Lopeing @ low RPM, what gives?

[LarryB]

This probably has been covered but I couldn't figure out how to prase my search, so here goes.



On hot days after a long drive, my engine lopes, sometimes pretty bad, at low rpm with slight throttle. Kind of a Brump, Brump, Brump type of thing. When it starts if I give it more throttle it just gets worse. I have to clutch it or change gears to get it pull smoothly. If I remember right the problem started after putting in the 4K gov kit.



Any out there have experience with this?

 

[illflem]

Do you have a fuel pressure gauge? I've had a lope (not what I'd call stutter) after driving long distances in hot weather with low fuel tank levels then coming down to a idle, fuel pressure is also quite a bit lower than normal. My theory, which could be wrong, has been that the spring in the overflow valve loses some force when hot due to hot fuel, causing the pressure to drop. Or could it be heat effect on the lift pump? Almost like vapor lock, which isn't possible with a diesel. Doesn't do it with a full tank or when cruising but once an idle triggers it stays at all rpms until things cool, usually takes about 15 minutes shut down. I've also noted that while at a loping idle that as soon as I start adding fuel to the tank the lope disappears. Must be heat related. I measured 180° on the bottom of the tank with an infrared temp gun after one episode. I know that some big rigs have fuel temp gauges, could this be the reason or are they looking for too cold of fuel to turn on their tank heaters? I just try to keep my tank level above half when driving long distances, no problem then. Also gives me a good excuse to stop and stretch my legs, 300 miles is enough for one sitting anyways. I don't think your governor springs have anything to do with it, more likely your driving habits since you installed them.



This is with my auto so I don't have the opportunity to load the engine by shifting, don't know about that fix, but while loping if I turn the OD off and run the rpms up it gets worse.

 

[LarryB]

I'll have to get a fuel press gauge and check that. fuel pressure irregularities can do funny things. Thanks Illflem.



This almost feels like you are giving it a quick blip of throttle and then letting off. Only doing it about 5 times/second. I thinking the govornor doesn't know which way to go, like there is slop in there. If I remember right I think Piers said to back off the gov spring pressure but I can't remember if I did it. Maybe I'll back em off some more. Maybe I'll give him a call again.

 

[SLang]

I had the same problem after installing a Piers governor kit. Called Piers and he said to back the governor springs off one click. In "cruise" traffic lit would almost jerk the drive trian apart. The first "lope" was caused by the fuel pump and the rest by my jerking foot. I would have to get off of the fuel and come back on slowly. Loosened them one click and it fixed most of the problem but not all. It is very controllable at low speed cruising in town.

 

[LarryB]

Thanks SLang. Your absolutely right about jerking the drivetrain apart. That clinches it, off comes the AFC/plate tonight. One more click out.



Wait! Now its comming back to me. I already turned the retainers out some. The first few clicks helped a lot. I turned them out a couple more but like you It's still there but managable. Still a nusance though. Is there any way to get this cleared up completely? I too thought it was my throttle foot but after paying close attention have determined it aint me. I also thought it might be a tight throttle cable causing an ossilation. Tried loosening it way up, no help.



Thanks for your response,

Larry

 

[Swamp Donkey]

I am also working on this problem a bit, and have been in contact with Piers. He told me that the stud should stick out . 050 from the retaining nut. This is a good starting point. I may be wrong, because I don't have the e-mail anymore but I usually have a good memory. I am tempted to try the overflow valve to see if that fixes the problem.





Mine only does the lopey idle thing when engine is operating temp, always just after I start it and try and back out of a parking spot. The idle will be really lopey, almost to the point of stalling. But again, if I start it, rap the throttle to 2,000-2,500 rpm's it idles good. Kinda scares all the soccer moms at the wallmart when I do this! Tree huggers also disaprove of the large clouds of smoke! So after driving for a while the idle is great all day until I shut it off and restart. Just a matter of me doing a little tinkering. But then again, it is cold up here in the frozen north, so I may wait till spring.....

 

[radixr]

Loping

I had/have the exact same problem. Enterprise Engine backed off the governor springs one click (I think) and the loping was much improved. However, it still occurs once in a while although not as severe as before. I too would like to know if there is a complete solution and does backing off the governor springs reduce the rpm limit?

 

[LarryB]

does backing off the governor springs reduce the rpm limit?



Good question. Although I'm not so concerned about that as I've never bumped the 4K gov yet.



Anyone??????

 

[SLang]

Backing off the governor spring can and will reduce RPM. But the point of doing this is to fix a to tight situation. When installing the springs it is very easy to go a little to far thus causing the lope. Backing off 1-2 clicks will really not hurt a thing especially if your running 4K springs.