94 Eddie; Carbon from exhaust; carbon fouled plugs...

[Tango51]

Hey Guys, need a little help here.
I'm in the Army and just recieved a new assignment. I have to clear my living quarters by Friday but the poor X doesn't want to go. Here's where I'm at right now:

1. 1994 Eddie Bauer 2wd 4.0L OHV 153K started running really rough like it was misfiring. I limped her home and noticed black soot in the driveway beneath the tailpipe.
2. Removed #4 spark plug as it's the easiest to get to and discovered it to be carbon fouled.
3. Removed #5 spark plug (again for ease of access) it also was carbon fouled.
4. Decided to change plugs ans wires.
Old Plugs: Autolite APP7 65
New Plugs: Motorcraft SP 486
Old Wires: Accel Red 8mm
New Wires: Duralast P/N 4144
5. Before changing plugs and wires, I tested for spark, compression and fuel pressure. Results:
Spark verified at all cylinders using Craftsman Inline Spark Plug Tester.
Compression Test: #1 - 170
#2 - 165
#3 - 160
#4 - 160
#5 - 180
#6 - 180
Test conducted with all plugs removed, coil and fuel disabled. Wet test not conducted.
Fuel pressure held steady at 38psi.
6. Replaced plugs and wires and started the engine. It hesitated a lot at at first and then felt like it was trying to even out. Then it just got progressively worse and worse. Again I have black carbon soot on the driveway under the tail pipe and carbon fouled spark plugs.

Could this be an injector problem? If one of them fouls, could it cause the computer to increase the "on-time" of the others creating a super rich condition?
Now she won't even start. I really need a mechanic buddy right now. I have to get this vehicle out of here and I know I can get this worked out, I just need a little help. Anybody willing?

Respectfully,
John H. Panowich
SFC, USA

 

[Turdle]

I bet the fuel pressure regulator has gone bad. Check for gas in the vacuum line to the regulator.

 

[Tango51]

Holy Quick Reply! Thank you Turdle...checking it out now.

 

[Tango51]

No fuel in the vacuum line. I disconnected the battery earlier to reset the computer so I reconnected it and fired her up. She started right up, ran good for all of about three seconds, then vacuum dropped and she went right back to acting crazy...

 

[Tango51]

This is a short article that I found while searching the internet:

Causes of Carbon Fouling:
Continuous low speed driving and/or short trips
(I do that but this situation occurred suddenly)
Spark plug heat range too cold
(I am using the manufacturer's recommended plug)
Air-fuel mixture too rich
(here is that question about the possible bad injector)
Reduced compression and oil usage due to worn piston rings / cylinder walls
(conducted test says compression is good)
Over-retarded ignition timing
(don't know how to go about approaching this)
Ignition system deterioration
(ignition system is all new)

Pre-delivery fouling:
Carbon fouling occurs when the spark plug firing end does not reach the self-cleaning temperature of approximately 450°C (842°F). Carbon deposits will begin to burn off from the insulator nose when the self-cleaning temperature is reached. When the heat range is too cold for the engine speed, the firing end temperature will stay below 450°C and carbon deposits will accumulate on the insulator nose. This is called carbon fouling. When enough carbon accumulates, the spark will travel the path of least resistance over the insulator nose to the metal shell instead of jumping across the gap. This usually results in a misfire and further fouling.
(this happened to an extreme)

If the selected spark plug heat range is too cold, the spark plug may begin to foul when the engine speed is low or when operating in cold conditions with rich air-fuel mixtures. In some cases, the insulator nose can usually be cleaned by operating the engine at higher speeds in order to reach the self-cleaning temperature. If the spark plug has completely fouled, and the engine will not operate correctly, the spark plug may need to be cleaned / replaced and the fouling cause identified.

Well, until I can get some more ideas, I'm going to try replacing the fuel injectors. I could probably fumble around with trying to figure out which one is bad, but since they are original, I will just replace them all. Looks like I will also be purchasing a timing light. Guess I need one anyway...

 

[Tango51]

How about the O2 sensor? Whether a bad injector is causing it to send a lean signal to the computer or the O2 sensor itself is bad, the computer would still interpret a lean condition and put more fuel into the cylinders right?
Maybe I should change the O2 sensor out first. It is also the original. Cheaper and less work...

