It's trying to save fuel, within safe/programmed bounds of leanness, emissions, catalyst life, etc.

I don't know what is meant by ignition duration in this context.

 

The best rated Jag mechanic on the Space Coast FL told me on the first week owning my car that I had a bad downstream O2 bank one after his test and was the cause of the P0420 so I changed that a while back. He wanted almost $300 for that alone. Since then I've been trying to understand this. I bought the iCarsoft OBD that tests everything on data stream. These were taken at idle with engine coolant temp @ 86-90c (186-194F) at idle.

O2 output bank 1s2 = 0.520-0.570 (P0420 code) new sensor

O2 output bank 2s2 = 0.210-0.675

o2 sensor current bank 1&2 was 0 uA -23.9 uA jumping around and I have no idea what "uA" is or what that means.

Long term fuel trims warmed to @ 86c = 3.9% bank 1 and 2.3% bank 2
A little later @ 90c = 5.5% bank 1 and 3.9% bank 2

 

u = micro, though m for milli is perhaps more common here

Obviously you expect banks to be similar side-to-side for the sensor outputs, but your downstreams aren't (thus the code).

If it was the right sensor then you seem to be saying it's flatlined and I suppose that would be a bad cat or some other fault (nothing else springs to mind).

 

I was a good mechanic in the 70s with a long break since touring with bands that I finally retired from. I went to Ford class many times and still have my book full of stamps studying EEC3 and EEC4 when all this was in it's infancy.EEC (electronic engine control) I'm going to stay after this until I understand it but as long as my car runs so good and is getting 28/18 mpg I'm not worried. I was just beginning to understand O2 sensors when you woke me up with "the upstream are wide band A/F".. Anyway I want to understand what all the data stream numbers mean and it's hard to get them when they jump around so much.. I sat there watching them jump looking for the lowest and highest and as soon as I wrote it down it changed again so I'm not even sure about the numbers I posted above..

 

There are many many OBD articles on the net - just google etc - from beginner to advanced.

EEC IV I think would just have been OBD II but no widebands.

 

As I remember in the very beginning they were called EGO (exhaust gas oxygen) and the first Ford tester was called the "Star Tester" with only 3 digit codes. There was also a Ford Tech ph number to call called Oasis for help.

Today I just need to learn what all those dancing numbers mean on my data stream and their relation to each other. Without that I'm in the dark so I have been reading up on it but different places explain it in various ways and all seem kind of vague to the old guy here..

 

I don't know why you're worrying about the ones that seem OK. Have you got recordings where you compare and they're not? Or what?

 

The EEC systems were quite different from the later OBD2 stuff. I miss playing with them, but diagnostics took longer. Fault codes didn't point to the problem as well as with OBD2, even tho it still doesn't always point to the right component. Pretty sure Ford didn't use widebands back then even tho they existed. I don't know who was first to use them but I recall Cadillac as my first experience with them.

It's kinda odd that part of the reason for widebands is to eliminate the switching, yet here we have a car apparently using the downstreams because of switching. Technology I guess, always improving accuracy with every new breakthrough.

My basic understanding of the widebands: They have a reference input signal and they output an amperage signal to the computer based on how much above or below the reference signal they are generating. So if they're generating the same as the reference its output would be 0. In some cases the computer converts this amperage signal to voltage for you to see with your scanner. The Jag gives you the amperage as witnessed by your milliamp readings. I haven't played with them much so I'm sure google will have better information for you.

 

I still don't see why you're thinking so much about the ones that seem OK.

 

Once my engine was warmed up to closed loop the output of both upstream was bouncing off zero but only for a blink. The only numbers that were not jumping around were LT Fuel Trim that were not the same side to side and both increased over a 5min idle as you can see in above post but I don't know what they're supposed to be anyway..

 

If you want more detail from this site see https://www.jaguarforums.com/forum/s...-149649/page2/

They're basically Steve's (xjrguy) posts about trims (General Tech forum?)

 

Thanks.. I saved this..It's golden...http://jagrepair.com/images/AutoRepairPhotos/P20003.PDF

I also am going to try a can of that BG44K as was discussed there.