2003 4.0L Rich & High idle...

[olsem101]

My 2003 explorer 4.0L has this odd idle condition where it runs too fast and really rich according to the computer. I have tried everything from a new IAC, TPS, MAF. Hell i even took it into my ford dealer but all they did was clean an already clean MAF and charged 180 bucks to do so. They also checked for the latest software for the computer but it already had it. While idling it will sit around 750 but it will speed up, all by itself, to about 1000 and sink down to about 800 again. Fuel trims while at the 750-850 idle that it has are around -17% long term bank 1 and -13% long term bank 2. There are no DTC's. I checked the fuel pressure dampner, thinking that leaked and it didnt seem too. Im just lost here and dont know what else to check. I have considered possibly a computer problem and not throwing a code. But replacing the PCM would be a simple process however the PATS system is a bit more complicated on the newer vehicles to get the keys to work. Any ideas or suggestions would be really helpful!!

 

[olsem101]

Help anybody!!

Nobody on here has any ideas???

 

[SyberTiger]

Did you ever get this problem resolved? If so, what did you do?

 

[olsem101]

nope.

 

[georgeumo]

I hav had the same problem, probably worse. Mine goes up 1200rpm and happens moslty after i run the ac and in traffic for any length of time.
I have changed almost all related items.....new and short of replacong the PCM, The problem remains same. Any ideas would be very helpful.

 

[Fix4Dirt]

I hav had the same problem, probably worse. Mine goes up 1200rpm and happens moslty after i run the ac and in traffic for any length of time.
I have changed almost all related items.....new and short of replacong the PCM, The problem remains same. Any ideas would be very helpful.

mine iirc did that with a vacuum leak. i forget if it made it richer or leaner though.

 

[georgeumo]

mine iirc did that with a vacuum leak. i forget if it made it richer or leaner though.

mine has been very rich and i get get a lot fuel loss daily. If i may ask, where did you find the vac leak?

 

[Fix4Dirt]

mine has been very rich and i get get a lot fuel loss daily. If i may ask, where did you find the vac leak?

ive got a 2nd gen, and mine was leaking at the Y piece for the IAC tube. iirc that was done away with for later 2nd gens though. my other leak was from the intake plenum gaskets. i wonder if its your FPR. whats pressure like?

 

[georgeumo]

I have a new plenum gasket and I will replace this, this week and see the difference. I will revert. Thanks.

 

[SyberTiger]

My best guess is that it's a vacuum leak somewhere. Could be a rubber vacuum line that is cracked or could be the gasket around the intake manifold. These things can be hard to find/diagnose when the leak only increases as the engine components heat up. In other words, the leak increases wherever it's leaking due to expansion at the point of the leak. As the leaking component (hose or rubber gasket) warms and the leak increases the computer tries to keep the air/fuel ration in "equilibrium" meaning the computer will increase the amount of fuel as the air increases (due to your leak). When you mash the gas peddle, the computer doesn't simply throw more fuel into the combustion chamber because you mashed the peddle. Rather, when you mash the peddle you increase the amount of air to the system then the computer sees more air then adds more fuel to maintain that equilibrium. The computer program knows what the ratio of fuel to air is supposed to be at any given temperature. I believe this is what you are seeing.

 

[SyberTiger]

If you have a plastic intake manifold (plenum) then it's highly possible it has warped so changing out just the gasket might not do the trick. Best to replace the plastic intake manifold. Those things often are only good for 80K - 120K miles plus or minus YMMV.

 

[donalds]

I would look at the coolant temperature sensor because it's running rich