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Stuck in open loop at idle, got new o2 .. whats wrong?

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Silver2GST

20+ Year Contributor
84
2
Feb 17, 2003
Northern VA (Washington DC), Virginia
Started up my new 6 bolt motor and noticed right away the idle was just as bad as when i took out the 7 bolt. The motor is running rich and missing alot. No CEL's. Well i hooked up my datalogger and saw my o2 voltage was .020 and that i was in 'Open Loop' (meaning the ECU is looking at the MAF and not o2 sensor -like if you were at WOT- for fuel control)

Well i replaced the 02 sensor and still not better! o2 voltage is still .02 and the car is still in Open Loop!

I hooked up my multimeter to the o2 signal wire at the o2 and got .0-.1 volts. i'm going to get another o2 but don't think this is the problem :(

Why is my car stuck in open loop at idle ? :confused:
 
What about your Throttle Position sensor? What's it showing? TPS position has alot to do with Open/Closed loop. So does Engine Coolant Temperature for that matter. It would be interesting to know what those sensors are telling you.
Doug
 
According to my datalogger at idle the TPS shows 12% and at WOT 95%, the ECT shows upto 212*F and has never gone above that (even with my fans not working anymore, i have to switch them on by myself). i reset the ECU and restarted the car and it said i was in Closed Loop for about 3 mins then went to Open loop. As for the o2 sensor

the ground wire shows ground
one heater wire shows 13 volt and the other ~3 volts
the signal wire floats in the .07 - .1 area (but only shows.02 - .04 on the datalogger)

I'm going to the store now to exchange the o2 sensor, hope maybe just by chance i got a bad one but somehow i doubt that. its dead now for sure but i fear maybe something in the wiring may have killed the new o2 almost instantly? :( using my multimeter i couldn't find anything abnormal ... the fuel trim is 17.8 and is flooding the engine with gas!

let me know if you got any ideas or anything at all i should look into ... the only part about the 6 bolt swap i did out of the normal was use the 1G ECT because it wouldn't come out.
 
bumping a 13 year old thread because NOBODY EVER FINDS AN ANSWER TO ANYHING ON THIS FORUM OR THESE CARS.

2g eprom ecu
2g engine harness
6 bolt swap
93 mirage body
car has been on the road after thw swap running awesome for 4 years.


car one day idles like crap after running for 3 YEARS. pull out laptop, it goes to open loop, only cycles front 02 when constantly revving it . new front 02 sensor does the same as the one in the car. voltage tested the 02 pigtail red with black stripe wire and its getting 11.7v in key on positon at the pigtail.

swapped out:
green top CAS to a black top
new temp sensor (large one) 1g style just like the OP used in his swap
coil packs
plugs
checked mechanical timing and base timing with a light and diag pin grounded in link. redid timing after cas swap.
swapped 2 fromt aem widebands out, car runs very rich but shows very lean idle and cruise.

3 WEEKS into diagnosing and its STILL bad.

just wanted to bump this up since we cant make a new thread and im SICK and TIRED of using google to find DEAD THREADS.

so, i am hijacking THIS ONE.
 
Last edited:
and now I shall reveal the issue: the factory wires are aged and they are not carring batter voltage to the o2 sensor harness. just pinned out all 4 today.

my brand new battery is showing 12.5v at rest and key on/fuel pumo on. when oinning out the front 02 sensor wire it shows in the red/black wire only 11.7v max. my harness is losing 1v and its kicking the o2 sensor off unless i rev it.

sonlution: rerun NEW wire in the harness or possibly use rear o2 harness as a front 02 source OR simulate front 02 with an AEM/other wideband on pin 74 IIRC on a 2g ecu harness.

one thread down, 10,000 left to go.
 
UPDATE: this issue was caused by the ECU SHIFTING the fuel trims from 650 inj to 900cc inj, -30 global to -47 global. this will cause the front 02 to not cycle.

so...check your global and desdtime and make them right and the front 02 will cycle again. mine did. the voltage issue fixed itself after the tune issue was fixed as well.

just reolying now that my car is back to 100%
 
UPDATE: this issue was caused by the ECU SHIFTING the fuel trims from 650 inj to 900cc inj, -30 global to -47 global. this will cause the front 02 to not cycle.

so...check your global and desdtime and make them right and the front 02 will cycle again. mine did. the voltage issue fixed itself after the tune issue was fixed as well.

just reolying now that my car is back to 100%

What caused the ECU to change the global?
 
LOL
LOL
LOL
LOL

Oh.. you just reminded me how embarrassed I am to be an American. :(

It may have reverted to default settings somehow, or to a previous setting. I'm honestly not sure, it's never happened to me.
 
Oh.. you just reminded me how embarrassed I am to be an American. :(
.

