UPDATE - Idle "Lope"/"Surge" on trucks w/ EZ

[Tomeygun]

ok, heres the deal



I hooked up the DRBIII - and read the fuel pressure sensor on the rail,

It has a "suppose to be" field, and a actual reading



(first without EZ hooked up):

When my truck was just started, the actual sensor reading would vary from 4900 to 6700 psi at the rail, but a noticable lope was present but only by ear, it did not shake the truck... It was like the sensor kept over compensating, then under, then over,etc -- So there is a definite problem with the truck, cause that is with NO chips on the rail pressure sensor



(NOW for the readings with EZ)

now after the truck was just started, the actual sensor reading would vary from 4100 to 7500 psi at the rail, and the lope was shaking the truck as each time the sub-4500ish PSI showed on the reading,



Of course that is now proof that the EZ is modifing the fuel pressure to SOME extend at idle... I put the EZ on its lowest level now, so we will see what it does



I tested a new 2005 model and the reading was never more than 250psi from the target pressure, so some varience is there, but just not so darn much!!!



The next step is to of course show my findings to the service manager that thinks I am just being picky...



If anything comes of this in my service dept. I will update!

 

[DaveMorris]

Mine has always been a little touchy in cold weather when you first start it up until a couple miles of driving. It will lope and vary it's idleing about 200 RPM's... I just start it up, hit the high idle, take it to about 1200 rpms and it will smooth out... I am sure this happens to stock trucks, but the EZ just magnafies it that much more. Same thing with the cruise control and around 55-60 on concrete highways, you get a on/off gas feeling.



Good luck (might be better to give the Cummins dealer in fenton a call and see what they say)...



Dave

 

[DIESELMAN]

Tomey - Wow, thats extreme. Mine does not lope, and I see DRB read of 5900 to 6100 PSI, with or without the EZ, at idle. Same with or without the BDog program loaded.



I do have an undershoot where when I press in the clutch and return to idle after being under load, the pressure drops to about 5500 and the idle drops below 600, it also shakes just a bit, it will overshoot to about 6400PSI and the idle will go to 900 or so. This happens a few times over 2-3 seconds before it settles, but then it idles rock solid and so is the pressure, +/- 100PSI.



This all sounds like a PID loop in software with too much proportional gain or too little derivative gain or a pressure sensor that is reacting slower than the PID loop feeding it dampened or late output or is not giving stable output. Those that Lope probably have a bad pressure sensor.



I think that when the pressure is over about 6800PSI the EZ has a logorithmic ramp that reduces pressure reported (pressure is higher than actual) and it is only skewing the error caused by a poor pressure sensor. I do not see any change in pressure on mine with the EZ in or out at idle.

 

[realsquash]

I'm so happy to see this thread. It's been like -5 to 10 above lately so high idle kicks in all the time. But it's not just during high idle and it's not just when the engine is cold.



Obviously I don't have a DRB to plug in but I'd love to try one It's either a weird pump or a weird rail sensor if it's not a software problem. I would bet on a pump or sensor issue.....



I agree with Dieselman's theory about the EZ. I also have the EZ (bought it from Tomey actually) but my truck's done it since the day it was driven home new. I don't think the EZ attempts to modify anything right at idle but it doesn't expect the FP fluctuations so it's trying to keep up with them and it exaggerates the problem.



Under load it runs great but it does hiccup once in a great while. It does the light-throttle/65mph surge rarely but it used to do it a lot more when it was warm out. I have a 6-speed so it's a helluva lot easier to feel every little miss.



It starts perfect, never missed on the first crank. It runs great under load. It gets great, consistent mileage. I just don't want to get stranded somewhere.



Tomey, how much is a rail pressure sensor? If it's under a hundred bux I'll just buy the damned thing and swap it out myself and see what it does. If it doesn't help you should find a spare CP3 and see what it does...



Andy

p. s. I'm going to be in St. Louis sometime in the next couple months if it would help. Heck I'd drive all the way down there just to play.

 

[Tomeygun]

I'm so happy to see this thread. ... ... . the Tomey, how much is a rail pressure sensor? If it's under a hundred bux I'll just buy the damned thing and swap it out myself and see what it does. If it doesn't help you should find a spare CP3 and see what it does...



Andy

p. s. I'm going to be in St. Louis sometime in the next couple months if it would help. Heck I'd drive all the way down there just to play.

I think it is about 200-300, but we must call STAR hotline before they will release it... I am very anxious to see what my service manager has to say about my findings, esp. when dieselman's truck does not do it



one step closer... ... .



