04 Explorer RPMs climb EXTREMELY SLOW

[yamahor]

From Park or Neutral I can put the pedal to the floor for a whole 3 seconds, and the RPMs will slowly climb to about 3000-3500.
They should jump, or shoot up....especially when its in park and there is ZERO load on the motor. but they climb as if i was trying to pull 50 thousand lbs starting in 5th gear.
but while in drive the engine revs normal with power.

odb thing found no codes..

AIR filter brand new...

The engine does have a pretty good shake at an idle, in gear and in park.


I have had it looked over for a misfire, but nothing.
So I'm going to replace plugs an wires.

|2004 Ford Explorer EddieBauer 4.0L V6

 

[yamahor]

Is everyone drawing a blank? lol

 

[QueenCitySleeper]

Excessive back pressure will cause poor acceleration. How is gas mileage? badly clogged catalytic converters? when the engine is hot do the converters glow red? if you have a laser thermometer they should be around 750 deg F at operating temp.

 

[yamahor]

the exhaust must be replaced and thats something that will happen down the road.... but gas mileage is crap as of right now.

Is there anyway to diagnose the cats as the problem?

 

[yamahor]

and is the resonator part of the cat in any case?? cause I couldnt see any in under my truck?

 

[QueenCitySleeper]

Resonator is basically a muffler before the main muffler and should be fine. Catalytic converters are always close to exhaust manifolds because they need high heat to function properly. Im not familiar with the SOHC exhaust but you probably have a cat in each bank of the y-pipe. They are probably barely visible and tucked along side the bellhousing. Has your truck ever had a problem running rich? That will cause converter failure. Do you have a tune on it that has turned off your rear O2 sensor? There really are not any ways to check for a bad converter in your case. The job of the rear O2 sensor is too check cat function and send CEL if a cat is bad.

what you are describing (bad mileage, poor acceleration) are symptoms of catalytic converter failure.

How many miles on the engine? Do you have any engine mods? You said exhaust will soon be replaced so I assume everything is original.

Maybe someone with a SOHC can give some insight....

 

[yamahor]

yes its all original. i purchased used with 125xxx khms on it..

But when i had my friend look for any codes nothing was coming up.
wouldnt the o2 sensors send a code if the cats weren't burning?

 

[yamahor]

maybe if i put in a 460 I wont have this poor acceleration problem anymore..lol
jk.

I have a feeling its going to be a clogged cat or a collapsed muffler, cause the muffler on it is rotted, but has yet to leak.

 

[yamahor]

my cats are operating at 500F

 

[QueenCitySleeper]

ok so cats are not too hot. Normal cat function is around 500-750. Rotted muffler would definitely cause excessive backpressure. Does it sound and feel solid or hollow when you hit it? If it sounds like a bucket full of water that may be your problem.

 

[michaelkill4]

I had the same problem, it was a bad o2 sensor

 

[swshawaii]

Air filter brand new. Has the fuel filter ever been replaced?

http://www.explorerforum.com/forums/showthread.php?t=223475&highlight=slow+acceleration&page=2

 

[yamahor]

The muffler is a good start cause theres holes in it and exhaust is coming right out of that.

I pulled the o2 sensors.. they were ashy white/brown...

I ran it with the o2's out. but still plugged in and no difference, So im assuming if the o2 sensors out of the pipe make no difference maybe its them.

and the muffler creates no sounds other then the holes in it.

 

[yamahor]

I had the same problem, it was a bad o2 sensor

Which o2 sensor was it? cause there is 3 of them on mine.

 

[yamahor]

And Theres no cel on while the vehicle is running... With the key in "on" position the light is on.... but never when running..there is no stores codes, nothing. could it still be the o2?

 

[QueenCitySleeper]

hmmm. With the O2's removed you got no CEL? With no O2s, a missing O2 signal code should pop up within 20 min of operation or whenever the O2s become hot enough to read.

Running like crap in open loop is another strike against the muffler. Unless there is some other kind of computer or sensor malfunction.

Was it parked in grass or something? That will cause severe undercarriage corrosion.

Regardless it sounds like your muffler is shot. Id start there.

 

[michaelkill4]

Which o2 sensor was it? cause there is 3 of them on mine.

Sorry for late response, been at work. It was the right bank o2 sensor. One of my cylinders was showing it was running Rich but it was Just a bad o2 sensor

 

[yamahor]

hmmm. With the O2's removed you got no CEL? With no O2s, a missing O2 signal code should pop up within 20 min of operation or whenever the O2s become hot enough to read.

Running like crap in open loop is another strike against the muffler. Unless there is some other kind of computer or sensor malfunction.

Was it parked in grass or something? That will cause severe undercarriage corrosion.

Regardless it sounds like your muffler is shot. Id start there.

A new muffler will be put on monday next week.

Untill then I will get a new o2 sensor and eliminate the bad one if there is one..
But no the under side is clean, minimal rust, no rot.. the whole truck is in very very good condition for its age..it was well taken care of.

 

[Joscibo]

My 04 with a new used Mustang engine with 52k does the same. In park there is no rev up to it! I recently took out on highway for the first time traveling an hour and had rpm surge when climbing a good size hill. This vehicle sat all winter in a snow bank and gravel lot waiting for a new engine. Not sure if the surge has anything to with the slow rev up in park?

 

[yamahor]

My 04 with a new used Mustang engine with 52k does the same. In park there is no rev up to it! I recently took out on highway for the first time traveling an hour and had rpm surge when climbing a good size hill. This vehicle sat all winter in a snow bank and gravel lot waiting for a new engine. Not sure if the surge has anything to with the slow rev up in park?

have you since figured out the problem?