Intermittent misfire

’96, 3.8L, 208k
I’ve been getting an intermittent CEL indication. The check engine codes always indicate Cyln #4. The misfire occurs at idle after the engine is hot, after stopping the engine for a short period (i.e. refueling). The CEL will blink, as the misfire is severe. When the car is driven after this occurs, it runs OK and the misfire does not occur at a later stop to idle. After a few warm-up cycles, the CEL will clear.

The engine codes have been ‘cleared’ by disconnecting the battery. When the condition reoccurred, it still indicated the #4 cylinder. No other code has been reported (rich/lean).

I changed the plugs, no change.

I’ve considered checking all the standard issues (fuel injector, plug wire, manifold gasket), but I thought I’d ask for any insight that might be available here to short circuit the process.

Im guessing your egr ports are plugged. A common problem on these.

I'd expect plug cables, or ignition packs ... as the most likely candidates. I think egr jets were not such a problem 'til '99 ... but I'm not sure.

Thanks for the suggestions.

EGR ports are probably not dirty. I forgot to mention that they were cleaned when the plugs were changed.

The plug wire/coil pack is something to be considered, however wouldn't two cylinders be reporting misfires, given the manner in which they are connected? (i.e. plugs #4 and #3 are serially driven through the same coil, that is if I remember correctly that the firing order is: 1,3,5,2,4,6)

Good thinking. But it turns out that the coil, which normally "floats" between the two plugs, can become grounded (or partially so) on one side. This results in the ungrounded side getting all the "juice" ... the grounded side getting none. A grounded/leaking plug cable will yield the same result.

Sometimes a good top cleaning is all that's needed on the coil pack ... along with cable wiping ... if you're lucky, that is.

I'd expect plug cables, or ignition packs ... as the most likely candidates. I think egr jets were not such a problem 'til '99 ... but I'm not sure.


Nope. the older ones did also.


When the ports were cleaned you had the intake off? Very common to have them plug, and lean out the last two cyls.

Good point regarding the plugs/wires/coil. I'll try to look into that one. I could swap two of the coils to see if it moves.

On the EGR ports, I removed the intake plenium, which exposes the EGR ports. I've had misfire problems in the past due to EGR cloggging, so that's one of the first places I look. While I had the plenium off, I changed the plugs since the rear bank is much easier to access without the plenium in the way.

On my '99, the coils are not "movable" ... but the plug cables on a single coil could be swapped, moving the misfire to the "sister" cylinder.... if its the coil and not the cable.

I just resolved a similar problem with my new to me '98 3.8L with 83k. After cleaning everything from the lower intake manifold gasket back to the air filter, replacing the plugs and wires, the DFE, and a couple of vacuum lines, I had an intermittent misfire in cylinder 5 at idle only when warm. Replacing the throttle position sensor did not solve the problem. Replacing the idle air control fixed it.

I have, on several occasions, chased around trying to deal with intermittent missing on my '96 3.8L.
My mechanic directed me to Berryman's B-12 Chemtool, which is a solvent based cleaner that you add to the gasoline tank.
I know that I sound like a broken record to those who frequent this forum, but this product has resolved the issue a number of times for me.
Even when other fuel additives have not worked.
I even tried using several fuel additives at each fuel up in a maintenance dose.....and still ended up using the Berryman's to clean things up.
The problem that seems to happen is some build up develops up inside the "end cap" of the fuel injectors, over the spray end.
I still use a fuel additive at each fill up, Schaeffers 131C Soy Ultra, but STILL need to use the Berryman's a couple times a year.

So, that said, I would try treating up to 3 tanks of gasoline with the Berryman's, as it is about the cheapest and easiest thing to try.
You can get this product at AutoZone, and many other auto part stores.
I use the one in the metal can.

Of course, plug wires can be old and failing, as well.
The issue that seems to come up with the coil "pack" is a small crack can develop in the epoxy body.....and the high voltage arcs at that point.
You may or may not be able to see the crack....but it involves removing and cleaning the coil pack to inspect it.

Myself.....if I am going to do that to a 10+ year old coil pack......I would buy a new one.....and install it....along with new plug wires.

Now....having outsmarted myself a few times in the past with other cars.....and crossing a plug wire now and then....VERY easy to do.
I only remove 1 plug wire at a time........so that I do not mix them up.

Some dielectric grease at each end of the spark plug wire (coil pack and spark plug ends) will help to provide a better weathertight connection by sealing out moisture.
It also makes removal the next time easier.

