wideband switches as narrow

[geewiz]

My wideband LSU4-2 got the jitters and began to frequently switch [violently] between 12 & 17 to 1 AFR. The car ran poorly & blackened two sets of plugs in about 20 minutes as I attempted to find the root of the problem. Then, it locked on to 12 to 1[as displayed by the TunerStudioMS dash] and stayed. At this point the car ran well. It seemed to be running as if the O2 sensor was disabled, and it was using the VE tables to operate. After 20 miles or so the plugs were still light tan so it can't be running at the 12 to 1 shown on the TS dash display. I am running a V3 board -MS2, with B&G code 2.920- which has worked well for several years. I assumed that I had cooked the LSU-4.2 again & installed a new one. This changed nothing. So, I benched the board and gave it a good alcohol scrub and inspection. Then, with the stim connected, it still stayed locked to 12 to 1[on the display AFR ]. When the O2 signal to the processor U2 - pin 28 reaches about 1 volt [+ or - 1/2 volt] , It will then rapidly moves to 17 to 1. Within 1/100 of zero volts or so it the display will go rapidly to 14.7 to 1. It's appearance is as if narrow band parameters are being used somewhere, instead of the innovate PLX 0-5 volt = 10:20 t0 1 .I have checked all programing and do not find narrow band enabled anywhere. I first tried a second U2 that has the same programing and had the same issue. My stim is producing a nice smooth transition from 4.88 volts [12 to 1] to "0" volts to the processor input. I have completely removed and reinstalled all programing [ TS 2.6.19] , & I even reburned the B&G code [V2.920] to one of the daughter cards. Thus far there has been no change, & I am out of ideas. The problem may not be with my TunerStudioMS , but I am posting here because it is a possibility, since I have no knowledge of how TS receives its information. MY knowledge of the system & ability to check stops at the input of the U2.

[geewiz]

I made an error in the post & can find no means to edit the post. I am therefore adding to the post via a reply. The daughter card [processor] I incorrectly referred to as U2. It is, in fact, U1. Also, I omitted to state that the TurnerStudioMS version is V 4.0.19. Since the post, I have used a computer back up to enable using the program as it was about one month prior. This did not help. The serial cable used with the stim is not the same one used in the car, so that rules out the cable. I also changed U6- no help- & have checked the clock & serial solder joints with a 20 X lighted loop and find no questionable solder points. I am going to reinstall the LC-1 program next. It could be the root of the problem.

[geewiz]

Another error! TS version is 2.6.19- I definitely need some sleep! The EFI passed all loop back tests as outlined in the manual. I also tried a beta version of TunerStudio to no avail. If an Exhaust gas oxygen gauge is used with the stim, It shows as a 0 to 1 volt gauge. I don't believe this is correct for the wide band LC-1 [0-5 volt]. It also shows voltages of 12.1 to 16.9 which again, seems odd to me since my stim is producing only about 10.5 volts. I am therefore forced to put a "0" entry in the "O2 operates below a MAP of:" box & run open loop. I can't fit it without HELP !!!!!!!!!!!!!

[Matt Cramer]

Please make sure you entered the right data under Tools -> Calibrate AFR Table.

[geewiz]

Matt hit the nail on the head. I did not enter the info necessary in tools, calibrate. As soon as the entry was burned, the gauge worked as it should with the stim . I don't know how the info was deleted when the car first started to act up- but I'll cross that bridge if and when it happens again. Thank you so much Matt, for taking the time to read & answer my posts. I was ready to give up on the Megasquirt entirely. My ignorance cost me a lot of time,{this AM I re soldered all points - no help}. Matt has helped me many times in the past & I sincerely appreciate his efforts. Thanks again.