Ahhhhh, I thought you were asking for an explanation, didn't think you were seeing a problem. Well, several things could cause that like a lazy o2 sensor, a biased Coolant temp, or even intake temp sensor, or a slightly leakingfuel pressure regulator diaphram etc......

 

From idle to 2500 rpm it hovers around 13.9 from no throttle to med throttle. I think it's unnecessarily rich but at the magic 2500 it switches and the powers and throttle response does not suffer at all.

 

yea that explains why my gas mileage is suffering around town cruising in overdrive from now on ill just leave it in 3... 13.9 is too rich just for cruising hondas are the same way at low rpm they run rich idk why

 

Same here except people think Im about to race or something if I rev that high. I don't have the quietest exhaust. I don't like revving below 2000 anyway.

YET..... still looking for a way to run leaner below 2500 rpm and not affect it above

 

What about some bigger tires? It would change your cruising rpm right? Don't know what size you'd be looking for.

 

Finely figured it out. I tested my MAP sensor and its withing specs then,
After driving around for 2 hours, entering several o2 inputs to the PCM and recording the results on my data logger I realized that the PCM ignores all O2 sensors input after 2500rpm and the computer reverts to other sensors.

So I Just programmed my sensor to run the engine at 15:1 (I want to tune it to 15.4 like the graph but I have to find a long flat stretch. To many hills and red lights here and it screws up my data) and when it passes 2500rpm it still goes closer to 14.7 ish anyway. At WOT it goes to about 13

When its programmed properly, Ill do a full tank gas mileage check to see the difference.

 

VTEC kicks in, duh.

What year is your XJ again? I remember in my 1999 FSM the transitions between various open and closed loops are actually based of MAP, TPS, and temperatures. I've not verified that of course but I don't remember anything even remotely like an RPM threshhold.

 

its an 98 auto PCM running a 6 speed manual. I built a transmission simulator to keep the TCM happy and not give me a code
https://www.cherokeeforum.com/f67/au...0-swap-168961/

I wish I had a Data logger with more data inputs. They are a little to expensive for just curiosity sake or tuning only one engine.
It does seem to be RPM related. I tried with minimal load and going uphill and the results are the same pass 2500 rpm.
I haven't tried with a stock O2 sensor but the wideband one has a response of 12 times/second so it should be adequate. besides, its the same result with the O2 line physically disconnected. Im just glad it doesn't go completely off the left field with air/fuel ratio at 2500rpm. I have no idea how I would compensate for it.

I would just like to know if all PCM have the same 2500 threshold.

 

6spd, did you swap in a trans from a TJ or something?

 

how did you program the jeep to run i the 15's afr under 2500 rpm? i have to figure this out since my **** automatic it rarely goes above 2300rpm and im only getting 14-15mpg on the FREEWAY

filled up went to sea world to day and back home.. all of it was freeway with maybe 10 miles total city got home its below half tank and only 152 miles

 

Yeah. 2005. Fits on 4.0L

 

It's my Innovate Motorsport wideband O2 sensor. It has a programable output you can feed in to the PCM instead of factory O2 narrow band sensor

 

i use the same one to tune cars to this day i use the innovative mtxl... have you noticed a difference yet in gas mileage?

 

I've been toying with the idea of putting a resistor/rheostat in the TCU input wire to change the shift points up higher.

 

I just finished fine tuning it yesterday to run a 15.4 it's hard to fine tune in trafic and city. I'll let you know what kind of improvements I get.