Rough engine idle and under load with no check engine light

[tylerparkersdad]

Hi guys...new the forum.
I have a 2001 Explorer Sport 4.0 v6 that started running rough the other day. The problem feels like a fouled plug....the problem is consistent at idle and under load. I tried to change the plugs and it didn't help. I also unplugged each wire at the coil hub and started and the problem got worse with each wire so I don't think its a plug wire.

I also cleaned the mass air sensor and replaced the air filter. Still no luck.

With the ECM not generating codes...I'm not sure what the next step is. I'm not in a financial position to take it to a mechanic.

Anyone had a similar problem? Everything that I've read on here that has a similar symptom they had codes. Any ideas?

Thanks

 

[jremington59]

What did the plugs look like?

 

[2000StreetRod]

Which engine?

Do you have the OHV or SOHC engine?

How many miles on the odometer?

How many miles since you changed the fuel filter?

Disconnecting one plug at a time only indicates that each cylinder is firing. The PCM uses the IAC valve to adjust the idle speed so it's difficult to tell if one disabled cylinder has more effect than another.

 

[tylerparkersdad]

What did the plugs look like?

the plugs looked normal to me...no buildup ...grey/white color

 

[tylerparkersdad]

Do you have the OHV or SOHC engine?

How many miles on the odometer?

How many miles since you changed the fuel filter?

Disconnecting one plug at a time only indicates that each cylinder is firing. The PCM uses the IAC valve to adjust the idle speed so it's difficult to tell if one disabled cylinder has more effect than another.

130 K on the odometer

I bought the truck 5yrs ago with 80k..I've never changed the fuel filter... I never suspected that could be the cause because the change was literally overnight.

As far as the disconnecting the plugs...the idle vibration got noticeably worse with each wire being disconnected.


thank you....more feeback welcome

 

[tylerparkersdad]

Do you have the OHV or SOHC engine?

How many miles on the odometer?

How many miles since you changed the fuel filter?

Disconnecting one plug at a time only indicates that each cylinder is firing. The PCM uses the IAC valve to adjust the idle speed so it's difficult to tell if one disabled cylinder has more effect than another.

I forgot to answer... it is a SOHC..thanks again.

 

[2000StreetRod]

no misfire DTCs

Since the PCM is not setting any misfire diagnostic trouble codes (DTCs) then your problem is probably not cylinder specific. This is supported by each cylinder when disabled results in reduced or unstable idle speed.

1. I suggest that you replace the fuel filter. It is long overdue and should be done whether or not it solves your problem. See my thread Why change fuel filter? The replacement may also prevent your fuel pump from early failure.

2. I suggest that you next pour two bottles of fuel injector cleaner into your full tank of fuel or one bottle into a half tank.

3. I suggest that you perform my Fuel pressure test procedure. You should have a nonreturn fuel system with a pressure always around 65 psi.

4. Next I suggest that you perform my TPS Test Procedure

All of the above can correct or detect problems that can adversely affect engine performance that is not cylinder specific.

 

[tylerparkersdad]

I'll try them in order..thanks

 

[96eb96]

check for any deteriorated vacuum hoses, especially around the PCV valve. The other thing could be bad intake gaskets, but check for vac leaks.

 

[mikepier]

When you say under load, do you mean when it's in gear and your foot on the brake?
Does the engine run smooth otherwise on the highway?

The reason I ask is that I thought I had a rough idle also on my 99 SOHC. It ran smooth othertimes. I had no CEL and the plugs looked fine.

Then I tracked it down to the vibrating twin catalytic converters under the truck. Do a test. Take a floor jack with a piece of wood on it and raise it under the cat just enough to put pressure on it. Then go in the truck and put it in gear. If the idle is smooth, then its the cats causing the vibration and causing it to resonate though the truck.

 

[tylerparkersdad]

When you say under load, do you mean when it's in gear and your foot on the brake?
Does the engine run smooth otherwise on the highway?

The reason I ask is that I thought I had a rough idle also on my 99 SOHC. It ran smooth othertimes. I had no CEL and the plugs looked fine.

Then I tracked it down to the vibrating twin catalytic converters under the truck. Do a test. Take a floor jack with a piece of wood on it and raise it under the cat just enough to put pressure on it. Then go in the truck and put it in gear. If the idle is smooth, then its the cats causing the vibration and causing it to resonate though the truck.

Interesting ....I wasn't aware that was possible. Did replacing your cats fix your problem?

My engine is running rough at idle and as you say with the brake on in gear as well as driving through town. It's not as noticable on the highway however there is a noticeable loss of power regardless of what type of driving.

 

[tylerparkersdad]

check for any deteriorated vacuum hoses, especially around the PCV valve. The other thing could be bad intake gaskets, but check for vac leaks.

I have visually inspected the hoses...at least as much as I could see. I'll take a closer look this weekend and also try spraying some starting fluid around the intake to see if I can get a blip on the rpm's


thanks guys....good stuff ...keep it coming

 

[mikepier]

Interesting ....I wasn't aware that was possible. Did replacing your cats fix your problem?

My engine is running rough at idle and as you say with the brake on in gear as well as driving through town. It's not as noticable on the highway however there is a noticeable loss of power regardless of what type of driving.

The vibrating cats are an inherent problem I believe. They resonate right at idle. I did not replace them because the cats themselves were fine. What I did was stick a piece of 1/2" copper elbow wedged between the 2 cats to "cancel" out the resonation. I have a picture somewhere at home on my computer. I'll post the pic when I get home from work.

 

[mikepier]

Here is the pic. The wire attached to the 45 elbow is in case it should come loose and not be lost.

 

[tylerparkersdad]

Here is the pic. The wire attached to the 45 elbow is in case it should come loose and not be lost.

very cool...thanks for taking the time to upload.

I have a 3 month old baby that is sick so I haven't been able to get much done. I'll update the thread with what I find.