Frustrated with rough idle when warm in drive

[Shore_Fun]

Hi all,
I have a 2000 Explorer 4.0L V-6 OHV (X) with the CE light on and codes P0306, P0171, P0174. It starts great runs good but has a rough idle stumbling when warm waiting at a light. It has 198K miles on her but the engine has less than 30K.

I've done a lot of work on this truck in the past few months chasing issues and have come to a point that I need to what else it could be.

History - Dec 2014 Engine replaced with Ford rebuilt Crate engine, “Y” Pipe Catalytic Converter replaced,
Dec 2017 - Trans slipping, changed in Mar 2018 , Feb 2018 CE light on

Mar 2018 replaced transmission, started, cooling fan

Apr 2018 replaced Exhaust (complete) , O2 sensors(3), DFPE sensor, Idle Air Control Valve, Spark Plugs and Wires, EGR Valve, EGR Solinoid, EGR Inlet ube

May 2018 Replaced PCV, MAF sensor, Throttle body gasket, intake manifold gasket (Fuel rail and plenum), fuel injector "O" rings, Coolant Temp sensor, Coolant, Serpentine Belt, Pulley and Tensioner, Fuel Filter, coil pack

Can not find any more vacuum leaks and the fuel pressure is 65 PSI steady.

Help???????

 

[974X4BLACKSPORT]

Mine did this too (1997 4.0l OHV SPort 4x4 130k miles), that is untill one day I accidentally filled with 89 octane (normally fill with 87), it has been a lot smoother ever since!

 

[Shore_Fun]

Mine did this too (1997 4.0l OHV SPort 4x4 130k miles), that is untill one day I accidentally filled with 89 octane (normally fill with 87), it has been a lot smoother ever since!

Thanks. I tried that a last week, but it did not make a difference.
The truck runs well on 87 octane, hits highway speeds quickly just has that stumbling idle and the gas mileage is down..... Tks

 

[FijiBill]

What do the fuel trims look like when it is cruising versus idle?

For P0171 and P0174 vacuum leaks, you could check the long EVAP hose connected to the underneath of the throttle body. My stock one is almost rotted out but still holding on. The green o-ring and silver gasket was OK on the EGR tube? I know you've probably sprayed the heck out of it!

For P0306, maybe try switching in a different coil pack or the alternator could be doing odd things at low RPM. Those are both really quick and easy to swap out and cheap from a salvage yard.

I had a VW with bad plug wires shake only when hot at idle. You could smell the fuel out the tailpipe and see the arcing at night (insulation doesn't work as well when hot).

 

[Shore_Fun]

What do the fuel trims look like when it is cruising versus idle?

For P0171 and P0174 vacuum leaks, you could check the long EVAP hose connected to the underneath of the throttle body. My stock one is almost rotted out but still holding on. The green o-ring and silver gasket was OK on the EGR tube? I know you've probably sprayed the heck out of it!

For P0306, maybe try switching in a different coil pack or the alternator could be doing odd things at low RPM. Those are both really quick and easy to swap out and cheap from a salvage yard.

I had a VW with bad plug wires shake only when hot at idle. You could smell the fuel out the tailpipe and see the arcing at night (insulation doesn't work as well when hot).

I will recheck the EVAP hose. I changed it last year, but will recheck. The EGR tube to the plenum is good, check it when I changed the plenum gaskets and EGR tube to exhaust manifold is new.

I will look at the fuel trim to see the differences.

The alternator was replaced about 18 months ago and the current output at idle is about 13.9 VDC.
Change coil pack yesterday, that was the last thing I could think of....

The EVAP system I do not know about, so this issue is pushing me in that direction.

Thanks for the help

 

[96eb96]

Posting codes without freeze frame data is very difficult to diagnose. I would like to know if the problem is at idle, warmed up, high/low rpm etc. The computer reports this, it is not always what you can just feel.
Being that your replaced the MAF and and gaskets, have you monitored fuel pressure when the symptoms happen(not just in your garage)?

 

[Shore_Fun]

Posting codes without freeze frame data is very difficult to diagnose. I would like to know if the problem is at idle, warmed up, high/low rpm etc. The computer reports this, it is not always what you can just feel.
Being that your replaced the MAF and and gaskets, have you monitored fuel pressure when the symptoms happen(not just in your garage)?

The problem was noticed a back in March. I already planned to change the exhaust and O2 sensors, in April, so i waited. After changing exhaust and O2's, the problem persisted. I then started checking and went through the list of common culprits and did find some issues, so it did progress well. The vehicle is quieter, smoother acceleration and engine is cleaner (LOL, I have to laugh as it drive me crazy) .
From my post you can see that I changed just about everything that could effect it.

My fuel pressure is about 65 PSI with the key on engine not running, with the engine idling in park and engine idling in drive it was about 65 PSI (63-66) and I checked it at idle in park with the vacuum hose removed from the damper and it stay solid at 65 PSI. I created 20 PSI leak in my test set-up to confirm the set-up was working and the pressure gauge responded correctly.

I even tried swapping the # 6 plug and wire to confirm they were good and they were.

