runs rough no codes set. OBD2 diagnosis without codes. part 1

[@jasonmartin9393]

Hi I need help I have a 98 Chevy Silverado 2wd I swapped the automatic transmission to a 5speed transmission Now my speedometer does not work I did have to go get a plug to splice in to my plug and I didn’t get a new speed sensor yet and it starts and runs but acts like it’s fluiding some times and when u push the clutch in to slow down it will just quit or try to or between shifting gears it try’s to quit and then it picks up and goes What u think is wrong with it I need help some one told me I might have to have a pcm flash

[@garrettgrantham7411]

The stalling and flooding is most likely the ecm software. The issue is the ecm is still operating as if it were an automatic. So it is adding fuel to maintain engine speed before it sends a shift signal to the tcm. Meanwhile you are just accelerating and the fuel mixture goes stupid rich and then back to normal then you push in the clutch to shift and engine speed drops (ecm reduces fueling for decel) you grab a gear and let off the clutch pedal and attempt to accelerate (ecm is still cutting fuel) fuel mixture is super lean, no combustion occurs, engine stalls. I had this same issue before getting my ecm reflashed.

[@garrettgrantham7411]

As for the speedometer, check that you have the correct speed sensor. (Gear driven cable, or magnetic pick up style with a tone ring.) My speedometer issues were caused by incorrect tone ring tooth count in the ecm software.

[@jasonmartin9393]

@@garrettgrantham7411 thanks for the reply I might have to find some one that can do that and my speed sensor is magnetic type speed sensor

[@jasonmartin9393]

@@garrettgrantham7411 I don't have no engine lights on nether

[@23RO]

I hate you because your so perfect.