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Discussion Starter #1
1995 4.6L w/ 228K miles.

Occasional P0402 code over the last few years. Sometimes it would go off on its own, sometimes stay off after I cleared it, sometimes come back on shortly after clearing it. Depends on mix of highway, local, and stop & go driving. EGR valve seems okay based on applying vacuum and hearing movement. Should have replaced it and cleaned the EGR tube when I redid the intake manifold gaskets but I was singularly focused on the immediate critical repair needed and it just looked too challenging at the time to take the EGR tube off with no replacement part available if I messed it up. Car is a daily driver. Will try to tackle it someday.

So now I'm trying to resolve a P1405 code. Differential Pressure Feedback Electronic Sensor Circuit Upstream Hose (off or plugged). Upstream hose is the one closer to the exhaust manifold, right? This diagram is correct? BTW, I ran the "6V Lantern Battery" test on the DPFE and it appears to be working properly.

I removed the larger DPFE hose and worked a wire into the tube. I could only push it in about one and one-half inch. But it's an awkward angle and that's where the bend in the tube is. Then I attached a one-quarter inch vacuum hose and blew into it. No flow. Should be some, right? So I sprayed some PB Blaster into the hose and will let it sit overnight, tomorrow repeat.

So the upstream hose is the larger one and the tube should allow flow when applying air pressure?

Thanks.
 

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WOT Junkie and avid corn burner
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I think it's the other way around. Upstream being closest to the EGR valve. Regardless, you should be able to get some air flow through those tubes. They are probably clogged with carbon.
 

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Discussion Starter #3
Thanks. I took and left the larger hose off, reset the MIL Just the P1405 came back. I'm going to throw some carb cleaner in the tube today, it's probably better for loosening carbon buildup.
 

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The sensor is just a sensor; I don't think air flows thru it.

The last time this happened to me, the EGR tube orifice was clogged up, so there was no egr flow.

There's an orifice, a piece of metal with a hole in it, welded inside the egr tube, between the two hose connections.

The sensor measures the pressure across it when the egr is flowing, and reads the flow level.

The fix is to carefully remove the egr tube and valve, and clean them out completely.

You also want to take the TB elbow off and clean all the gunk out of it too.
Especially on the 94-95 models; the passages there are a *****.

An easy search finds links going bact to 2002 for this exact thing...


http://forums.tccoa.com/7-engine-4-6l-5-4l/123897-94-95-egr-trouble-code-p0401.html
http://forums.tccoa.com/7-engine-4-6l-5-4l/101891-p0402-angering-me.html
http://forums.tccoa.com/7-engine-4-6l-5-4l/7334-carbon-gunk-build-up.html
http://forums.tccoa.com/7-engine-4-6l-5-4l/44787-there-something-special-about-95-egr-valve.html
http://www.lincolnsonline.com/tech/00015.html
 

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If you get to the point that those orifices are clogged, forget it. I had my intake manifold off, so I had good access to it, but couldn't do much with it. Those orifices are so small, a SS wire won't even push in there. There are bends and such in both parts of the pipe that makes almost impossible to push a snake down the tubes.

I soaked both the big pipe and the orifices for days with the highly recommended GM top engine cleaner. It loosened up the big pipe, but not the orifices. I had a contraption (funnel system) rigged up to soak it with. Also hit it with 110 psi of compressed air, hose blew off every time.

I agree that the first thing to clean is the passages under the TB elbow. I've done mine twice over the years. **** the 94-95 EGR system!

Al
 

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Yup, gotta love the early 4.6 intake/egr setup.

 

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I got to the point I just left the light on. It still passed our strict inspections here in Houston so I didn't care any more.
 

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^You can do that one of two ways:

The slow, drawn out way - leave the light on till it burns out. Or the fast way - pull the bulb and "modify" it. Either way, the CE light is useless as a warning system.

I have heard about the strict Houston inspections - honk the horn, and turn on the lights.

Al
 

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I am so glad that I live in a state with no vehicle inspections. True automotive freedom.
 

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Discussion Starter #10
Thanks for all the suggestions. Side note- don't have another emission test until February 2017. In the past I've put black electrical tape over the check engine light, but for the small chance that something serious happens and the light blinks, I leave the tape off now. Last resort will be to remove and clean the EGR tube, just don't have the resources to tie up the car for that long right now.

I cleaned the intake manifold ports below the throttle body adapter ("elbow") when I replaced the intake manifold gaskets 5K miles ago. I understand that the DPFE sensor is just that, and the upstream and downstream hoses feed the DPFE's ability to read the pressure differential across the orifice in the EGR tube. The orifice may be clogged but for now I am working on the upstream tube being clogged. Still spraying carb cleaner into the upstream tube and letting it soak. I tried compressed air too but with the same result, couldn't keep the hose from popping off. I have not gotten a P1406 downstream hose clogged or off code, so possibly the orifice is not clogged, just the port off the EGR tube going to the upstream hose.

