At my wits end with this issue

[TwistedFish]

Hi all, I've been trying to use this ex as a learning experience for myself, as well as to eventually use as my daily driver. Obviously, for that to be the case, it needs to be running perfectly, and i shouldn't have to worry about it being a danger to myself or others. However, with this particular issue, I'm stumped.

The ole' rough idle. Ah yes, the very bane of my existence. Starts up rough when warm, idles rough no matter what i do, and (sometimes) will stall at stoplights, or long periods of idle.

What have I done to fix it? Well, i've replaced the positive battery cable, checked for vacuum leaks, cleaned the maf, replaced the ects, replaced sparkplugs and wires, cleaned the throttle body, checked the large intake tube (plastic) for cracks, checked each vacuum line on the tree for leaks (done by plugging them simultaneously, this provided no change to the idle), and checked the iac (I unplugged it, and the engine slowly died).

At this point, the only things I HAVEN'T done, are replacing the MAF, replacing the pcv valve, replacing IAC (though it seems to be working fine), or anything relating to fuel.

Fortunately, it's annoyed me enough at this point to document it, so here's a video of a (warm) start.



Note, the oil guage ALWAYS reads high, and always "flickers" like that. When the idle is getting rough, the voltage meter also does this (because its about to stall).

Main points to take away here are the surging and rough idle. If anyone else notices anything that is ALSO an issue, or has any questions, please let me know.

Thanks in advance, and have a great day!



EDIT: UPDATE

Hi all, just got back inside from running some codes and checking a few other things people recommended. First off, I'd just like to say thank you for your support so far! This forum has one of the best communities by far.

Down to the nitty gritty:

1: I checked the PCM. Unplugged it, started the engine, plugged it back in, started the engine. No change

2: While looking around for the PCM (before i realized it was under the dash) I found 3 or so wiring harnesses just hanging around. This had to be something done by the previous owner, but I'm not sure what they do. Pics are posted below (or above idk)

3: I noticed that one of the main air intake hoses ( near the lower radiator hose) is just... broken. Pics posted below.

4: I used the paperclip method to run the codes, and got 3 while KOEO:

1. 79: A/C is on or pin 10 is shorted to power
2. 66: Vane Air Flow (VAF) or Mass Air Flow (MAF) signal low – VAF MAF (Also listed on the website: Transmission Oil Temperature (TOT) signal low (possibly grounded) – Transmissions)
3. 63: Throttle Position Sensor (TPS) signal too low TPS

This is pretty informative! Maybe now we're on to something? Idk.

5: I took the radiator cap off and looked inside. Pics are attached. It smells off, and upon closer inspection of what dripped off the radiator cap, it seems to have some sort of dirt or particles in it. The liquid itself does seem to still have somewhat of a green-ish sheen.

That wraps up my update! I hope you all can help me, and know that I'm putting in as much effort to fix this as you all are to help me. Again, thank you so much!


EDIT: UPDATE UPDATE UPDATE

Welcome back everyone! I've certainly had a hard time finding the time to work on my ex. Pretty quick update here: I did the compression test (FINALLY), and the results aren't great:

Cylinder 1 (closest to the grill, bottom left) 180
Cylinder 2 (Middle left) 180
Cylinder 3 (Top Left closest to the firewall) 170
Cylinder 4 (Bottom right) 30...I actually tested this one a few times, but kept getting 30. Weird thing is too, when cranking the engine to test it, it didn't really sound like a crank, almost like a continuous crank, it didn't have the same solid stopping and starting sounds (hard to explain, but hopefully you guys understand)
Cylinder 5 (Middle right) 190
Cylinder 6 (Top right) 170

That's the update! Turns out i have an issue with cylinder 4. Any and all replies are greatly appreciated! Thanks!

UPDATE UPDATE UPDATE

Hello again all, this time i think I’ve pinpointed the issue. After letting everything sit for a while, I opened the radiator cap to show a friend the coolant, but instead was greeted with what looked to be oil sitting on top. Shiny and black. Pictures are attached below, but yeah. I guess this definitely screams blown head gasket, which is weird because I’ve personally never had it overheat, but it is what it is I suppose. What are you guys’ thoughts on this? Im not really sure what else this could be... Thanks!

 

[xartic]

I never owned a 1st gen, but I have had issues with an 01 Sport and my current 02 Mountaineer with the IAC. You could get one from the parts store and swap it in and see if it makes any difference.

Also, what are the chances you have checked your motor mounts?

 

[TwistedFish]

I never owned a 1st gen, but I have had issues with an 01 Sport and my current 02 Mountaineer with the IAC. You could get one from the parts store and swap it in and see if it makes any difference.

Also, what are the chances you have checked your motor mounts?

Hi! Thanks for your reply. It very well could be an IAC issue, but as stated, when i unplugged it, thew engine chugged down and died like it should, so i just figured it was fine. As for the motor mounts, no, i haven't done anything with them.

