Fighting Rough Idle

[cessnageek]

Couple things on cam selection

#1 - Never said it was a great cam. I'm still figuring out this stuff and there is probably(certainly) a better option out there. But here I am, sucked in by the marketing and all, and I'm just trying to make the best of what is in the truck. It is what it is. I'm not married to this cam, and am open to better suggestions if you got a good off the shelf truck cam recommendation for a daily driver. But I'm going to give it an honest shot to make it idle decent while it's in the truck.

#2 - It's a 212/22x with 107 LSA. I don't know why they don't tell the last digit of the exhaust duration, that's dumb but whatever. Either way, that puts the overlap somewhere between 2 and 6.5 deg. I guess that doesn't seem like a ton to me, but like I said, I don't really know what I'm doing. Seems like that should be able to idle decent.

[2xLS1]

That overlap is at .050 lift. What's the overlap at .002 or .006? 60 or 70 degrees? You don't name a cam with reasonable overlap Truck Norris.

[Cringer]

Thanks! Definitely runs better. Looks like you changed a bunch of stuff. Anything in particular major that helped it improve, or just a bunch of little things?

Here is a datalog of ~5 min warmup and ~8 min warm idle.

There is just some best idle practices I have picked up over the years as well as some other best practices to help keep your tune on point. Use this as your go forward tune for making modifications.

Here are some other tips and stuff to consider.

• After flashing the ECM, it is best to start and drive around for a while, even if the engine is already hot. A lot of variables get reset and they have to come back to their natural set point which comes from a drive cycle (15-20 min or so)
• There is also "rich after reflash"...google that if you haven't already. Your injector vs offset table is zero'd out (and in the stock file too). So either one of two things is happening:
  
  • The tune is accounting for this heat internally and we don't have access to it via HPT
  • It is not being accounted for and the heat is throwing off fueling (due to real world physics).
  
  
• Also when flashing a hot car it will have set for a few minutes and the heat soak really messes with the IAT and that also throws fueling off (it will cause a false lean condition in the logs)
• Again, driving around will settle the injector and IAT temps and not skew the results. FYI I am not a fan of zero'ing out the temp offset table like most people will tell you to do. You are kinda out of luck since it came that way from the factory.

When doing an idle log

• 
  
  • Yes: drive around and get the car hot first
  • Yes: stop the car, and let it idle for 30 seconds or so to let the rpms, air, fuel, spark settle down
  • Yes: either keep it in drive, or put in park for a single log
  • Yes: a 1-2 min log is more than enough data
  • No: log the start up process
  • No: log Open Loop stuff after start while it is waiting to transition to CL
  • No: touch the gas pedal
  • No: move the gear selector
  • No: touch any controls including turning on/off the A/C

The reason I say this because (and maybe this is just me), I build my histograms and charts to aggregate data for idle only. As soon as you introduce dirty data (touching the gas pedal, shifting gears, etc) it muddies the data. Now, if you have having specific problems with the start up process, or OL idle, then yes log them, but I prefer to try to log and isolate specific scenarios whenever possible. Same thing with reving the engine...if you have an issue with it returning to idle or surging, then log that, but don't add that to a static idle log.

One other tip, your burst knock is enabled and that may cause poot drivability (and maybe idle issues if you move the throttle), but I am not going to mess with your spark and knock remotely. Was this tuned by a shop?

[cessnageek]

Thanks for the constructive feedback! I'll keep those things in mind when taking logs next time.

I'm away from the truck for the long weekend. I think it is misfiring at idle, and I'm going to spend some time next week checking my ignition system. Misfire could be the cam/tune too of course, but I want to check everything mechanically/electrically before I get too frustrated trying to tune it. The only reason I haven't checked this earlier is the misfire counter wasn't indicating a problem.

No, it has not been tuned by a shop. Did the email tune thing, they sent a MAF only tune. Not impressed, so far my attempts have been better. If I decide to throw in the towel, I'll take it to a shop. Got any recommendations around the western Illinois, central Iowa area by chance?

[Alvin]

You will not be able to trust that the misfire diag will work with that cam.

