So we have a 98 pete with a detroit. This is a problem that recently started occuring only when the truck is warm. At idling it starts to like miss and make the you know purr purr noises. everything vibrates. Truck hasnt lost any power, no codes, no fuel milage change no starting problems no smoke.When i hit the pedal it will go away. It doesnt do this when its cold only when the engine is warmed up. Got the injectors tested they seem to be good. Havent really asked my mechanic yet but i thought to ask on the forum if anyones seen something similar.
12.7 Detroit missing
Discussion in 'Trucks [ Eighteen Wheelers ]' started by Peterbiltt, Mar 28, 2018.
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Most of the older Detroit do this I call it the Detroit stumble sometimes you revive it up and problems go away sometimes not Pittsburgh power thinks it's ecm related and they can fix it or gust get used to it best of luck
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I have a 98 pete 379 with a 12.7 Detroit in it, been having this problem for months now. the problem is intermittent some days its great some days it acts up, right as you start rolling in the the throttle at lower speed and low rpm "1500 to 1600" it will start to pop and stumble and blow whiter grey smoke out the stacks it smells of raw fuel. does not do it at high way speeds. so far i have replaced the suction lines, filter head, new filter, new fuel pump, new map sensor, check check valve on return line and 0.80 restricted 90 on return. currently pulled all injectors out and re oringing them and putting new cups in, injectors have about 50,000 on them along with the entire motor, any help would be appreciated.
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I realize Detroit did not have approved procedure for repair, account of resistance difference on that harness section being compromised, and the fact that the wires had silicone under the insulation which rendered it not conducive to soldering or traditional repair. But ya gotta do what ya gotta do to get him goin! They eventually worked that issue out and later models rarely had those issues that I’m aware.Last edited: Nov 28, 2021
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@MAMservices Thank you for the reply, if it were to be the injector terminal connections would that throw any sort of check engine light? Because currently when the issue happens i have no check engine light fuel pressure holds the same.
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It will not illuminate a light if happens quickly. A fault must occur for a certain length of time to set a code to turn on the MIL. 3 or 4 seconds if i remember correctly. If you check this and you can move the wire any at all in the terminal it is bad connection and subject to problems. Many times all that is required is to use a set of small crimping pliers and crimp the terminal tight again.
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OK i will try to inspect and try to see if any of those wires are loose on there connections, iI really appreciate your feed back. Thank you
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Also look at the Ambient air temp or Intake air temp, it’s been several years and I can’t remember for sure which term they use. I found several that the temp would be way off, read 0 degrees in 80 degrees weather for instance and cause a stumble with smoke. Or a smoke after cold start. Doesn’t set a code, you can see it in the data list though.
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So I've only been able to find the air intake temp sensor, sits right next to the MAP sensor in the intake manifold. I replaced that sensor thinking it may be bad but no change. I have yet to be able to find the ambient air temp sensor, I didn't know if they had them on these older trucks. -
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