96 explorer 4.0 rough idle on every start

[96V8Xploder]

Wow, you got a good one to find. After replacing all that stuff I would think you would have found it.

Well, have you ever done the sea foam cleaner yet. This product sometimes helps issues like this. And its only $8. It may be worth a shot to try. Thats my suggestion. Besides you might have a fouled spark plug, but you already replaced them.

One last suggestion is to unplug the battery for a little to reset the computer.

 

[mudbug0426]

96V8Xploder, yes i have tried seafoam, its been a while back though.

after going to autozone for the 1,000th time i actually found someone there who knows what they are talking about. so he came out and overlooked everything i did. i started it up and i pointed out the noise it was making. after after talking through everything ive done so far he was stumped just like i am.

so let me put this up to date for everyone,


the motor idles like crap on every start up 'hot and cold' for roughly 20 seconds. during that 20 seconds you can hear a leak 'air being sucked in from somewhere' after 20, the motor smoothes out and you cant hear the leak anymore..

my exhaust isnt very quiet, so one thing the guy at autozone did point out was, if you give the motor gas while its idling rough within that 20 second time frame, the exhaust will pop, which he said that usually means the motor is sucking too much air and not enough fuel. or in other words air is being sucked in from somewhere its not suppose to.. after it smoothes out, if you rev it the motor the exhaust wont pop and it sounds normal.

i have replaced the vacuum lines, pcv valve, all rubber lines and hoses i could find have been checked, and if were bad have been replaced.

some have mentioned on this forum that if the egr tube 'that sticks up inside the upper intake housing' has a crack or a hole in it, would cause a bad idle. but that doesnt explain the leak i hear


some have mentioned testing the temp sensor, if it is bad the computer may thing the motor is cold when its not, therefor would cause it to idle rough.. well i bought both new sensors tonight, left and right side of the thermostat housing and i will install them shortly. i dont think that would be the problem either.. no connection to the leaking sound that i can think of.



im stumped

 

[96V8Xploder]

You got an air leak still. Im thinking it must be some kind of vacuum solenoid or valve. I dont think the intake is leaking because that wouldn't go away.

There are two things it might be.

1. EGR vacuum solenoid
or
2. canister purge solenoid

Also check the coonections to the brake booster.

 

[mudbug0426]

well i know where the egr vacuum solenoid is, but i dont know where the canister purge solenoid is.

is there any way i can test either one of those to see if they are bad or leaking before i replace them?

the connections on the brake booster look good.

 

[96V8Xploder]

To be honest with you the purge soleoid is a part I have never delt with yet. It would be rare for that to go out, And I personaly wouldnt no if that could cause your bad idle. There really is not any info around for that part. I would just do some testing by ear. Try to see were the leaks coming from. Have someone keep starting it for you tell you find or see something leaking.

 

[mudbug0426]

well what im hearing i cant really say its coming from one small area, to be honest it really sounds like its coming from the intake manifold, but like you said if that was leaking it would leak all the time, unlike what im hearing. ill play around with the solenoid and see what i can find

 

[96eb96]

wow 96eb96 thank you thats alot of info, buts try one thing at a time

im going to leave replacing the lower intake gaskets at a last resort if i can.

which intake tube are you talking about? i will check and replace the pcv palve tonight. the grommet and hoses looked ok.

when i replaced my upper intake gaskets, the egr tube was pretty nasty so i tried to clean it the best i could, but did not notice and holes or cracks.. but then again i was not looking for any.

which air sensor are you talking about?

and my temp gauge is no where near accurate, the needle always goes up and down and has done this for sometime now.. i know there are 2 sensors there, one the computer reads i guess and then the temp sensor? i have replaced the temp sensor about a year ago but did not replace the one on the left side, im guessing thats the one the computer reads.. ill replace that tonight..

no i do not have a scan tool tight on money right now but one day i will get one.

my maf sensor was a reman from autozone

Ok, lets go slow. I just want to eliminate everything before you tear into the engine. The air tube is the black flexible tube between the throttle body and the MAF. A hole in there could let air in. Unlikely but worth checking out.

