Hi everyone,

I have a problem that I would greatly appreciate any help offered. I own a '99 F150 4.6 auto 4x4 Supercab with almost 92,000 miles. About 3 months or so ago when my truck neared the 88K mark, my CEL came on so I got it checked at Autozone (who also told my sister that the PCV needed replacing in her Sporttrac when in reality, a new DFPE fixed the problem). The code came up "Insufficient EGR Flow" and claimed I needed a new EGR valve. Not really believing them anyway, I've left it alone for about 3 mo. with no real problems except a little bit of surging going up long hills with constant throttle pressure, and noticeable decrease in gas mileage. In the beginning, it would go off occassionally (coincidentally after I filled up with premium and then came right back on after filling up the next time with regular), now it's on for good. I had one guy tell me that EGR shouldn't be failing with only 88K miles and that it could be the sensor. I went in Advance Auto Parts to look up prices for valves and sensors, and the guy told me that his Mustang had EGR replaced at 54K and that I should take it off, clean it and the ports, and reset the codes. I did that last night, and of course as soon as the computer reset this morning, the CEL came back. I checked the EVR regulator and DFPE sensor with a volt/ohmmeter for voltage and resistance just as the Haynes repair manual shows, and all numbers checked out good, so I'm thinking new EGR valve. Well, I decided to check the TPS just for the hell of it, and my Ref. voltage was ok (3.77 out of recommended ~5.0 volts), but no signal voltage was showing at all (0 volts). It showed 0 whether at closed or WOT. Does this mean a bad wire or harness? Also, is this really the cause of the EGR problem? (Haynes says that TPS and other things can affect EGR problems.) Could a new TPS harness fix the problem and how is it already affecting my truck? I'm thinking about just letting Ford put it on their computer and have at it. I don't understand why the Haynes manual says that if the correct voltages don't show up on the sensors, then you should replace the sensor. Doesn't that indicate that the wire is bad?, because if there's no signal voltage going to the sensor, then how can you know if it's a bad sensor? Truck still runs decent, but would just like to get this problem over and done with. I know it's a drawn-out story, but I'm just seeking any advice. Thanks everyone.

 

Respectfully, your all over the field.
What are the codes? Then we go from there.

 

P0401...sorry, in all that mess I wrote, I put "insufficient EGR flow" in there somewhere, i think.

 

Ok, 401 is a specific test of the whole EGR system for a calibrated flow rate detection.
The PCM commands the EVR to open the EGR a specified amount for flow measurement.
This measirement is taken by the DPFE across a calibrated orfice in the main tube.
If the EGR port is not letting enough flow, the orfice is plugged, the small hoses are defective,the DPFE is faulty; the 401 code is set.
I would vote to change the DPFE unless you find something very obvious.
To test the DPFE it has to have pressure applied to simulate the pressures it sees in the system.
TPS is not setting a code so don't waist time on that unless it is indicated by code, for now.

 

How would I go about testing the DPFE? Thanks again for the help.

 

if you do have 2 separate problems, they are separate.
EGR=ehxaust gas recirculation

If you have insufficient EGR flow it means that your EGR valve is not allowing exhaust gas back into the intake. The reason we recycle some exhaust gas is for emissions reasons, it also loweres combustion temperatures because of the unpure air, it also keeps the exhaust sysem and cat cool, which means lower levels of things like nitrogen oxide, carbon monoxide, and unburned hydrocarbons.

you CAN run the vehicle without the EGR valve installed, its just going to suck in regular air. Right now it sounds like the valve is stuck shut, and the O2 sensors are getting mad because they are seeing increased emissions in the exhaust system, so they talk to the PCM and he sets the code. Try it without the EGR installed, it may run better-bad egr valve

some new vehicles dont have EGR valves, the use overlap valve timing through variable valve timing to keep some exhaust gases in the combustion chamber for the next ignition.

If you DO have a TPS problem, you would have a code. TPS voltage low, ref low, something to that sort, you may not be measuring it correctly, the manual may not be giving you good instructions. A TPS is a variable resistor, so it should have like you said 5V going to it, then the depending on the TP angle it sends some voltage to ground, and the PCM monitors this. If you had a good scan tool you can do a lot more with the TPS than just get codes.

 

Would the port on the intake and the EGR pipe just be left open? Is it bad for the truck in the long run? Thanks again.

 

yeah i mean take off the EGR valve and drive it around the block, dont leave it off, replace it seems to be the problem. Its really more of an emission standard of OBD II, so it puts on the check engine light. Not going to hurt the engine, maybe hurt the cat in the long run. but just do a couple checks, if the valve isnt opening and closing properly you could have a restriction, but more likely a bad valve

 

Why is this conversation taking place?
Are you not going to repair the problem instead of taking things a part!
No EGR valve lets air into the intake and will probibly cause 171/174 lean codes.
No EGR in place amounts to an exhaust leak in the engine bay plus noise and a 402 code failure as well as the 401 code.
You are just getting deeper into problems and not proving anything.
This is all from me if you don't want to fix it after asking.

 

Yeah, thanks for the advice. I'm sure I'll end up just giving Advance the $50 and hope it'll clear up the headache. I have a feeling it could be a stuck valve. I'm planning on installing a Superchip soon, so I want to get this out of the way before the chip is installed.

 

No need to jump on me about it. I wasn't planning on taking the thing off and driving around anyway. I'm just asking for anyone's opinion about my problem and what they think. I mean I came here after I tried everything I could think of, so I'm open to hearing any suggestions.

 

Check the PIDs for the DPFE sensor. It should be under 1 volt. Watch for it to change when the EGVP changes telling u the EGR opened. Then manually open the EGR and see if it almost kills the engine at idle. this will tell u the EGR is working and the ports aren't plugged. The DPFE is sensing a pressure change between the exhause side and the intake side of a metered orifice to determine if the EGR did infact open when commanded. And it's telling u that the sensor DIDN'T see that pressure drop it needed when it commanded the EGR open..... Also Check for vacuum going to the EGR when it is commanded open.

 

What ports did you clean? The ones in the throttle body are the ones that need to be cleaned to clear a P0401 on a 4.6.