I've been battling some driveability issues on my 98 Ranger 2.5. Worst it's ever been running since I've had it. Awhile ago randomly driving it would just fall flat and go into limp mode. You couldn't get it to move more than a couple mph. It would do that randomly but sometimes not for thousands of miles, but lately it was doing it more often. I believe I've tracked that down to a failed MAF. I've since replaced it and it's been fine. However, after that a few weeks later I got a P0402 code. I scanned using FORScan software and watched the values and couldn't see anything far off from the recommended values from the FSM. So I replaced the EGR vacuum solenoid first. Still it came back a couple hundred miles later. So I ordered a EGR pressure sensor and replaced it as well as the silicone hoses. When I did that I didn't notice any excessive buildup in the pipes. Well I drove it back and forth for a couple weeks and then a P0401 and P0402 came up. At that same time was when I started noticing the loping idle at stops. I figured because I went the cheap route and bought the EGR sensor on Ebay it was no good. Well I went to my FSM and it recommened cleaning egr valve and intake ports. Well I had an egr valve under warranty so I swapped it out but there was nothing to clean. The intake ports were clear and the pipe was too. I'm getting tired of it loping up and down everytime I stop at a redlight. I also replaced the idle air control valve under warranty too while I was near the throttle body. Now one thing i do know that is wrong is the baffles in my muffler are broken. They weren't bad awhile ago but now they're really bad, it makes it sound like the motor is going to die because of the clanking. But it is without a doubt the muffler. I had an exhaust shop check it a few years ago and they said the muffler baffles inside are broken. But back then it didn't make any noise like it does now. So does that contribute to the loping idle? Also sometimes it won't start in Park but will in Neutral, sometimes even the shifter gets stuck. I put up all the PIDs I could think to look at on the FORScan scanner but everything was in range according to the Ford charts. I still have a Pending P0401 code even after clearing the codes and driving for several days. Plus it's been real cold lately and it sits outside all day. Any ideas?

 

I see you don't have any replies yet, so I'll see if I can get things started.
Hook up your vacuum gauge & scroll down to have a look through the various test scenarios here How to Use and Interpret a Vacuum Gauge to see if anything stands out, especially #14, clogged exhaust.
Good idea to use the ELM scan tool & FORScan.
BWD parts are a good choice if you aren't using Motorcraft.

 

Yeah I've since done some work because I couldn't wait. I have to drive this truck daily. I even reposted the updated symptoms of what's going on now and what I've done. I'm still constantly getting a P0401 every 20-25 miles after I reset it. I've replaced DPFE sensor, hoses, EGR Solenoid, and EGR Valve. I also replaced the DPFE connector because mine was broken and I'm wondering if I mixed up the wires because the wires were different colors and hard to see anymore. Even the new connectors have all the same color wires. So I'm trying to figure out how to test each wire in the connector to make sure I have them connected right. When I unplugged it with the FORSCAN on it did shoot up to 5 volts like it's suppose to. I was being cheap and because money was tight so I bought the DPFE sensor on EBAY because of the price. The solenoid and valve didn't cost me anything. I attempted to clean behind the egr valve in the manifold but there was nothing to clean, it was free. But after all that still getting constant P0401. I've been watching all kinds of youtube P0401 videos even one that did on the exact same truck a 98 Ranger 2.5. The 98 Ranger video the mechanic says the DPFEGR reading should be 4 volts at 1500RPM and about 1-1.5 volts at idle. I checked my old one with FORSCAN and it was steady at .28 volts at idle and the new one was at .40-.42 at idle, even hot idle. I even drove around and it never went about .40-.42 volts. According to the Ford chart the specs are .2-4.5 volts at 30MPH which is what I made sure I was going when I was watching the PID. The same video the mechanic showed how to test for good flow by removing the EPR filter cap and plugging the hole while it's running and if it has good flow the engine should stumble, which mine did when we tried that. I've not found any vacuum leaks, we've checked all the hoses leading to the components. Today I had the tailpipe and muffler replaced because the baffle in the muffler was broken. It smoothed out the idle but it still has a P0401 and you can still feel the hesitation sometimes when you're idling. After getting the muffler fixed we determined something in the catalytic converter is rattling now. I can't afford a converter right now. It's not but a couple years old and it's a bolt on replacement but don't remember who I got it from. I'll bet that happened and got blown out when I was having the loss of power, stumbling, backfire randomly, which was a bad MAF. I haven't done a vacuum gauge test yet because I don't have a vacuum gauge anymore. I could probably get one fairly inexpensive. Where do you hook it to on this 2.5? When I hook it up does the hose I disconnect need to be plugged while testing? I also don't have a hand vacuum pump.

