off idle stumble/hesitation (BOMBED or stock)

[JStieger]

In the past 1. 5 weeks I have been trying to figure out this stumble/hesitation at no to low throttle just off idle until about 1200 rpms.



What happens is that when I let out the clutch the rpms will drop down to about 700, then a bunch a light grey smoke will come out the pipe, the truck will stumble and barely pop once out the exhaust, and then just take off as normal. Also, around idle rpms when letting out the clutch the truck knocks like an old cummins as if the pilot injection was turned off. From 1500 rpm and up it runs like a raped ape! I can duplicate the stumble between every shift if I let the rpms fall below 1500 or so. I can also duplicate the stumble if I coast to say a red light in gear, but don't down shift, and then take off when the light turns. If I take off from a stop with authority or basically hot-rod the truck, then no stumble or knock sounds whatsoever.



I also noticed lately at low boost and rpm conditions when I apply some throttle more grey smoke than black. Smoke used to be black during these conditions. It is almost as if the truck is getting lots of air, but no fuel at low rpms. Fuel pressure to the CP3 is good at 14 psi, but I changed the fuel filter just in case and it still stumbles. Mileage hasn't changed at all. Oil looks good with no fuel smell and no change in level.



So thinking this was my Juice box causing this due to its manipulation of injection timing, I traced the lines and checked the connections this morning and only found my Attitude control cable wrapped around the steering column with some bare wiring exposed (don't tie-wrap wires to the steering column!!). I then removed the Attitude letting the Juice default to level 2 and went for a ride and the truck still stumbled.



I went back home removed everything and went back to stock form, except with DD3 injectors and the truck still stumbled!



Also, yesterday evening (with Juice still connected) I was playing around on Level 5 on the back country dirt roads (4-wheel power slides yee-haw!!) and tripped my MIL light and got the code P0193 - Fuel Rail Pressure Sensor Circuit High. I used my scan tool to erase the code and it hasn't come back since.



So here I am in stock form with the truck still stumbling or hesitating at idle to low rpms with light throttle. No codes either! Otherwise, the truck runs like a scalded cat!



I am wondering if my pressure relief valve is going out? Say at idle there's minimal rail pressure, but when you give throttle the ECM asks for a major increase in rail pressure and the CP3 can't initially keep up due to the rail pressure bleeding off?



Does Cummins have a computer to hook up to our truck or this a dealer only computer? The local dealer is ... . so I would like to avoid them even if it means a 240-mile drive to the next town. Or I may just have to bite the bullet...



Are there any scan tools that can measure rail pressure? I just have the AutoXray 4000 (basic version).



Any ideas are much appreciated!

 

[rbattelle]

I think it's probably in the fuel system exactly as you suggest. Perhaps a pressure relief valve, perhaps an injector going bad. Isn't that overpressure valve only good for a couple uses before it's shot?



I don't know of any scan tools able to read rail pressure except a DRB-III (and Matt400's famous rail pressure gauge).



-Ryan

 

[JStieger]

might have solved it - I HOPE

I think the problem is my MAP sensor. This is what I did:



First I disconnected my injector harnesses one by one to see how much the engine lugged down - to see if one pair of injectors may have been more "dead" than the others. Only the harness for #3/#4 injectors didn't cause a major change in sound when disconnected. It was a noticeable drop in sound, but I think being in the middle of the block might insulate the sounds better. (?)



So then I disconnected my MAP sensor and the exact sounding injection knock occured. I then reconnected it and my truck then sounded a lot smoother and quieter than before I disconnected it.



I also disconnected the fuel pressure sensor harness and the truck just died so I reconnected it.



Anyhow, I then went for a drive and no sputtering or popping or grey smoke! From a stop and letting the clutch out, the rpms dropped a bit as the engine loaded up but NO INJECTOR KNOCK!



Then I turned off on some back roads (dirt and bumpy) and stopped and started out and grey smoke and popping again, but it was not as pronounced as before and it was also intermittent.



I am thinking that the MAP is toast and sending false boost signals to the ECM thereby affecting the injection timing since our trucks fuel off boost readings.



This might explain why this started after the Juice install since I was playing around with those plugs (and the MAP was probably on the verge of going out), but still continues when I am running stock.



Also, might explain the code P0193 - Fuel Rail Pressure Sensor Circuit High - i. e. , reading the wrong boost so sending the wrong fuel pressure.



Any thoughts?



