Ok, I need help diagnosing a problem. I've got a '98 Ranger, 3.0L. Several days ago, the check engine light came on, I took it to AutoZone and they said I needed an new EGR Valve. I had replaced the EGR valve about 4 months ago so I thought this was a bit unusual. But, I also installed a cold air intake a couple of months ago, so I thought maybe some carbon got blown loose. So I drove around town with the check engine light on looking for a new EGR valve. I finally found one and bought it. On the way home the check engine light went off and the truck ran great, no hesitation or anything. So I didn't replace the EGR vavle. As a matter of fact, a couple of days later I took it back and got a refund. Then this morning, the truck started hesitating horribly. I'd slow at a redlight and it'd idol down to 500 RPMs. Then it stalled on me. I restarted it, threw it into drive and got to work. But I had to keep one foot on the gas while I was breaking and idoling. Then I got to work and it shut off when I stopped and let off the gas. Now it wont crank up. It fires, and sputters and then coughs and sputters, then dies. I went and got a scanner and the code is now P0402, "EGR flow excessive". So I'm trying to figure out what needs to be replaced, EGR Valve itself, or EGR position sensor, or what? The DPFE, oxygen sensors (all 3 of them), the PCV valve, and the fuel filter were all replaced about 4 months ago, when I put a new EGR valve on. I did not however replace the EGR position sensor, nor the EGR Vacuum Regulator Selenoid (is this the same as the EGR position sensor?). A little help would be greatly appreciated! Thanks.

 

How many miles are on it? I had a similar situation on my '02 4.0 and it was the tube that goes from the airbox to somewhere on the engine. But mine was a warranty thing, so all I did was drive in and say 'it's broke' and they gave it back fixed; didn't really have to do any lookin around. I think mine was the PCV valve. All I can think is that since it's an EGR VALVE it might got stuck in one position or another, then driving around it got un-stuck and ran good, and now it's stuck again, only in a BAD way. On mine, it would idle down real low, and then right between 3000-3300 it would fall on it's face unless I took it real easy thru that RPM range. Under 3k, it was fine, and over 3500 (heh heh ) it was fine.

 

The ranger has 105,500. Deffinatly not under warranty. A friend of mine also suggested it maybe a vacuum leak, but the tell the truth, I don't think it is. All of the hoses are in really good shape, not dry rotted, etc. The only thing I can think of is cleaning out the EGR valve and give it a shot. If that doesn't work, replace the EGR position sensor. If that doesn't work...I'll check back here for additional suggestions tonight...thanks for your help!

 

Doesn't that just figure...when I got my 98 Ranger (used at 35k) they told me that they're required to warranty, under any circumstances, the entire emissions system up to 100k miles. EGR, PCV, catalytic convertor, etc. Sounds like yours crapped out right on schedule. Those EGR valves can get pretty gummed up over time. Probably pretty well coated with carbon deposits and the like.

 

The code P0402 problem is in all liklihood a bad DPFE sensor. However, you should also check the hoses running to and from the DPFE and the EGR Tube and make sure they aren't clogged, pinched or burned, etc.

Look up the P0402 code here for more possible causes: 1995+ Ford OBD-II Diagnostic Trouble Codes (PDF)

The DPFE on my '98 4.0L looks like this plastic one, although they also can look like the metal one below it, too.





The DPFE is easy to replace, two screws, a couple of vacuum hoses and an electrical connector. You want to try and get the plastic one as the replacment unit, inasmuch as they last longer.

An overview of the Ford EGR System can be found here: Ford DPFE/EGR System Summary[/QUOTE]