2003 Explorer Rough Idle

[plasticseng]

You will need an app with Ford specific data like Forscan. It is free for a laptop, 5 or 6 bucks for a phone.

Look for 'DPFEGR' and 'EGRVP%'.

DPFEGR is the voltage from the DPFE sensor. It should read about 1 volt at idle and any other time the system is not calling for EGR.

EGRVP% is the amount of EGR the system is calling for (duty cycle). It should be zero at idle. As it goes up, the DPFE sensor voltage should go up also. The correlation may not be exact, but you should see a reaction in the sensor voltage as the PCM calls for EGR flow.

 

[Cashcrazy]

Thanks for the Foracan recommendation. The EGR appears to be functioning properly. Any other data from forscan I should pull?

 

[plasticseng]

I would look at the throttle position sensor next. I know you don't have error codes, but I have seen a TPS that would never go out of range, but had flat spots or spikes in the voltage curve. You want a clean rise in voltage from the closed throttle position to wide open throttle. Check out this thread:
http://www.explorerforum.com/forums...rd-explorer-ranger-tps-test-procedure.263699/

 

[plasticseng]

Also, instead of back-probing the wires, you should be able to use the oscilloscope function on your Forscan app to trace the voltage off of the TPS as you sweep through the throttle range. I haven't tried it, but I feel sure you can.

Edit - I tried it. Here is the scan. The bottom graph is the throttle position sensor voltage. It varies from 1.0 volts (closed) to 4.6 volts(wide open). The rough spots are where I wasn't as smooth as I could have been pushing the pedal down and letting up. Of course, do this test with the key on and the engine off.

 

[Cashcrazy]

That's an excellent function! I just receive notification that the new MAF was delivered. I hope this works so I can move on to servicing the trans and rear differential with synthetic lubricants. I have a feeling the MAF is good, but at least it will be eliminated from the equation. I'll move on to the TPS if this does not work.

 

[Cashcrazy]

New MAF installed and no change to idle. The LT fuel trim % increased with the new sensor. I sprayed with carb cleaner in different areas again and still didn't find a vacuum leak. I added the TPS to the Forscan data below. I am out of ideas and ready to throw in the towel. FSBO????

 

[evaskulleader]

hi my 02 explorer had a rough idle and they replace the intake manifold gaskets. 4.0 v6 hopefully that will help

 

[plasticseng]

New MAF installed and no change to idle. The LT fuel trim % increased with the new sensor. I sprayed with carb cleaner in different areas again and still didn't find a vacuum leak. I added the TPS to the Forscan data below. I am out of ideas and ready to throw in the towel. FSBO????

I don't think you are going to find a vacuum leak with negative long term trims.

Can you graph the TPS voltage over time as you idle so you can see if it is varying any?

 

[plasticseng]

Don't give up.

Have you run several tanks of fuel through during this time? Just trying to rule out high ethanol content or just plain bad gas.

You have me doing some reading now. It sounds like bad vapor canister purge and vent valves could cause these types of problems. I would need to do more reading to understand how to test them.

 

[Cashcrazy]

evaskulleader- thanks for the suggestion. I have considered replacing the gaskets on a Saturday just to eliminate the possibility, but the idle is more like a studder than the RPMs moving up and down like a vacuum leak.

Plasticseng- i watched the TPS voltage and there was no change, but I will watch it more closely tomorrow as I drive.

I have ran many tanks of gas through it. At first I thought it might be water in the tank from the ethanol in the fuel so I ran ethanol treatment through several tanks since it is supposed to eliminate the water. I've even tried a couple tanks with water remover. From there I moved to the various fuel injector/system cleaner I have tried. Any bad gas would be gone by now.

I've read every thread I can find for a rough idle and will have to do more googling on the vapor canister.

I sincerely appreciate all your help.

 

[Cashcrazy]

There is some type of service port on the vapor canister purge valve solenoid. Any idea how this works?

 

[plasticseng]

Cashcrazy - another thought occurred to me. Forscan can access what Ford calls 'Mode 6' data that will identify how many misfires you have on each cylinder, even if there aren't enough misfires to trip a code. It may help to at least know if the majority of your misfires at idle are coming from a few cylinders or all of them equally.

You may need the PC version. I don't think the Android version has Mode 6.

 

[Cashcrazy]

I don't see that on the app. I'll have to see about downloading the PC version tonight. It feels like an ignition issue I encountered in the past on a Carbed vehicle. For that I upgraded the ignition to a MSD box and widened the gap on the plugs, problem solved. The difference with this is that it will idle super smooth at times while in drive and then horrible at other times. It's always rough in Park although it does get somewhat better at times. Its not a constant pattern. I can't find a good writeup or video for intake gasket replacement with this one piece intake design or I'd probably replace the gaskets to eliminate that also. I'm out of ideas. Everything at this point is just a guess.

 

[Cashcrazy]

I had time to mess with the graphing part of the forscan app. The LT fuel trims seem to be graphing very similar. However, the ST fuel trims are different. Does this mean anything?

 

[plasticseng]

I had time to mess with the graphing part of the forscan app. The LT fuel trims seem to be graphing very similar. However, the ST fuel trims are different. Does this mean anything?

I wouldn't read too much into the short term trims as long as they aren't varying wildly. After about 30 seconds, if the short term trims are away from zero, the long term trims will adjust to bring them back to zero on average. You can think of the short term trims as a constant, instant adjustment, and the long term trims as a recalibration of your zero point. When your long term trims get too far away from the factory original setting, you will get an error code.

Here is a good read on fuel trims:

http://www.autoserviceprofessional....-works-and-how-to-make-it-work-for-you?Page=1

 

[plasticseng]

Can you graph your O2 sensors at idle? You should see sensor 1 and sensor 2 for both bank 1 and bank 2 (4 total).

Also for the mode 6 misfire test, I took some screenshots from the Windows version of Forscan:

 

[Cashcrazy]

Misfire test below. Working on O2 graph now.

 

[Cashcrazy]

I really appreciate the time you have put into this. O2 graph below. Does this tell you anything?

 

[Cashcrazy]

And finally here is a graph from forscan. Plasticeng- I can send you a log with several minutes of idling if that is better. If so just msg me you email.

 

[plasticseng]

Misfire test below. Working on O2 graph now.

I thought for sure we would see misfires there with the stumble you are feeling.