Civic EG

hey, so my original setup was a d16y7 with a b7 intake manifold and y7 throttle body, iac on mani blocked off, no evap, idled perfect and pulled thru the powerband

swapped to a z6 mani, same block off setup, ob1 h22 throttle body, idled perfect pulled thru the power band, but at high idle and at 1500 rpm will bounce slowly like a step 2 launch control lol, and under engine braking will spudder and jerk between 2000 and 1500

new setup, b18b1, p2e virgin ecu, stock 97 cx harness, crank sensor bypass mod, obd2 d series injectors, repinned 3 wire mani mounted iac for 2 wire, b series throttle body that came with the motor, car the swap came out of ran perfect, no issues

same studder issue, have tryed new ecu and different injectors, any ideas peeps, drives awesome just an enoying problem

The bouncing is caused when the idle RPMs go high enough to exit idle mode. The ecu closes the IACV, cuts ignition timing, idle RPMs fall abruptly, which in turn brings it back into idle mode. The ECU quickly advances the ignition timing, opens the IACV, and the process begins again.

You're exactly right that it's like 2 step launch control.

The only thing that can raise idle RPM this high is a vacuum leak. Since you swapped the motor, I would focus on the hoses that remained in the engine bay after the swap. But don't neglect the usual suspects (gaskets, etc). The original problem may have been caused by the H22 tb on a D series leaving a passage open that's normally blocked by the intake mani or something similar.

BTW you lose power in almost all throttle body swaps except on high boost forced induction motors.

Also, I know you can't set ignition timing when it wont idle steady, but just make sure you don't have the distributor over advanced.

nice info got me thinking, im gonna run out to the shop and check a couple things, i left the purge valve on the mani not plugged into anything, could be leaking when the throttle opens and vacuum is lost, sounds like my motors have the same problems two different causes, perfect idle, bounces at 1500 when throttle is applied, but straightens out at 1600, shutters between 2000 and 1500 under deceleration and engine breaking

the only things the two motors physically have in common are the injectors, ecu, wiring harness, i ruled two of those out, the dizzy is alittle weird cause its the d series internals, b series shaft, all in the b series case, i have p1381 code, cylinder position sensor, but im blaming that on the dizzy being upside and backwards lol

ps i figured id lose power with the throttle body, but the d series was pretty much on its last breaths was just lookin for alittle more intake noise lol

removed the purge valve and checked for vacuum leaks, no deference..

Okay but there's a couple more vacuum hoses still. And the brake booster check valve. And the TB and intake mani gasket. The IACV gasket. The MAP sensor.

Some people spray carb cleaner around suspected areas. If there's a vacuum leak, it will pull the carb cleaner in and rev up a bit.

fixed it kinda.. pluged in a obd1 p75 with a conversion harness, tahda no more studder so i guess ill just live with it for now till i have my p06 chipped and tuned for my crvtec !