Injector Misfire, Sticky IPR, HPOP, ?...

19406 Views 168 Replies 13 Participants Last post by bismic, 24 d ago

jokester00

Discussion Starter · Jun 29, 2021

I'll try to be as concise as possible without being lengthy. Please ask questions if I forgot to include the data. This problem only happens once in a blue moon, so it's been hard to track down.

Every so often after running the truck on a long run (>150 miles), I pull in somewhere, shut it off, go inside for 10 mins and come back out to start the truck. Truck fires right up, but then starts to act like it's missing on a cylinder. Put it in gear and it gets worse. My normal IPR at hot idle is 21-22%, but when this happens, IPR stays steady at 25%. My normal ICPv at hot idle is ~0.8 - 0.85v (~580psi), but when this happens, ICPv jumps around from 0.8 - 1.0v and ICP jumps with it (~580 - 610psi). If you give it some pedal and pull away from the parking lot, stoplight, etc. the truck goes right back back into normal rhythm with ICP & IPR values & the feeling of a misfire stops.

I have changed ICP sensor & pigtail just to rule that out, but plan on unplugging the ICP sensor the next time it does this to see if it clears up.

Do you think the IPR is sticking? Kinda seems like to me that it wants a bit more ICP, so it commands the IPR to 25% to get that last little bit, but it might not be moving to that position. I did try to take off the IRP when my turbo was out a couple years ago, but it was in there TIGHT and I was on a time crunch, so I figured i'd leave well-enough alone! Wishing I had pulled it now.

What say ye? Ideas?

@bismic @Hydro @TooManyToys

-jokester

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Hydro

· #2 · Jun 29, 2021

The IPR valve could be too tight, they only need to be 15-20 foot pounds -- too tight distorts the valve sleeve at the threads, and will bind up the internal poppet. Seen this many times in my line of work. Heat expanding the metals can cause the valve to work fine at lower temperatures and bind when hot.

Just one theory, but since you said it was in there tight, that may be the exact problem

Reactions: 5

TwinExcursions

· #3 · Jul 1, 2021

Unplug ICP and plug back in. Read you already replaced pigtail and ICP. I need to do same (when I get the time - parts sitting in toolbox saying "hello") but as stop gap I have been unplugging and plugging back in and makes similar problem go away for awhile.

Also @Hydro has good info.

Sent from my SM-G973W using Tapatalk

Reactions: 1

jokester00

Discussion Starter · #4 · Jul 25, 2021

Bringing this back to the top.

I had an issue yesterday that i've never had before. Again, truck was fully up to temp when it happened. Was sitting there idling and we were getting ready to hook up the trailer. All of a sudden, truck started loping/romping up, back down to idle, then acted like it was going to stall, then back up to idle again. I waited 10-15 seconds to see if it would clear itself, but it didn't. No smoke from the tailpipe. ICP pressure was fluctuating, but not ICPv (stayed at .9v). IPR was fluctuating too 22%-30%). No codes showing on my edge CTS2. I shut the truck off and it fired right back up like nothing was wrong. We pulled the trailer to storage and came home without any other issues.

The only recent work done was I changed the oil & did fuel filters on Friday. Nothing crazy or out of the ordinary. I checked all my work again and didn't see anything wrong.

Hmmmmm...I think i'm gonna have to get that IPR out and check it.

-jokester

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Reactions: 2

Hydro

· #5 · Jul 25, 2021

Interesting, ...thing is tho, if ICP pressure is fluctuating -- sensor voltage also has to fluctuate
the pressure reading is directly from the voltage -- unless it is switching to an inferred number

Possible your IPR is hanging a little bit?
you could screw the top part off and clean the armature of the fine metal particles -- also lets you access the tiny pintle valve (dont drop it)
my thread on the IPR tear down may help with details

Reactions: 2

jokester00

Discussion Starter · #6 · Jul 25, 2021

Hydro said:
Interesting, ...thing is tho, if ICP pressure is fluctuating -- sensor voltage also has to fluctuate
the pressure reading is directly from the voltage -- unless it is switching to an inferred number

I thought about that too. Odd that V wouldn't move, but pressure would. It might have been bouncing between .8-.9 and I didn't catch it. Gonna inspect things a bit more this weekend sometime. If I have to pull the IPR, It's gonna get replaced. Call it preventative maintenance 😁

-jokester

Reactions: 2

jokester00

Discussion Starter · #7 · Jul 27, 2021

The plot thickens...BUM BUM BUUUUUUUMMMM

Pulling into work this morning, and the truck starts it's missing again. Watch everything and ICPv moves slightly from .8-.9, ICP moves a bit, but not much, and IPR goes from 22% straight to 34% and stays. However, this time, truck threw a P0284 cylinder 8 contribution code. Luckily, no smoke out the tailpipe, so, that's a bonus...I guess LOL.

Like I said, this only happens when it's fully warmed up, so gonna do some poking around this weekend to see if anything's chafing, etc. Hopefully I can get it home tonight.

