cmccloud

I have a 99 boxster 2.5L tiptronic....just replaced all O2 sensors to clear CEL so I can trade for a newer model. After replacing sensors car runs very rough (poping ,misfire,no power) much like when I replaced battery. I searched Internet at that time and found a step by step seqence like turn key on, depress accelerator for so many seconds turn key off...that reset ECU back to factory baselines...can't find this article anymore...anyone have any info on this or correct procedure for this and if this sounds like the right process for introducing these new O2 sensors into the mix...??? Thanks for any help..

Macster

ECU.

How did you get the code(s) that indicated new O2 sensors required? (And what were these codes?) Typically the devices that connect to the OBD2 port offer not only the ability to read these error codes (and associated freeze frame data) but to clear/erase the codes as well.

In clearing the codes other things are reset, including the long term fuel trims.

Thus upon restart and for several driving cycles afterwards the ECU will 'relearn' the optimum settings/trims/etc. for the engine and as long as these learned values stay within acceptable ranges of adjustment no error codes should arise.

Absent a device to clear any error codes, you can disconnect the battery.

Read your owners manual to understand how to safely do this. Get any radio security code before you disconnect the battery and any other info you need 'from' the car before you proceed.

Leaving the battery disconnected for a few minutes will result in the ECU losing some learned information but maybe not all.

Can't believe though the engine would react so strongly to the new sensors. Upon cold start and for a few moments (minute or more) after the engine will be running with the ECU in open loop which means the fuel/ignition maps come into play. The symptoms do not sound like the ECU needs to be reset but that something is wrong either from the O2 sensor installation or something that was wrong before and for which O2 sensor replacement was not the correct step.

Sincerely,

Macster.

sahtt57

Hopefully the battery was disconnected before the o2 sensor installation regardless. Based on what you've said, I'd suggest double checking the o2 sensor installation. The odds of both o2 sensors going out simultaneously without a relating cause is low. I'd verify your exhaust system is working correctly, your cat isn't clogged, etc.

There is strong evidence to suggest if your car is idling this poorly, there is an underlying issue perhaps it's running far too rich. Try looking here porsche boxster misfire and see if any of it rings a bell.