged. If the cats are bad the computer should throw a check engine light. I have had the same problem with my 2000 windstar. often when this happens the computer will throw an engine code of insufficient EGR flow. I hope that this helps you sort out your problem and can save you some money and headache.