White spark plugs with DTC 101 + 104

[StuckInMudLots]

Ok, I know theres a lot of posts about these DTCs out there, but none of them mentioned white spark plugs. I've got a '00 Explorer, 4.0 V6 OHV, 100k miles, and I'm being haunted by these P0171 and P0174 codes. So far, I've: Run 2 bottles of injector cleaner, changed the fuel filter, changed pcv valve, checked vacuum lines coming from/ going to all sorts of things including the brake booster and egr valve, sprayed the MAF with electronic parts cleaner. The other day I went to go change the plugs and all 6 of them had a white color near the tips... from what I recall this means that the mixture is too lean and the plugs are getting too hot. The 101 +104 means that the maximum rich limit has been hit but the car is still running too lean. I'm wondering if these symptoms rule out an intake manifold leak? I've got a smoke machine that we use for haloween... should I use it to test for a vacuum leak?
The only thing I can think of is a faulty fuel regulator or pump. I went and bought a fuel pressure gauge but it sounds like there may be 2 places to hook it up: one place pre regulator and one post? Can anyone tell me how to check the pressure and what it's supposed to be on this vehicle? Anything else I'm missing?

THANKS!

 

[Runnin'OnEmpty]

Welcome StuckInMud.

Here's a good thread of Glacier's about checking fuel pressure.
http://www.explorerforum.com/forums/showthread.php?t=142801&highlight=FPR

Your problem sure sounds like leaking intake gaskets to me. Try snugging up the intake bolts to start with, and see if that has any affect.....

Good luck,
ROE

 

[StuckInMudLots]

Ok, well I haven't gotten around to testing the fuel pressure yet. However, on a trip to AAMCO to have the transmission fluid flushed I broke down and paid them to do a pin point diagnostic. They said the "02 sensor after the cat is bad". Fine, so I replaced it. Now a couple of weeks later the P0174 code triggered the MIL BUT the P0171 isn't even pending... I guess that's progress. I took it back and they wanted another $170 to figure out what was bad... I have yet to give in and pay. While the engine was already warm, I took a propane torch and leaked propane in around the intake manifold while watching the short term fuel trim.. no dramatic changes (although it was breezy outside and this could have made this test not work). As far as the 02 sensors go, the one after the cat is brand new and the ones in the left and right pretty much mirror each other and stay between 0 and 1 Volts; there seems to be a 4th device that shows a 1.25 V reading consistently. I'm also now doubting that this is a fuel delivery problem because I would think that if the rail wasn't at a certain pressure then I'd be getting both the 171 and 174 codes simultaneously.There's no extremely rough idle, acceleration is normal. The only 1 thing that's weird is that I went to the mountains and at about 8,000 ft, going up hill, >3k RPM I occasionally get something that feels like the engine is missing... but normal day to day freeway driving is normal. Grrrr... Any Ideas?

 

[rookieshooter]

I have no idea about if your engine meters gas flow at different alltitudes. But at 8000 feet there is less atmospheric press. hence less air rushing in when the piston is creating a negative press. during the down stroke in the clyinder. This would cause a rich mix
When I used to go frome the east coast to CO. with my Toyato land cruiser I would allways change jets in the carb to a smaller orifice. The toy was towed and only used at high elev during a hunting trips.

I like my plugs to look more white. It's only when they show white and some yellowing spots that I get concren. Also if you get blistering or the gap increases more then normal then there is a problem. One other thing if the plug is fouled or the gap is to large it can take up to 100% more voltage to get the same performance of a plug that's in good condition. A good running plug should show some white.

 

[exploded99]

Since you can scan real time, there are a couple of things that may give you some direction.

Vacuum leaks are worst when you have high engine vacuum - idle and deceleration. Also, the engine gets very little air thru the throttle body at idle - so vacuum leaks are a higher percentage of the total air entering the engine at idle. So thats usually when the p0171 and p0174 gets set. As you rev the engine, more air comes in thru the throttle body and manifold vacuum drops, so the vacuum leak becomes a smaller and smaller percentage of total air sucked into the engine. That means the LTFT and STFT don't have to be adjusted very much at higher engine loads - the vacuum leak isn't significant enough to the total air coming in to cause an adjustment.

So, check your LTFT and STFT on both banks at idle - are they about the same, near or at limit rich? If the bank with the new O2 sensor is near normal, that is a clue that the O2 sensor fixed the issue.

Next, take the car up a long hill, monitor LTFT and STFT at higher rpms (open throttle) on both banks - do they drop to normal at higher rpm's or stay high near limit rich? If they drop drop to near normal, then suspect a vacuum leak - for the reason explained above. If they stay high, check fuel pressure to eliminate that as an issue, and if thats ok then check the O2's carefully - mechanical issues tend to cause high LTFT and STFT at all rpm's, not just at idle.

Also, I seem to remember that the intake air tube on the 00 V6's was a problem - not positive, but you might check it carefully. They had a problem with cracks.

And heck, you can find the other three O2 sensors on the internet for $170 if you shop a little.