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 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....

 

[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.