95 explorer idle and acceleration problems

[Banjoes]

Hi i have 95 explorer xlt 2wd 4.0l v6 OHV and I have a rough idle and throbbing/surging acceleration at part throttle when under load (accompanied by a small whistling noise) but accelerates fine above 2200 RPM.I can accelerate to WOT with no performance hickups. By the way there is no Check engine light on.

Tried so far:
Fuel filter replaced with motorcraft filter in 2011
Fuel pressure regulator replaced with BWD today
Idle air control valve replaced with BWD 2013
DPFE sensor replaced-codes 335 and 332 in 2012
MAF sensor cleaned in 2012
spark plugs (not wires) replaced in 2009
thermostat replaced along with coolant temp sensor(gauge only)-2013
Throttle position sensor replaced with BWD in 2013
Throttle body removed cleaned with TB cleaner and toothbrush (new gasket o-ring) and even took IAC off and cleaned IAC passages on intake manifold.-something of note here, when taking off throttle body the bolts were loose (the bolts felt like they barely had any torque on them)

I think I'm leaning towards maybe new spark plugs, wires and maybe coil pack

I've checked for vacuum leaks by spraying carb cleaner around various intake areas especially around the upper intake manifold o-rings-nothing

I'm open to any suggestions, please Help!

 

[lobo411]

I'm open to any suggestions, please Help!

You should try visually inspecting the upper intake manifold gaskets. I know you said you checked for air leaks there, but nothing beats actually looking at them, they're right on top of the engine/easily accessed, and for the price ($20?) you can afford to just change them on general principles.

http://www.explorerforum.com/forums/showthread.php?t=171819

 

[1992fordgreen]

Try a smoke test on the TB. Inspect for lacerated vacuum lines. I'm guessing it could be the o2 sensors, or the TPS that is not set to spec or bad.
GL

 

[Banjoes]

Update: Fuel pressure leakdown seems to be my issue.
Started up truck this morning (fresh start) and was hard to start-struggled to make combustion happen, had to keep starter going about 3-4 seconds before engine would catch, unless I cycled key to ON position a few times before starting-could that new fuel pressure regulator be defective?

Once again no check engine light on.

 

[Banjoes]

Update: Tested coil pack resistance and got 14.5K and almost 15k on back(towards firewall).

New coil pack at Advance auto parts consistently reads almost 13K ohms and I thought specs were between 6,500 to 11,500 ohms, maybe coil pack needs replacement?

 

[IslandofOne]

@Banjoes - I also have a 1995 Explorer XLT but with 4WD 4.0L V6. The weather here in Maryland exceeded 90F last week and the engine began displaying similar symptoms to yours except I am also having transmission slippage between 35-45 mph. I've checked through my repair invoices for the past 18 years to see what was done when I had a similar conditions. Possibilities include: 1) EGR system - DPFE sensor (replaced twice before); 2) Engine spark plugs-distributor; and 3) Transmission - vacuum line or internal failure (w/ over 250K and on 3rd transmission). Vehicle going to the shop later this week. I'll report the "fix".

 

[1992fordgreen]

Unplug the coil pack while the truck is at idle and see if it idles different. If it doesn't, replace. If it does, search further...

 

[R1dd1cK]

Unplug the coil pack while the truck is at idle and see if it idles different. If it doesn't, replace. If it does, search further...

Well wouldn't the truck die if you unplugged the coil pack? I mean I don't think an engine can run on hopes and dreams even with out spark.

 

[1992fordgreen]

The engine likely has 2 coils. It makes no difference, as if the coil IS bad, the truck would run the same. Without a coil pack, your engine will run, but it will run like crap.

 

[IslandofOne]

@Banjoes- As promised, I am sharing the repair information. My 1995 Explorer XLT 4WD 4.0L V6 has been repaired and is purring like new. My ASE Certified repair shop pulled freeze frame data from the PCM on misfire and DPFE codes. No ignition on cylinders 1 and 5. Found 2 burned terminals on Ignition Coil. DPFE sensor readings were way out of range for specs.

Ignition coil assembly and ignition wires were replaced. Techs talked to Ford and learned that a newly redesigned EGR system sub-harness and DPFE sensor setup was released about 3 months ago. The sub-harness and sensor were replaced. Parts about $425 plus ASE labor. Thankfully, there were no problems identified with the transmission.

I hope that this information helps.

 

[Banjoes]

thanks for repair info Islandofone, I also found the crankcase breather hose had at least one crack in each bend, bought some new hose from advance auto and saved the little plastic grommet inside the one end that slides into intake tube, unplugged battery for 15 minutes, started it up and made a noticeable difference in idle (it actually idled at 850-900 RPM warm, 750 in gear and A/C on) as well as during driving, the hesitation was not as bad even when warmed up (thats when the problem is more pronounced). however the problem still remains, but agian more pronounced when hot, not so bad when fresh started.

