Rough idle intermit hesitations and more

[The_Hammer]

Hey everyone,

I'm having a weird problem(s) with my explorer. Its a 1998 XLT 4x4, 145k km.

Everything was fine and dandy with the truck, it ran beautiful and no signs of a problem. When I was driving about 40km/hr on a road the engine just turned off like a light switch, no hesitation or roughness or any sign of trouble just turned off. All accessories/stereo etc still worked and i coasted to a stop. I put the vehicle in park and tried to start it and it cranks (tries to start) but wouldn't actually start. So I got towed and had my buddy come take a look at it whom is a mechanic.

Unfortuneatly when he came to look at it the darn thing decided to actually start, although beit pretty rough. No codes were given by the vehicle, no check engine light on. The vehicle idles extremely rough and has a hard time keeping a steady idle. Sometimes its near 1k rpm, sometimes 500 etc. Sometimes it keeps slowly dropping while running extremely rough to the point where you think its going to stall out and then the idle will just pick itself back up again. While accelerating there is an intermitten hesistation, sometimes it accelerates normally and sometimes it feels extremely underpowered.

There was only about 1/5th tank of gas so we put in a fresh tank thinking possibly bad gas. It seemed to help the problem a tiny bit but still mostly the same. My buddy cleaned the throttle body, checked the maf for dirtyness, cleaned battery terminals, threw some stuff in the gas tank to dry the water (not sure what its called), still has the same problem.

So as of right now the problem is ongoing but it seems to consistently start and run. Not really sure where to go from here, but the problem still exists. Thinking something like fuel pump, computer, maf, coil pack, some sort of sensor....obviously thats a long list.

Thoughts/opinions/help???

Thanks alot,

Mike

 

[1337_3xp0r3r]

sounds familiar

Yeah, I had that prob too a couple of years ago, too us ###in forEVER to figure it out what it was.






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[2000StreetRod]

clogged fuel filter?

The first thing I would check is the fuel pressure, especially if you have never changed the fuel filter.

 

[The_Hammer]

Yeah, I had that prob too a couple of years ago, too us ###in forEVER to figure it out what it was.






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What did it end up being? hah.

I actually just recently changed the fuel filter. I did alot of maintenance about 4k km ago. Oil/filter, plugs/wires, air filter, coolant flush, fuel filter, injector cleaner. But i've been driving fine for 4k km with all of that done and even took it on a long 3k km road trip with no problems.

After driving it around the past day now the problem seems more clear to me. There is definitly something wrong at idle. Every time i come to stop the idle is initially fine and holds steady, then will slowly drop and get really rough, sometimes the idle will then pick itself backup to normal and sometimes it will just stay idleing really rough around 400 rpm as it appears on the stock tach. When you accelerate when it is idleing rough the initial acceleration is pretty rough and gutless then it gets better.

It seems to be more or less fine while driving at cruising speeds, although it does still seem a bit underpowered and seems to not run as smooth as it did before, although this is pretty minor and could be my imagination.

The idle problem is very consistent.

 

[2000StreetRod]

Check the plugs

I would try to determine if the problem is for all cylinders, one bank or the other, or for an individual cylinder. Although it's a pain to pull the spark plugs, that's the fastest way I know to make the determination assuming it has been happening for enough miles that a plug would show it.

 

[The_Hammer]

New Updates

I have some new updates on this problem which is still ongoing.

The vehicle never gave a check engine light originally untill yesterday. Just after accelerating through the rough idling the light came on. So I got it scanned, just one code.

P0305 - cylinder 5 misfire.

We pulled out the plug from cylinder 5 and it looked like it was golden brown, different from cylinder 6 plug which we also took out to look at, which looked normal. So I swapped the cylinder 5+6 plugs to see if that was the problem. I hooked up the scanner/logger to the vehicle and when idling rough it still showed cylinder 5 misfire. I took this as a sign that the plug was fine. Then swapped the plug wires from cylinder 5 + 6. Still misfire cylinder 5. I took this as a sign that the plug wires are fine.

We then hooked up the fuel pressure guage and it seems to be fine. Stays at 30 when the vehicle is idling like ****, doesn't drop off or bounce around, seems fine while accelerating. So the fuel pressure/filter/pump should all be good I assume.

We then did a fairly quick check for vaccuum leaks by spraying with some cleaner while the vehicle was running. Didn't find any major or minor leaks. There still may be a leak that we didn't find, but no majorly obvious leaks.

So I am still not sure what is wrong, we definitly eliminated a few things I think.

Coil pack? Or is there some sort of air control device like an EGR on these vehicles? Computer?

