RPMs and Hard Shifting....

[BOLTO57]

I have a 1993 Pontiac Bonneville SE I'm happy to say the engine swap was successful...... But here's the problem now I'm having RPM issues when the car is cold sitting idle at first it's appears ok but when I rev it up it stumbles then the RPMs go up but when I let go of the throttle the RPMs drop all the way down to the point it either almost stalls or stalls completely. ( Never did that with the other engine) Now the weird part is that when the cars warms up the shoots up and now the car idles between 2000-3000 RPMs. ( never did that with old engine either. Also the trans has been shifting hard just going from park to reverse neutral and drive but I think it might be because the RPMs are so high But I'm not sure.

[SSEI99]

Are you using the same computer?? And the hard is shift is deff caused by shifting while at 3000 rpm at a stop. But thats not the trans at all. Deff engine side of it

[BOLTO57]

I think the same computer is still there I don't think it got changed when the mechanic did the engine swap. I checked my Haynes manual and it said something about a possible EGR or PCV valve problem but I'll look into seeing if the computer got changed as well.

[BOLTO57]

What kind of computer would I look under ECM or ECU??

[MattStrike]

What year is the new engine (N/A or L67)? I know that the L67 in '93 has a different injector wiring.

Also the new engine may have had a bad mass airflow sensor, throttle position sensor, or idle air control valve. If you still have the old one, you might try swapping those parts.

[BOLTO57]

It's the same year as the bonneville L67 1993 unfortunately I do not have the other motor because the mechanic did the swap at his shop and he got rid of it. Im thinking about just getting that mass airflow sensor, throttle position sensor, and the idle air control valve anyway and just swap them out. I'll keep you posted bit anymore possibilities let me know.

[Jrs3800]

Did the mechanic change the PCM( Powertrain Control Module ) or swap out the MEM-CAL( Memory Calibration ) Chip?

The MAF tables, Timing tables, Fueling tables and the like are all different between the L27 and L67