This is exactly what it is doing.........
It starts fine, one crank and its running.

Then after it idles for about 30 seconds it has what appears to be a mis or rough idle, and the electrical gauge dips. Then it idles fine for another 15 seconds or so then bam! It does it again and continues with the same interval.
It does this weather the engine is cold or hot.
If it is in drive, when it misses it will stall sometimes but it fires back up.
If I come to a stop or red light and put it in park or neutral it does not stall.
I hear some kind of odd lazer sound coming from the exaust when it does this misfire/rough idle thing.
Ive had two vacuum leaks fixed already and a tuneup was done last year sometime. I do have a much more oil than I should because it has a leak and I keep adding oil every so often.

 

And this is on your 1994, Club Wagon (E250 or E350) with a 5.8 (351W) engine, and E4OD transmission??

You wrote that the oil leaks out the rear of the valve cover at the grommet for the PVC valve, replace the grommet, there $2.95. the 351W leans to the rear, and the oil in the valve covers fill up and will leak from this grommet, easy fix.

After reading your expiation on this New post, have you have any of the electrical sensors checked??

Here's the link to checking all sensors on this era engine - Link.

Just as a quick guest, I would look into the Ignition Control Module (ICM) first, as this would give you the problems you explaining.
That located on the drivers side fender, way in the back, near the bulkhead, tucked into a little offset in the fender, just above the wheel well. (some times hard to find)

Second, check the MAP sensor, and the Coil, Coil could give the same mis-fire condition as your explaining.

Read the link, the 3 above sensors, and you might narrow down what the engine is doing, and it will explain the problems, and testing of the sensors.

If the engine RPM drop, the belt is NOT spinning the Alternator as it should, and the voltage gauge will drop/bounce around as there is NO voltage being produced at low/stall RPM's. Take this out of the problem cycle for now.

You also wrote before that you had a buzzing sound from the fuel pressure regulator, with the engine running, pull the vacuum line off the top, and see if any raw fuel is coming out of the top of the regulator, if it is, it's shot, and needs replacement.

The other sound you hear from the exhaust, it either back pressure, or the sound made from the Air Pump Check Valve, mounted on the rear of the engine, at the head cross over pipe (center). $10-$14 part.

Question.......have you ever had the fuel pressure checked, off the Schrader valve???

And......to got back where you left off........get that back pressure checker and do the test, it take 15 minutes and tells you if the cats are plugged or not.

Side Note.......starting this new tread clears up all the other problem that you have fixed, and not having to go back and read thru everything helps us all

 

Thanks for the input and taking the time to help

5.8, E4OD
No electrical sensors checked.

The Ignition Control Module, Coil and, Map were the next things I was going to replace but I dont want to get sucked into the hole of replacing parts until the problem is fixed LOL But...... I might anyway

I tried pulling the tube off of the fuel pressure regulator but it was very hard and I did want to break it.

Never had the fuel pressure checked.
I dont think there is a downstream O2 sensor, I think it is before the cats, If that matters.
I will check out that link.
Thanks again Wild.

 

After searching online I keep seeing these posts, over and over about bad capacitors on the PCM, and replacing them has fixed many rough idle problems.
I am going to give that a try, next chance I get and will post the results.

 

That would be the Next thing to check, After you run the tests on the sensors.

You don't need to run out and replace all the sensors, that's what the link is for TESTING them (If you can?)

I have replaced a couple of ECU's because of the bad capacitors (leaking) but from what you describing, that might not be the cause.

The ECU (not the PCM, that's the older model) on our era engines run in "open loop" at start-up, and after the engine gets to operation temperature, appox 195*, then the ECU operates in "closed loop" where it's taking readings from all the senors and adjusting timing, fuel inlet, ect, ect......

Your having problems with-in 15 seconds of start up, that kind of takes the ECU out of the picture for now.......see??

I tossed out the fuel pressure test, because, if the fuel pump is getting "ill" it's not keep the pressure up and you could be stumbling/stalling because of lack of fuel in the rail.
KOEO - the fuel pressure should be 35-45psi.

Here, read this Link.

I like posting links.........saves me a whole lot of typing........

The O2 sensor is "up-stream" of the cats on this era engine.

The fuel pressure regulator vacuum tube is just a rubber angle grommet that holds the hard (red) plastic vacuum line to it, should just slip right off.
As I said, if raw fuel it coming out of the top of the FPR, that could be causing raw fuel being sucked into the intake manifold, and your actuality flooding the engine with gas, that that can cause other problems, like cylinder wash (you'd smell gas in the oil) and even hydro-locking

 

Yea, I gotcha. Tomorrow morning I am going to install a new PCV valve and grommet.
If it was the fuel pump or regulator wouldnt that show up as a much more severe stumble/rough idle?

