Does a swap from auto to manual transmission affect emissions on a 95 GMC Sierra
Asked by GuruYWHW3 Feb 26, 2018 at 07:56 PM about the 1995 GMC Sierra 1500 K1500 SL 4WD Extended Cab SB
Question type: Maintenance & Repair
I swapped the automatic to manual transmission on a 1995 GMC Sierra and I
have trouble passing emissions at idle in the state of Arizona. Just wondering
if anyone knows if it has anything to do with the swap
7 Answers
They should give you a printout with the reason why it failed the test. Nothing inherently about a transmission swap would cause it to fail.
You might need an ECU reflash to manual transmission specs.
HC loaded reading 162 and standard is 220, CO loaded reading 0.41 and standard is 1.20 so it passed under load easily but at idle HC reading 601 and CO 5.80. The readings went really high and I don’t know if changing spark plugs will help that much. Tried finding information on Ecuador reflash but didn’t find anything on those years. I left the transmissions shifter in park to trick the computer into thinking it’s in park.
High HC & CO, you are likely running too rich. I doubt this is tranny related, you need a tune up and should check timing, pcv, egr, and for vacuum leaks.
Look on youtube for "High HC at idle", you'll see many times cause is cracked and/or split hoses to intake causing vacuum leaks.
Yeah maybe it’s best to leave it automatic since I still have everything to put back to original and avoid all the troubles. I only did the swap to get my son involved in a project because he really likes to see this kind of work. If I have to mess with the ecm it’s probably not worth it. It’s a bummer because I prefer manual over auto. Thanks for the help everyone.
