Another theory on the shudder/low idle. It could be that the RPM sampling rate of the ECM(engine control module) is a bit slow. If the RPM's drop rapidly through the target 900rpm idle and continues downward, The ECM may not notice it in time and then tries to make up for it with an excessive boost of throttle that causes a high BMEP stall, similar to detonation, with the ignition too advanced. The net effect is that power is being made on the upstroke. That's what it feels like to me, anyway.

 

My car was running rough also for almost a month. Well, I changed all four injectors and problem solved. I also tried swap all spark plugs and doesn't help.

It is always Fuel or Spark.

 

Oh I didn't have the AC on when this happened. The car is fine while driving in all RPM ranges; the shudder only happens at a stanstill when the RPMs are returning to idle. Mine does not dip down to 700 it happens closer to 1200 as it is returning to the 900 idle.

Thanks for your continued input all.

T

[QUOTE]Originally posted by S2K2GO!!!
[B]Another theory on the shudder/low idle. It could be that the RPM sampling rate of the ECM(engine control module) is a bit slow. If the RPM's drop rapidly through the target 900rpm idle and continues downward, The ECM may not notice it in time and then tries to make up for it with an excessive boost of throttle that causes a high BMEP stall, similar to detonation, with the ignition too advanced. The net effect is that power is being made on the upstroke.

 

i checked my plugs and the gaps were as follows: .39, .40, .40, .40, I have 4400 miles on my '02.

regapped to factory protocol .43, idle is stablized and my gas mileage has increased by a few miles per gallon.

mine does the drop with airconditioning is on and at a stop light after driving for awhile in mid day, it isn't has frequent since the insulator gasket was installed.