New thread, and it's a doozy, LOL... throwing 5 CEL codes

[Ck111484]

So as I mentioned in my other thread, I picked up an '02 Explorer with the 4.0 SOHC V6. It had a loud ticking noise coming from the front driver's side, which the owner convinced me (and I convinced myself) that it was a bad tensioner. Otherwise it seemed to run decent, down on power and hesitant, but I figured it was all due to the tensioner.

So I removed the intake manifold and both valve covers (both were leaking), replaced the tensioner, put new gaskets on the valve covers and manifold, and put everything back together. Unfortunately, I cracked the corner of the passenger side valve cover, so I will have to take everything apart again and replace it. But now that I've done it once, I bet I can do it in 1/4 of the time.

However, after everything was put back together, the car wouldn't run. It would start, idle hunt for a while, and eventually the RPM's would drop so low that it would stall. Eventually, it just wouldn't fire at all, as if it was flooded.
For whatever reason, I was determined to get it running before tearing it down again. So I changed the spark plugs and replaced the MAF, since the car actually ran better without the MAF plugged in. No dice.

Until today, when reading on the forums, that you have to do a PCM reset; so I did, and it fired right up! Still ticking as loud as ever unfortunately, and it began to idle hunt a bit, but I was able to get it relatively stable by using the stop screw on the throttle body. Tested the TPS; checked out fine.
Then I actually took it for a spin around the block; no overheating, no stalling, but still running very poorly and ticking loudly (sounds like a diesel). Definitely not very responsive, low on power, etc.

So I pulled the codes, and got FIVE:

- P0112, intake air temperature sensor 1 circuit low
- P1000, obd systems readiness test not complete
- P1112, intake air temperature circuit intermittent
- P1131, lack of H02S11 switches sensor indicates lean P21951
- P1151, lack of H02S11 switches sensor indicates lean (see P2197)

So, where do I start? LOL.
Seems like cleaning the IAC would be a good place to start since there seem to be several intake temperature issues; but I don't even know where to begin on anything else. Why is it running so poorly? And why would it still be ticking so loudly?

What would you recommend my course of action be (other than buying a new car?)?
Any suggestions are appreciated,
Thanks!

P.S. I'll post pictures of the car once I clean it up, and hopefully make you understand why I'm trying to get it running smoothly; it needs a lot of little things but it's in quite nice shape.

 

[jmdirk]

Ignore P1000 for now. That's only showing up becasue there are other emissions related codes.

You're correct to start with the IAT sensor. Upstream problems can cause codes further down the line. For example if sensors in the intake stream are causing the engine to run poorly, it can cause sensors in the exhaust stream to throw codes.

I'd start with the IAT circuit intermittent code. Might not be that it's faulty, but just a poor connection. Make sure it's seated properly, check the contacts make sure it's not corroded or damaged.

The diagnostic guides for that code in particular suggest one of:
- faulty sensor
- faulty connector
- open circuit or ground in harness
- faulty PCM

The ticking could be a faulty lifter or something along that line

 

[Ck111484]

Cleaned the IAT today, and the engine was having trouble starting/running.
Disconnected the MAF and it runs much better...

I am at a complete loss.

 

[jmdirk]

Your codes are indicating it's getting an intermittent signal from the IAT. It's either the IAT itself or the wiring/connector.

Does your MAF use all 6 pins? If it does your IAT is integrated as part of the MAF and whatever you think is the IAT sensor, is not the IAT

If you have only 4 wires, then it is separate and I would start by replacing that

The wiring diagrams that I have show a 6 wire MAF with integrated IAT, so I'm not sure what you're cleaning.

FYI, this is the wiring diagram I have for an '02 w/ 4.0 SOHC showing the MAF/IAT lines

I believe you can measure the resistance across the Grey and Tan/Light Blue wires to check the IAT portion itself. I don't have a table of values for an '02 but an older one from a 1993 with a separate IAT is below. Maybe they're the same...I'm not sure. Find your ambient temperature on the table, measure the resistance across the sensor and it should match (relatively closely) what's on the table

 

[Ck111484]

Hmm, you're right, I have a 6 wire MAF... I cleaned whatever the silver thing that looks like an IAT that sits on top of the throttle body.

To be honest I'm much more concerned about the tapping than anything else... I'm sure the idle and running crappy is a leak or a connection or something and just requires troubleshooting and a little money in parts, something I'm able and willing to deal with.
The tapping could mean engine removal, tear-down and lots of money, something I'm not prepared to do.
I originally intended to pick up this car, fix the tapping, clean it up and re-sell it, but if it's going to be an expensive fix, I may as well just part it out or something.

I was planning on taking off the serpentine belt and running the motor for ~30 seconds to see if its still tapping. Then I would at least know whether or not its the motor.

 

[jmdirk]

If you have a mechanics stethoscope that can help you locate the noise.

I'm not overly familiar with the SOHC layout. Bu tI think running without the serpentine is a decent troubleshooting step. Could even be a leak in the exhaust manifold - that can sound like a ticking noise as well. Worst case would be excessive valve lash caused by a worn out lifter. Which would be a lot easier to deal with on a SOHC than an OHV

 

[Ck111484]

If you have a mechanics stethoscope that can help you locate the noise.

I'm not overly familiar with the SOHC layout. Bu tI think running without the serpentine is a decent troubleshooting step. Could even be a leak in the exhaust manifold - that can sound like a ticking noise as well. Worst case would be excessive valve lash caused by a worn out lifter. Which would be a lot easier to deal with on a SOHC than an OHV

I guess that's what I'm trying to figure out/asking... is this clacking noise likely something a novice mechanic like myself could handle, or something more major that would require engine removal/timing/etc.

I know it's impossible to answer that question with any certainty, but it basically determines the course of action I take.

 

[Turdle]

thread moved to stock 3rd gen sub forum for more views.