There is a sensor that goes in that tube, it measures intake air. You can't miss it.

The ECT sensor is near the thermostat, it has 2 wires. There is also a coolant sender (one wire) that feeds the instrument gauge (that is causing your gauge to act up, but is unrelated to this issue).

There are cases where the ECT gives the computer erroneous data and the engine may run bad because it thinks its warm when cold or vice versa.

**I see you did some of that**

Reman MAFs could have issues, but honestly without a scan tool it is difficult to say. How does it run with the MAF disconnected?

I think an EGR solenoid would give an EGR code. You can disconnect the EGR vac line and plug the line to eliminate that part before you throw more parts. You don't really need the EGR right now.

Another thing is to spray carb cleaner or unlit butane/propane around areas where you suspect a leak. See if the idle changes. JUST BE VERY CAREFUL.

The 20 second thing..like the other poster said could be the evap system. there is a canister and a purge valve and some lines that run to the back of the truck. It may close the solenoid a few seconds after startup. I wonder if you can plug the port to the evap system. I know its under the battery tray where that "test port" sticks up. Maybe disconnect the electrical connector and see what happens.

 

[96eb96]

Canister purge valve procedure:

Remove the battery tray; refer to Section 414-01 .
Disconnect the vapor management valve return tubes.
Disconnect the electrical connector from the vapor management valve.
Disconnect the evaporative emissions return tubes from the vapor management valve.

Disconnect the vapor management valve and bracket.
Remove the vapor management valve bracket bolt.

Remove the vapor management valve.
Disconnect the vacuum line from the fuel vapor management valve.
Remove the vapor management valve.

 

[mudbug0426]

ok now i know what your talking about when you said air tube there are no holes there, and i know what sensor thats in the tube, i cleaned it so i think thats ok.

unrelated to this issue, but as far as the ect sensor and coolant sender are concerned, tonight i replaced the one on the left side of the thermostat, the one that has a plug that plugs on top like a spark plug wire, and last year i replaced the sensor on the right side. still the gauge goes up and down, could be some air in the system causing the gauge to do so?

as far as the maf sensor, i have not unplugged it and see how it runs, ill do that tomorrow.

as far as the egr solenoid goes, your saying to unplug both vacuum lines and plug the ends up? what will that do?

ive tried spraying carb cleaner as close as i could to the lower intake manifold gaskets thinking that might be the problem, but number one i doubt thats what it is, it would be leaking all of the time, and number two, there is just too much crap on top of the motor for me to get the cleaner all the way down there.


now lets talk a little more about this canister and purge valve on the evap system? how does this system work and what does it do? the lines going to the back of the truck i assume run to the gas tank for something? you said plug the port to the evap system? what will that do? what does the test port look like? can you take a picture?

 

[96V8Xploder]

The 20 second thing..like the other poster said could be the evap system. there is a canister and a purge valve and some lines that run to the back of the truck. It may close the solenoid a few seconds after startup. I wonder if you can plug the port to the evap system. I know its under the battery tray where that "test port" sticks up. Maybe disconnect the electrical connector and see what happens.

I have a feeling it could be this, the canister purge valve. Never had a problem with one before but you never no.

Also 96eb96 do you think a misadjusted TPS could cause this. The computer might take that 20 seconds to adjust to the bad readings.

 

[mudbug0426]

wow i completely missed the Canister purge valve procedure you posted until i already put that last post up

 

[96eb96]

I have a feeling it could be this, the canister purge valve. Never had a problem with one before but you never no.

Also 96eb96 do you think a misadjusted TPS could cause this. The computer might take that 20 seconds to adjust to the bad readings.

I doubt a tps would cause this, but you can check it with an ohm meter very easily.

As for the temp gauge moving around, my 96 gauge moves around between a bit over 1/4 and 1/2. There was a TSB about this issue stating steam formation in the system, and they suggest adding a bypass, changing the sender, thermostat and gauge. I changed the T-stat(motorcraft), sender and I believe I burped the system correctly and it don't help. I monitored the computer and it varies down to the low 180s sometimes, so the gauge must be accurate. I have a theory that tiny holes in either the intake gasket or head gasket cause a bit of pressure loss, losing temperature and causing the gauge movement. They may also take in tiny amount of air when you turn the car off.