 

Have a read here for P0401 code suspects. https://www.obd-codes.com/p0401

You should Not have any EGR feedback at idle.

A common problem with our systems is a faulty DPFE sensor, plugged orifice Below the EGR valve, where the larger diameter high temp hose connects. If the engine uses oil, or has been out of tune, it's rather common for the orifice to plug with deposits & corrupt exhaust feedback to the DPFE sensor.
Faulty high temp feedback hose, hard baked out with cracks, splits, loose fit, clogged with deposits.
Faulty vacuum line to the DPFE sensor, (the smaller line between the DPFE sensor & intake manifold).

On the vacuum gauge connection question, you can "T" into that smaller vacuum line with your vacuum gauge if you wanted to. Yes any disconnected/open vacuum line should be plugged so it's not leaking vacuum, but if you "T" into it, no need to plug it.
Another easy to get at vacuum line is on the brake booster, you could "T" into that one also.
The "Help" section in most auto parts stores will have various size "T" fittings for you to construct a vacuum gauge test setup.

SO, if your EGR reference voltage is present & correct, the high temp DPFE feedback hose & orifice feeding it is open, the vacuum line feeding the DPFE sensor is good, you don't have any vacuum being applied to the EGR diaphragm at idle, but are still getting the 401 code, then the off brand DPFE sensor belongs on the suspect list.

If the DPFE reads ok, but you have vacuum to the EGR valve diaphragm at idle, put the vacuum switching valve on the suspect list.

More thoughts for consideration, let us know what you find.

 

I didn't get to the vacuum gauge today because I've been working on getting my R/T into the body shop to be repainted. I did however recheck my work on the DPFE connector that I had to replace initially when I replaced the DPFE sensor. One of the wires was connected wrong. I initially did it late in the evening so couldn't see the colors well because of the shade and age of the wiring. We fixed it and all wires are 100% definitely hooked up right on the DPFE sensor. I drove it around probably 30-40 miles and the light didn't come back on. However, it still surges when you first start it up and put it in reverse. Also when driving at cruise speed and punch it. You can feel a jerk that was never there, like a struggle. Also when you're cruising and then come to a hard stop or stop sign it idles down real low but never cuts off. I maybe able to get a vacuum gauge tomorrow and check that. We did notice that the PCV area is real greasy and we popped it up and you can see into the baffle. It's pretty nasty where you can see. I've always keep the oil changed at 3,000 miles and tune-ups regular. I used mid grade or high test fuel. The truck runs great cruising just at those points described is where it's having problems. I'll have to drive it more tomorrow to see if the P0401 comes back. I posted a video after we drove it probably 30 miles tonight and I just started it to go home and in the video it's in reverse. You can hear when it starts surging. Let me know what you'll think. https://www.youtube.com/watch?v=y9d25M1C_YI

 

Well lets see, lots of thoughts come to mind that might figure in one way or another, as you've been busy doing & fixing things that can mess with idle quality.

Seeing as how you like turning your own wrenches, you can look up wiring pictorials here.
Search Wiring Diagrams

Ford caution's us Not to use Premium fuel in these engines, as their compression, spark & valve timing aren't set up to properly use premium fuel & as such it can cause troublesome engine deposits. Our engines are designed to use Regular fuel. So get a tank of regular fuel & make sure you have the proper viscosity & service oil in this puppy before doing the following.

Don't know what viscosity & service grade oil you've been using, but with the described PCV area deposits, it sounds like you may have some kind of oil consumption problems.
Maybe excessive blow-by from worn, or stuck piston rings, or maybe from the wrong viscosity, or service grade oil, so tell us what you've been & are now using.

