CEL Misfire

[tebo77]

Hi all. I have a 96 Windstar 3.8 with 217,000 miles. I have found some valuable information on this forum, but I've tried almost everything and still getting a misfire. My question is does it take a few hundred miles for the codes to reset or could there still be a problem? I have done a tune-up including wires and used double platinum plugs gapped correctly, all O2 sensors, egr valve (replaced as cleaning did not get it to stop leaking), and cleaned egr ports and all injectors. I'm not losing any antifreeze.
I know the Chilton's manual says you may still get undesirable results until the codes clear. Trying to get a NYS inspection, which includes emissions and will not pass with CEL on! My misfire codes are for cylinders 1 and 4.
Also what is DPFE and should I clean or replace that? Thanks for any help!!

[khadma]

All the electronic/electrical parts require the computer to be reset after the installation of new parts. It is a good idea to disconnect the neg side of the battery when doing this type of work.
Letting the van sit for about a half an hour unplugged will reset the computer.

After that the van needs to be driven through many different conditions so the computer can relearn parameters.
This could be the reason for CEL - COULD BE. There still can be other items missed that needs attention.

Codes may have to be cleared through the OBD scanner too.

Can you actually feel the misfire?

Camshaft position sensor, coil(pack), DPFE may need replacing.
DPFE - differential pressure feedback EGR or backpressure transducer.

Check that the 1 and 4 wires are in the proper location.

[tripletdaddy]

The DPFE, is the differential pressure feedback sensor measures two exhaust pressures across a special metering hole. This info is used to control the EGR system (how much to open the EGR valve). Typically, if there is a big enough problem with the dpfe, a code will be set (P1400 -P1408) See for details on these codes,
http://www.automotiveforums.com/vbul...d.php?t=677408

If you don't have a code, it probably is all right. If it was working badly enough, I would think you would get fault codes for the EGR system or something like that in addition. On my 95, long story short, the heat of the exhaust broke down the aluminum body of the dpfe sensor, making it crumble. It was hard to keep the hoses on the deteriorating hose nipples, and the inlets became plugged with the white powdery crud. I couldn't get it out past a 90 deg turn. So, I think it made it have at least one code, and the codes would return after every time I reset the codes. The code I think was for the dpfe sensor having incorrect pressure readings. Between the condition of the sensor body, the plugged inlets and the codes, the wife said, "replace it." It would have needed it eventually. She didn't see the point in putting it off for later, when we both knew eventually, it would need to be replaced. Sigh.....

[tebo77]

Yes, the camshaft position sensor was the first and only code that came up when I purchased the vehicle 2 months ago. Once that was replaced, we got oxygen sensor 1 bank 2, misfire cylinder 1, egr valve, and catalytic convertor may be getting damaged (my neighbor's bf has the code reader and told me, so I don't know the numbers that came up). Since O2's were $25 on ebay, I just got all of them figuring it couldn't hurt with the price of gas today plus the mileage of the vehicle, and we were planning a tune-up anyway for the same reasons. Cleaned the egr valve but could still blow through it, so we replaced that too. Ran 2 tanks of sea foam through.
Then after disconnecting the battery and driving until the light came back on, we got misfire cylinders 1 and 4, nothing on the catalytic convertor (phew!). Yesterday I took the upper intake off and cleaned the egr ports and fuel injectors...though I doubted it was fuel-related since we ran cleaners and ended up with another misfire...I was there to do the egr ports and wasn't gonna leave the injectors undone! So this is where we're at now with the light back on.
I think if I take out the wires for the bad cylinders one at a time and use a test plug, that should tell me if its the coil pack, correct? I'll do that today and have the codes cleared/read again and see what happens. I'll see if there is a code for DPFE coming up. I'll ask him this time for the number codes. Thanks and I'll let you know what happens.

[tebo77]

I can feel the misfire when accelerating and it is evident at idle. I will also check in the manual for correct wire placement. They went exactly where I took them off, but who knows if that was right?!

[tripletdaddy]

You could also test you coil for cylinders 1 and 4 by swapping those cylinder wires to the paired cylinders of the coil. Move 1 to 5 and 4 to 3. For now we can assume your new wires aren't part of the problem. However, there have been some people who have found lower quality wires to create problems that only high quality wires like Ford's wouldn't have. The coil can also be resistance tested with an ohm meter, but it isn't 100%.

[tebo77]

Everything checks out with the firing. The misfire code does not come up on the local Monro Muffler shop's diagnostic comp. That one just says the egr valve code has not cleared yet, and when it does it should pass inspection. I can still feel it misfire, so it's weird but hey, I can deal with that if I could just get a sticker and then I won't feel rushed! I will keep the forum posted. Thanks for all the help, tripletdaddy and khadma!

[wiswind]

A misfire can also be caused by a dirty fuel injector.
I have been bit by this bug several times......and chased all over....only to find that it was dirt inside the "end cap" which is over the spray end of the fuel injector.