C'mon now, I wasn't embarrassed when Barry shoved his SJW agenda down everybody's throats for the past 8 years, ALWAYS be proud to be an American, whomever occupies the oval office should not and does not matter..
 
1. Trump is the best shit since Reagan.

2. global just CHANGED. to 900cc inj. the guy with the RWD blue 1g drag car said its been seen by him before....a few times in 2 decades. like Joe Dirts dad said: it just DOES.
 
So what if your running an non LINK enabled car and your getting code for open loop due to insufficient temps, but temps are spot on and fully up to temp within whatever (10min I think) Oh and brand new temp sensor that is perfectly in spec as per ohm readings and its only running in open loop? I have researched a ton and it looks like I may have bad 02 but no codes throwing for a bad 02
 
2G Open loop mode (any one true)
  • Throttle position too high (varies by RPM)
  • Airflow too low (units are tricky, but it's very low)
  • Coolant temp < 51F
  • Coolant temp > 228F
  • The O2 sensor did not switch around 0.5v for over 128 seconds while running in closed loop mode. In that case, the ECU locks itself in open loop mode.
All of the following have to be true for a full 5 seconds. If any single one is not true even for a millisecond, the timer starts over and trends in STFT will *not* be moved into LTFT.
 
Thought I'd throw my experience in here.
Car ran like ass/lean for a few years on startup with evo 8 ecu.
I had to blip the pedal a few times to get it to go into closed loop(cycle the o2)
Adjusting the injector latency so the car would not start full lean fixed it for me. (as posted above the sensor did not switch over .5v, and stayed in open loop)
 
Can these be applied in a 1g? I am having same issue word for word. But 1gb. Had this issue start about 2 weeks ago.. then it turned i to idle surging.. which i for the life of me and these forums could not fi d the actual issue. Everything was in check.. every step. So i just did the fiav/isc blocked off and got it back to the first issue. Aem wb says its idling lean. Running nb sim. (Because 2 brand new denzo sensors will not cycle) it will cycle for awhile when warming up. Then kick to open loop. Hit the gas back to closed loop. Will just repeat process. Any input will be appreciated. Keep in mind this car was running fine before. Just had a lean idle.
 
1G Open loop mode (any one true)
  • Throttle position too high (varies by RPM)
  • Airflow too low (units are tricky, but it's very low)
  • Coolant temp < 87F
  • The O2 sensor did not switch around 0.5v for over 20 seconds while running in closed loop mode. In that case, the ECU locks itself in open loop mode.
 
Can these be applied in a 1g? I am having same issue word for word. But 1gb. Had this issue start about 2 weeks ago.. then it turned i to idle surging.. which i for the life of me and these forums could not fi d the actual issue. Everything was in check.. every step. So i just did the fiav/isc blocked off and got it back to the first issue. Aem wb says its idling lean. Running nb sim. (Because 2 brand new denzo sensors will not cycle) it will cycle for awhile when warming up. Then kick to open loop. Hit the gas back to closed loop. Will just repeat process. Any input will be appreciated. Keep in mind this car was running fine before. Just had a lean idle.
Do you have ecmlink? If so, post a log.
 
Do you have ecmlink? If so, post a log.

I do. Ill post a log from last night when i got everything back to normal. Have to get my laptop. I would suspect maybe o2 not switching perhaps. Both nb and wb brand new sensors. But running nb sim because nb wont cycle. Neither would theb other one i have. Maybe a setting for nb sim is incorrect but unsure where it should be
 
Your idle switch doesn't appear to be working or at least it's not switching between 1 and 0. Try unclicking "enable idle switch operation" and see if that makes a difference.
 
Your idle switch doesn't appear to be working or at least it's not switching between 1 and 0. Try unclicking "enable idle switch operation" and see if that makes a difference.



I don't use the factory idle switch because I was having issues and I enabled simulation with tps, and when I dis able it ( this was before I installed a block off plate for fiav and isc) the idle jumped up to 2k and held steady.

but your right. I didn't notice that till you just said something. I know it was working prior to this log, and un sure why it wouldn't be now. I had to leave immediately after this log was taken and didn't really get to digest much of it. I may go up to the shop and ck it over again.
 
NM, sorry I was looking at the wrong value on your log.


no problem, heres a log from just now, this is from cold start I have to keep it alive being its a block off now, but seems to idle alright just keeps kicking off into open loop. I captured the raw o2 values maybe you know more about it then I do, possible switch points setting for nb sim?
this needs retuned for cruise. not sure why the iac is jumping I assume its the ecu commanding it. weird though it never moved from zero when I had the isc installed. im sure I can drive it this way I don't care for the lean idle though. if I give it some gas it hops back to closed loop but wont cycle front o2. I dono if a cruise tune will help that. this all started out of the clear blue, but im not sure if it was always like this had other problems I was working out while this started also.
 

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