I all!:licka: I have a 98 Windstar with the same problem. I have read the code and p0171 and p1506 and a misfire on cylinder #2. I have changed the IAC removed and cleaned the Throtle Boby and Upper intake. :banghead: Cleaned the egr ports, they were not pluged but cleaned anyways. Changed the plugs and wires still no change. Fuel pump was changed 1yr ago and the IMRC plastic inserts were change. Still no change. HELP :shakehead

Any sugestions would be great. I still have to look into the Coil pack and fuel injectors.

Thanks

P1506 is IAC overspeed error, do you still get this code after changine the IAC?
If so, did you get this same code before?

Dirty fuel injectors(s) can cause the misfire code, in fact that is what caused a misfire on cylinder #2 on my '96.
Dirty fuel injectors can also cause lean code(s) due to the fact that the PCM is trying to compensate for the lack of fuel from dirty fuel injectors......and cannot.

Otherwise, vaccum leaks are the most common cause of lean code(s).

P1506 is IAC overspeed error, do you still get this code after changine the IAC?
If so, did you get this same code before?

Dirty fuel injectors(s) can cause the misfire code, in fact that is what caused a misfire on cylinder #2 on my '96.
Dirty fuel injectors can also cause lean code(s) due to the fact that the PCM is trying to compensate for the lack of fuel from dirty fuel injectors......and cannot.

Otherwise, vaccum leaks are the most common cause of lean code(s).
Yes I still get all the codes after changing the IAC. I leaning towards the fuel injector myself. It is cold here right now so hard to do the woork right no waiting for a warm spell. Any suggestion on changing the injector before I get started?

OK, I read in your first post that you have had the upper intake manifold off and cleaned the EGR ports.
Hopefully the upper intake manifold is seated correctly, and you are not getting a vaccum leak there.
The original upper intake manifold gaskets are re-usable....and mine were in very good condition, when I replaced them trying to track down my slight misfire issue........and it did not solve the issue (dirty fuel injector at the spray end)

From what all you have done......and my personal experience that every time I take something apart, I introduce the chance for something to go wrong.......and the weather is not the best for doing quality work....unless you have a heated garage......I would lean away from taking the upper intake manifold back off at this time.

Removing the fuel injector for cylinder #2, which is in the rear bank......middle cylinder......would call for removing the upper intake manifold.
Add to that, I will bet that all 6 injectors have some degree of the nasty sludge up inside the "end cap" over the spray end of the injector......
So, my recommendation is to buy 2 cans of Berryman's B-12 Chemtool in the metal can.
Put one in each of the next 2 tanks of gasoline and drive the vehicle.
This does seem to help cut the sludge in there....and clear it out.
This is the cheapest and easiest thing to try.....and has a good chance of working.

Changinging the fuel injector, you will need to release the stored pressure from the fuel rail, by pressing inward on the needle valve in the pressure test point in the middle of the front of the fuel rail.
I hold a BIG rag to let the fuel spray into......and soak it up.
Then you will remove the upper intake manifold (I remove the throttle body and set it aside with the throttle linkage attached as much as possible.
I also leave the fuel line CONNECTED to the fuel rail (why risk the chance of a leak from not connecting it back right...or bending something).

NEXT I use some spray brake parts cleaner to thoroughly clean the area in the head around each fuel injector.
Spray the cleaner liberally to flush the dirt away......as it will be very likely to fall down inside the head upon removal of the fuel injector(s).

Then, I remove the screws that hold the fuel rail to the motor.
I also unplug the electrical connection to each injector.
Now, it might be good to look at all the injectors.......so you can pull UP on the fuel rail....and it will pull the injectors up out of the head.
You can then slide the clip that holds the injector to the fuel rail.
Then you can clip the new fuel injector into place.
If you just want to spray cleaner up inside the end cap, leave them clipped to the fuel rail and use spray INJECTOR cleaner to spray up inside the end cap and let the liquid run out.
I say with confidence that the input to the fuel injector......with a screen is just fine.....so don't worry about that.

Before putting the fuel injectors back into the head, put some clean motor oil onto your clean finger....and rub it onto the "O" rings on each injector.
This will help the injector to slide into the head without damaging the "O" ring gasket.
Use ONLY motor oil for this.

Now, what I observed on my injectors is a tar-like build up inside the end cap....which caused the injector to not spray.
The input side of the injectors was squeeky clean.
I have been told that the goo is from a combination of the condensation of the oil vapors from the PCV line combining with the soot from the EGR gases.
This tar gets onto the IMRC butterflies......you may have seen it when you cleaned the EGR ports.
Anyhow, understanding where the dirt comes from.....you will understand that it is NOT the fuel causing the issue....

