89 vert. This is more a curiosity than a problem but starting cold idle is high like normal. Then it slows, surges up and down. Upon final stage it idles at 900 rpm, no surging, runs perfect. I’ve adjusted TPS, replaced vac lines.
Anyone else experience this?

 

My 10AE will surge when first started if it sits for a few days and I forget to depress the throttle once and release it before starting the engine. It lasts a couple seconds and then idles normally. I haven't looked into the issue yet, but checking the TPS adjustment would be my first step. I would then clean the throttle body and go from there. The car runs excellent otherwise soni haven't worried about it too much.

 

Like mazdaverx713b suggested, try readjusting your TPS after your car is fully warmed up.

 

the 89-91 cars have a closed loop idle control, and if the actual idle is out of range it'll try to correct it, and fail, result is the surging.

if the TPS is correct, the thermowax is the next step. see the FSM, but there is an adjustment for the time its on (or the temp it clicks off) and how high the rpm goes.

mine does this too, its fine when its cold, and hot, but there is a spot in the middle where its surging.

it doesn't hurt anything, just annoying

 

Thanks all, I’ll check the thermowax, otherwise I’ll just leave it be since it’s not really a problem.

 

My 90 tII does this also....somewhere I read the thermwax coolant passage there being partially plugged as a possible culprit/contributor.