 

[Tango51]

Turdle,
I got to thinking about your FPR suggestion and I agree that if the diaphragm was torn inside fuel would get into the manifold, but wouldn't the fuel pressure test have told me if fuel was leaking by?
The other thing (that I forgot to mention) is that when I did the initial testing I connected a vacuum pressure gauge to the main vacuum tree and my reading was kind of erratic at idle. The instructions that came with the gauge say:
"A pointer which sweeps erratically through several inches indicates a malfunction affecting all cylinders unequally and inconsistently. To isolate the troubled area, run the engine at about 2000 RPM. If the pointer steadies, check for:
1. Ignition and/or timing.
2. Carburetor mixture adjustment at idle.

Ok, it I did that and it leveled out at 2000RPM. After I changed the plugs and wires, it won't. Any ideas on that?

I don't have a carburetor, and I didn't think timing was even adjustable on these vehicles.

 

[Turdle]

You said earlier "the vacuum dropped" and then the idle stumbled.

The only thing I can think of with "switched" vacuum is the egr. If there was a leak in the egr vacuum circuit, it would affect all vacuum related components. If vacuum drops, fuel pressure rises.

Try to slow down a tad. Shotgunning this with a lot of parts is not the answer. Neither is questioning everything.


Also, since things have "changed" since you installed new plugs and wires, I would triple check the firing order. It is easy to get the driver side mixed up--

 

[Tango51]

Sorry, just a bit anxious because of the time I have to get this going.
You are right about throwing parts at it (especially with money that I might not have) but I've just been looking at it from the stand point of just about everything is original OEM circa 1994 so replacing them while I'm in there and if I can afford it may not be a bad idea.
I don't mean to question everything, I just understand that you have to build a big picture during diagnosis and every time I discover a new piece of information I have a tendency to second guess myself. PLEASE DO NOT think that I am second guessing you. You have been in this business way too long and I have the utmost respect for you. You've been around the forums for quite some time and I'm actually surprised that one of the "famous" guys would answer my post, so with that thank you very, very much for your time and attention.
Oh, and the firing order thing? I think quintuple checked because I don't trust myself. Haha!

 

[Turdle]

Whoa!
While I appreciate the compliment, rest assured I am no more an expert than you. All I have is experience and busted knuckles. Well, and a few engine swaps. In other words, All I know about explorers I learned here, or, by busting a part or 2 then asking folks here how to fix it.

 

[Tango51]

Haha! Well, you're quite welcome Brother. That's a lot more experience then I have. That's why I'm here.
My wife bought this truck for me in 2004 when I returned home from my 2nd tour in Iraq. It was a surprise and it means a lot to me that's why I won't get rid of it. I am the 3rd owner. It was our family car for a while but it started to show it's age with a lot of problems and she got to where she didn't trust it anymore so I bought her our first new car and I have been nursing my explorer along all this time with big dreams of turning it into something to be proud of. It wasn't until I found this site that I realized that could actually happen! I was amazed that there is a whole community of dudes out there with trucks just like mine...freaking awesome.
Now if I could just get the time and money at the same time I'd be good to go. Unfortunately in the military that never happens. I don't want to take my truck to some mechanic guy that I don't't know, pay a lot of money for stuff and then have no idea what actually got done. Built not bought right?
Well, sometimes I think my pride and sentimental feelings about my truck get in the way. Can't help it. I love it and want to learn how to take care of it myself.
Sorry! Thanks for listening to me rant!

Anyway, what if I were to try cranking it with all vacuum related components disconnected in order to take that out of the equation....?

 

[Turdle]

If the vacuum lines are disconnected there will be no vacuum. So, no this is not a good idea.

Back to the " vacuum went down then it stumbled" ---I wonder if we need to back way up a minute. The truck will have a "high idle" for a few moments until the engine warms up. Then the iac takes over to stabilize the idle. If the idle stumbles, vacuum will also crash. So, is it crashing idle speed, or, is the vacuum indeed crashing???
Could the IAC valve be dirty-sticking which will not allow it to raise and hold the idle speed? Does the internal plunger of the iac valve operate freely ( grip it with a small needle nose pliers and move it back and forth)



If this checks, the next thing I would try is to run the truck with the egr vacuum regulator disconnected. There is an electrical connection to a "top hat" looking device near the egr valve. Unplug it and run engine to see if the idle will stabilize and if vacuum holds steady. You will get a "check engine" light for non functioning egr but ignore it-what you want to know is if the vacuum issue happens when the egr valve is opened. Disconnecting the vacuum regulator might help isolate this function, and allow the idle to hold.