If the PCV valve, or Any of it's plumbing needs replacement do that now. If it's time for replacement Don't clean the PCV valve, Replace it with a Ford part.
The reason is, seeing as how the PCV valve is downstream of & it's a calculated for vacuum leak feedback & is Not being monitored by the MAF sensor, the PCV system Must be operating correctly or it'll corrupt fuel trim.
If this engine has a lot of blow-by from worn, or stuck rings, or the wrong viscosity or service grade crank case oil is being used, or the PCV system has a leak/think vacuum leak, all that can corrupt fuel trim, load up the PCV valve, intake manifold & combustion chambers with deposits & cause idle & driveability woes.

Once you know for sure the PCV system is operating correctly & the DPFE sensor electrical connector is wired & operating the DPFE sensor correctly & you don't have vacuum being applied to the EGR valve diaphragm at idle, so you know you Don't have EGR feedback at idle corrupting things, shut the engine down & disconnect the battery B- cable to wipe the computer KAM = Keep Alive Memory. Turning a light switch on, or leaving a door open, or pushing the cigar lighter in, will have their resistive load safely hasten the KAM wipe. Just be sure to turn them Off before reconnecting the battery B- cable so as not to get a big arc.

This will wipe the fuel trim tables & cold & warm idle strategy that's been corrupted by the DPFE wiring woes & any PCV system anomalies that have corrupted PCV, or EGR system operation that's in turn corrupted idle & fuel trim.

After reconnecting the battery B- cable, let the engine Completely cool down, then restart it cold & perform the cold & warm base idle relearn procedure here. Ford Truck Enthusiasts Forums - View Single Post - high idle problem

EDIT: When your certain all that's ok, if you still have idle rpm problems, remember that the IAC = Idle Air Control valve located on the intake air tube, just in front of the throttle body, is responsible for bleeding computer controlled idle air around the closed throttle plate, thus maintaining idle speed as engine load changes. If you come to suspect the IAC, inspect it internally for deposits from the PCV system vapors. Cleaning mine didn't last when I had idle up woes & is probably why Ford recommends replacement when they act out but cleaning mine was a good trouble shooting step for me. I replaced mine with a BWD part from Advance Auto, as it was a good bit less with online discount promo codes, than the Motorcraft part. It's been fine for 10 years & it's doing fine, so the BWD part seems to have been of good quality as others had suggested. If you replace the IAC, redo the base idle relearn routine. More thoughts for consideration.

Let us know how it goes.

 

On my original engine it lasted 226,000-228,000 miles before it spun a bearing and was gone. On that engine I used only Motorcraft parts and Valvoline 5W-30 or at a few times Motorcraft 5W-30. When the engine blew I was on vacation by myself in the middle of winter on the KY and OH border. It was 3 degrees. I had to leave the truck there and get the engine replaced by a local shop with a used 2.5 from a 2000 Ranger. But I wasn't the owner of the truck at that time it was my father's so he had it repaired up there at some small shop. There was no receipt and I have no idea of the mileage of the engine that was put in. My father said he thought it was around 50,000 miles but I can't be sure. So if all that was right this engine would have about 174,000 plus miles on it. I was rather disappointed in the mileage I got out of the original engine knowing how well I tried to take care of it. So on this one I've just used whatever was available as tune up parts but still doing them at the specified intervals. As for oil I still run 5W-30 but it's whatever is on sale and sometimes even the house brand wherever I'm at. I hardly ever put any additives in the engine, maybe once or twice. The timing belt is changed every 100,000 miles, I do plugs, wires, coils, fuel, air, pcv at 60,000 miles. My friend who is a shadetree mobile mechanic was looking at it tonight with me and suggested I remove the intake and clean it out with throttle body cleaner really good. I can probably do the throttle body but I usually only take the upper intake off if I have to change the plugs. Plus I'm not even sure it will remedy any problems. If I have to get a new PCV Motorcraft thats no problem. But the PCV hose I'm sure has been discontinued. What about the PCV oil separator box? How involved is that to change? I had to use the Premium Fuel because I had the Superchip in and just never have changed back to 87. The chip is gone.

 

OK, good feedback.

