Engine Miss / Rough Idle

[BurghFan]

I know there are countless threads related to this issue, but I'd like to get some second opinions with my truck in particular.

On a cold start (after sitting overnight), the engine seems to idle fine, with the exception of sometimes the first second or so. Once it warms up, there seems to be what sounds/feels like a cylinder missing. The severity seems to constantly vary while driving, but one way it's pretty consistent is after coming to a stop from highway speed. The idle almost always seems rough under that condition, at least for a few seconds. Then sometimes when accelerating from a stop, there's what seems to be a dead miss at low RPMs until the truck gets moving (manual tranny).

At times, there seems to be a knock associated with the condition as well, especially at idle.

Sometimes I'll get a little bit of a hard start after the engine is warm, also. I may have to crank it a little longer (no more than 2 seconds at most) or else it will (or almost) stall after letting off the starter. But again, this doesn't happen consistently.

So here's what I've already checked: just pulled the valve covers and UVC harnesses today - no problems that I can see. Also checked the glow plugs with an ohmmeter. Prior to that, I replaced the IPR o-rings just as a possible cheap fix. No change there, either. Oil consumption seems to be almost zero after about 1500 miles on the oil change, which makes me wonder if I'm losing oil and gaining fuel, but the mileage seems to be fairly good. I'm averaging 13-13.5 on it, and it's an F-450 with a lightly-loaded utility bed.

Any ideas on what I should look into next? The truck has about 186,000 miles on it now - just bought it a few months ago with 183,000. So I don't have any idea how new or old the injectors, etc. are. Any suggestions are greatly appreciated, and thanks in advance for your time.

 

[action4478]

The next step is under the valve covers....O rings or

From deisel mans page....




Rough idle, especially hot:
Could be caused by anti-foaming agent depletion, incorrect oil, or leak at the oil pump pickup tube.
Get the engine and oil hot and run up to 3300 RPM for three minutes. If the ICP reading goes above 1600 within the first thirty seconds of testing there could be a cracked pickup tube or missing seal. The pick-up tube can be checked by adding two quarts of oil to the crankcase and raising the rear of the vehicle approximately ten inches. If the ICP readings at 3300 RPM drop, then the pick-up tube is cracked or leaking.
If at the end of the three minute high RPM test the ICP readings are above 1400 for Federal or 1250 for California and Econoline or 1500 on 99.5, the anti-foaming agents are depleted from the oil or the wrong oil is being used.


Or...

From swamps

Though it could be the IPR, I don't think it's likely in this case.

I'm betting that you have some injector issues...specifically surrounding the poppet valve on one (or more) injectors.

The poppet valve is the one single area of a PSD injector that just flat out wears. It's similar to a valve in a cylinder head that beats itself into it's valveseat.

As the poppet valve opens and closes (with each injection), it meters the high pressure oil flow in/out of the inj.

With each opening and closing, the seat is being hammered by the valve...causing it (over millions of cycles) to seat lower and lower into the injector...until clearance under the armature is lost.

Once the armature bottoms out on the inj body, the valve cannot "reach" the seat to seal high pressure oil from leaking out of the injector.

The reason that the truck runs when cold, and dies (and won't restart until it has cooled significantly) is that cold oil is thick...and can bridge the gap created by a poor valve & seat seal.

once the oil is warm, it thins out, and can now leak around that valve creating a tremendous amount of "spillage" that the oil pump can not now keep up with...once the amount of the leak exceeds the capacity of the pump...pressure falls, and the injectors simply cannot fire without (approx) 450psi of high pressure oil...so the truck dies.

you can physically measure this yourself.

Pull both valvecovers, and start the truck...it won't be horribly messy, just a little oil splash around the valvetrain.

As the truck (oil) heats up and dies, have someone crank on the starter attempting to restart the truck.

You should be able to look at each injector, and find one that it puking oil out from around the (just above) the hold down clamp.

You may need to mop up any oil that settles down in the low spot of the head to help you see which injector is actually puking...

once you've isolated which inj(s) are puking, pull the solenoid (4 # torx 15 screws), remove the harness to that inj, remove the little aluminum spacer plate...

what you are now looking at is the armature plate...the little ~1"x1" square plate, with the goofy screw (poppet screw) going through it's center.

On a brand new injector, there should typically be .003"-.004" (three to four thousanths of an inch) gap under that armature (measured with a feeler gauge)...

My bet is that your injectors have enough poppet seat wear that they have less than .0015 (less than one and one half thou of an inch) gap...practically zero.

if you can't get a .0015" feeler under the armature plate, then that injector is a problem, and it is a good indication that the others within that set need some machining to bring them back into spec. so that they will operate correctly.

if you have any questions, feel free to call the shop~

take care~

Dave


Choose your poison....

 

[BurghFan]

Thanks - hopefully I'll have the opportunity to test some things tomorrow. In the meantime, your post gave me a theory - let me know if you think it sounds possible at all. I apologize for the long post, but I want to try and explain this in fairly good detail so you can tell me if I could be right:

Diesel mans page mentioned a possible leak at the oil pump pickup tube. With that in mind, I recall that the engine oil level was well over-filled when I bought the truck (maybe around 3/4" higher than full on the dipstick?), and altough I'm not 100% sure, I can't say that I noticed the problem I'm having until after I changed the oil. After the oil change, I made sure that the oil level was right at the full mark on the dipstick. Is it possible that the pickup tube could be cracked or broken towards the top end, and the cracked/broken portion was covered by oil in the pan when the level was over-filled, thus "eliminating" the bad section?

Another point of interest in all of this: according to service stickers in multiple places on the truck when I bought it, it was supposedly inspected and had the oil changed within about 10 miles (on the odometer) from when I bought it. Part of the reason I changed the oil after buying the truck was that I wanted to make sure it was in fact changed, and not just in writing.

But assuming it had already been changed as the stickers said, the engine oil was already black on the dipstick when I bought the truck, which didn't surprise me. Now, even after the 1500 or so miles I have on my own oil change, the oil on the dipstick still only has a grayish cast to it; it looks almost like new oil. To continue the theory of the broken/cracked pickup tube - maybe it's only picking up oil off the very top of the level in the pan, and either re-circulating the same small amount of dirty oil, or not reaching down far enough to get the dirty stuff off the bottom of the oil pan?

Again, sorry for the long post. Aside from that, any thoughts on this?

 

[95_stroker]

Injector harness/GP harness shorted out. Better know as the UVC harness.

 

[action4478]

Injector harness/GP harness shorted out. Better know as the UVC harness.

Do you have the truck that goes with the badge in the avitar?....

 

[95_stroker]

Do you have the truck that goes with the badge in the avitar?....

Why yes, yes I do....

 

[action4478]

I see you moved up to Administrator ,Congrats...

I see in your sig , the 95 is gone... to a good home I hope.......

 

[fordtrucker4life!]

I had similar issues that have been described in this thread. Action helped told me to check the ICP and sure enough that was the cause. Oil was leaking through the plug onto the terminals.

 

[action4478]

For sure..There are many things that can cause the symptoms , but without a scanner , we try to do the cheap tests first....(guesses)......