BobQ

When at idle, the motor seams fine, but if I am going at about 20mph, threw a parking lot or such, with no throttle, the engine kind of lopes, or goes up and down alittle. It seams as though it started after the 275 injectors? No codes. It pulls hard and seams to run well other wise. Should I worry? What do you guys think?

Thanks Bob

sleds

Its nothing to worry about.

Big Smoky

Perfectly normal. I have the same deal with my truck.

Eric

RJF

My dad has DonM mach 1 injectors and it kind of does the same thing at idle when the clutch is let out. Sounds pretty cool actually....

I think I have heard my motor do the same thing you described, like going through a parking lot and right when you let off the throttle before it returns to idle...it's fine.

rebal

seems to be common with bigger sticks

Dieseldude4x4

Mine does it too. Cool................

RustyJC

It's because the larger injectors throw off the calibration of the ECM's idle speed control circuitry - it now has too much gain. In other words, when the ECM tries to speed up or slow down the engine, the amount of fuel added or taken away is more than the stock injectors provided, so the engine speed overshoots and undershoots as the ECM struggles to hold a constant speed. You'll notice that, if you just barely touch the accelerator pedal to bring the APPS off of its idle position, the surging will disappear since the idle speed control circuitry is no longer in control of the engine speed.

Rusty

Diesel-Dan

The Mach II's do it.....haha...and now with the 315's....this truck doesnt like 30 MPH anymore!!!! 4th..starts to buck (RPM too low)....3rd...your running a spit over 2000.......cant win!!! hahaha.....I can see a 6 speed haveing an advantage here over the 5 speed.......

I think the surge is cool as well!!

Dieseldude4x4

When I'm using the cruise control on mine, I have to cut the one box all the way back to zero. The engine is too responsive for the cruise control to handle and it overshoots by about five MPH or more and then it's just up and down up and down. Scared me one day until I figured out what to do.

RustyJC

Same situation as described in post #7 - too much gain in the control circuitry with the bigger injectors, box or anything that provides more fueling than stock. With the vacuum servo-operated cruise control systems, one could kill this with a needle valve in the vacuum line to the servo. Just pinch it down until the hunting goes away - this is diminishing the responsiveness (gain) of the cruise control system.

Rusty

MARKY MARK

I was just about to ask this same question since I put in my RV275's. Sometimes when I start my truck and put it drive really quick, it does the loping thing. Though maybe I had a problems but it sounds like a normal thing.

Mark