2000 Explorer XLS, V6 Rough Idle, Multiple Codes

[delicreepp]

Hello all,


Several months ago, I noticed our Explorer had a mildly perceptible rough idle. This coincided with the check engine light coming on. I hooked up our OBII and got the p0401 code. Not being fantastically patient enough for systematic component checking, I replaced the EGR vacuum solenoid and the DPFE sensor and hoses. No change in the idling, so I replaced the EGR valve. Lo and behold, the rough idle got *worse*, but the 401 code was gone. However, there was now a P0402 code.

I had to let the problem lie while I took care of some issues with our new house (installing a new main water line and doing a full repipe, among other things). Lousy weather and the need to replace the hood struts also kept me away.

With the rain and wind finally over, I fixed the hood was ready to get back to figuring out the Explorer.

I hooked up the OBDII once again and found new codes! in addition to the P0402, I now have p0171, p0175 and misfires (p0301, 303 and 306)! I did vacuum leak test with a smoke machine and found nothing wrong with any hoses, etc. BUT, there was smoke coming from the IAC valve itself, as well as from where the throttle body sensor connects to the throttle body. I replaced the IAC valve, but could not get the screws for the throttle body sensor to budge and left it for now.

There is also a loud, intermittent clicking when idling. This occurs whether the A/C is on or off, and vanishes when accelerating/driving.

And, this is where I am at. I haven't yet done another leak test to check the IAC valve.

So, any advice on which direction I should go? Any help is appreciated.

 

[EB4X]

FYI, smoke coming out the IAC is normal during a smoke test as well as the throttle body plate....but not the TPS, throttle position sensor, did you have the air intake hose off during test?, thus is it possible the smoke you saw near the TPS was just some creeping up from the throttle body plate..?
Having an XLS I assume your 4.0 is the ohv version...?

 

[delicreepp]

I appreciate your response. Yes, I have the 4.0 OHV engine.

Going left to right from the intake filter box, I blocked the intake hose with a plastic bag just after the MAF, clamped it back on and ran the smoke through the brake booster hose. During that test, the smoke came through the IAC and where the TPS meets the throttle body. After reading your post, I put the old IAC back on and returned the new one, while also purchasing a new TPS and hex-headed bolts (I cut into the original screws with a hacksaw and was able to get them out with a flathead).

No change in the rough idle or the codes or anything else with the new TPS. I performed a second smoke test, this time passing the smoke through the main intake just before the MAF. There was smoke from the hose leading to the oil fill neck, right where the hose connects to the neck nipple--there is a crack there. Smoke also came out through the IAC as before. No smoke came from the new TPS.

Otherwise, no smoke anywhere else. I checked all of the vacuum hoses visually again, which reminded me that the intake manifold gasket and vacuum hoses had all been replaced during the lockdown, three or so year ago, so they all are still in great shape. The PCV valve was also replaced at the time and is still in working order.

One thing that I didn't remember until recently was that way back at the beginning of this saga, after replacing the EGR and seeing no improvement, I popped the narrow hose off the top of the valve and plugged the end with my thumb. That evened out the idling.

So, I still have a rough idle, the intermittent clicking, and codes: 171, 175, 301, 303, 306 and 402.

New components: EGR, EGR vacuum solenoid, DPFE sensor + hoses, throttle position sensor.

 

[EB4X]

I've read a partially clogged fuel filter can trigger about half of those codes....as for the ticking, is it possible it could be a loose heat shield vibrating at idle ? ...or exhaust leak....
JUST occurred to me while typing out this post....the ticking COULD be a compromised plug wire causing spark to jump to exhaust manifold which WILL produce a loud ticking along with, of course, serious missing / rough idle....start up engine tonight in the dark and look for "firework show" somewhere around the plug wires and exhaust manifolds.
Or with all these, 301, 303, 306 going on, maybe your coil is shot...go over plug wires and make sure a critter wasn't chewing on a few of them overnight....

 

[delicreepp]

I've read a partially clogged fuel filter can trigger about half of those codes....as for the ticking, is it possible it could be a loose heat shield vibrating at idle ? ...or exhaust leak....
JUST occurred to me while typing out this post....the ticking COULD be a compromised plug wire causing spark to jum,p to exhaust manifold which WILL produce a loud ticking along with, of course, serious missing / rough idle....start up engine tonight in the dark and look for "firework show" somewhere around the plug wires and exhaust manifolds.
Or with all these, 301, 303, 306 going on, maybe your coil is shot...go over plug wires and make sure a critter wasn't chewing on a few of them overnight....

I checked last night and no fireworks. I have a new digital multimeter arriving today to replace my analog one and will be checking the coil. I've been so focused on the supposed vacuum leak that I haven't even checked the spark plug wires (in my defense, the misfire codes are a new development). So, I'll be doing all of that tonight and tomorrow.

I also let the engine run while I listened, and it seems that very loud clicking is coming from driver's side by the A/C compressor. Haven't timed it yet.

 

[delicreepp]

Another update:

Driving home from work yesterday, I noticed that the clicking noise was gone.

