1999 Explorer SOHC Stumble at Idle

[markfothebeast]

1999 Explorer 4.0L SOHC 4x4

I have had a stumble at idle since around June. I have live data logs from before and after the stumble. I have compared data but I can't seem to pinpoint the issue. By a stumble I mean that the engine idles fine and will randomly drop down to 600ish and bounce back up to 750rpm "hunting" for a steady idle. During this stumble you can feel the vibration of the engine in the seat. You can also see the engine physically vibrate more than it should. I don't drive this vehicle as much as my roomate but she says that it was beginning to have a harder time starting.

I have replaced the following:
-Upper/Lower intake gaskets
-Plugs
-Wires
-DPFE
-Fuel Filter
-PCV

Also
-Cleaned Grounds
-Cleaned distribution box terminals
-Cleaned MAF
-Cleaned IAC (which was incredibly clean already)
-Steady Fuel Pressure @ 64psi

Fuel pressure immediately drops to 0 in 10-15 seconds after shutdown. I understand that the FPR is in the tank so I could not get a good look at it. Fuel trim data is around +2 for each bank at average. Passengers side runs a bit richer during the idle stumble. The only possible thing I can imagine is a sticking injector. I had injector pulse data that showed an injector sticking but I cannot recreate the scenario as it hasn't done it again. I have no codes. However, live data logged misfires but it does not specify which cylinder. I cannot find software with enhanced Ford DTCs that logs each cylinder misfire. FPR or injector is my thought. Any input? Possible bad ground wiring points maybe?

 

[markfothebeast]

Ran ForScan for Fords. No injector faults on 20 minutes of livedata. Checked grounds, no voltage backing up. I will check the platinum plugs that are about a year old. I usually run copper so i'm not sure what the failure rate on platinum is.

 

[Flash]

Ran ForScan for Fords. No injector faults on 20 minutes of livedata. Checked grounds, no voltage backing up. I will check the platinum plugs that are about a year old. I usually run copper so i'm not sure what the failure rate on platinum is.

I don't know if this is it but I do know platinums don't run as well as copper.
Iridium is the best.

Coil?

 

[J_C]

Failure rate on platinum is very low. With any type either it's defective or damaged during installation, or not and with platinum they won't wear out in a year. Copper would give a hotter spark (if all else were equal but insulator length might be adjusted so it's a wash) but it's designed to use platinum so that difference shouldn't be the problem.

What is the fuel pressure while it is running, especially during the erratic idle? Does it drop to 600-ish for only a moment or stay there, or back and forth continually and if so for how long? Could it be that the A/C compressor is kicking on? Have you tried putting injector cleaner in the tank and running through that fuel?

What is the usage pattern, how often is it driven and how long does it sit between uses? Have you checked battery voltage? Does the problem get better, worse, or stay the same after the engine has ran for a while and/or fully warmed up?

 

[markfothebeast]

Everything you mentioned I have done or has been checked, besides for the A/C. I havent thought about that one. Fuel pressure always stays at 64psi regardless of idle. But drops to zero after ignition off.

The idle is always there, cold or hot. It has escalated since June. It was non existent before June 2015. It is now getting a bit harder to start. The engine shakes even more. I need to do a compression test. I read a similar story which happened to be something like a valve - never finished reading but the guy just replaced the engine. His problem was only under 1200rpm, just like mine. Just need to test each cyl but im not sure if there's a strategy to get to the passengers rear cylinders.

The previous poster mentioned the ignition coil. I could swap that out. I do have another. But I want to learn how to test this type of ignition coil first. I wouldn't know which pins to test.

Speaking of coils. I tested my new plug wires and the resistance is much higher. The old wires are literally half the resistance of the new ones - almost that of a spiral core. Could be good or bad. Maybe leaking voltage. I have the 2 in the passengers rear to change yet.

 

[markfothebeast]

For the injector cleaner, I did add Berryman's B12 to the fuel tank. I don't expect immediate results by adding to the tank but only preventative results. I typically run it directly through the rail to flush out the injectors but my air compressor has been down. A different subject here but I was using Seafoam and it got too expensive. I began using Berryman's B12 when I was flushing injectors on my injector cleaning machine (injectors out of vehicle in machine). It is much more concentrated with petrol based products than Seafoam. It is fairly harsh and will melt through plastic containers. This gave me much quicker results when flushing injectors out. I haven't replaced an injector other than solenoid failure.

Anyhow, I have yet to run the pneumatic cleaner through the rail. It only lasts about 10 seconds before I use an entire can of cleaner. I need a wiring harness for the injectors to adapt to the cleaning machine rather than wiring up terminals for 6 injectors. That way I can sort out the injector issue by viewing the spray patterns.

 

[Macgiobuin]

I have a similar problem with my '06 Mazda B3000 (Ranger). I took off the downstream cat to see which side if any was causing my stumble which occurs at exactly 3000 rpm. While a helper presses down on the throttle til it stumbles, I feel which side is misfiring. For me it is always and only the passenger side. Why? I still don't know but I have eliminated plugs, injectors, fuel pressure, upper cats, coils. I'm getting close, though.

