Idling too fast??

[z28cp]

Hi folks!

So, I replaced by Rocker Arm Retainers. Easy enough job, even for a diesel virgin. Also found that the lifter where the rocker arm had moved was messed up. Apparently the snap ring had broken at some point, and once there was no longer pressure on the pushrod, the little cup up top popped out. So, that got replaced too. Obviously, the same guy that came up with the idea for the little plastic retainers (junk...) is not the same guy who designed it so you can change lifters without any further disassembly (very nice idea).

Anyway, got it back together and running. Started up much easier than I expected. Runs and idles smoother than it ever has since I have owned it, and I thought it was fine before.

However, when I took it for a drive, I discovered something odd. The engine speed returns much more slowly to idle than it did previously. And sometimes seems to kinda hang up at around 1500rpm, then will slowly return to idle. And the idle seems a little higher than previous also. Used to be about 850-900, now about 1050rpm.

Any thoughts about what may be causing these idle speed issues? Any help is greatly appreciated.

Thanks,
DaveZ.

[DmaxMaverick]

Air in the fuel system will cause what you describe. Still, 850-900 is too high on an engine up to operating temp. OK during cold warm-up (HPCA/high idle). It should bleed itself and return to "normal" after a short period of running. If it doesn't, the timing needs to be checked (did you move the pump?), and the pump fuel return checked for air (install a temporary clear line at the pump return and watch for air).

[z28cp]

Dmax-

Did not move the pump that I am aware of. Only touched it enough to remove and install the fuel lines. As far as air in the lines, it has been driven about 20 miles now, still same issue. Would think if there was air in the lines, it would have worked it's way out by now.

Thanks,
DaveZ.

[DmaxMaverick]

Hmmmmmm....

Back to basics. Start with the basic troubleshooting steps. I'd still check for air, first. 20 miles should have purged it, though.

If you didn't loosen the pump and/or remove the timing set, there's no reason it should be timed different than before. Also verify your injector lines are connected in the right order. Is it possible they were wrong before? Two lines can be crossed (bottom 2). This would lead to a rough idle and slight to profound miss. Could explain your now smoother idle. Did you change anything other than the rocker button and lifter?

[z28cp]

It seemed to idle fine before, just seems to be a little bit smoother now. Made very sure to put lines back on where they came from, which is also the order they show in the service manual. Only things replaced were the rocker retainers on the drivers side, and that one lifter.

Is it possible that the cable is just hanging up slightly? Maybe even the cable from the Cruise? I realize it is sudden, but I have seen stranger things... Or, is it possible that the fast idle solenoid is hanging up a little?

It runs fine, just has this (hopefully...) minor idle issue.

[DmaxMaverick]

Anything is possible. You need to witness the linkage while the pedal is released. If it operates smooth and normal, you are back to square one. The cruise has a long slider type connection, so it shouldn't interfere with the pedal input. If you have it installed upside down, or with the cable twisted, it could interfere with the throttle. I doubt it, as the throttle return is pretty stout compared to the resistance. Remove the high idle solenoid to eliminate that as a possible. Also, check to be sure you don't have a hose, harness or other part interfering with the throttle. W/o seeing it, it's hard to tell. The RPM should fall quick and steady until reaching idle.

[daustin]

When you did the rocker work, maybe the temp sensor in the water crossover got bumped and it's crapping out now? Also check to see if the cold high idle solinoid isn't sticking. With your's being a 4911 MIP, you may be able to just reset it on the side of the pump.
Don