Texas5.0

I ran the KOEO and KOER tests and got a 41 and 91R code both times. The book says that means sensor voltage low / system lean.

I thought bad O2 sensors... they were the original ones.

Today I went and bought two new sensors. Put them in, cleared the codes in the computer, ran another KOEO test and got the all clear. Ran the KOER test and got 91R again and a 13. 13 is RPM at idle out of range / low.

The I ran a cylinder balance self test and got the all clear.

Whats the deal with the getting the 91R again and the 13?

Also, a couple of weeks ago I was looking for a idle surge problem and reset my base idle to 950 - 1000. How in the hell can this cause a 13 code -out of range low? I was told by lots of people here thatbase idleshould be set at 850 or so. I am very confused.

Joel5.0

Nope....EEC-IV programmed "target" idle is 672 rpms.....if you adjust the base idle too high with the IAC off (=closed)....the system will not be able to "hit" the target idle setting during the self-test routine and output the code. Suggest to reset the base idle (IAC disconnected) to ~650-700 rpms.

For code 91, make sure you heat up those new O2 sensors good (hold rpms @2000 rpms for ~2 minutes) and then rerun the KOER self-test. If code 91 continues to show, check for exhaust leaks on the driver's side header...if OK, swap the O2s from sides.....if code 41 shows afterwards, warranty that O2 sensor...it's defective.

Texas5.0

So... 91 is drivers side and 41 is passenger?

Joel5.0

Yep...41 is bank 1 and 91 is bank 2

Texas5.0

Thanks for your help Joel.

I am not excited about getting underneath the car again. I don't have a lift. I squeeze under the damn thing in the driveway... no jack or stands just blocks for the tires.

Just out of curiosity, why did the codes not show up in the KOEO test

TwotoneVert

Tex, can you tell me how to run that test?

Texas5.0

I sure can... buy one of these. Best 40 bucks I have spent on my car so far.

http://www.amazon.com/Equus-3145-For...788707-8240433

There is a way to run those tests without the reader but I don't know how. Do a search on cylinder balance self test and I am sure you can find it. I would just buy the reader.

Joel5.0

Idle "range" test is a real time test the systems does with the engine running at different duty cycles of the IAC. It is not "memorized" as a code either.

O2 codes are also based on real time tests the system does in KOER by increasing/lowering A/F and checking the O2s lean/rich states switching pattern. O2 codes will only show up as KOEO CM (Continuous Memory) codes, when a fault counter condition is reached in a drive cycle. Simply said (as an example), 40 failures in a row, over x time of the driver's side O2 not switching to rich status = code 91 showing up as a CM code in a KOEO self-test afterwards.

Joel5.0

Not Tex here, but you may want to check the DIY KOEO/KOER/Cylinder Balance Self-Test procedure.

TwotoneVert

Thanks tex, thanks joel.