engine stumbles when changing between D-N-R - throttle body cable issue? (1 Viewer)

[semlin]

can a badly adjusted accelerator cable cause the truck to stumble and nearly stall out when changing between drive/ neutral and reverse?

the truck is back together and running after an extended h/g repair. last problem is the above symptom. cables are the prime suspect followed by the timing, which I have not yet set, but the engine runs fine except for this one symptom and the occasional pulse or stumble. despite wrapping the cables in masking tape they came unadjusted. i can only find directions for the throttle cable, not the other two in the FSM and my throttle cable lacks the little sleeve thing I am supposed to work off. I have tried to give them each 1mm of slack but am still getting this issue.

 

[cruiserdan]

How many start-up cycles has it beem through since the repair?

 

[semlin]

it idled maybe 20 minutes in a series of stops and starts, then has been started and gone around the block twice, idling for maybe 2 minutes beforehand. you think i just need to run it a few times?

 

[cruiserdan]

The engine ECU needs to go through about 10-20 start-up cycles to re-establish parameters. Start it and let it run for about a minute and then shut it off and re-start. Repeat that process until the hot curb idle stabilizes.

 

[semlin]

thanks dan, will do.

 

[semlin]

ok 23 more start up cycles of at least 2 mins each and a couple of times around the block and i still get it. i think i have a missfire and need to figure out where. dan could this still be ecu?

1. at start up the idle goes to 900-1000 then drops quickly to 800 rpm and stays steady there, but also after about 15 seconds has a distinct rhythmic stumble/miss that drops the revs down momentarily as low as 600. the engine vibrates from the miss.

2. when you shift into drive reverse about 50% of the time it drops down to 600 rpm momentarily and the tranny makes a lugging sound like you were trying to pull awey in third in a manual. i am thinking it does this if you happened to shift when the miss hits

3. once in drive or reverse it is rock steady at 700 rpm with no discernible miss

4. if you shift out of reverse/drive into park or neutral the revs jump to 1100 rpm and you get the noticable miss

i have checked very carefully for a vacuum leak. i'll try and isolate the cylinder tomorrow. at least the overflow is blowing no bubbles.