I am going to buy a new map sensor on Tuesday and try that out.

 

[rbattelle]

Fascinating. If it works, that will be something for people with the infamous knock to look into. Let us know what happens!!



-Ryan

 

[Scrappy]

Yeah' I am curious if this fixes yours since mine has the rattle like you're seeing, just no stumble usually.

 

[speedyjdl]

I have the same problem and wondering if its injectors, map sensor or rail pressure relief valve. I have the hesitation and grey smoke but haven't really noticed any noise difference.
I just got the twins program in my TST box and it did it before and still does it now. I was hoping that the twins program would clear up my hesitation on bottom cause I was suppose to have 100% fuelling at 3 psi. It does seem to spool faster now and I can build 40 psi on level 3,3 but still hesitation down low.
I was suppose to have the early twins program. The one where you plan on not doing any injector modifications. Maybe they got me mixed up and gave me the later not so aggresive twins program. I don't know.
If anybody has any answers about the grey smoke or the early hesitation please let me know.

 

[Kday]

I've got a similar situation but my truck is a 05 auto. No popping but smoke and knocking on light throttle application, and after a long highway drive if I open her up she dumps out smoke like it's chipped and has big injectors. The only problem is it's got no more power even if I turn up the Quad box. I've tryed taking the box off changing the fuel filter, fuel additives and as a last resort taking it to the the dealer to no avail. These symptoms came on all of a sudden and the truck has no guts but more smoke. If I can't get the dealer to fix/find the problem how much is a map sensor and is there any way to test my current one by either unplugging it or voltmeter. Thanks, hopefully this will fix the gremlins.

 

[JStieger]

Well I pm'ed Keith Lockliear in case he might have seen these problems in his work. He suggested that I hook up a scan tool while driving my truck to see what my MAP sensor is reading. So I took his advice and this is what I measured. Keep in mind that the MAP measures absolute pressure so one has to subtract atmospheric pressure to get gauge pressure. In a perfect world, this gauge pressure should equal your boost gauge pressure:



*Elko current barometric pressure @ 5,000 ft = 30. 05 in. Hg = 14. 74 psi

*Corrected for altitude @ 1 in. Hg decrease per 1000 ft elevation = 25. 05 in. Hg = 12. 3 psi

*Note sea level atmospheric pressure = 14. 7 psi in a perfect world



Map @ idle = 25 in. Hg = 12. 28 psi (note COULD NOT DUPLICATE STUMBLING ETC AT ALL WHEN I MEASURED THE MAP THIS EVENING :-{} :-{} )



I feel like a dealer technician, but I digress...



If I subtract the corrected atmospheric pressure I get 0 psi = 0 boost psi



Interestingly, if I subtract the sea level atmospheric pressure = 14. 7 psi, then boost = -2. 42 psi (negative boost)



So if the MAP was reading wrong, i. e. lower than 12. 28 psi from poor connections, then the ECM would be seeing negative boost. When the ECM sees negative boost, then minimal fueling. Note that when I physically disconnected the MAP sensor the injectors started knocking from what seemed like the lack of pilot injection (= less fuel??) so I am wondering in this case that the ECM reads 0 psi absolute pressure, subtracts out the atmospheric pressure, which in turns equals negative boost.



Now say if the MAP connection was marginal then eventually the ECM will read boost and add fueling late. Adding fuel late = retarded injection timing = grey smoke and stumbling.



Now when I get on it some more, the ECM is seeing boost all the time so it is adding fuel, which would explain why my truck runs great at above 1200 rpm to redline.



Does this sound right in terms of my interpretation?



I am still ticked though that I couldn't duplicate the stumbling problem this evening! This is probably because I reseated everything better yesterday after taking apart the harness connections systematically one-by-one.



I am going to Cummins Intermountain tomorrow to buy a new MAP sensor. My truck will also be in a body shop until Friday morning after an unfortunate incident with an invisible wood pole so I will not be able to update until at least Friday.

 

[JStieger]

Well I got the truck back from the body shop - $750 later and it looks brand new again.



However, the MAP sensor didn't come in yet until probably next week. It's a $50 part by the way.