 

[2000StreetRod]

actual misfire

The following is from the Ford 1998 OBD System Operation Summary:
"If a single cylinder is determined to be consistently misfiring in excess of the catalyst damage criteria, the fuel
injector to that cylinder may be shut off for 30 seconds to prevent catalyst damage. Up to two cylinders may be
disabled at the same time. This fuel shut-off feature is used on many 8-cylinder engine and some 6-cylinder
engines. It is never used on a 4-cylinder engine. After 30 seconds, the injector is re-enabled. If misfire on that
cylinder is again detected after 200 revs (about 5 to 10 seconds), the fuel injector will be shut off again and the
process will repeat until the misfire is no longer present. Note that ignition coil primary circuit failures (see CCM
section) will trigger the same type of fuel injector disablement."

The funtional sensors to detect misfire are CKP and CMP. I assume they are functional or you would have other DTCs set. One way to confirm that #5 is actually misfiring is to let the engine warm up fully then shut the engine off and disconnect the IAC valve electrical connecter. Immediately try to restart and see if the engine will idle. If so, note the rpm and then attach ground to #5 plug wire and note the rpm drop. Then unground #5 and let the engine rpm speed up and level off. Then attach ground to #6 plug wire and note the rpm drop. It should be more than that for #5 if #5 was actually misfiring. If the engine won't idle with the IAC valve disconnected then try the same process with it connected. The rpm drop will be brief and harder to note because the IAC valve will bring the rpm back up.

You can also perform a compression test and compare #5 to another cylinder making sure that the test is done at WOT. If #5 compression is comparable to other cylinders then you can conclude the problem source is injector or spark. If you had a V8 you could swap the coil packs to see if the misfire moved to another cylinder. Ford uses a waste spark ignition system (two plugs fire at the same time - one in compression and one in exhaust stroke). For V6 engines #1 and #5 are paired. You should be able to swap wires for #1 and #5 at the coil pack without impacting how the engine runs. If the misfire moves to #1 then the problem is ignition. If it stays with #5 then the problem is the injector or compression. Don't forget to clear the DTC before each test.

 

[The_Hammer]

The problem seems to be getting worse and worse. Yesterday I had my check engine light actually flashing at me and the vehicle was extremely underpowered. I just barely made it home. I decided to pick up a new coil pack. I installed that today. It didn't seem to make much of a difference. The vehicle seemed to be idling higher than normal when cold after putting in the new coil pack but it didn't fix the rough idle or loss of power problem. I didn't venture to far away from home so didn't drive it much with the new coil pack, but it was obvious the problem was still there.

Are there any other ignition parts which could be faulty besides the plugs, wires, coil pack?

 

[The_Hammer]

So if the coil pack didn't fix it, whatyou're suggesting is that its the fuel injector(s)?

 

[2000StreetRod]

injector or compression

So if the coil pack didn't fix it, whatyou're suggesting is that its the fuel injector(s)?

The easiest thing to try is disconnecting the electrical connector to the #5 injector to see if the idle rpm is any lower than when its connected. If not, you need to clean or replace the injector.

 

[The_Hammer]

Ok I will attempt that.

Any chance it is some sort of sensor. I've been reading about problems with IAC, DPFE, ACT, IAT etc etc. ???

 

[2000StreetRod]

make sure not ignition

I'm still a little concerned that ignition to #5 could be the problem. So far you have swapped the plugs and wires between #5 & #6 and the misfire DTC stayed with #5. You also replaced the coil pack with virtually no improvement. But you haven't actually proved that there is spark to #5. Do you have one of those inexpensive ignition testers? They're less than $10 at AutoZone or Advance Auto and well worth the money.

 

[2000StreetRod]

Sensors & misfire

. . .

Any chance it is some sort of sensor. I've been reading about problems with IAC, DPFE, ACT, IAT etc etc. ???

A bad sensor or bad IAC or DPFE definitely could affect your engine but should not trigger a single cylinder misfire DTC.

 

[The_Hammer]

So we checked all injectors and they are all working equally fine...also all working equally fine while the vehicle is misfiring. We hooked it up to the scanner again and now are getting misfires in other cylinders. I think Cyl 1 and 2 are the only ones we didn't get a misfire in. I got P0300 CEL code : random misfire.

We have pretty given up on it now and i'm going to take it to the dreadded dealership and hope they have can quickly fix it. I've been dickin around with it for too long now. I will let you guys know what the eventual fix/problem was...if there is one.

 

[The_Hammer]

Eventual fix: There was water and a bunch of sediment in the gas tank, fuel filter filled with water. Gas tank needed to be ripped out and cleaned, get rid of all water, new fuel filter, clean lines.

We had originally thought of this when we were looking at the vehicle. We put some drying chemical into the tank and that didn't fix it. We had also just replaced the fuel filter like 2k km ago. So with these two things we kind of discounted this and didn't pull the fuel filter off (which was filled with water).

Truck runs mint now 600 bucks later.