With all the PCV deposits noticed, probably a good idea to tidy up the intake, throttle plate & PCV system plumbing. Be careful to use "coating safe" spray cleaner on the throttle plate area. Make sure the OD of the throttle plate & the bore it fits in are squeaky clean, so it closes properly & isn't sticking from deposits. Don't damage the coating on these parts, so be persnickety about the spray cleaner & any rubbing device you use so it doesn't damage, or remove the anti-stick coating.

Once you get everything tidy & have checked for vacuum leaks, replaced faulty parts that would affect idle quality, perform the base idle relearn routine & see how it goes.

That engine was originally specified to use 5W-30 & in about 02 it could use 5W-20 that met Fords oil specifications, which most 5W-20 engine oils of the time couldn't.
A low NOACK/High Flash Point oil is a good choice, as it'll have fewer vapors & less foaming for the PCV system to have to deal with.
For instance, Havoline SN/GF-5 service grade flash point was improved Greatly in Dec 2015 to 447 deg F, so would be a good choice & it's inexpensive if bought at WalMart.

Since you were using a chip, it makes me want to ask if you installed a oiled foam, or cotton gauze air filter & if so, it might have fouled up & corrupted the MAF sensors calibrated heated air flow sensor, such that it's sending the computer corrupt intake air flow info.
The specified Motorcraft air filter is recommended.
If you've modified the factory cold air intake system, it's recommended that you put the factory plumbing back on, as it's carefully calibrated for this engine & it's air flow Isn't restrictive.

More thoughts for consideration, in getting this puppy back to factory original operation set up, let us know how it goes.

 

Well it started off as a good day in my 98 Ranger. I had a friend help me take my 99 R/T to finally go to the body shop for paint and body work. But it turned out later to be bad news. I drove around all day probably 60-70 miles total in my Ranger. I didn't get anymore P0401 codes but I now have a new one a P0171. It still hesitates at idle and idles low. So when I went to pick up my friend we stopped by my house to get my R/T while there we did a fuel pressure test on my Ranger. It was running 60-62 PSI pressure so it's well within specs. Specs are 64+/-8. We put a complete fuel pump assembly and filter on about 2 years ago. I watched the SHRTFT1 and it was high up and down. So I suspected a O2 sensor bank 1. Probably got fouled out when the MAF was bad for so long. I haven't taken out the O2 sensor to look at it. Because later on this evening my Ranger became basically undriveable. It turned out that the truck not starting sometimes in Park and the hard shift through the gears was the shift tube. Tonight it finally broke at the end that controls the shift cable and I could no longer get it in Park or Reverse. The end of the tube with the two brass Torque screws completely broke off. I had to have a friend ride with me home so I could hold the brake and he had to manually put it in Park on the transmission. So now tomorrow I have to go try and find a steering column. I don't know what other years will fit. There are no 98's at the yards around here to pull. I don't know if a 99, 00, 01 will work or if it can be tilt or standard. But right now it's not going to be able to be safely driven. And I've got to be back at work Sunday and just dropped off my other truck that's already being torn down for paint. So we didn't get the vacuum gauge either because they were sold out where I was going to get it. We didn't get to remove the throttle body or clean it out. Because now priority is to get the column fixed. I will have to get a whole other used upper column with steering wheel. I don't know how much trouble it will be and how much of a plug and play job it will be. My friend said it won't take him long at all to remove and reinstall one. It will be awhile before I can even tackle the P0171 code.

 

Dang, when it rains on you it Pours but don't despair, hang in there & knock the problems down one at a time & sooner you'll likely get them all put right.
Have a read here on the P0171 code http://www.obd-codes.com/p0171, don't be surprised if some of the items on the suspect list sound familiar.

 