I am at work so I will have to try to capture freeze data info tonight when i get home. I just have a simple scan tool, so what specific data would be helpful and under what conditions?

I appreciate the assistance.

Thank you

 

[96eb96]

The problem was noticed a back in March. I already planned to change the exhaust and O2 sensors, in April, so i waited. After changing exhaust and O2's, the problem persisted. I then started checking and went through the list of common culprits and did find some issues, so it did progress well. The vehicle is quieter, smoother acceleration and engine is cleaner (LOL, I have to laugh as it drive me crazy) .
From my post you can see that I changed just about everything that could effect it.

My fuel pressure is about 65 PSI with the key on engine not running, with the engine idling in park and engine idling in drive it was about 65 PSI (63-66) and I checked it at idle in park with the vacuum hose removed from the damper and it stay solid at 65 PSI. I created 20 PSI leak in my test set-up to confirm the set-up was working and the pressure gauge responded correctly.

I even tried swapping the # 6 plug and wire to confirm they were good and they were.

I am at work so I will have to try to capture freeze data info tonight when i get home. I just have a simple scan tool, so what specific data would be helpful and under what conditions?

I appreciate the assistance.

Thank you

Changing O2 sensors for those codes usually won't solve the problem. Changing the coil, probably won't help either, because there are 3 coils feeding 6 cyls. Swapping the plug and wire eliminates that issue. A plugged injector could be an issue too.

I would hate to believe you have a cracked head on that new engine, that would be sad. It is a problem with these engines at very high mileage. Maybe do a compression test on it. Do you lose any coolant?

A good scan tool may read fuel pressure as you drive. Also, can your scan tool read "Live" misfires? You can watch exactly when they happen. Warm, cold, etc. I suggest Forscan as a great scan tool. It is actually free.

With any scan tool, report back fuel trims at idle, 1500 , and 2500 RPM.
Need long and short term FTs. This can give a big clue.

 

[Shore_Fun]

Changing O2 sensors for those codes usually won't solve the problem. Changing the coil, probably won't help either, because there are 3 coils feeding 6 cyls. Swapping the plug and wire eliminates that issue. A plugged injector could be an issue too.

I would hate to believe you have a cracked head on that new engine, that would be sad. It is a problem with these engines at very high mileage. Maybe do a compression test on it. Do you lose any coolant?

A good scan tool may read fuel pressure as you drive. Also, can your scan tool read "Live" misfires? You can watch exactly when they happen. Warm, cold, etc. I suggest Forscan as a great scan tool. It is actually free.

With any scan tool, report back fuel trims at idle, 1500 , and 2000 RPM.
Need long and short term FTs. This can give a big clue.

I planned to change the O2 sensors with the exhaust before the CE light showed up, so when that happen and I was hoping that it would solve the problem as well. No such luck....

The engine runs cool about 170, but I will check that as i drive to see. No coolant loss and when I changed the plugs, no abnormal discoloring they did have a bit of a fuel smell from running rich. I don't think it is a head or cylinder, as the trucks runs smooth and has power. I bought that truck with 6K miles on it and still under warranty and the top of the engine was replaced at 40K by ford (warranty) and i recall when I was having those problems what a bad cylinder felt like.....(yuck)

I will look at my scan tool later and see what I can do with it Thanks

 

[96eb96]

Where did you get the MAF sensor? Some reman ones are garbage. Also, what is your BARO paramter? A good scan tool will reveal it. (Like forscan). Should be around 159Hz...Jersey shore is close to sea level :lol:. That can vary based on altitude and even weather. It is supposed to read corrected air pressure, but it is indirectly computed.

That number also indirectly checks your exhaust for blockage.

 

[Jacob Williams]

I had a similar problem that I couldn’t figure out for the longest time, accompanied by the same error codes. I tried almost every possible fix, but I finally figured it out the other day.

I know this is in a wholly different ballpark than the other causes suggested, but it turned out that the cause was my AC system being very low on refrigerant, but having just enough to cycle the air compressor. When it was hot out, often when I wasn’t even running the AC, it would idle very erratically in hot weather. When the AC was running, the engine would surge in tune with the compressor cycling on and off. It was trying so hard to compress the tiny amount of coolant that it bogged the engine down. Recharged it (they take a pretty large amount of refrigerant, I must have been too scared of overfilling beforehand) and the problem has entirely disappeared. I can now blast the AC while sitting still in a parking lot with no trouble

While this problem is more likely than not caused by something else, it's worth checking this out because it'll be a very easy and almost free fix if it is indeed the same problem I had. Make sure you have enough refrigerant and your AC compressor is cycling for a long time and shutting off for a long time when you’re idling. If not, just keep working with the guys on this forum.

 

[Macgiobuin]

It sounds like your idle air control valve is sticking open when hot. Get a beer can, cut off the top, put the idle air control valve in the can. Fill it with sea foam and let it sit over night. Take a tooth brush and clean it out while moving up and down the central valve, then rinse it out again. Put it back in. Should be fine for a while; if it recurs, then you need a new IAC valve.

 

[gmanpaint]

Did you change both temp sensors?
This sounds like the pcm temp sensor is bad to me.

The other temp sensor is just for the dash cluster.