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Rough when cold


Brandt

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In the morning my truck runs rough and is now starting to backfire. It may have always had a slight backfire, but I notice it more now running straight pipe. This happens between 1200 and 1650rpm when the temp gauge is below 155*. It will spitter and have reduced power. It also blows a lot of smoke (bluish white). From 156* to 180* there is an improvement, then at 180* all is good. If I keep the rpm's up above 1650 the truck runs OK, except in top gear then she falls on her face.

Is this typical for a cold engine or is something amiss??

'91 RD 690

EM7 300 HP

1070B 12 spd trans (.78 OD)

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take a temp gun and shoot the temps at the exhaust ports, it sounds like a bad injector this should help you find the bad one. my guess is that it blew off a tip off of one injector and its spraying nonatomized fuel causing the off color smoke and once hot enough it burns and cleans up

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Looks like #1 read 97*, and #3 read 106*. The rest were at 197-210*, while warming up.

The old Detroits could get more HP with bigger injectors, can the same be true for 4 stroke Macks?? I'd like to get more HP from this engine and will eventually be getting a larger turbo also.

What injector # should I look for??

Is this something an average wrech turner (me) can do, or do I have to get everything calibrated to each other?

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