Help me pin point this rought idle...!

[Ed_Strong]

A couple a weeks ago my 2000 Windstar 3.8L started having a slight rought idle at around 51K miles and now it has progressed to a bad engine shake like a plug is missing. Weird thing is that it doesn't feel like the engine is loosing power.
The trembling feels the strongest from idle to about 1500RPMs and it almost dissapears after RPMs go higher. When I let go off the gas pedal it coasts down normally but then wobbles the engine when it goes thru the same RPM range (1500 and lower).

I've been using Berrymans B12 on the tank regularly, bout every 6mos.
Had the IAC cleaned and sprayed the inside of the plenum thru the PCV and Fuel Pressure Regulator openings 2 week ago.
Replaced the Air & Fuel Filters, cleaned the MAF & TPS Sensors and the TB and sprayed the inside of the plenum thru the TB a little more today.
I looked over the wires and vacuum hoses and didn't see anything wrong.

Nothing seemed to work...
What else do you guys suggest?

[wiswind]

I would think that you would get a CEL...which would get you a code to help you pinpoint the cylinder.

It could be a spark plug, spark plug wire, or coil pack.

A IMRC problem should light a CEL also....but give them a look to see if they are actually connected.
I seem to remember that your 2000 will have electrically actuated ones.......and they may be a bit different than my vaccum ones.
A broken "clip" may have one or both sides not following the actuator.....and cause a problem.

[Ed_Strong]

Thanks wiswind...
I knew I was forgeting something! There's no CEL, intermitent or constant, the IMRC are connected and yes, they're electric. Also, when I did the Isolator Bolt fix last summer I also cleaned the EGR Ports real good and put new AutoLite Plats.

[wiswind]

You could sill have a coil pack or plug wire issue.
The other thing that seems to have come up a few times is fuel delivery issues.
There is no sensor for fuel pressure or fuel flow....so there will not be a code to indicate a problem there.....just symptoms......an maybe a code indicating the symptom.
From reading posts, there are a couple of relays in the power distribution box in the engine compartment that can cause fuel pump issues.
Also, more difficult to track down......there have been a few problems posted that ended up being a failing fuel pump.....good pressure at idle...but cannot keep up under load.
The only way to really troubleshoot that would be to use a remote fuel pressure gauge, and take it for a drive.
That is something that I would go to my mechanic for.....as I am sure that a quality fuel pressure gauge for this would cost at least as much as paying for a couple hours of qualified labor.

[Ed_Strong]

I sure hope is not the fuel pump...! One thing to note tho the roughness as stated in the original post is worst from idle to about 1500 RPM and almost clears at anything above 1500 RPM. The engine doesn't starve for fuel or hesitates under load.
I'll see what I can do with the plug wires and coil first

[northern piper]

this is just a shot as you've really covered things well but on my 2000 the upside down "U" vacuum tube that's at the front of the plenum (can't recall the name -(coffee kick in!)) had a very loose fitting. I think the rubber over time just simply expands. Coupled with this at 1000 to 1.5k rpm was a high pitched whine. Anyway, in getting a new vacuum line that fit snug as it should the stall, roughness went away. This never coughed up a CEL for me but at low rpm it would act as you've said.

FWIW, my

Piper

[Ed_Strong]

That was the first thing I checked as at one time it had come undone on it's own as it was too loose and gave me a lot of trouble. It gets soaked with the oil from the PCV and cannot hold it self in place.
I clean it periodically to avoid trouble so right now it's holding on real good!
Thank for helping out.

[tomj76]

Listen for hissing noises while the engine is running. I've found several vacuum leaks using that time tested method. Don't let you long hair (or your clothes) fall into any moving parts.

One of the leaks I found was a split rubber fitting on the PCV breather pipe. The rubber was extreemly soft and gummy, but it was also making noise. Another one that I found was due to a plastic vacuum line rubbing against a metal AC pipe, back along the firewall. I just let my ears do the looking.

[Ed_Strong]

Update:

I just got done putting a new Ignition Coil and AutoLite Wire Set (black box) and the problem was still the same, no change whatsoever with the original problem. I removed the Cowl for better clearance and checked vacuum lines and electrical connections from problem and could find anything wrong. I numbered the wires to avoid crossing them over and marked the plugs orientatin on the coil.
But, now i get this new problem.

When I went to crank the engine it started turning really slow and then the starter motor started skipping, like it does when the battery dies. I plugged the voltmeter and the battery was holding 12.29 volts, at cranking went down to 7.99volts and after the engine started it went up to 13.85volts... revving the engine to 2500 wnet up to 14.09. Those numbers look fine to me, not sure why it's acting up.

Any way, I cleaned the battery contacts and put everything back together and same thing, it tries to crank then skips, then cranks and the engine starts running. After the engine starts there's a faint smell of raw fuel coming off the engine and the tail pipe, but it doesn't blow black smoke off the pipe. I disconnected the "U" line from the Fuel Pressure Regulator and didn't notice much difference (I was expecting the engine to stall), plugged it back in and the vacuum sucked it right in. Disconnected the EGR and plugged the line, sucked on the EGR thru a straw at idle and engine RPM went up a bit. So those look fine!

Went to take it for a drive and then everything went down south even farther. The engine started backfiring (sounded like it was making popcorn) and loosing power when put in gear, but it didn't stall. Drove for like 10 miles and didn't improve! I really don't know what else to do, don't understand how it got worse... Could it be the Fuel Pressure Regulator gonne bad or is it something else?
I can't believe I still don't have a CEL to track.