Well today I was luckily able to fix the disastrous shifter issue. Luckily I saw a Youtube video on replacing the shifter tube on Ford Rangers. Which is what turned out to be the problem on mine. The shifter has always been very tight on the column after having a new shift cable installed a few years ago. I thought it would loosen up thinking it was just the new tightness of the cable. The guy that put it on also tighten the screws on the end of the shift tube and I think maybe too tight. Because the whole end of it broken off. We had to manually shift it in to gear from the transmission to get it home last night. I thought I was going to have to replace the whole column but luckily it was a 20 minute job remove and 20 minute install. But we had to go to a u-pull yard to get a shifter out of an 03 Ranger. It works and I got the needle all lined up. It still feels a little tighter than I want it to be but nothing like before. The shift tube I got was clean and the bushings were nice. The internal shift tube actually broke on my old one and the end of it broke too. I guess that's why it wouldn't start it park sometimes. We even got done in enough time to clean the throttle body. I didn't decide to remove the whole upper intake but just the throttle body. It was rather filthy. I usually clean at every tune-up. But it had a lot of black build up on the backside of the throttle plate. We cleaned it really good and I also swapped out the TPS while it was off because of the trouble getting to it while it's on. New gaskets too. The idle air was swapped last week so we left it on. I drove around a good while after that and I haven't got any lights. But also while I did the shift tube the battery was disconnected for quite awhile. So everything was reset. I probably drove it 30 miles after we got done. So what's next? I read the P0171 link. It's got good fuel pressure, I'm not able to locate any vacuum leaks. I don't feel an ignition miss. Exhaust leaks are taken care of with the next muffler and tailpipe. I've got to order some parts so I went ahead and threw in a Bank 1 O2 sensor since it's been a long time. Plus when the MAF was bad for so long it could've fouled it up. The throttle cleaning didn't have any effect on it except maybe for better throttle response. The surging idle is still there when backing up and hard stops. So I've got it up and driving just haven't figured out the idle problem. Still trying to get the vacuum gauge to test. Probably will tomorrow.

 

Ok, good to hear the shifter fix wasn't too bad & went well.
Was probably a good idea to have replaced the old O2 sensor if it had more than 75K on it.
How many miles on the current PCV valve?
Will be interesting to hear what additional trouble shooting clues the vacuum gauge tests suggest.

 

Unfortunately again I wasn't able to make it to get the vacuum gauge. The other location that had it is like 30 miles away. But it's worth the price difference. Of course something else came up on this Ranger today. The fuel pressure test valve was leaking on the manifold. I guess from when we did the test. It's the original with 362,000 miles. It was actually leaking the night the shifter broke and we removed and tightened the schrader valve. We also put some new teflon around it. I thought it was fixed but I could smell gas today and sure enough it was leaking. I had to run back to the salvage yard because none of the parts stores had a new one. I picked up 4 while at the salvage yard and it only cost $1 to get in. I replaced it with one from a 2004 Ranger. I came home installed it, washed it off. I just got back from driving it around and it appears to be dry. It took up all my day running around so I didn't make it to get the vacuum gauge. I'm back to work tomorrow so I had to make sure I can make it there. I haven't got any CEL back on. There still is the idle problem when putting it in reverse and coming to stops. So there is definitely something wrong. Driving is ok. While I was at the salvage yard I looked at another 2.5 that had the ps pump bracket off and I could get a good shot at the PCV vapor separator box. I was going to grab it as a spare because I see they are no longer available. But I see why Ford says you have to remove the entire intake. One bolt and the intake runner blocks it from coming out. Can you spray any kind of cleaner down into the PCV box when you remove the PCV valve? Where would the cleaner go? It looks like the box sticks into the block. I would say my PCV has been on probably 30,000-40,000 miles. It is a Motorcraft. I just ordered a new Motorcraft PCV too with the O2 sensor. We looked at it, it rattled nice and free and the bottom of it wasn't gunked. Inside the PCV box you could see some oily buildup. But we weren't sure if it was ok to spray any kind of cleaner down in there since we couldn't remove the whole box. It probably wouldn't hurt to change the grommet but I'm not sure if it will be easy to change with the limited access.

 

with only 30-40 K on the PCV valve, it looking ok for sludge, & having free movement, I'd leave it alone. Same for the separator, don't spray anything in there right now.

Any cleaners & crud they remove on the intake side, can end up in the combustion chamber, or leak past the piston rings, into the oil sump, so best to remove things for cleaning, so the engine & lubricants don't have to process those putrid things.

Good to hear you got it running well enough to drive to work.

Good feedback on no lit CEL after the latest drive cycle. Also a good idea to have fixed the leaking fuel rail Schrader test valve.

I assume this puppy has an auto tranny & if so, try slipping it into "N" when coming to a stop & let us know if the idle responds favorably.

 

Have you checked/replaced the Idle Air Control Valve?