The Berryman(s) will NOT clean the IMRC butterflies or the EGR ports, as the fuel sprays through the injectors, and goes right into the cylinders.....never gets to these other items (if it did....you would have serious problems).

If you get a replacement fuel injector.....I would stick with OEM so that it will be matched to OEM specifications.
There are a lot of fuel injectors available, and if you get one that sprays more fuel for the electrical pulse that the PCM sends....you will have issues with engine performance.
The PCM is counting on each injector spraying the same as all the other injectors for a equal electrical pulse.

tomj76'
Did you get your problem resolved? By the way, the firing order on all Windstars (I believe) is 1-4-2-5-3-6. Therefore, the "pairs" are 1&5, 2&6, 3&4.

Windimpala,
Is there a chance someone has adjusted the throttle stop screw ... leaving the plate "too open" when the plate should be closed?

tomj76'

Windimpala,
Is there a chance someone has adjusted the throttle stop screw ... leaving the plate "too open" when the plate should be closed?

I can't see the stop screw being moved. It looks like a set screw with out a hex for an allen key!:) But it would be possible to do this with a couple of nuts jammed up together. Any ways to answer your question NO it has not be tampered with. Good thought.:wave: Still waiting for warm spell here or Santa to bring me a heater for my garage.!!:grinyes: The van is running well when it not missing. 256K and counting.

[quote=12Ounce]tomj76'
Did you get your problem resolved? By the way, the firing order on all Windstars (I believe) is 1-4-2-5-3-6. Therefore, the "pairs" are 1&5, 2&6, 3&4.

Well, as the problem is intermittent, it's been gone for a while now. The MIL came on one day last week when my wife was driving it, presumable for the same symptom, then went off the next day. In short, I haven't tried any fixes yet.

You may want to purchase new fuel injector end caps (also called "pintle" caps) before you clean the injectors. One of my end caps had become brittle. Auto parts stores carry the o-rings but not the end caps. You can find pintle caps on e-bay.

You may want to purchase new fuel injector end caps (also called "pintle" caps) before you clean the injectors. One of my end caps had become brittle. Auto parts stores carry the o-rings but not the end caps. You can find pintle caps on e-bay.

I got oring/cap kits for my inj's from a guy called Mr Injector on ebay. GREAT service!!!! I have rebuilt the ones on my Windstar, and my Bronco

Still have not yet found the cause of this, however I noticed while driving on Monday that it now makes a gurgling sound in the back (gas tank?) when you first turn the key on after it has sat for 15-20 minutes, after being driven. If you start it right away, it misfires. If you don't but turn the key on/off several times until the gurgling stops, then it runs OK. I'm guessing that turning the key several times is needed since the pump only runs for one or two seconds when you turn the key on.

I need to check for a possible leak in the fuel line (air getting into the fuel line, apparently on the supply side, if misfire is due to air in the fuel line).

It's interesting that you don't notice this when the vehicle has sat for long periods of time.

Aha! New clues! It's possible that the gurgling you are hearing is caused by the fuel pressure regulator (located on fuel rail) is not re-closing properly. I would replace the regulator ... not that expensive.

... you could first test the gasoline pressure if you have access to a test gauge.

I have a fuel pressure gauge and I was planning to check fuel rail pressure at the fitting as well. I'm not sure how even an open regulator would cause this, but I'm open to anything on the path to uncovering the real cause. I want to fix the real problem. Right now I'd expect that the gauge will read low before turning on the key. I think the fitting is behind the regulator, on the fuel rail, so I won't see the pump output pressure directly.

My idea of this problem is that once the gurggling sound stops any bubbles (air or gas vapor) have been pumped through the fuel circulation lines and back to the tank.

I downloaded the troubleshooting chart from Autozone website, and I checked the fuel pressure as described. It's 38 psi without the engine running, with the pump running. It drops to 30 psi when the engine is running. It goes up to 40 when the engine is running and the vacuum is disconnect from the regulator. It holds pressure when the engine is turned off. It follows (albeit very slowly) variations in the vacuum level.

However, things were "working right" (i.e. no symptoms) when these tests were performed. In addition, I tried to get it to "make bubbles" as mentioned in my previous post, but I couldn't get that to happen. It still happens, but only under the right conditions (including away from my garage!). Fortunately, the vehicle works and passes emissions, so I'll continue to keep and eye open until I can get to the cause of all this.