[busboy4]

Hi
FWIW, to my knowledge and by personal experience, if you "suck open" the EGR at idle, the van dies. So, perhaps, just maybe your EGR is stuck shut. Now I would certainly think you would trigger a CEL if this were indeed true, but it is a thought.

With the engine off and putting "man vacuum" on and off of the EGR I usually can hear the valve opening and closing.

Good luck

[Ed_Strong]

hmmm interesting...

Actually the RPM went up just a bit when I applied "man vacuum" to the EGR at idle and then the RPM went back down just a bit when I stopped applying vacuum at idle. While I was doing this test I could hear the EGR making some hissing sound.

The little tube that goes connected to EGR had just a little bit of vacuum to it but it was enough to hold a cap on it. Then, as soon as shut the engine off the cap fell off. Don't know if that would be the normal amount of vacuum needed, but I found it to be somewhat too low.

But none of this would cause a backfire condition would it? I don't understand how it went from bad to worse so suddenly. Is it possible I got a bad coil? The 1st time after the coil and wire set replacement the engine started with the same old simptoms (not so severe problem) and by the 3rd time I started it and took it for a ride all went worse!

I cannot figure why.

[wiswind]

It is normal for there to be a very slight amount of vaccum in the EGR valve's vaccum line at idle......it is not enough to open the valve though.

If you apply vaccum to the EGR valve's vaccum fitting, the valve should open.
If the valve is open at idle......the engine should die.
The EGR valve should be closed, and stay closed at idle.
It should take a fair amount of vaccum to open it.
If the valve is not fully closed when it should be......your vehicle will not run properly.
The EGR valve itself is not a high failure item.....but it can happen.
I would try working the valve manually by manually applying vaccum to it....with the engine OFF.....just in case you may have some carbon particles causing it to not seat properly.

Your slow turn over could be a weak battery or connection.
This can also cause you to have a wide variety of problems as electronic controls are sensitive to voltage issues.

As you smell fuel when trying to start......I would think that you are getting fuel......
Fuel pressure regulator is also not a high failure item.....but the vaccum line to it can have issues seating to it.
The pressure regulator will give you maximum fuel pressure with no vaccum applied, and adding vaccum reduces fuel pressure.
You can test the fuel pressure at the test point on the fuel rail......middle of the front of it.

You may need a good diagnostic at a well equiped shop that can monitor the various aspects of you engine controls.
Fuel injector firing, Camshaft position sensor, MAF, and vaccum leaks can be slight enough that the PCM does not throw a code....but is trying to compensate for a reading that is wrong, but within range.

[Ed_Strong]

So how about the relays? I should not worry about the relays?

When I tried cranking and it started skipping, the first thing I though of was the Starter Relay since the battery checked out good with the voltmeter.
I remember before reading about owners having weird stuff and being caused by a relay, Starter relay, Fuel Pump relay etc. I don't know where they are or what do they look like or how to test them.

[Ed_Strong]

OK I tried "man vacuum" on the EGR this time with engine off and the EGR operated normally, I could hear the diaphram move and it tasted awful...LOL
The Valve was able to hold vacuum pressure and stay put, altho with engine running it still revs up just a tiny bit when applying vacuum and settles down when vacuum is off but it won't stall as is supposed to. But I don't think thats the issue with the engine running rough and backfiring.

I Also unplugged the "U" shaped vacuum hose for the Fuel Pressure Regulator at the regulator and didn't notice much difference on engine rpm at idle, but when I unplugged the Plenum side (clam shell) it almost stalled. Today there was a stronger gas smell from the engine area and tail pipe fumes. Not sure if it was caused by unplugging the "U" shaped vacuum hose while the engine was running.

Another thing I didn't notice before was that when I put the tranny in gear, I hear something that sounds like when air comes off a fire extinguisher, it doesn't have the familiar hissing accompanied by a vacuum leak and it only happens when in Reverse or Drive gear, it doesn't happen in Park or Neutral. Anyone knows if that's normal behavior?

Now I have a broken Belt Idler... I guess from revving the engine yesterday doing tests, so I couldn't take it out for a drive to see if it's still backfiring.

[wiswind]

The thing about fuel pressure / delivery, there will be NO CEL to tell you about it.
There is NO sensor for fuel flow or pressure.
There have been a few posts where people had fuel delivery issues, but backfiring was not mentioned in any of them.
The best way to troubleshoot the fuel system is to connect a fuel pressure gauge to the test point on the fuel rail.
A good shop will have a isolator......which will isolate the gauge from the fuel.
This would enable them to use a long line to the gauge.....and be able to take the vehicle for a drive, while monitoring the fuel pressure at the fuel rail.
Not having the isolator would make this a unsafe practice.

A good shop will also have the equipment to connect up and monitor various engine functions......and know how to interpret them.
There are OBDII monitoring programs that you run on your laptop computer.....but those also require one to be able to interpret the data that you see.
A good diagnostic can save you money over guessing.....and a lot of frustration.

I would certainly get the battery checked out to make sure that it is not contributing to your issues.
I would expect the battery voltage to be pretty constant over various RPMs.....once it is charged up.

A starter relay could contribute to starter problems.....but not to the driveability problems.

A fuel pump relay is a higher failure item....but again....it would be throwing a part at the vehicle...
Spark plug wires and (in my opinion if still original) a coil pack are tune-up items ....that are good to do at this point anyhow.
Another good to do would be to replace the fuel filter, air filter and clean the MAF with MAF cleaner that you can buy at most auto part stores.