1996 Explorer Coolant Gauge Fluctuating and PO171 and PO174!

[dblock217]

First, my Explorer is a 1996 4.0L XLT 4x4 with 106,000 miles. The only modification I know of is the cone type K&N Air Filter added. A couple of weeks ago I noticed that the Coolant Temperature Gauge on the dash would fluctuate from a 1/4 to 1/2 and back and forth throughout driving. It has never did this before, always stayed right inbetween the 1/4 and 1/2. A week after I noticed this, the check engline light came on and codes PO171 and PO174 popped up. I have already drained and flushed the radiator, replaced thermostat, and coolant temp. sensor. Also cleaned the MAF sensor and throttle body. I do not think it is the head or head gasket, no white smoke or sweet smelling steam out of the exhaust, and the old antifreeze had no oil in it, and the oil has no antifreeze in it. Still fluctuates and still getting the codes. Any help would be greatly appreciated???

 

[brianjwilson]

I'll look around, but I believe those are "bank 1 too lean" and "bank 2 too lean" if memory serves me correctly. Is the truck running a little rough when it's cold?
The most common cause of those codes is bad upper intake manifold gaskets. Check for any vacuum leaks or any leaks in the intake, but it is most likely the intake manifold gaskets. There is a good write up here somewhere, I did this repair on my 97 for the same codes.
It was the little rubber gaskets on the intake with mine. Appearantly when the truck warmed up, the rubber expanded and sealed up, ran fine. But air got past them when it was cold and it ran like crap.
I think the coolant gauge is another problem. Use some other tool to monitor the coolant temp and see if there is really a big fluctuation or something else.

Here is the write up I used for the intake manifold gaskets...
http://www.explorerforum.com/forums/showthread.php?t=171819

 

[dblock217]

Thanks

Thanks Brian. I used an oiled K&N air filter and I guess I did not clean the MAF sensor right, didn't have the tamper proof torx bits. Gonna pick those up tomorrow and try again. Will post on here and let everyone know if that was the fix, if not, then will vacuum test and probably replace those gaskets. Looks simple enough with the thread/walkthrough you provided. Will also post the fix for the fluctuating coolant gauge when I figure that out also. Thanks again! This site is VERY VERY VERY helpful!!

 

[burtonbrd138]

i had the same thing. Replaced intake gaskets and cleaned the MAF sensor (4 times!). Found out that i did have a blown head gasket. It was not a fast lose but it made my truck misfire like crazy. I am just getting rid of mine becuase i really do not want to deal with it. I hope your problem is not that.

 

[Cobraguy]

Turn your heater on to full hot. Check the air temp at the heater outlet. Does it tend to change temp with the temp gauge? That's not a conclusive test by any means...but if it does, it indicates something is definitely changing temps rather than a gauge malfunction. Best test is to install a manual gauge and see what it does.

 

[brianjwilson]

Sticking a probe thermometer in between the radiator fins while it's idling might even do the trick.

 

[briwayjones]

Has the spark plugs and wires ever been changed on it or does it still have factory? If they haven't been changed change them. They can cause those codes.

 

[dblock217]

Spark Plugs and Wires were changed a year and a half ago, still look good!

 

[toypaseo]

Burp your cooling system...?

 

[dblock217]

Burped the cooling system, and found a note in the owners manual that say "Particularly on the 4.0L OHV" coolant loss from 3-7 ounces I think is normal for up to 7,500 miles after flushing the system due to air being trapped. So I guess this problem will eventually fix itself and I notice it is getting better as time goes on.

Another note about my PO174 and PO171 CEL Codes. I noticed that when I have these codes cleared when they finally do return I am always stopped at a light or something and idling. Would this point the direction maybe towards my IAC?

Love this site, on it for 2-3 hours almost everynight!!!

 

[brianjwilson]

Burped the cooling system, and found a note in the owners manual that say "Particularly on the 4.0L OHV" coolant loss from 3-7 ounces I think is normal for up to 7,500 miles after flushing the system due to air being trapped. So I guess this problem will eventually fix itself and I notice it is getting better as time goes on.

Another note about my PO174 and PO171 CEL Codes. I noticed that when I have these codes cleared when they finally do return I am always stopped at a light or something and idling. Would this point the direction maybe towards my IAC?

Love this site, on it for 2-3 hours almost everynight!!!

I suppose if there was a big leak where the IAC valve bolts in it could cause the codes. But I don't think the IAC valve itself would cause those, never seen it anyway. I still think there is a leak in the intake system somewhere. . .
I think there is some trick to spraying something around the intake/vacuum to see if there is a leak, but I have no idea what it is. Lots of help, huh?

 

[dblock217]

Brian I believe you spray carb cleaner around the intake/hose/anywhere you suspect leaks and when you hear a change in the idle you have spotted the leak. Will go out there this weekend with the bottle of my carb cleaner and see what I find. Will post again when I find the source.

 

[adambodkins]

ok for your post on the temp guage fluctuating I had the same problem not even a week ago from the day I bought my ex. I replaced everything on mine and still had the same problem except mine would actually go to hot and then rapidly drop down. I cleaned out my heater core do to low heat coming out of and I guess it burped the system. But I thought I would give you my experience. When I did mine some sludge build up came out of the heater core and been doing great ever since. So I would check to see if you didn't have a blockage somewhere.

 

[killswitchfan134]

i've seen people take a propane tank with a hose on the end of it and aim it at spots where they thought it was a leak and if it smoothed out the idle u have a leak

 

[muhl5443]

the codes you have are for a vacuum leak. i would be willing to bet that it is ur intake plenum gaskets.

 

[briwayjones]

i would be willing to bet that it is ur intake plenum gaskets.

That was a problem I just had fixed on mine.

 

[Cobraguy]

Remember...he's got an OHV engine and not the SOHC motor which has the majority of the intake problems. But you are correct...they could still be leaking.