I know they are high mileage failure points on this engine (especially the intake). I wouldn't worry about it though, its like that for many years and miles.

This 4.0L engine is weird, it says in the owners manual it may take 7500 miles to completely purge air and you may lose some coolant in the process. Maybe that is the reason for the variation.

 

[mudbug0426]

stupid ford.. you would think they would get these small things right but i guess not.

back to this evap system, how to see if thats what the problem is. any idea what to do first?

 

[96eb96]

stupid ford.. you would think they would get these small things right but i guess not.

back to this evap system, how to see if thats what the problem is. any idea what to do first?

I would try to take the electrical connector off the solenoid. It is under the battery tray and has a bunch of vac lines coming out of it. I think you may have to remove the tray. Maybe after 20 secs the computer is commanding it off?

 

[mudbug0426]

ill try that tomorrow, and if your right about the computer commanding it of after the 20 secs, then when its on could be why it idles rough? ill look at those vacuum lines tomorrow and check everything out.

oh and i forgot to mention, when i was at autozone earlier i use their vacuum gauge, hooked the tube right onto the black upper part of the manifold, started the motor and the gauge read from 20 to 22, the needle was going crazy. meaning i have a vacuum leak somewhere correct?

 

[96V8Xploder]

Earlier you said that when you replaced the MAF sensor is when things went wrong. Try to put the old MAF sensor back on and see what happens.

I have got many new/bad parts before. This could be it all along.

 

[96eb96]

ill try that tomorrow, and if your right about the computer commanding it of after the 20 secs, then when its on could be why it idles rough? ill look at those vacuum lines tomorrow and check everything out.

oh and i forgot to mention, when i was at autozone earlier i use their vacuum gauge, hooked the tube right onto the black upper part of the manifold, started the motor and the gauge read from 20 to 22, the needle was going crazy. meaning i have a vacuum leak somewhere correct?

vac leaks are usually a consistent low reading, but its hard to tell sometimes from a vac gauge.

I know there are a lot of lines in the evap system that look like they could rust out and suck air. The evap system is sometimes tested with a smoke machine, they put smoke in and see where it comes out.

The evap has its own diagnostics and codes, but who knows if it will trigger if there is a major leak.

Do you have a service manual? You can download it from my sig. Its an overwhelming amount of info, but it may help you.

 

[96eb96]

Earlier you said that when you replaced the MAF sensor is when things went wrong. Try to put the old MAF sensor back on and see what happens.

I have got many new/bad parts before. This could be it all along.

Reman mafs can have issues. They usually take your old core though when you get one. Doing this without a scan tool is like feeling around in darkness.....

 

[mudbug0426]

96V8Xploder, I had this problem before I replaced the maf sensor, it just didn’t happen on every start, but got a little worse over time. Very shortly after I replaced it is when it started this on every start, and they took my core so I don’t have my old maf sensor L

96eb96, do you think my unplugging the electrical connector off the vapor management valve will stop the rough idle? Since this whole system is just used for emissions, if it I unplug it and it it idles fine on startup then wouldn’t that narrow down where the problem is?

I still don’t understand how this system acting up relates to the leaking sound im hearing around the intake manifold area.. if the evap system was leaking, shouldn’t I be hearing this noise closer to where its located?

 

[mudbug0426]

ok, i have done 2 things this morning

96eb96, i unhooked the electrical connection off of the solenoid under the battery tray like you were talking about, took it around the block, got it up to running temp came back and parked it. started it back up with it still unplugged, no change. killed it plugged it back in and started it, no change. both times i heard the leak.

then i remember when i was getting my iac valve at autozone they guy said there were 2 different ones. so thinking i might have gotten the wrong one, i started it back up and unhooked the iac valve, it dropped down from 1000rpm to about 600 rpm and the leaking noise went away as soon as i unplugged it!

as soon as i plugged it back in the noise comes back like something is leaking.

now this iac valve i bought was brand new.

maybe i have the wrong one?