-jokester

Hydro

· #8 · Jul 27, 2021

So, then PCM commanded more oil pressure, but the ICP only reported a 0.1 increase -- the change from 22 to 34 should have been more than that
would be good to know the ICP "desired" PID

Possibly the #8 injector is sticking part time? and causing the higher IPR value to be used to compensate?
is the fuel pressure good?

Reactions: 1

jokester00

Discussion Starter · #9 · Jul 27, 2021

Yup....fuel pressure is 62psi at idle, 55psi at WOT. I was wondering about that too, thinking maybe I had some compression gases leaking by that injector, but pressure shows probably not.

I'm now thinking I might have an HPO leak...or that IPR issue still.

-jokester

jokester00

Discussion Starter · #10 · Aug 3, 2021 (Edited)

The saga continues...

This time though, it started to miss on a cold start (well, not cold, but ECT/EOT was ~90° when I fired it up after 12.5hrs of sitting while I worked). Drive like crap, but no smoke, so I tried to limp it home. IPR would go above 40% and it would drive semi normal, but once I slowed to an idle, IPR reading would NOT go below 40% at all! Plus, it would idle (still rough) at 900RPM instead of ~600. I cleared the P0284 #8 contribution code in hopes that it would throw it again, but it never did. About 1/2 way home, truck smoothed out, IPR dropped to normal levels (21%) and it ran like it normally does the rest of the way home! Good grief...I hate intermittent issues!

youtube.com

6.0 misfiring

youtube.com

-jokester

Reactions: 1

6riders

· #11 · Aug 3, 2021

Are you running any sort of tune?

jokester00

Discussion Starter · #12 · Aug 3, 2021

6riders said:
Are you running any sort of tune?

Yes...40HP tow PCM tune with Atlas 40 FICM tune.

-jokester

Hydro

· #13 · Aug 3, 2021

Sounds like one of those "lope" tunes -- not sure what the tuners do to make the engine run line that, but may be a clue as to what to look for

Would have been a good time to use ForScan to change the value of the IPR and see if that affected the engine
Did the engine start like that? or had it idled long enough to go into high idle mode?

jokester00

Discussion Starter · #14 · Aug 3, 2021

Hydro said:
Sounds like one of those "lope" tunes -- not sure what the tuners do to make the engine run line that, but may be a clue as to what to look for

Would have been a good time to use ForScan to change the value of the IPR and see if that affected the engine
Did the engine start like that? or had it idled long enough to go into high idle mode?

I had my Bluetooth dongle and my phone with the app, but I don't have it setup yet (note to self... 😁).

As soon as I started it, it sounded like injector sticking on a cold cold morning, and the started loping like that. I pulled my phone out and started recording ~10 seconds after I fired it up. In my thinking, when it doesn't act up, and the IPR is 21%, that kinda points to it NOT being an HPO leak, right?

I did put this new 40HP Two Tune on there on July 22nd. Changed oil and fuel filters on the 23rd, and this started for the first time on the 24th. Hmmmm...coincidence, or????

-jokester

FordDoctor

· #15 · Aug 3, 2021 (Edited)

Has it occurred to you that the misfire is CAUSING the raised IPR command? I think you are looking at this backward. The PCM is going to increase the IPR duty cycle when an injection concern is present regardless of the cause whether it's something affecting all injectors or just one. This reaction is most observable at idle. Now that you have a code pointing to cylinder #8 you might look a bit closer there. I know I would.

Reactions: 3

jokester00

Discussion Starter · #16 · Aug 3, 2021 (Edited)

I agree with you! I was pretty dang happy when I saw that code - at least it's a good start!

And although I agree, I still can't wrap my head around WHY the PCM raises the IPR duty cycle during a misfire (to increase fuel delivery on that cylinder, maybe??). Can someone please elaborate so a guy like me can better understand? @Hydro and others have mentioned that the IPR in this case could be more of an effect, rather than a cause.

Appreciate all the info!

-jokester

Hydro

· #17 · Aug 3, 2021

Could just use ForScan to disable a cylinder, or disconnect a injector harness plug -- to test the theory

Reactions: 2

jokester00

Discussion Starter · #18 · Aug 3, 2021

Hydro said:
Could just use ForScan to disable a cylinder, or disconnect a injector harness plug -- to test the theory

Exactly what I plan on doing this weekend (man, time gets away from me so friggin' fast)! I have AE and Forscan, so should be able to do that.

-jokester

Reactions: 2

Hydro

· #19 · Aug 3, 2021

Good, good, ...both of those will do the job
I would also command the IPR to see how the engine responds to the variations
about 480 psi, my engine will fail -- and the injectors get pretty noisy as the pressure goes higher -- but the engine still runs smooth

Reactions: 2

jokester00

Discussion Starter · #20 · Aug 7, 2021

@FordDoctor @Hydro @bismic

What tests would you run without IDS before condemning an injector? It passed the buzz test this morning, but then again, the truck wasn't misfiring either. Cranking with remote wire is even with no hiccups.

Thinking about running bubble test & injector disable test one at a time with AE to see which affects idle while the truck isn't acting up. Then drive it around to see if I can get it to start misfiring and rerun those tests + the buzz test while it's being temperamental.

Thoughts?

-jokester

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