Also island of one, did you get a motorcraft coil pack? If so , what are the resistance readings on the coils?, a BWD brand one from advance auto is reading about 13,000 ohms on all three coil packs.

 

[Banjoes]

Update: Changed coil pack distributor (BWD) new MOTORCRAFT ignition wires and new MOTORCRAFT spark plugs gapped to 0.54 and computer reset(unplugged battery for about 20 minutes).

I also noticed I have a small exhaust leak on the drivers side manifold (only noticeable under load).

Tried experiment(after viewing another thread) I disconnected the DPFE, the EVR and disconnected little vacuum line on top of EGR valve and taped both sides with piece of duct tape and tried driving and guess what, the hesitation when accelerating when warmed up under load significantly went down, but is still slightly there. (vacuum leak?) Whistling noise is still present.

One thing to note here, the vacuum line I disconnected from the EGR valve revealed it was still sucking a little bit of air (I'm sure it wasn't just engine vibration as it could only be felt at the tip, and it happens whether EVR electrical harness is connected or not. is it possible for it to get stuck slightly open and suck a little air?

 

[Banjoes]

NEW MAF sensor

Update: after driving around with EVR and DPFE unplugged the symptoms returned shortly after. So plugged them back in.

NEW update though, I unplugged MAF sensor and went for a test drive, and the truck runs AMAZING, the throttle is SO much more RESPONSIVE and the idle is better, it idles around 850 smoothly with AC on and headlights on and about 750 to 800 with it in drive. No more SURGING!!!

I already tried cleaning the wires inside 5 times already with CRCs MAF sensor cleaner and initially when first done it improved idle and acceleration a little but not much.

Once again NO check engine light and no codes get 1-1-1 pass codes.

 

[Banjoes]

More

:roll:MAF tested with voltmeter and my dad in drivers seat, read good and voltage readout was smooth for different rpm values-no dropouts or erratic readings-so MAF sensor is good. IAT sensor was tested good.

However I do seem to be loosing coolant slowly and with no leaks apparent. I replaced radiator cap just in case. I also do hear a whistling noise when accelerating under load. When I drive for a while and stop engine and restart it 10-20 minutes later, it sputters and shakes and acts like its going to die, but is ok after 30 seconds or clears up if I immediately drive off. What do you Guys think?

Once again NO check engine light, however I do seem to keep getting a code 99 which says pcm has not learned to control idle.

 

[1992fordgreen]

Reset the PCM first.

If there is NO CEL but there IS A CODE, the CEL IS OUT.

 

[Banjoes]

Check engine light works, illuminates every time I turn key to on position without starting. BTW, i got code 99 from paperclip and flashing check engine light.

 

[Banjoes]

o2 Sensors?

Hey, I did some more experimenting. I unplugged both oxygen sensors (which are the original factory units) and the surging and hesitating went away. Does this absolutely mean that the sensor(s) are bad?

 

[Banjoes]

Why does unplugging MAF sensor correct issue?-Slightly

My issue happens when I let the truck sit in a parking lot and go inside to get stuff in the store for 10-20 minutes and come back out, the engine idles really low and miss fires, but is okay in a few seconds if I put it in gear and drive off. I can easily recreate the conditions. However the stumbling does not happen if I unplug the MAF sensor-Why?

 

[Banjoes]

My symptoms haven't improved much

I wound up buying a remanufactured MAF sensor from advance auto.http://shop.advanceautoparts.com/p/cardone-mass-air-flow-sensor-maf-remanufactured-74-9520/18060098-P?searchTerm=maf+sensor#

Truck is still the same and I still hear a vacuum leak when accelerating lightly(below 30%) still cannot pinpoint it underneath the hood

But something that did help recently, I drove my truck until it warmed up and went back home and shut it off and set up the truck to read flash codes and this is what I got:

KOEO: 631, 631-CM-111,111

KOER: (sputters and misfires then clears up) 172(right HO2s indicates lean and not switching) 538 and 632

but why would only one o2 sensor be flagged? If I was running lean wouldn,t both 02 sensor be reading lean?

Goose test: code 99(hasn't learned idle) I bought a new IAC valve a year ago. this code 99 ALWAYS comes up when doing the self test (can a vacuum leak cause this)

I'm going to replace fuel filter again and see if it helps any, its been at least two years.

 

[Banjoes]

Problem fixed

Well I can finally say the problem is fixed. The causes of problems were using Ethanol blended (10%) fuel and a weak fuel pump. A new wawa gas station was just built where I live and they have 89 octane ethanol free gasoline. I bought a new carter fuel pump, installed, been in for almost a month never had the problem since. I also did replace the upper intake manifold gaskets and tightened down the lower intake, helped some.