PS - keep in mind the sensor could only be doing what it was designed to do, and it could be acting upon info from earlier in the fuel line

 

[realsquash]

I think it is about 200-300, but we must call STAR hotline before they will release it... I am very anxious to see what my service manager has to say about my findings, esp. when dieselman's truck does not do it



one step closer... ... .



PS - keep in mind the sensor could only be doing what it was designed to do, and it could be acting upon info from earlier in the fuel line

What's a CP3 go for? I wonder what the GM CP3 costs? Hmmm...



I wonder if there's a TDR member with a 555 that doesn't have this problem and is willing to loan out some parts? BBQ's on me!



I personally have a feeling it's the CP3 being "slow" if you will. It's not reacting as fast as it should or it's just drifting around. I'd be interested to see what happens at cruise w/o the EZ (well, and with it, too) with the rail pressure.



Andy



Andy

 

[amsoilman]

What's a CP3 go for? I wonder what the GM CP3 costs? Hmmm...



I wonder if there's a TDR member with a 555 that doesn't have this problem and is willing to loan out some parts? BBQ's on me!



I personally have a feeling it's the CP3 being "slow" if you will. It's not reacting as fast as it should or it's just drifting around. I'd be interested to see what happens at cruise w/o the EZ (well, and with it, too) with the rail pressure.



Andy



Andy

I have an 03' 555 that has the same "lope" when the EZ is installed. If I take it off, the "lope" goes away.



Wayne

amsoilman

 

[realsquash]

I have an 03' 555 that has the same "lope" when the EZ is installed. If I take it off, the "lope" goes away.



Wayne

amsoilman

Wanna swap pressure sensors? Oo. Great!



Andy

 

[lawdog]

My 03 has the idle lope or surge with the EZ as well, smooth without

 

[realsquash]

My 03 has the idle lope or surge with the EZ as well, smooth without

I would bet that your truck has the same issue but to a lesser extent. I don't think the EZ intends to modify FP at idle/zero boost.



Andy

 

[Bob4x4]

I doubt that the issue is with the sensor... ... ... it is only telling you what it sees. The pressure bouncing around is the problem. Check for fuel contamination,low pressure to the cp3 or a faulty fca,whitch is only available with the cp3 at this time.



Bob

 

[DocDetonancour]

Seems like all these boxes cause some problem? Hard starting is a BIG issue with me, and wouldn't run a box if that was part of the deal, MO, Doc.

 

[Jeff_K]

I have never experienced hard starting with the EZ. Just the lope at idle. Some have it, some don't. Its not bad, but it is noticable to the ear.

 

[Gypsyman]

All of the above is why I went with the VA C3. 1 and I haven't had any of the problems since. It doesn't have the top end all by itself but it is glass smooth with no issues.



jm02



Richard

 

[realsquash]

People are blaming the EZ for this lope issue and it's NOT at fault. Someone else mentioned a loooong time ago that there was a part in the CP3 that was bad (FCA) but unserviceable and that replacing the pump cured the issue for him. That must have been over 6 months ago.



I'm afraid to take my truck to the dealer (only has 41k miles) because I can't be left w/o a vehicle to get 40 miles to work and I've never trusted dealers. IIRC someone said a CP3 was $900 and made from unobtanium so I might have to break down and visit the dealer. The only mod I have is the EZ and gauges...



Andy

 

[Gary - K7GLD]

YUP, usually boxes like the EZ and Comp only MAGNIFY an issue that already exists...

 

[Tomeygun]

OK, semi-good news



the head diesel tech here had ran into this problem before, where the target PSI and the actual PSI never catch up-- We are now searching for the Repair order to see what stuff we changed to fix it



another step closer

 

[realsquash]

Great, I can't wait to see what it is!



Andy

 

[dkosheba]

My truck does this as well on cold morning starts when temps are in the single digits. Seems to be osilating the RPM in a 3-4 second cycle and really shakes the truck. My high idle feature does not smooth this out until I'm up to the 1500 RPM. At 1200 it really shakes the truck.



It goes away as soon as I put it in gear and move the truck down the drive to hook up trailer as by then I have already poured the fuel to it to get the beast to move with the stock TC.

 

[Bob4x4]

Tomeygun,why doesn't your head tech just test your truck?There is a procedure for this. You won't get any parts from star till he runs the tests anyway. Or would he cheat and rattle off the same results as his last check out



Bob