 

[J_C]

Just need to test each cyl but im not sure if there's a strategy to get to the passengers rear cylinders.

I found them easier to get to with the wheel and well liner off, going in that way.

 

[markfothebeast]

I have a similar problem with my '06 Mazda B3000 (Ranger). I took off the downstream cat to see which side if any was causing my stumble which occurs at exactly 3000 rpm. While a helper presses down on the throttle til it stumbles, I feel which side is misfiring. For me it is always and only the passenger side. Why? I still don't know but I have eliminated plugs, injectors, fuel pressure, upper cats, coils. I'm getting close, though.

The only time this one hits 3,000RPM is when the 5R55E transmission doesn't go in to overdrive. Which is about 50% of the time. I hope that this Ford lasts atleast another 6 months. Really tired of swapping engines and transmissions. Everyone keeps borrowing my Chevy because i'm fixing their Ford or Dodge.

 

[markfothebeast]

I have another question. Fortunately, I found ForScan for my Elm327 adapter. This software works awesome for Fords (and even does a IAC test). It scanned additional computer modules such as the GEM and ABS. I have read about the GEM being corroded from water dripping down the dash. I have a GEM code as follows;

Code: B1834 - All Doors Unlock/Disarm Output Circuit Failure

Module: Generic Electronic Module

Diagnostic Trouble Code details

All Doors Unlock/Disarm Output Circuit Failure

--- Possible Causes --------

-Short to GND between Door Unlock Relay coil & Master Window/LF Power Door Lock Switch Door Unlock Relay coil & RF Power Door Lock Switch

Door Unlock Relay coil & Lift-Gate Lock Switch Door Unlock Relay coil & Remote Anti-Theft Personality Module Door Unlock Relay coil & Generic

Electronic Module

-Suspect Master Window/LF Power Door Lock Switch RF Power Door Lock Switch Lift-Gate Lock Switch Auxiliary Relay Box #4 (Door Unlock Relay

coil) Remote Anti-Theft Personality Module Generic Electronic Module


Perhaps I have some faulty/corroded wiring at the GEM? Is it possible that the GEM can cause the engine to run strangely?

 

[J_C]

^ Given the vehicle age there's bound to be residual dust buildup around the gem so you should be able to pull it and see if there's evidence of water exposure and possibly corrosion too. I've never heard of that causing the engine idle issue, can't think of why it would but don't know enough to rule it out.

 

[markfothebeast]

I'm not a great spark plug analyzer. I'm not sure if this is normal or the lean running "hot" spark plug look.Also, are the electrodes supposed to look like that on Platinum plugs?

The gap was about .045. Regapped the plugs. Are Autolite Platinums a good plug for this engine? I know some engines are picky.

 

[markfothebeast]

It has been raining for the last couple days. It is stalling at intersections possible because of the rain.

 

[markfothebeast]

I seem to have multiple issues that may or may not be related.

After reading about GEM functions I did not realize there was a door chime. Either it is not functioning or someone had intentionally removed it (car dealership) because it may have been stuck on due to early GEM failure signs.

The OD light started flashing. Torque converter solenoid. Won't lock up when transmission is warm. Sometimes it will lock up when warm. Tranny is really clunking during shifts now. Tranny is 2 years old.

Passengers side door window sometimes does not operate.

Hatchdoor is shut completely but "door ajar" light is on. Shutting the hatch again fixes it. It has done this several times making me think the hatch was open but now it just wants to play games.

After 2 days of rain the vehicle is running even worse. There has to be some faulty wiring or bad communication between modules. Can this vehicle be this dumb not to report misfires, stalling engine, an injector fault, vacuum leak from intake manifold (traced from fuel trim) or for that matter even GIVE ME A DTC! Did Ford create the most unintelligent OBD2 network of modules or does this sound electrical? I sure hope that this isn't how all Fords operate now days.

 

[wcjeep]

Any chance the intake gaskets were not in their groove during reassembly? Have you checked vacuum by hand (not computer)?

 

[SoNic67]

Did you clean the IAC valve? I had idle issues too and I had to replace it, cleaning didn't help.
BTW, a bad IAC valve won't throw any codes.

 

[my98nnj]

Clean the throttle body and the idle air control valve. Bet it's the a/c cycle your feeling because the iacv is having trouble stabilizing the idle speed as loads change.

 

[Winniethepooh]

had that problem when my O2 sensor went out.

 

[SoNic67]

I'm not a great spark plug analyzer. I'm not sure if this is normal or the lean running "hot" spark plug look.Also, are the electrodes supposed to look like that on Platinum plugs?

The gap was about .045. Regapped the plugs. Are Autolite Platinums a good plug for this engine? I know some engines are picky.

Is that a Bosch spark plug? I am asking this because it doesn't have any tip showing and only Bosch use "surface" flame. Bosch are known to have issues with our engines.
And if is not Bosch, that tip no way can create the needed flame, no matter how much you are "gapping" it.

Or maybe the angle of the pic was wrong and I don't see the tip.

 

[J_C]

^ ?? Looks like a normal non-fine-wire platinum plug to me... with a bit of ash (probably burning a "little" bit of oil) that I'd clean off the electrode before reinstalling it.