I always hear the pump come on, everytime I start it I hear it, I know, Doesnt mean its working correctly but it sounds the same as it has for the last 10 years.

I can test the fuel pressure and the exaust backpressure once I purchase the tools.

It is up for smog at the end of this month, I am going to take it in and see what happens.

Thanks.

 

Installed new PCV valve and grommet and cleaned up the elbow this morning, No change I thought for sure something would happen, Oil was spewing from the grommet.

Took it to have it smogged, theyre machine was down but the tech told me about this electrical shop that has A ford breakout box. I went there and the tech there used what looked like a plain old Snap On obd box, He got a code 167 (TPS) but I never saw him hit the pedal for the WOT test like it says to do in my computer manual.

Of course on my way to his shop the van stalled two times on a busy street when I was stopped at red lights and the check engine light came on. Oddly.... He was not able to see any codes during KOEO, but when Idleing he got the 167 code.
I am wondering if he really did get code 167 or was it because he did not hit the throttle?
Check engine light definately came on two times, there should be some code he got right?

Just pulled the vacuum line off of the FPR, no gas just a very strong vacuum, although it was not at Operating temp. if that matters.

 

Took it to have it smogged this morning, It passed easily.
Can I rule out clogged Cats or Muffer?

 

Installed new, Much better quality rotor and cap this morning, No change in the rough idle situation.

Since the computer is in a closed loop until the engine warms up and the computer is taking reading from the mass air flow sensor, and my idle issue is before the engine warms up, wouldnt that mean that I can rule it out as a cause of the problem?

Possible Next steps, Check mass air flow sensor? , Test the ingnition control module, Check fuel pressure.

 

Been out on the road the past few days........got to work the day job too......

Seen your post on the problem with the distributor.
You got that repaired, and fitting better, good

Pasting smog is a good thing, we don't need to worry about that here, only after the '96 model years

First, No, the muffler should not be a problem, it's the Cats that plug.
Normal Idle would not show a problem, where the Cat shows a problem is when you punch it, or add right foot pressure to go up a grade, or hill, or kick the tranny down for more power, that's when you loose power, because the Cat is being plugged.
Last one I replaced, it ran fine, Idle, running around town, ect..... until I hit a hill, and then I lost power = basically the exhaust was restricted, too much "back-pressure". I got a new cat, and when I removed the old one, I could hear something rolling around inside, I knew it was the gunk, and had broke loose, and was like a golf ball rolling around, and I'm sure about the perfect size to plug up the outlet port
No, I didn't punch it out, and left it in rolling around, because......It was worth $45 at the scrap yard, if it is not punch out, and yea that off set the cost of the new one.

You getting - Code 167 =
Insufficient Throttle Position Change During Dynamic Response Test

That right there leads to your problem...........TPS.

My thought.......change it out, (or do the test?) if you going to start replacing parts, start right there, get a new TPS and replace the old one.

I was thinking about your problem, and it has to be an electrical problem, or a sensor problem that's causing all this. READ up on that link about what the TPS does and think about the problems your having.

On a side note, I replace mine last year, sometimes when I start with a warm engine, the idle roars up, and I have to hit the gas pedal to get the idle down, been several months doing this......Then the other day, it stalled out when I came to a red light, re-started no problem, it's the quick drop in gas pedal to brake that I thought caused this.

This story sound familiar??

Driving back last night, the 150 mile trip, on the super highway (toll road) I noticed the engine was skipping every so often, and this was pushing 70-75 all the way, then today, running around town, it stalled again coming to a quick stop for a red light.

The TPS signals the ECU on how far the throttle plates are open, and trims the fuel and timing.

I'm picking a new TPS and installing it in my van Monday. (and the old one should be under warranty) Cause I have a job to get to tomorrow and no time.

Your other question, Yes, the MAF could be a problem also. I don't have to deal with that, because my vans are over 8500 gvw and did not install the MAF on that series.

You need to pull the air duct off to replace the TPS, you should clean the MAF while your there, the Throttle body has to be removed from the upper intake to replace the TPS, you'll need to replace the TB gasket.
Should you also replace the IAC? or clean that? most cases, cleaning works, for a short time.......replacement is next. If your budget is there, replace the IAC at the same time.

 

If it passed smog wouldnt that mean that it unlikely that one of the cats is plugged?

I changed out the IAC last week and I just installed a new PCV valve and grommett a few days ago.

I also cleaned the throttle body with TB cleaner but it did not look very bad at all.

I only got code 167 because I didnt hit the pedal at a certain point during the test that the manual for my code reader says to, When I redo the test correctly I dont get code 167.