I'll keep working the carb cleaner route for now.
 

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New tubes have not been available for some time. At least that is what everyone has said on here. Advance is the only place I checked personally.

Al
 

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Discussion Starter #13
I've got new hoses. Now I see Advance and Rockauto have EGR tubes: different names, different part numbers, same picture, same description (...EGR products contain feature rich design and componentry yielding market leadership performance.) I'll get one for when I get up the ambition to try to replace the tube or can't pass an emission test if needed for registration renewal.

I fabricated a tube, hose, and cable assembly to try to work at the clog in the upstream port on the EGR tube. 1/4" brake line cut to size and bent to line up with the port, 1/4" vacuum hose connecting the two, 3/32" cable inside that I rotated thinking it would scrape at the clog. Worked at it for about an hour and gave up... the tip would unravel and cutting it down to a new point with my dremel was marginally effective... thinking the resistance was more from the cable not able to make the bend in the upstream tube rather than hitting the clog. I may try it again in a couple weeks after all the scrapes and cuts on my hands heal. Next time I'll try putting the cable in my hand drill for better leverage and pressure, fasten down the brake line tube, put oil in it with the cable, and use slow-speed counter-clockwise rotation to reduce unraveling.
 

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Exactly. There are all kinds of bends and kinks in that damn thing, also reduces in diameter. I found my EGR valve was VERY clogged, ie: no way it could possibly work. I wasted $70 on a brand new Ford one specifically for the 1995. I say "wasted" because the system as a whole is still not operational/

If you buy the "replacement" Ford one, the vac port is in a different spot, and you will break the plastic tubing trying to get it on there. I didn't attempt it, and ordered a vintage 1995 one, which is almost obsolete. Jason had to source it from out of state.

I was in the Advance store, they also listed a part #, but said it was not available. I didn't do a lot searching because I could barely see the other end of the pipe where it connects to the exhaust manifold.

Al
 

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Discussion Starter #15
Thanks Al. Advance.com says the EGR tube is only available on-line then on-line says the item is unavailable. I selected the notify-me-when-available option on Rockauto. Sorry to hear what you tried did not work out. Plastic tubing to the EGR vacuum port on my 95 is still flexible. It's the EGR tube threaded connection to the exhaust manifold I am worried about. I have a lot of confidence that my 95's EGR tube is clogged but aside from being a real knuckle-scraper, I'm reluctant to attempt pulling it without a replacement part. For now car I'll continue to use the car as a daily driver.
 

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Easiest way around this without losing MIL functionality is a tune to turn off the EGR. As a side bonus, you can have the speed limiter disabled at the same time! My buddy's 95 Cougar had this problem, and there was no way in hell I was going to try getting that rusted old tube off, and it wouldn't have passed inspection with the check engine light on, so a tune to turn it off was literally the cheapest and fastest fix.
 

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Yes, but how much is a tune? I wanted to do that, but was talked out of it.

Jim, what I was referring to is if you replace the EGR valve, the plastic hose won't connect easily w/o making a custom hose setup. That particular line is very short. The EGR port on the new valve is not in the same place, unless you specifically source out a new old stock part from 1995.

Al
 

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It is likely clogged, I went thru this with my 95. I spent about 2 hours cleaning it, I doubt it could be done with the tube on the car. The carbon was extremely hard and caked in most of the tube. I ended up heating the tube, pouring in all kinds of chemicals, using a wire attached to a drill, etc. I would have probably bought a new tube if I knew it was that bad, but I just wanted to get the job done and not wait 3 days. The Ford place that I ordered it from said they had experience with that part from some Lincolns and suggested to replace it. I also got an EGR valve (the vac port was off center too) but the hose had no problem fitting. Again the dealer that sold it to me said they use that valve on many older lincolns. It works fine for many years.

Taking it off is not fun either. A large crows foot may help, or even removing the A/C. Then there is the under the car route. If you do take it off spray it with penetrating oil for a few days. Surprisingly it came off in tact, but I did heat the nut with mapp.

I am pretty sure this happens because of the valve seals. Since I replaced the valve seals there is little to no buildup in the channel. Your oil has to go somehwere!

Being a 95, inspection in NY is not an issue because the light for this issue will not go on unless you drive it over a certain speed. Pre-96 only gets a visual emissions check that components are present. So you simply reset when you arrive at the shop. I'm not even sure pre-96 vehicles can fail for a light, the rules change with that.
 

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Last time I priced it out, a basic tune was around $325, and takes all of 15 minutes to install a j3 chip. Compare that to how many hours trying to get the rusted EGR tube off, how many more hours trying to clean it, trying to track down a new one or fabricate one if you can't clean it, I'd rather just spend some money for a tune and be done with it forever.
 
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