So today I went for about a 2 hour drive and left my scan tool plugged in and recorded absolute MAP (Ma) sensor readings against boost gauge (BG) readings. Atmospheric (A) air pressure was ~12. 3 psi. Here's the summary in the form:



Ma = xx" HG = yy psi; M-A=boost psi; BG = zz psi



Ma = 25" = 12. 3 psi; 12. 3 - 12. 3 = 0 ; BG = 0 psi

Ma = 39" = 19. 2 psi; 19. 2 - 12. 3 = 6. 9; BG = 6 psi

Ma = 44" = 21. 6 psi; 21. 6 - 12. 3 = 9. 3; BG = 8 psi

Ma = 50" = 24. 6 psi; 24. 6 - 12. 3 = 12. 3; BG = 10 psi

Ma = 57" = 28. 0 psi; 28. 0 - 12. 3 = 15. 7; BG = 14 psi

Ma = 76" = 37. 3 psi; 37. 3 - 12. 3 = 25. 0; BG = 30 psi



My boost gauge is tapped into the intake manifold about 12" from the MAP sensor so I would expect the readings to be pretty close, yet they are not. Note I do have my VA C3. 1 plugged in, but it's off (boost fool mode only) so I can drive around with my injectors without setting "overboost codes" so maybe the last reading is the "boost fooled" signal or it could be the true reading prior to the VA intercepting it and capping it (the VA plugs into the ECM on the side of the engine). Also, note that I previously tried running without any box too and it still did the "poof/stutter" so that ruled out box problems and hence why the VA is on for now.



I was also able to duplicate today the grey "poof/sputter" by driving along at any speed, depressing the clutch pedal and coast in gear, letting the rpms fall to ~1200 rpm and then blipping the throttle. If I didn't let the rpms fall as much, say only to 1500, then blipping the throttle gave the black smoke.



I just can't wait until the new MAP comes in to prove or disprove my hunch #@$%! .

 

[RankRam]

JStieger can you talk one of the other CTD owners in the Elko area into letting you try their MAP sensor?

 

[JStieger]

JStieger can you talk one of the other CTD owners in the Elko area into letting you try their MAP sensor?

I thought of it yesterday after I helped one of them install a SDC dual disk clutch for about 7 hours, but I lost my train of thought when we went out for the test drive around the back roads! :-laf



Now I know why they have the holy crap handle on the passenger side...

 

[F-15I Ra'am]

Those of you with a possible bad MAP sensor, are you getting P0236 code and would this code mean the MAP sensor was bad?

 

[Kday]

Do any of you guy's have smoke on a steady cruise on the highway? I've got a knock if I rev it up and let it idle down and no power increase from my Quad. I'm wondering if the MAP is bad and I'm not getting the proper timing adjustments from boost and or the chip. It'l even smoke at 1200 rpm at light throttle from a stop sign. Any ideas!

 

[JStieger]

Well... I'm not totally convinced now that the MAP sensor is the true culprit, especially after digesting all my measurements and reflecting back on the past 1/2 year or so of truck idiosyncracies. I think there is something much more sinister going on with my truck...



I think my CP3 is starting to go TU.



The earliest my truck did this "poof/sputter" was when I had TST PMCR installed. It basically messed with my injection timing etc to cause the stumbling and gray smoke, but significantly a lot worse than now. The TST also gave all the crank and cam sensor codes associated with it being directly plugged into these sensors. After removing the TST this problem went away. Note that when I had the TST I ran it a few weeks without a pusher pump and routinely pulled my CP3 feed pressure to 0 (truck would jerk and almost die as if an anchor was thrown from it onto the road).



Now the problem has come back with the same symptoms, albeit not as severe, so I am pretty confident I have it narrowed down to an injection timing issue - probably late because of the gray smoke = partially unburnt fuel. What I am also seeing is:



1) No fuel in oil

2) No coolant in oil or vice versa

3) Good fuel pressure to the CP3 @ ~14 psi max & 10 psi min @ WOT

4) changing fuel filters did not improve anything

5) adding fuel additive through numerous tanks of various brand name diesel did not change anything

6) starting to get a lopy idle on cold or warm starts

7) slight diesel smell out the exhaust at idle or when wind catches the exhaust right while moving into an open window

8) truck does this with or without electronic boxes

9) knock and sputter appears to happen more when the truck is operated during warmer temperatures right off of idle to ~1200 rpm. Above this truck is fine with no smoke or black smoke when matted.



