Rough idle and surge after turning up IP

[jonstine]

I've been researching the heck out of this site and a few others about a problem I'm having. Hopefully someone here can help me out.

I have a K&N air filter, 2.25' mandrel bent dual exhaust from the manifolds back with h-pipe, and hi flow Hooker Aero mufflers. The truck has always had a little clackity clack when it's cold, but has been a generally smooth, albeit underwhelming engine.

Over the weekend I turned up the IP on my M1028 about 1/8 turn. Everything came off and went back on exactly as planned. Started right back up. Immediately I noticed the idle had a different "lope" to it. Much rougher, a lot more vibration, and almost a twisting of the engine in the mounts. The exhaust now has a deeper tone that almost sounds like it's got a big block cam or something. Once the truck warms up, it stays about the same. Sitting at a red light the whole truck shakes more than it ever has before, again like there's a big block loping under the hood. My wife got in a couple days ago, and immediately looked at me and said "ummm what did you do to the truck, it's running really rough?".

When I drive it, it definitely has more get up if I give it 1/4 to 1/3 pedal. If I give it much more than that it almost seems to bog down and performance drops off. I do get some black smoke out the exhaust at 2/3 to WOT, but nothing excessive and completely inline with expectations after turning up the IP. I also notice that as I cruise at roughly 40-50MPH it seems to stutter and surge if I'm not actively applying the go pedal. If I'm going up a slight grade it runs relatively smooth. If I'm going down a slight grade it runs relatively smooth. If I'm going flat and my foot isn't pushing or letting off the gas pedal it will alternately stutter, then lunge, then stutter. It's slight. More like a feeling that you can tell something is going on with the engine, but not like the truck is lurching and then jumping forward. Feels like I am getting ready to run out of gas. As soon as I either apply more pedal or take my foot off the pedal some it evens out. Returns as soon as I am coasting with no increase/decrease in the pedal.

The ONLY thing that changed was turning the IP up 1/8 turn. I have been RESEARCHING advancing/retarding the IP (which I've never done, but am willing to try), taking off the IP cover and verifying hooked up correctly (which I'd rather not due to those **** small screws), replacing the Racor fuel filter (which I already had done about 1,000 mi ago), adjusting the throttle screw, verifying the cold advance is working (but the engine still runs rough after warm), and a couple of other things like replacing fuel lines, etc. Before I jump into any of those, I am hoping that someone reads this and goes "Yep, its x".

I took it on a nice little 100mi drive with a topped off fuel tank and some extra Opti-Lube XPD dumped in there. Hoped to clear out anything that might have been gumming up an injector or something, but still does the same thing.

I took a video of it to try to give you an idea of how it sounds now. It is difficult to pick up the rough idle over the noise of the diesel in my garage, but the tail pipe part does give a better idea of how it sounds.

I appreciate any help you guys can give me on this. Thanks!

http://youtu.be/ZXdOI9-dHH8

 

[jonstine]

I should add, this may be entirely normal for those that turn up their IP, but if so I was not expecting it. My gut tells me there's an issue with the fuel - whether it's delivery, injectors, timing, etc. Is it possible that the extra 1/8 turn has magnified a possibly worn out or faulty injector or injectors that are just struggling to keep up with the new delivery requirements? Maybe the same for the IP? The engine has 46kmi on it. I bought it over a year ago with 39k, and it hasn't been driven hard by me at all.

Is it possible I didn't put something back together in the IP correctly? I did try to make sure everything was put back on correctly, and worked properly before tightening it all down. Again, the only change was taking off the IP cover, adjusting the screw 1/8 turn and reassembling. Immediate rough idle and surging when driving on flat roads.

 

[richingalveston]

turn it back down and see if it goes away. It may have already been turned up and you just went to far.

The IP is your timing system and will act the same as distributor. You might try turning the IP pump itself in the mount to retard the timing back ( I believe turning it towards the passenger side retards timing and toward driver advances) but most likely the pump just got turned up to much fuel wise. Diesels will bog when there is to much fuel and not enough air.

But this is the internet and therefore I could be wrong.

 

[Chaski]

Are you sure you put it back together correctly? The guide pin and governor spring can be finicky if anything is sticking. Other thing is that when you turn up the pump (clockwise) you are increasing the roller to roller dimension in the pump, and that means that the roller contacts the eccentric ring earlier. Turning up your pump advances your timing, turning down your pump retards it.

You said you just removed the cover and turned the screw 1/8 of a turn. In my experience it is impossible to turn up the pump without removing the guide pin and the governor spring assembly. If you tweaked that pesky bit to the side instead of removing it get to the Allen screw you may have caused an issue.

 

[jonstine]

Chaski, sorry for the confusion. Yes, I removed the guide pin and governor spring in order to line up the hole to turn up the pump. Reinstalled the governor spring assembly, reinserted and tightened down the guide pin screw, etc. Good eye, I just skipped over that part since it was inconsequential, but I should have mentioned it in my description.

Richingalveston, I'm thinking that may be the case, too. Possible that the PO had turned up the pump some, and I unknowingly turned it up even more. I was hoping someone would have said it was something else, but sounds like I need to turn it back down and see if that changes it back to pre-turn up idle and running. It definitely bogs when I give it full pedal. The odd thing is the surging when I'm not giving it pedal and just cruising. I thought that might have been indicative of something else, but perhaps it's all tied together.

I appreciate the feedback so far. I have some stuff to do this evening, but will turn it back down in the morning and report back if it changes anything.

 

[richingalveston]

The IP at proper calibration is pretty much putting as much fuel into the heads with the proper amount of air that the design allows. The amount of additional power when turning up the IP on a N/A diesel is very small and many times takes you backwards.

The only real reason to turn up the IP on a 6.2 is when you add a turbo. a turbo puts more air and fuel in the heads (in the proper proportion) by pressuring them. Thus you can use a little more fuel, but not to much.

Turning up the pump on a N/A 6.2 is almost futile.
Turning up a pump that you do not no the history of can be a dangerous thing to your wallet.

You turned up the fuel which increases the timing, sometimes you can retard it back by rotating the IP. There is a timing mark on the IP and on part it bots to.

I would turn it back to where you it was. If you want more power add turbo. If you just want a little more speed get bigger tires. IF you want a hot rod get a different truck

 

[Chaski]

Any update?

 

[cucvrus]

I will not say another word on this subject. We all know where that goes. I was called the CUCV Daddy.

 

[jonstine]

Been a busy week, but I did get a chance to turn it back down to approx. where it was before. Rough idle and surging are completely gone now. I assume that a previous owner had already turned up the IP and I just pushed it too far with my additional 1/8 turn. The EGTs never got too high with it turned up, but it was rough idling and surging enough that it's not worth the potential for extra wear and tear.

Rich, I appreciate your insight on troubleshooting and how things work with the IP, advance, etc. Truly helpful. The hot rod comment doesn't apply to me.

 

[richingalveston]

I am glad you got it resolved. I hope you continue to enjoy your truck as much as I do mine

 

[svlsmokey]

Just added turbo and I'm experiencing some of the same rough idle, surging, stalling (almost always when the engine is cold) problems. Per Banks' instructions I gave it a 1/4 turn increase. Might try turning it back a little and see if it smooths out. So far no issues with EGT getting too hot but until I'm able to resolve the transmission shifting issue, I haven't been able to test it out under load.