So far in the last week or so I have:

Cleaned the throttle body
installed new IAC valve
Installed new PVC valve and grommett
Installed new Cap and rotor
Pulled 6 of the eight spark plugs, Look good and gapped correctly
Pulled the vacuum line off the Fuel Pressure regulator, strong vacuum and no gas came out

Thanks Wild

 

Of past items that were repaired/fixed, only leads up to solving the real problem to get the stumble/stalling issue resolved

If a sensor is malfunctioning, at times, it could report/test as in good condition, and then have a "burp" and throw the ECU into confusion.

Maybe?? Or would it be in the condition that I wrote of an experience I had??
It only plugged/restricted when under heavy power conditions.

Put the Cat issue on the back burner for now, and think more into a sensor/electrical problem at this time.

The fact that you did get a Code 167 could be a factor that the TPS is malfunctioning at time.
Did you clear the codes and then do another test? Did you drive at least 50+ miles under close loop to gather any codes??


Yes, and that took the guest work out of the posibilly of the IAC of being the problem for what you started with.

That was done to solve an oil leak problem, not the stumbling problem, and needed to be done.

Another thing you found that could have been the original problem, still needed to be addressed as an issue.


Didn't hurt to double check that, even thought you only had that done a year ago, But was it needed to solve the current problem??

Again, didn't hurt to double check that, to see if that was causing the current problem.


What I or anyone on this forum is suggesting is what we have experienced or have solved as a problem in the past on our vehicles, we are all sitting boo-coo miles away from the problem vehicle, and it's not right in front of us, we can't check, hear, see what's it doing, and what to check/replace/repair next, so your the one that has to do the work, and do the testing, and relay that to us for the next suggestion of repair.

So, what was done to date did not solve the original problem, Correct?

Move away from what was done, and check/test/replace the next item.

We all toss parts into the mix, and at times hit it the first time, and other times have to throw more parts at it, and then the problem is solved, that's the way things work, and just replacing all the senors at once will work, but the real issue is, what caused the problem in the first place???

That's why we Test/check/read codes, to narrow down the real problem.

It was brought up that you were going to check the ECU for corroded capacitors, did you get to that yet? Yes, that needs to be addressed too.
It could be the main cause of this topic and the original topic of 7 pages.

I'm not, nor anyone else here is telling you to just buy all new parts, and just replace everything at once, I know some mechanics that work that way, and then hand you a bill that is equal to the cost of a new vehicle. Yea, I'v heard of people paying $1400 for brake jobs at all four corners, and for what, all new parts. Did it really need all new parts?? Don't know, didn't see what was needed myself, But, people get paranoid about it, and just fork over the cash for 'safe-mind' and then complain about it latter.

I know one ASE mechanic that I send people to all the time, he's fair, honest and Checks before he starts tossing parts in, and also has the experience of trouble shooting problems. There are not a lot of them mechanics around anymore, and the "Total Car Centers" are not like that. Any time you walk in and see a "service writer" sitting up front.......beware!!!

So.......off soap box now........you need to check a few things, I would start with replacing the TPS. Pull the ECU out and check that. if the problem precises, then we'll check the next item. Have you checked the condition of the coil?? This could be another factor in the stumbling problem.

 

* EDIT *
I cleaned the throttle body better today. It is really nasty inside the butterfly valves.

I dont know if I mentioned this before but I know I have way too much oil. When I say too much Im talking probably a quart or more extra.
After letting it sit, The oil is way past the full line.

The reason for the excess oil is that It has a bad rear main seal leak, If I run low the van will not start, I then put in a quart and it starts. This has happened almost a dozen times. A mechanic told me there is a sensor that will not let the engine start if the oil level or pressure is too low.

Could something be or have gotten got gummed up ?

* EDIT *
How do you tell if the ECU is bad? Will a Capacitor look blown like on a computer power supply?

Yes, I ran the test many times with the same result, If i dont hit the pedal at a certain point then I always get code 167, If I do hit it, then no code 167.
Thats what the manual says will happen if you dont hit the pedal.

Why would the van need to be driven 50 miles to get codes?

Thanks.

 

Today, Changed Oil and filter, Ran seafoam through the tank. Cleaned Throttle body again.

I dont know if it was the New Cap and rotor, oilchange, seafoam or, cleaning the throttle body, but It definately runs better but still has some kind of mis.

 

I pulled out the computer this morning. One of the capacitors has a burn mark under the negative lead. I tried to take some pics but they look too blurry. The other caps look good, no leakage or burn marks.

Its a 10 microfarad, 63V cap.

Radio shack only has a 10 microfarad 50V cap. I will have to order one, cannot find it locally.

When I get a chance I am going desolder the cap and test it.

Thanks.