Thanks again for your reply!

 

[LG57]

Does it run rough when driving? The next thing I would consider is fouled or bad injectors. Try cleaning or replacing them. There are lots of videos of how to clean injectors. It's not hard, but lots of work taking the upper intake off to get at them.

 

[974X4BLACKSPORT]

Put a vacuum gauge hooked up to FULL MANIFOLD vacuum, report back what the needle on the gauge does, or take a video of the gauge with the engine running. A simple vacuum gauge reading can give loads of information.

 

[TwistedFish]

Does it run rough when driving? The next thing I would consider is fouled or bad injectors. Try cleaning or replacing them. There are lots of videos of how to clean injectors. It's not hard, but lots of work taking the upper intake off to get at them.

So when i give it gas, it still feels a little rough, but it (obviously) cant surge so theres not much worry for stalling. However, I have noticed (and this is unrelated) when going up inclines, after switching from 2nd to 3rd, or 3rd to 4th, for a brief moment when the RPMs are low, there's a loud and very noticeable "clunking" sound... Additionally, I've never really been able to drive it for long periods, because it starts to overheat, but I'm pretty sure that's just because I need to change out the radiator and it's hosing, since it's so old, the coolant doesn't look so good (very gummy and brown).

 

[TwistedFish]

Put a vacuum gauge hooked up to FULL MANIFOLD vacuum, report back what the needle on the gauge does, or take a video of the gauge with the engine running. A simple vacuum gauge reading can give loads of information.

That's an interesting idea! Pardon my ignorance, but where is the "full manifold" vacuum line?

 

[xartic]

Hi! Thanks for your reply. It very well could be an IAC issue, but as stated, when i unplugged it, thew engine chugged down and died like it should, so i just figured it was fine. As for the motor mounts, no, i haven't done anything with them.

Thanks again for your reply!

My Mountaineer was having different issues after I tried 1 non Motorcraft brand (bought advance auto) until I actually got a Motorcraft one. This was 6 years ago and I haven’t had idle issues since.

If you do the vacuum test and there is a vacuum leak, you could try using starting fluid and spray around hoses and your intake/ valve covers to see if your idle jumps around more.

 

[974X4BLACKSPORT]

That knocking noise could be many things, most common being broken engine mount, or a bad connecting rod bearing, or even piston slap.
Check your engine oil, look at it very close for metal flakes, or if it looks like metal flake paint, this could tell you if you have a rod bearing issue.
Also, double check and make sure your firing order is correct, often times after installing new plugs and wires, it is easy to get the wires mixed up on the driver side for (#4,5,6).
As for your "FULL MANIFOLD VACUUM" question, look on the radiator support, there should be a sticker that shows all the vacuum hose routing for your particular vehicle. You want to hook up a vacuum gauge to a port or hose that goes directly into the intake manifold.
Additionally, if you don't have a CHILTON, HAYNES, or Ford Service and repair manual, I suggest getting one and studying it, read it cover to cover, as many times as it takes.

 

[410Fortune]

allright you guys Ill bite
First off it sounds like you have a dead miss, this would be one or more cylinder that are not firing, ever...not at idle, not when running, a dead miss does not "fix itself"
This could be due to a bad injector or low fuel pressure, bad coil pack, spark plug wire, water, etc etc many things
Running on 4-5 cylinders will cause the conditions you describe and will cause engine to heat up quickly

What you need to do is eliminate things as the cause
First I would do a fuel pressure test
Next I would do a full visual inspection on the engine block. Brown and yucky coolant is a sign of a cracked head or bad head gasket. You may be getting water in your combustion chambers.......
Next do a proper manifold vacuum test
Next I would pull the spark plugs and look at them........... the plugs will tell you which cylinder(s) are the problem child.
After this if all checks out it is time for a compression test

the pushrod 4.0 is known to:
Crack heads or blow head gaskets when they get old or hot. The 91-92 engines were really really bad at this.
They also can develop oil pressure issues with age
The Computers are getting old enough to where we are seeing more and more 91-94 trucks with bad PCM's causing strange issues.

quit replacing parts until you know where the problem is!! Why? because it is always the last part you buy that fixes it....and there are ALOT of parts in there............

 

[TwistedFish]

That knocking noise could be many things, most common being broken engine mount, or a bad connecting rod bearing, or even piston slap.
Check your engine oil, look at it very close for metal flakes, or if it looks like metal flake paint, this could tell you if you have a rod bearing issue.
Also, double check and make sure your firing order is correct, often times after installing new plugs and wires, it is easy to get the wires mixed up on the driver side for (#4,5,6).
As for your "FULL MANIFOLD VACUUM" question, look on the radiator support, there should be a sticker that shows all the vacuum hose routing for your particular vehicle. You want to hook up a vacuum gauge to a port or hose that goes directly into the intake manifold.
Additionally, if you don't have a CHILTON, HAYNES, or Ford Service and repair manual, I suggest getting one and studying it, read it cover to cover, as many times as it takes.