Later that day, not wanting to drive too much longer with misfires, I pulled the ignition coil and checked it with the multimeter. It was fine--which I was not expecting. I blasted the coil ports with air and small fragments came out of at least one. I reinstalled the coil and checked the wire connectors before securing them. I also checked--was well as I could--the wires at the spark plugs to see if they were snug. No problems there.

After that, there was a pinhole leak in the upper left side of the radiator that I had been planning to fix, so I cleaned it up and spread on some J-B Weld. This morning, after I drove my son to school, I checked the leak and saw that a crack had traveled about an inch from beneath the repair, even splitting the rib on the outside surface of the radiator. No coolant had leaked out. I applied more J-B Weld, spreading an inch in every direction from the crack and heavily coating the cracked rib.

I popped off the radiator cap and checked the coolant level. To my shock, there was barely any in there--it was maybe a bit more than 1/4 full! I refilled the radiator and the overflow (to the cold level). After that, I left the repair cure for about 7-8 hours before going to pick up my son.

I wonder if that clicking noise was associated with the cooling system trying to pump coolant that was barely there, and it stopped clicking because the level had fallen too far?

Anyway, after getting home today, I checked the repair on the radiator and it looked fine. The coolant reservoir was still at the right level. I hooked up the scanner and, to my surprise, only the p0171 and p0174 codes remain. The 300 and 402 codes are all gone! Still idling rough, though.

 

[EB4X]

How does the oil look on the dipstick....and is level high? How does the exhaust look?...any steam coming out exhaust after warmed up? Wondering about possibly cracked head. Might want to remove plugs and examine, smell for coolant.

 

[Pete Deering]

See link ford P0174 code

 

[delicreepp]

How does the oil look on the dipstick....and is level high? How does the exhaust look?...any steam coming out exhaust after warmed up? Wondering about possibly cracked head. Might want to remove plugs and examine, smell for coolant.

The oil looks fine, not creamy or sludgy, and rides where it should on the dipstick.

 

[delicreepp]

So, another update.

Last weekend, I replaced the leaking radiator and thermostat. After the radiator was out and the coolant hoses were out of the way, I replaced the spark plugs and wires (Autolite XP104's for the plugs, Duralast for the wires). Collateral damage was the heater control valve, where the bottom half split off when I was removing the core hoses to make more room. Easy fix. It was nice to not have to go through the wheel well on the passenger side, though the the middle plug on the driver's side was a huge pain and would not sit properly for the threads to catch. That one plug took forever!

I held off on the fuel filter since I was working at the curb in front of the house and it didn't want to have to get fully under the car to get to it. I figured if I still had issues after the new plugs/wires, I could move to the driveway. Anyhoo, after a new radiator, thermostat, plugs/wires and and oil change, I went off for a drive. The idling was still poor. However, the misfires were now gone. So, progress!

Remaining codes: 171, 174 and that damn 402.

Still not wanting to screw around with the fuel line, I decided to try something that I had been considering for a while. The third part I replaced when this saga began--after the DPFE sensor and the EGR vacuum solenoid--was the EGR valve itself. The thing is, that's when the idle really got rough. So, I removed the new one and reinstalled the original EGR.

No more rough idle! No more problem codes! The main issue all along, as far as the 402 and lean codes, was a damn junk replacement EGR. I only wish I had swapped them at the beginning, because I'm way past the return date with O'Reilly.

Thanks to everyone who chimed in with advice.

 

[C420sailor]

Why’d you change the EGR in the first place? They can be cleaned, as long as the diaphragm is intact

 

[delicreepp]

Why’d you change the EGR in the first place? They can be cleaned, as long as the diaphragm is intact

I had replaced the DPFE sensor and the vacuum solenoid and was still getting codes and a slightly rough idle. The EGR looked fine with no carbon buildup, but I swapped it out anyway. (Swapping parts instead of diagnosing). The idle roughened noticeably, but I had to step away from car repair because of other projects and worsening weather, and it just ended up being a longer sojourn than anticipated.

 

[delicreepp]

Honeymoon is over. The idling started getting a bit rough a couple of days ago (not as bad as before, though) and the check engine light popped back on yesterday afternoon. OBII tells me P0171, P0174 and, in a return engagement, P0401.

A quick recap:

Initial issue: Rough idle, noticeable dip in MPG, P0401 code.

Replaced: DPFE sensor, EGR vacuum solenoid.

Result: P0401 code goes away. Rough idle persists. P0402 appears.

Replaced: EGR valve.

Result: Rough idle worsens. P0402 remains.

(took a break of several months due to other projects/bad weather)

New OBII scan: P0171, P0174, misfires on 1,3 and 6 appear; P0402 remains.

Visual inspection doesn't reveal any cracked hoses, etc.; Smoke test shows no hose or gasket leaks. However, smoke does leak out from around the TPS sensor. Screws cannot be tightened. Ignition coil pack tested, no issues.

Replaced: TPS sensor (and bolts instead of screws)

Result: Smoke test shows no leaks, cracks etc. All codes remain.

