Unsolvable Explorer Rough Idle. Any OBD II experts?

[Autolabs]

TPS volts at idle 1.04. Are you able to see a PID showing either c/t or p/t? I would like to see c/t TPS volts to be a little lower. Can you adjust your TPS? You also said when you 1st replaced your IAC that it stopped stalling. So is it possible you have a failed oem and an under performing aftermarket one that your testing with?

 

[Cashcrazy]

Anything is possible but there was no noticeable difference between the two. Maybe I should just unplug it to see what happens. What is the c/t and p/t PID and I will look? I unplugged the alternator and AC compressor with no change. I'll check out the tos tomorrow.

 

[Autolabs]

C/t and p/t stands for closed and part throttle. The pcm gets its c/t voltage at start up assuming you aren't pressing the gas.

One more thing, due to the low mileage and age, I suggest you call around for a professional motor vac or top engine cleaner. A bit pricey but well worth it. Much better than anything you could poor in the tank. Fuel additives are more of a 'keep it clean' rather than a good carbon scrub.

 

[2000StreetRod]

After the 1st Generation Explorer there is no longer a need to adjust the TPS closed throttle voltage. There is a routine in the PCM that measures the TPS voltage when the ignition is switched on and assumes that voltage is for a closed throttle. It uses that voltage as the reference but periodically checks for a lower voltage. If one occurs then the PCM makes that the new closed throttle reference voltage.

 

[Cashcrazy]

I've thought about running some marvel mystery oil with the oil for a couple hundred miles. I have had that cure lifter tick in some prior dirty old engines

 

[Cashcrazy]

I'm showing that I have a "Fuel Pressure Regulator" that is Dorman part number 911260. Is this located somewhere that is accessible without dropping the tank and could this cause the rich condition?

 

[2000StreetRod]

The fuel pressure regulator is in the fuel tank and your fuel pressure is normal.

 

[Autolabs]

If you don't want the motor vac, at least 'smoke it' with sea foam a couple of times. Google it and see if your up to it. Note that motor vac can also clean up convertors for inefficiency issues as well.
As far as your tps voltage, does your closed throttle voltage stay constant after opening the throttle and closing it a few times?

 

[Cashcrazy]

The tps sensor always returned back to the same voltage when I tested it awhile back. I will have to google the motor vac and try to find somewhere that has the equipment. I like the idea of clearing out carbon and clearing the converters.

 

[2000StreetRod]

Be careful using Sea Foam if you plan to add it thru the vacuum system. If fed very rapidly it can pool in the combustion chambers and lock the engine from rotating. Also, some members have to replace their spark plugs after an intake manifold Sea Foam treatment because the loosened deposits foul the spark plugs.

 

[Cashcrazy]

I just tested the EGR valve with a vacuum pump and it passes the test. Would I have a rich condition and rough idle If the valve is functioning but something is keeping it just barely open at idle?

 

[MostlyNewExplorer]

Do you have any custom exhaust fittings on it that might create back pressure?

 

[Cashcrazy]

The explorer is 100% stock

 

[MostlyNewExplorer]

I would drop the oil pan next time I change the oil, to eliminate that from the check list.

 

[Cashcrazy]

I really hate dropping oil pans.....

 

[2000StreetRod]

I just tested the EGR valve with a vacuum pump and it passes the test. Would I have a rich condition and rough idle If the valve is functioning but something is keeping it just barely open at idle?

The EGR valve should be completely closed at idle. If it isn't then the idle would be rough. However, I thought you posted earlier that you disconnected the EVR electrical connector and there was no change in the EGR flow as indicated by the DPFE voltage. It is possible that the valve could be mechanically stuck slightly open. Did you try blowing thru it when you had it removed? I suspect that EGR would result in a lean condition instead of rich since the O2 in the exhaust gas is depleted due to combustion.

 

[MostlyNewExplorer]

I really hate dropping oil pans.....

It's not that bad. Drain the oil, which you'll be doing anyway, let it drain for about an hour so there's not as much drippage.

Then pull the pan and check for pieces of nylon guides or anything else that shouldn't be there. Clean up the pan and the mating surfaces put on a new gasket and snug the bolts, torque according 2 the manual.

 

[Cashcrazy]

I did disconnect the egr solenoid and had no change. I also have no change when I just pull the vacuum line off the EGR at idle. I didn't try to blow through it when it was off. I may pull the EGR off this weekend for further inspection. Other than the MAF it's the only thing before the manifold that could cause a change in both banks. I'll check the vacuum with a gauge this evening.

I start mentally preparing myself to pull the oil pan.

 

[MostlyNewExplorer]

I start mentally preparing myself to pull the oil pan.

LMAO, I can't believe you're dreading the oil pan after all the other stuff you've already changed out.

I just changed out the transmission on my 4x4 explorer, twice in 2 weeks. Oil pan is a walk in the park. I also changed the oil pan gasket, the rear pinion seal, and the Left rear parking brake cable while I was at it. Oh and the rear differential cover.

 

[plasticseng]

CashCrazy, Pulling the pan is not what you think if you are used to working on old school stuff like I was. There is an upper and lower pan, and you should be able to see what you need by pulling just the lower. The lower pan looks like an automatic transmission pan, so you don't have any end seals to deal with, no 4 pc. gaskets or any of that. It really is a 10 minute job to remove, 10 minutes to clean up, and 15 minutes to replace.