While the knocking noise is pretty annoying, thats actually not the particular issue im looking to fix at the moment... although ill still definitely do some checks, i'm pretty sure the culprit is an engine mount, since the whole thing seems to move around and shake alot. Unfortunately, the firing order I'm 100 certain is correct ( i wish it was that easy lol). I'll also look into getting the vacuum guage next paycheck, as well as a chilton/haynes manual.

Thanks for your reply!

 

[MrQ]

A bad motor mount could cause the shaking, but 410's comment about a bad cylinder would also very likely explain it as well. I would not disregard the knocking to focus on the rough idle. Knocking is ALWAYS bad and is usually the precursor to a very bad day.

 

[410Fortune]

a bad engine mount will only allow a shaking engine to shake

A properly running 4.0 runs smooth like butter and will not shake, even left loose on its mounts. Just FYI

the shaking is a result of a miss, likely being caused by the knocking noise........fix the knock you will fix the shake

 

[TwistedFish]

a bad engine mount will only allow a shaking engine to shake

A properly running 4.0 runs smooth like butter and will not shake, even left loose on its mounts. Just FYI

the shaking is a result of a miss, likely being caused by the knocking noise........fix the knock you will fix the shake

So when i changed out the spark plugs, I did note that some (not all) of them had oil on the threads (not the electrodes themselves, just the threads). Could this be where my issue lies? All i thought when i saw that was that i had an oil leak haha.

 

[LG57]

Yep you have an oil leak. Now either pull one plug wire at a time to isolate the bad cylinder or pull the plugs and see which isn't a normal color.

 

[TwistedFish]

Yep you have an oil leak. Now either pull one plug wire at a time to isolate the bad cylinder or pull the plugs and see which isn't a normal color.

Hey, so I wasn't exactly sure what you meant, but here's what I did"

Pull out a plug wire, start the engine. Turn the engine off, put the plug wire back. Pull another one, etc etc. Doing this, I wasn't entirely sure what I was looking for, because there was really no change. The engine would still start up each time, albeit seemingly a little rougher, but not towards any particular cylinder.

 

[Centaurious]

Have you read the codes yet? while the first gen's ECU is primitive reading the codes will provide clues we can use to help you. You can try Chanting under moonlight while naked and smeared with chicken blood, casting chicken bones on the ground and reading the patterns for clues. But, others have found this method less reliable and your neighbors and local law enforcement frown on it.

I was bothered by an occasional stumble that I could not figure out. After several years it finally got bad enough to cause a code in the ECU. It was the MAF very slowly going bad and a new one cured the problem.

I hate seeing people buying lots of expensive parts and throwing them at the truck, hoping that it will solve the problem.

Read the codes, run the fuel pressure test, run the compression test remembering to pull all the plugs and hold the throttle open. Check the condition of the plugs, if they all look the same, great. If one or more look different let us know.

 

[Gazios]

Twisted:

As I was reading your initial post I was ready to say that you need a new MAF, fortunately, when they completely fail, it will not run.

I am way more concerned about this "chocolate milk colored" coolant. YOU NEED TO GET ON TOP OF THIS IMMEDIATELY. Oil in your coolant inevitable leads to coolant in your oil. If your lucky you have a bad head gasket, the culprits go downhill from there; cracked cylinder head, cracked block.

 

[TwistedFish]

Have you read the codes yet? while the first gen's ECU is primitive reading the codes will provide clues we can use to help you. You can try Chanting under moonlight while naked and smeared with chicken blood, casting chicken bones on the ground and reading the patterns for clues. But, others have found this method less reliable and your neighbors and local law enforcement frown on it.

I was bothered by an occasional stumble that I could not figure out. After several years it finally got bad enough to cause a code in the ECU. It was the MAF very slowly going bad and a new one cured the problem.

I hate seeing people buying lots of expensive parts and throwing them at the truck, hoping that it will solve the problem.

Read the codes, run the fuel pressure test, run the compression test remembering to pull all the plugs and hold the throttle open. Check the condition of the plugs, if they all look the same, great. If one or more look different let us know.

Wait, are you saying i DONT need a CEL to get a code?

 

[TwistedFish]

Twisted:

As I was reading your initial post I was ready to say that you need a new MAF, fortunately, when they completely fail, it will not run.

I am way more concerned about this "chocolate milk colored" coolant. YOU NEED TO GET ON TOP OF THIS IMMEDIATELY. Oil in your coolant inevitable leads to coolant in your oil. If your lucky you have a bad head gasket, the culprits go downhill from there; cracked cylinder head, cracked block.

yeahhhhhhhh. It's pretty gunked up, and definitely needs to be flushed. How can i really tell if oil is mixed in though? I've smelled it, and while it doesnt smell great (at all) it doesnt really smell like oil. But i could be wrong :/