The ONLY cleaner that I have found that I can add to the gas tank to clean this up is Berryman's B-12 Chemtool, in the metal can.
So I would try this......as it is a cheap and easy thing.
It might take a couple of tanks of gasoline....each treated with a can of Berryman's.

For the EGR code.....if it says not enough flow....and I think I saw that you said that you cleaned the EGR ports in the intake.......that would leave the DPFE.....or possibly the vaccum connection to the top of the EGR valve (maybe got bumped, etc)
DPFE is easy to change.

[northern piper]

if you do end up getting a new dpfe, make sure it's one of the black plastic models, not the cast aluminum one that may be installed on your van. There are problems with the aluminum ones corroding and I've seen some auto parts places that still have the old aluminum stock ones around. You want the plastic one.

Piper

[tebo77]

Pardon my ignorance, wiswind, but is the spray end the "up" side or down in the intake? I did the "up" side when I had it apart, the caps that are on the fuel rail. I have read several of your posts and thought I was cleaning those caps you mentioned when I did the ones on the rail.
I am also wondering, does the CEL go off by itself when the codes are cleared (by the car, not resetting them manually)? For instance, when I went to the Monro shop and they told me once the parts are changed, it takes 50-100 miles for the codes to clear. Hence the egr still coming on their reading. The O2 sensor codes were still being read until appr 150 miles went by. So once I've driven 150 miles or so, should I disconnect the battery and reset it or will it reset itself? I'm just wondering if it's possible to confuse the vehicle computer by resetting it so many times, or worse yet if I'm making it take longer for codes to clear by resetting to see if the CEL comes back on.
Oh one more thing we were curious about...when the upper intake was off, there are some butterfly looking valves visible inside the lower intake. Can you move these with your hand? If so they are seized. Thank you.

[wiswind]

If you removed the injectors...and cleaned the end that goes into the head....then you cleaned the spray end.
I would STILL put a can of the Berryman's in to finish it up.

The "butterfly" should move...but they are held OPEN by a pretty strong spring.
They are mounted on a shaft....that runs through the lower intake manifold.....1 rod with 3 "butterflies" on each rod.
The actuator uses vaccum from the intake to pull them CLOSED when you start the engine.
Then....under hard accelleration, the PCM sends a signal to the IMRC actuator Solenoid to interrupt the vaccum to the actuators.....and the springs pull them open.
So.....it is like the old time "4 barrel" carborators.......the extra port per cylinder is opened up only under hard accelleration......
If they are not working....you will get a code that indicates this.....and the CEL will be lit.

The CEL stays lit for a certain number of failure free "drive cycles".....so it will still be lit and the code(s) will still be there until the PCM sees a certain period to time without a fault.
This is to make it possible to troubleshoot intermittent problems.....as the code his held long enough for you to get them read.

You can reset them by removing the negative battery cable and leaving the headlights ON (to drain any remaining power from the system) for 15 minutes......then turn the headlights OFF....and reconnect the negative battery terminal.
You will need to have some time driving the vehicle for it to "relearn" the "drivability" information........and until this happens, there will be a code stored (but no CEL)....and most state testing facilities will still fail you until this "learning in process" code is cleared.....

[derffred]

Read my thread, http://www.automotiveforums.com/vbul...d.php?t=903467
name of thread is "98 3.8 rough idle missing? tried many things "
It is on page 2 of the windstar thread, I also tried many things
the best thing I did was get a scan tool, I bought the Mac tools ET50
http://www.mactools.com/Mac/Mac+Prod...can+Tools/ET50
so after each thing I tried I could clear the codes and see what codes returned.
in the end I had the clogged egr ports which I took off the intake upper and cleaned, I changed the fuel injectors that came up as misfires and the biggest problem was a vacumm leak (for me it was the thin white plastic vacumm line snapped off going to the evap which is on the firewall which I only saw when I changed the injectors (easier to see back there when you remove the cowl) so I reconnected that line and the engine has run perfect ever since and I have no codes what so ever in the last couple of weeks.

[tripletdaddy]

Ditto on the plastic rather than metal dpfe sensor to avoid the metal from breaking down and plugging it up.

[tebo77]

Ok, running my first tank of Berryman's presently. We cleared the egr code so can probably rule out DPFE but are still getting the misfire on 1 and 4 coming up, I think p0301 & p0304. It is getting spark so that probably rules out the coil pack. My neighbor's bf with the scan tool says if the injectors are dirty inside it may not have fixed the problem cleaning them externally. But hopefully the Berryman's will solve this. I tested all the wire harnesses while it was apart so the injectors are getting power to them. So unless the injectors themselves are failing, I'm not sure what else it could be. Derffred I may be getting a few injectors from the boneyard like you did!

[Ed_Strong]

Originally Posted by tebo77

It is getting spark so that probably rules out the coil pack.

Not necesarily...! I would recommend you remove and inspect the coil pack for cracks or hairline fractures around the plastic molding of the bottom casing. This cracks could be causing the coil to deflect spark to ground causing a missfire condition.
Also you could check at a dark night with the engine running for arcing of the coil or spark plug wires.