 

[Tango51]

Wow you are sharp. I think we may be in the ballpark.
IAC was gummed up inside but the piston moved great. I replaced the IAC and she started up perfect , engine vacuum at 20. Then, when it got to the point where you say the IAC takes over is where it started to get wonky again. Engine starts stumbling and vacuum starts to drop. Erratic needle slowly dropping, stumbling getting progressively worse.
Ended up with a violently erratic needle between 5 and 10 with smoking exhaust. I let it go for about two minutes thinking that it might just clear itself which it did to my surprise. It ran good for about three minutes then went back to stumbling and erratic low vacuum. Shut the engine off. Tried it again to see if it would repeat itself, which it did except this time it didn't level back out. Shut the engine off.
Disconnected the EGR Vacuum regulator. Engine fired up perfect, idle dropped after the IAC kicked in (is that right?) and it continued to idle! Yay! It ran good for at least five or six minutes and then went back to the same symptoms. Boo! Shut the engine off.
Bad EGR?

 

[Turdle]

Boy--seems like it is going rich when it goes into "closed loop"

I'm moving this to the 1st gen sub forum for more views and help.

 

[Tango51]

I found and article on oldfuelinjection.com that talks about testing the EVR. I guess that would let me know if that part is doing what it is supposed to, but I don't know enough bough the EGR system to understand how it could cause my problem(s).

 

[Tango51]

Closed loop...what does that mean? Using exhaust gas recirculation with minimal outside air?

Thank you Turdle...

 

[Turdle]

When the engine is first started, it runs under " open loop" engine control, meaning the ECM sends signals to keep the engine running under known tolerances.
For economy though, you need the sensors input to modify this "known logic"

Once the o2 sensors warm up, and, the coolant temp reaches 192 degrees, the ECM goes into "closed loop" control using sensor input and internal formulas to modify injector pulse, timing etc.

I was hoping for a vacuum leak in the evr, but I do not think this is the case. One of the sensors is reporting bad data, causing the ecm to dump fuel in, or, the ecm is faulty. The only way to be sure is to measure each sensor.
You might be correct when suspecting the 02 sensors-


There are 2 coolant temp sensors-one is for the gauge , the other is for the ecm. I point this out now because you might have to check it's resistance when cold, then when warmed. You want to check the correct one--

 

[Tango51]

Ahhh....closed loop electronically. So the ECM needs input from both of these sensors in order to go closed loop and do it's thing. ECM gets bad poop from the sensors, it tries to compensate. Cool, I think I got it.
I have to run and take care of some business but when I get back I will test the sensors and see whats up. I'll let you know...thanks again.

 

[Tango51]

Well, ECT sensor is a PITA. Can't get to it with my probes as it sits and looks like I have to replace engine coolant if I remove it.
Still haven't located my O2 sensor yet. Apparently I need a special wrench to remove it. Today is my day to learn how operate a multi-meter...

 

[Tango51]

Ok, I removed the throttle body in order to get to the ECT Sensor and drained some coolant so I could remove it. I connected my probes to the terminals according to the Chilton manual and ran it under cold water in the shop sink. It did just what it was supposed to. Temperature goes down, resistance goes up. Next I run it under hot water. Again, it does what it is supposed to. Temperature goes up, resistance goes down. ECT Sensor is good. I didn't have a thermometer to accurately gauge the water temperature but for this, it tells me enough. So, I go to put the thing back in (I don't have a box end or deep well socket that large so I'm using a crescent) and I break the POS!

http://www.flickr.com/photos/johnhpanowich/7304905036/in/set-72157624657112943

http://www.flickr.com/photos/johnhpanowich/7304904548/in/set-72157624657112943/

Like I said, all original OEM. It was dry rotted. Rock Auto has a Motorcraft replacement for $30 bucks but because of my situation I don't have the time to order it. Looks like it's going to be Duracraft. Although I haven't heard anything good about Duracraft electrical parts.

On a side note, I also noticed all this oil or fuel in my intake plenum. Probably not good.

http://www.flickr.com/photos/johnhpanowich/7304958500/in/set-72157624657112943/
(image is rotated about 45 degrees clockwise)

I'm going to get some chow and a beer, hit the "Zone" for a new ECT Sensor and then test my O2 Sensors. The book says to back probe at the sensor. Is testing at the ECM easier?

More to follow....