I need some help here. I've noticed as of late that my '96 SE 5 speed has developed an even periodic pulsation when accelerating at moderate throttle. The power rises and falls in an even pattern (think sine wave) with peaks coming about every second. I can feel and hear it as the RPMs rise. It will even do this when revving in neutral, revving quickly to 2k RPMs, pausing, and continuing to 3k, etc. It's not dramatic but definitely noticeable (my passengers noticed this as well). It seems to be more pronounced with the A/C on.

Looking online, it seems everyone has an opinion of what could be the problem: O2 sensors, spark plugs, coil packs, fuel injectors, fuel pressure sensor, fuel filter, fuel pump, etc. It seems to me that bad injectors/plugs would cause hesitation from a stop and a rough idle, none of which I have. I know that I do have a bad O2 sensor, but it is the benign downstream sensor that doesn't have any real effect on performance or fuel economy. This sensor has been bad since I bought the car last November and hasn't caused problems.

Idle is still Lexus-smooth, I'm still getting 26+ mpg. I'm pretty easy on this car and it's been trouble-free until now. Before I take my Max to a shop, I'd like to see if this is a common or well-known problem and if anyone could offer up some advice.

 

i had a problem kind of like this, i didnt think to much of it because i didnt have any new codes or anything, just an occasional o2 sensor ( the one up against the fire wall). When i replaced my exhaust i realized that my o2 sensor was all deformed and bulged over where you need to put the soket on so i assumed it was messed up. I replaced that and it hasnt done that pulsing thing since.