I would replace the coil pack as suggested by 12Ounce as this could be the cause of the problem. Another member who has been posting for a while now, has just figured out that the issue with his van was the coil.

http://www.automotiveforums.com/vbulletin/showthread.php?t=756904&page=3

Thanks for your suggestion Marz. I saw that thread and for a lot of misfires that might be the cause. I'm not so sure in this case, because of the whole gurggling symptom. I've started the car, noticed it misfiring and then turned it back off. Then upon turning the key to run without starting the engine, the gurggling can be heard. Once you cycle the key enough to get it to stop making that sound, it starts and runs fine.In addition, I've heard the car gurggling before starting it, and if I did start it then it would misfire. On the other hand, if I cycled it until the gurggling stoped (without ever starting it), then it would start and run fine.I firmly believe (right now) that the misfire is fuel related, not spark, but as always it's best to keep an open mind. I'll just have to wait for more evidence before running out to buy parts.

It seems you have clearly described a situation where air or maybe a vapor/vacuum is being created in your fuel lines, likely due to the draining or loss of fuel, after you shutoff and before you start your van. So the million dollar question is where it's coming from or what is creating it, ie. what is allowing the movement of fuel? 12ounce suggested the fuel pressure regulator could be faulty. It could be allowing drainback if not closing fully, causing a gap in the fuel. It also could have a diaphram leak into the vac connection. Pull the vac line to the fpr to see if it is leaking fuel there. What sort of fuel pressure do you have after letting it sit for awhile? Is there a strong odor of gas at the engine? For some reason I think there is also a check valve in the fuel system, but I would need someone else to confirm that and its name. Could this also be related to the evaporative emissions control system, EVAP ? It's been know to cause poor idling, stalling, and poor driveability. I know there is a vapor management valve on the top the tank that's part of the evap. If not closing properly, it could allow air to leave the tank via the evap line and allow fuel drainback. Any supporters?

tripplet:

Thanks for the suggestions.

I detected no gasoline odors either in the engine compartment in general, or at the regulator vacuum port.

It repeated the behavoir last night after I drove it 15 miles and let it sit for ~30 minutes. Upon turning the key to "ON" I could hear the gurggling sounds. Later I tried to repeat the event, so I ran it at idle while parked until the fans came on. Then I turned it off and let it sit for 30 minutes. It did not gurggle again when I turned the key to "ON". I don't know if taking it for a drive would cause it or not.

Those are good places to look. So far, I've eliminated the fuel filter as there is good pressure both prior to startup (no flow) and while running without the vacuum connection to the regulator (heavy flow). The pressure with the vacuum connected is low (30 psi compared to spec of 35 to 45 psi), so the regulator is still suspect in my opinion. The pressure responds as expected to low vacuum.

The pressure is well maintained with the engine off, with no noticeable drop after five minutes. I does drop to ~20 psi after 30-60 minutes.

I didn't notice a check valve described in the manual, but I'll check for that again. I'll also check for any potential connection to any EVP issues. I don't recall how the EVP is connected to the fuel injector delivery loop, if at all.

Well, I replaced the pressure regulator ~4 weeks ago, and since then I've not heard the gurggling noise. There were a few times when I thought it might have been running rough at startup, but the CEL never indicated that there was a significant misfire.

It looks like the regulator was somehow the culprit, although there was no reason to suspect it. I ran the troubleshooting proceedure outlined in the manual, but did not find any fault. The only reason I changed it was due to a confusion in the service manual about the spec for the regulated fuel pressure (two different values/ranges quoted in different parts of the manual). I didn't notice my mistake until after the regualtor was changed.

Thanks for the help.

I guess I spoke too soon. My wife reported that the gurggling was heard again resulting in the CEL turning on when she drive it on Thursday. The search continues.

I think/hope this was resolved recently as it has not occured for about two months. It stopped after the transmission was removed (via subframe removal), torque converter replaced, and reinstalled.

I'm guessing that the routing or connection of some fuel line was not done properly the first time the transmission was serviced, which introduced the problem. The redo must have "got it right".

Although this is an old thread, I wanted to provide a final update, because the gurggling sound has now been completely eliminated. I can't definitely prove it, but believe there was an issue with either the fuel line connections to the fuel rail, or the connections to one of the fuel injectors.

This spring I was forced to replace in lower intake manifold gasket due to a coolant leak. Since this work requires removing the entire intake manifold, the fuel lines needed to be disconnected. In the course of this I also decided to remove each fuel injector for reasons that I now don't remember. There has not been any reoccurance of the gurggling or the misfiring associated with it since this repair was completed. I don't believe the intake gasket was involved in the gurggling, since it is not part of the fuel delievery system. My best guess is that the o-ring seal between the fuel line and the fuel rail was somehow causing this.

The gasket leak was in the area of cyl 4, so the misfire on that cyl may have been related, at least in part.