My favorite way to find misses at idle is to use a toy squirt gun. Works 100% of the time and it's very obvious when you find a weak cylinder.

Temp guns do not work.. the reflectivity of different parts will show different readings.

When you say it has periods of running smooth. Sometimes if the idle is low you'll have a good chop but it will settle out if the engine is loaded like the A/C cycyling.. Is this what is happening?

[cessnageek]

My favorite way to find misses at idle is to use a toy squirt gun. Works 100% of the time and it's very obvious when you find a weak cylinder.

I like this. Looking for how it evaporates off the header?

When you say it has periods of running smooth. Sometimes if the idle is low you'll have a good chop but it will settle out if the engine is loaded like the A/C cycyling.. Is this what is happening?

I was thinking that too, but no, it will idle smooth for a while with A/C off, then it starts shaking. When I say smooth - there is still a little chop. That's fine. But then it starts shaking irregularly. I can't really see the shaking in the logs, at least with my untrained eye, but I definitely feel it in the cab. I know, it's hard to diagnose/describe a feel thing over the internet. At the same time, if I go to the back of the truck and listen, the exhaust will make a "puff" sound. I don't know a better way to describe it than that, or if that even means anything. I've spent a lot of time around an unmodified gen 4 6.0 on a 3/4 ton truck, and the exhaust doesn't make that sound as far as I remember.

I can't think of any other intermittent loads that would happen at idle. A/C off. Battery is charged, so alternator current should be roughly constant. Otherwise it's just water pump and power steering unless I'm forgetting an accessory. I'm not turning the steering wheel or anything like that.

[Cringer]

I disabled the misfire tables in the tune I sent. I cannot believe the ECM was not showing misfire counts with it enabled. I almost said something but, the O2 voltage readings seem off to me. They are lean. Remember O2 sensors can only detect the presence of oxygen, so a misfire shows a lot of unburned oxygen and will give a lean reading. The raw fuel passes by O2 sensors undetected. Here is what your O2 voltages looked like on the last log. This can also be a problem due to an exhaust leak (or placement of the O2 sensors on the exhaust system, but I imagine you have them in the stock locations).

geeky O2.jpg

[cessnageek]

It would show single digit misfires intermittently. Not often. I was also surprised it wasn't consistently showing a misfire, but again I don't really have the experience to know what's a problem and what's not.

I checked headers were tight to the heads last night. I'll try to check the ypipe to headers tonight.

Yes O2 sensors are in stock location in stock ypipe. There is a wideband maybe 6 inches before the driver side one. The O2 sensors are probably pretty old. I got the truck with ~265K on it, put ~1000 miles on it, then did the engine and trans rebuild. I don't know if the sensors were ever replaced before I owned it. But it ran ok before I rebuilt it with no related CEL(had evap CEL for a while due to evap hose coming disconnected), so they were *probably* working fine.

Also installed brand new OEM injectors as part of the rebuild. So those should *hopefully* be fine.

[cessnageek]

Did the water thing. Looks like 2 and possibly 6 are misfiring. Will continue to investigate. Haven't checked y pipe bolts and probably won't tonight because everything is hot.

[Alvin]

When you notice this rough idle.. Look at the commanded AFR / EQ. Some will run themselves lean as a CAT check. This happens usually at an idle.

[cessnageek]

I've never seen commanded EQ deviate from 1, except for the first 10ish seconds after startup and during PE. So far the only thing that has helped is reducing the timing to ~11-12*
It's silky smooth down there. But as we discussed above, that's pretty low.

Got some more mechanical/electrical diagnostic steps to try tonight. Also, I've read a little bit about a crank relearn procedure. Not sure if that is only for gen 3s or if it also applies to gen 4s, but I might give that a shot as well.

Another weird thing - my misfire diagnostics just don't work at all at idle. I can completely unplug an injector and it reads 0 misfires. Unless I have bluetooth injectors, I'd say the diagnostic is pretty much worthless. This is with a tune with stock misfire tables.

This is intended to be a daily, so I'm also running 87 for the time being. Not sure how much/if octane level affects things at idle?

[edcmat-l1]

The cam is going to have a noticeably rough idle.