These trucks fuel off boost so say the MAP is faulty then the fuel could be injected late. I tested this theory by unplugging the MAP sensor and sure enough my truck started knocking like a 2nd gen 24 valve, but the MAP defaulted to 70" Hg (22 psi gauge) and gives an overboost code. At this boost level the ECM should add fuel in theory due to the boost fooling of the VA, but it is not. I am thinking lack of pilot injection due to the fuel rail pressure being out of whack. So anyhow I have a new MAP on order ($50) to eliminate this out of the picture, but still kind of skeptical...



... so my other theory is that my injection pump may be going out or some sort of valving inside of it is going out. It may be stumbling because of NOT ENOUGH fuel pressure at idle or perhaps the transition from idle to road rpms is out of sync. I would love to measure my rail pressure at idle or off idle via a multimeter to measure volts then convert to psi. Unfortunately, I do not have such a meter readily at my disposal.



So on a whim I called up a local diesel shop first to ask if they had a DRB-3 (No) and then explained my symptons and the first thing they said was "injection pump" without me saying it. They asked about codes (none) and clarified that they have seen a few injection pump failures without codes. They do have a Snap-On scanner though and will do some tests on my truck to rule out any other faults this Friday morning.



I also ordered a bunch of manuals etc from Tech Authority in regards to understanding the ECM and Cummins CR system.



:{ :{ "I am my own warranty station"



If this problem is in fact my CP3, then I do have some consolation via a search on TDR that CP3's have gone out on stock trucks too.

 

[RankRam]

Julius, I wish I could help ya.



Best of luck though.

 

[Big_H316]

I had almost the same identical problem and no dealership could diagnose it for a year. It was a real pain in the tailpipe. MAP was fine, tried replacing pressure relief valve, no change, come to find out, it was the solenoid on the back of the cp-3 the whole time. Here's the kicker, you can't buy that solenoid without buying the whole ding-dang cp-3. Cheap suggestion: go to a wrecking yard and see if you can find the solenoid to replace yours with. An easy way to tell if your cp-3 is bad is when it starts leaking fuel from the seals. After I replaced my pump it ran like a new one.

 

[JStieger]

I've actually come to the same conclusion the past week! Intermingled with the knocking injectors sound and lopy idle (probably from low rail pressure) I can hear a clicking sound just off-idle coming from the driver's side engine compartment. It sounds just like a bad starter solenoid going out on a gas rig and even having the same symptoms such as FUBARed/acting up when hot only. It's as if the solenoid cannot make up its mind which way it wants to send fuel so hence my late injection timing. Unfortunately I don't have any wrecking yards nearby around me so I will be getting a new CP3 this Friday and hopefully keep this as a spare so when I get to a place with a wrecking yard I can pick up the solenoid. Otherwise I have no leaks around/on the CP3. The clicking sound is getting worse as the days go by, but it should last the 3-hour drive to Industrial Injection in Salt Lake to get it replaced (I have no problems or clicking sounds during steady cruise).



BTW I did replace the MAP and it was good! I also have a new pressure relief valve "just in case" for future problems.



Pretty soon my truck will be carrying tons of spare parts (I kept my stock clutch, stock turbo, etc... )!

 

[milehigh.o.]

This is the same problem I had with my '03 305/555. They replaced the high injection pump and 2 months later it came back. Then I just traded it in on the 04. 5. And they had the vehicle for almost 10 days to diag. the problem.

 

[rbattelle]

I can hear a clicking sound just off-idle coming from the driver's side engine compartment.

Interesting. I have a clicking noise that happens on startup. Maybe 5 or 6 clicks at random from the drivers side at idle and that's it. Not sure if it's abnormal. No other negative symptoms.



-Ryan

 

[JStieger]

Interesting. I have a clicking noise that happens on startup. Maybe 5 or 6 clicks at random from the drivers side at idle and that's it. Not sure if it's abnormal. No other negative symptoms.



-Ryan

If I lightly press the throttle when my truck is fully warmed up, I can now (as of the past few days) get the clicking sound repeatedly for about 5 seconds. Kind of sounds like those set of clattering teeth one can buy at a joke shop.



However, if I press the throttle more like accelerating from a stop sign, then it is just one longer click followed by the "poof/sputter".



No codes still though, but interestingly enough I did a search on CP3 in this forum and CP3 failures happened different ways: codes, no codes, noises, no noises, stumbling, no stumbling, slow failure, sudden failure.



Then VMackenzie (sp?) had the fuel rich gray smoke, but it turned out to be the ECM was going TU. Can't remember if he had codes or any other symptoms though.