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Discussion Starter · #1 ·
I have an 85 GMC K10, with the 6.2. I just bought the truck about two weeks ago, and its my first experience with owning a diesel. It starts/runs/drives fine, but after it warms up i have a couple problems.

The first problem is that my idle seems like it's too high, I don't have a tach, but i would guess that it is idling at around 1000 rpm. If i shut off the truck, and immediately start it back up, the idle is normal again, but If I goose the throttle, it will stay too high again.

The second problem is an idle surge. This usually happens when the truck is really warmed up, I usually notice it after some freeway driving. The idle is already high, but when this problem starts, the idle seems to fluctuate between 1000 and 1800 rpm. again, thats just a guesstimate at the rpm based on the sound since i have no tach. This is all while in gear, if its doing this and i put it in park, the rpms shoot way up, probably to about 2500, and then it settles down and surges between 1000 and 1800 again. If I just let it sit in park and do its thing, it will eventually settle down to just idling at 1000 rpm again, but if i touch the throttle at all it goes back to surging again.

If needed i can throw up a video to better explain it, but I am hoping someone could help me without going through that trouble.
 

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Discussion Starter · #3 ·
well, like i said, even if its hot and doing the high idle thing, if i turn it off and then back on right away, the idle will be normal until i touch the gas pedal, so between that and the idle surge problem, i don't think its actually the idle screw setting. i could be totally wrong though, as i don't even fully understand how a diesel works :)

thanks for the quick reply though!
 

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check for broken or missing spring on pump trottle lever.
check for free movement of trottle cable.
if both checks out good,flip pump trottle lever and see if it snaps back fully against the stop,if it does and rpm still fluctuates then the prob is internal. you may need overhaul or rebuild.diesel fuel conditioner may free up sticky parts,try that first.
 

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the cold advance mec or the cold electrical rpm advanc can do that as well

to know you can disconnect and try it without those acessories .

you have 3 electrical wires on you IP the pink one need to stay in place but you disconnect the 2 other wirer .

Next test, install a clear tube on the top of your IP it is the return fuel line . You need to look for bubble in that hose . air can cause erratic rpm for sure .

Ed
 

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Sounds like there's the possibility that the temp switch that controls the operation of the cold advance and fast idle may not be opening when its supposed to (may be stuck in closed position). As tigman says disconnect the 2 wires, 1 to cold advance and the other to cold idle solenoid. If the prob goes away then the 2 wire temp switch is either stuck in closed position or shorted internally. The switch is supplied with power from the ignition switch and feeds power to those 2 items untill the engine temp hits 95 degrees, at which time it is supposed to open, cutting power from cold advance and idle solenoid.
 

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Discussion Starter · #7 ·
thanks for the replies, I will check it out tomorrow when I leave for work.
 
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