If you can get it smooth with the timing that low check your header or manifold temps. If you have headers the timing being that low will make them really hot and they'll glow in the daylight. If you have manifolds they'll handle the heat a lot better. If it's not burning plug wires or more you'll probably be fine with it that low.

A crank relearn will do nothing for you. Other than maybe fix your lack of misfire detection. It will in no way help the idle quality. It's not intended to.

[Cringer]

I've never seen commanded EQ deviate from 1, except for the first 10ish seconds after startup and during PE. So far the only thing that has helped is reducing the timing to ~11-12*
It's silky smooth down there. But as we discussed above, that's pretty low.

Got some more mechanical/electrical diagnostic steps to try tonight. Also, I've read a little bit about a crank relearn procedure. Not sure if that is only for gen 3s or if it also applies to gen 4s, but I might give that a shot as well.

Another weird thing - my misfire diagnostics just don't work at all at idle. I can completely unplug an injector and it reads 0 misfires. Unless I have bluetooth injectors, I'd say the diagnostic is pretty much worthless. This is with a tune with stock misfire tables.

This is intended to be a daily, so I'm also running 87 for the time being. Not sure how much/if octane level affects things at idle?

I disabled the cat checks so commanded AFR should not be an issue. I also disabled the misfire tables since those are worthless with a cam. Rather than unplugging each injector, use the scanner vehicle controls and special functions to disable each injector one at a time while the motor is running to see if your butt dyno notices any changes to the motion of the ocean.

[cessnageek]

Smart, I'll try that.

Fuel pressure - is 43.9 psi normal for a flex fuel truck at idle? I see conflicting information on the Internet. Some say yes some say no.

EDIT - The other thing is looking at a log where I went through a startup cycle. Key on engine off psi is 72, then 58 psi while running rich commanded AFR after startup, then 43.5 while running stoich commanded AFR. Engine runs great while running rich commanded AFR, shaking starts after it goes stoich. Looks like this is the "Low Flow" and "Normal" modes = 300 kpa in the fuel sys -> fuel pressure tab.

[Cringer]

Smart, I'll try that.

Fuel pressure - is 43.9 psi normal for a flex fuel truck at idle? I see conflicting information on the Internet. Some say yes some say no.

AFAIK all Gen4 stuff is 58 PSI (4 Bar). Gen3 is 43 PSI (3 Bar). There may be exceptions, IDK.

[cessnageek]

I spent the $20 on the service manual subscription, might as well use it. I have a FPCM, service manual says idle should be 43-45 psi. So all good there. False alarm.

[Alvin]

AFAIK all Gen4 stuff is 58 PSI (4 Bar). Gen3 is 43 PSI (3 Bar). There may be exceptions, IDK.

Some GEN 4 trucks go up and down on the FP. You can scan desired and actual and see them follow each other.

I don't know if it's a flex fuel thing or not.. FPCM equipped trucks are sorta random. I don't know why some do and some don't.

[cessnageek]

Found an exhaust leak at driver y-pipe to header connection. Could feel hot air with my hand. Fixed it. Got all excited, but it still runs rough and WBs read lean.
I tightened the passenger side y-pipe to header, but can't really feel around it with my hand without taking the inner fenderwell off. So going to try that tonight to make sure there is no leak there.

[gtstorey]

If you tuned with the exhaust leak and then fixed the exhaust leak, you will have to retune again since the error was baked in. Just because you fixed the leak, it won't start running correctly. This is why so much emphasis is put on making sure everything is done right to start with.

Doesn't mean you don't have other problems though.

[blindsquirrel]

AFAIK all Gen4 stuff is 58 PSI (4 Bar). Gen3 is 43 PSI (3 Bar). There may be exceptions, IDK.

Gen 3 non-flex is 58psi, and that's the same whether it's returnless ('05-up) or the return-style's base pressure ('04-down) with the vacuum hose off.

The '04-down return-style L59 flex fuel is the only one that has a non-58psi spec: those are 51psi (service manual: "VIN Z Ethanol: 335-375 kPa (48-54 psi)"). In 2005 the L59 went returnless and also changed to the same 58psi as everything else.