Replaced: Spark plugs and wires, serpentine belt (old one was starting to squeal on start-up), radiator (leaking), thermostat, heater valve (collateral damage), oil change.

Result: Misfires gone, P0171, P0174 and P0402 remain.

Replace: remove new EGR and replace with old one.

Result: No codes, smooth idle (though the car would idle high at start-up, around 2000-2200 RPMs, before settling down to just below 1000 after 15-20 seconds.


I went almost two weeks without issues. City driving, no freeway. Right back where I started with the P0401 popping back up, but with the bonus 171 and 174 codes.


EDIT: neglected to mention that amongst the repairs, I also cleaned the MAF sensor.

 

[EB4X]

Result: Misfires gone, P0171, P0174 and P0402 remain.
For the P0171 and P0174 it's probably your upper intake gasket....not incredibly uncommon for those to have issues especially with the age of our vehicles. They are a rubber composite gasket inserted into grooves of intake, as they are now dried out and hardened they'll appear to be PART of the upper intake, you will need a sharp hook took to gouge them and pull out of intake....like shown in pic... couple bucks at Harbor Freight. The kit will come with both gaskets....one for underneath your fuel rail...some ohv's have "cardboard" gasket on top and bottom of fuel rail as well as rubber inserted gasket. When removing fuel injector wire connections the common paint can opener tool is great for releasing clips so they don't break, (free at Home Depot or Lowes paint counter) .... tug up one side a bit then move to other side to pop all the way off.....little hook on tool is perfect. Might want to install new o-rings on fuel injectors while you're in there already.
Also might want to have new EGR tube rubber O-ring that goes into side of intake on hand, although original can often be reused... depends. Will want to have an E7 socket on hand for the intake studs

 

[delicreepp]

Result: Misfires gone, P0171, P0174 and P0402 remain.
For the P0171 and P0174 it's probably your upper intake gasket....not incredibly uncommon for those to have issues especially with the age of our vehicles. They are a rubber composite gasket inserted into grooves of intake, as they are now dried out and hardened they'll appear to be PART of the upper intake, you will need a sharp hook took to gouge them and pull out of intake....like shown in pic... couple bucks at Harbor Freight. The kit will come with both gaskets....one for underneath your fuel rail...some ohv's have "cardboard" gasket on top and bottom of fuel rail as well as rubber inserted gasket. When removing fuel injector wire connections the common paint can opener tool is great for releasing clips so they don't break, (free at Home Depot or Lowes paint counter) .... tug up one side a bit then move to other side to pop all the way off.....little hook on tool is perfect. Might want to install new o-rings on fuel injectors while you're in there already.
Also might want to have new EGR tube rubber O-ring that goes into side of intake on hand, although original can often be reused... depends. Will want to have an E7 socket on hand for the intake studs View attachment 453259View attachment 453260

The intake gaskets were certainly on my mind at the start of this process, but I believe those were replaced at a local shop during lockdown a few years ago--that's also the reason the PCV valve and hose look virtually brand-new. I've been meaning to double-check the repair receipt, but haven't come across it yet. I'm going through papers this weekend and am going to be on the lookout for it so that I can verify what work was actually done.

 

[410Fortune]

What is fuel pressure? Lean both banks usually a air leak in intake or a lack of fuel pressure to the injectors

 

[delicreepp]

Fuel pressure check was a wash. Try as I might, I could not get any readings. I'm assuming that the pins were not lining up in the pressure outlet and adapter. I removed, reattached and retightened everything several times.

So, I moved on to the intake gaskets. I've been thinking I hear a slight hiss when the engine idles, but have never felt 100% sure about it. Anyway, I got the upper intake off and saw this. That's some of the nice, fresh oil I filled the car with a month ago. I assume that this is not OK. I purchased a kit that came with valve cover gaskets, and I was able to confirm that the driver's side has a minute oil leak there (whicb expl;ains thr sticky crud that plagued me when I was installing fresh spark plugs). Looks like I'm doing everything: upper and lower intake gaskets, fuel injector o-rings and valve cover gaskets.

Should I replace the camshaft position sensor at the rear while I've got is exposed? I'm at 160k-ish miles.

 

[delicreepp]

As I suspected, the rubber upper gaskets are all still in good shape--probably having been replaced in 2020 or 21. The gasket underneath the fuel rail looks good, too. I won't get a good look at it until tomorrow, though, when I pull everything else off.

 

[410Fortune]

I would leave the cam synchro alone if it’s working fine and not making noise, the factory part is way better then anything aftermarket
You can remove the sensor (two 5.5mm) and drop two drops of oil in the housing this can help lube the upper bushing

I would still replace the intake o rings and gaskets with the new stuff, 3 years is old enough and you are in there now and have parts in hand.

 

[delicreepp]

I've pulled the intakes off with some expected hassles, though not too many. At the rear of the engine by the camshaft position sensor, I saw this. I'm pretty sure there should be no blockage normally. Both in the rear are clogged like this. I'm hoping the gunk is firm enough that I can cut around it to create a flap that I can peel out. I don't want this garbage falling down further into the engine.