 OBD II on a 94 st?, its got 2 oxygen senesors? |
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 Mar 12, 2004 - 1:55 PM
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Enthusiast  Joined Oct 9, '03 From Indianapolis, In Currently Offline Reputation: 0 (0%)  |
so i have a 94 celica st and it has 2 o2 sensors? wtf? it cant be OBD II b/c its speed density and not hot wire Mass Air Flow Meter...plus OBD II wasnt around until 96? can anyone help me? please...i want to put my header on.
 torrey
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Mar 12, 2004 - 2:25 PM
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Enthusiast Joined Sep 4, '03 From Gardena, South Bay Currently Offline Reputation: 0 (0%) |
the o2 sensers on the exhaust manifold are the air fuel ratios mixtures the top senser measrues the how rich or lean the mixtures then sends the info to the ECU then adjusts the ratio to have perfect combustion the bottem one makes sure the mixture perfect. if you want to see if your obd 1 or 2 id look at the bottem of the steering coloem see where the obd plugs in, it should say 1 or 2..
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Mar 12, 2004 - 3:51 PM
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 Moderator Joined Oct 1, '02 From fall river, ma Currently Offline Reputation: 13 (100%) |
i believe only 96+ are obd2
-------------------- Former Team 5SFTE pro member ;)
 13.6@108MPH, 5SFTE Powered |
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Mar 12, 2004 - 4:42 PM
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Enthusiast Joined Oct 9, '03 From Indianapolis, In Currently Offline Reputation: 0 (0%) |
so if im eliminating both cats....what to do with the sensors...b/c if there is a header then the readings between the top sensor and the bottom sensor are going to be the same. ....?
torrey |
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Mar 12, 2004 - 8:09 PM
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 Enthusiast Joined Aug 29, '02 From Dallas, Tx Currently Offline Reputation: 0 (0%) |
Where the hell did you hear this? Totally, absolutely incorrect. The '94 is not an OBDII car. It will run just fine with no O2 sensors plugged in. Try it sometime. It doesn't even trigger a CEL under any conditions I've tried. Even OBDII cars don't run in closed loop under WOT. They only use the O2 sensor at idle and cruise. |
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Mar 12, 2004 - 8:39 PM
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Enthusiast Joined Oct 9, '03 From Indianapolis, In Currently Offline Reputation: 0 (0%) |
so i dont need the sensors plugged in...and no
check engine light? This post has been edited by RoverGuy: Mar 12, 2004 - 9:56 PM |
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Mar 12, 2004 - 11:50 PM
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 Enthusiast Joined Dec 27, '03 From Nor Cal Currently Offline Reputation: 0 (0%) |
I guess you got that header from celica performance huh? Or from somewhere else? You don't necessarily need to have the O2's pluged in to run the engine, however, that doesn't mean it's not worth getting them both in, so don't interpret what Spedtoe says as "So I don't need the sensors pluged in..." You need them in. Running w/o the O2 can trigger little problems and cause the car to run funky... The first O2 on the header should fit fine, however, the lower O2 will need to have an O2 bung drilled and welded in... Also, the header will be roughly a foot short of the cat... so unless you've some fair welding skills... take it to an exhaust shop. -------------------- "It's ok to be naked girl... I'm an artist!"
1995 AT200 Celica ST: stocked out daily driver... 1984 AE86 Corolla GT-SR5: silvertop 20V 4AGE project car jacked up with goodies... 1991 SW2x MR2 n/a: bare bones hardtop model soon to be... |
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Mar 13, 2004 - 1:58 PM
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Enthusiast Joined Aug 29, '02 From Dallas, Tx Currently Offline Reputation: 0 (0%) |
I would have thought that was true as well, but I'm not convinced now. Mike (Qatar11) and I have been discussing it some and I really don't see anything the engine is using them for that I would be able to tune around. The fact that it doesn't even trigger a CEL seems a bit odd to me. Thats the whole point of the CEL, to tell the user when one of the sensors is messed up. If it needed them, why wouldn't it say so? I don't suggest anyone else do this, but I'm going to do some more testing on this subject and see what I come up with. I want to have a definitive answer before I go FI. |
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Mar 13, 2004 - 5:37 PM
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 Enthusiast Joined Mar 2, '04 From Louisiana, USA Currently Offline Reputation: 2 (100%) |
I've run my '95 ST with only the primary O2 sensor for about 3 years now. I used to get a CEL under specific curcumstances with a header and the stock exhaust. Once I got rid of the stock system and secondary catalytic converter, I no longer get a CEL. Mileage is 27-29mpg depending on circumstances, and I have larger injectors installed. You should be ok with running the single O2 sensor, if you can't get a boss welded in for the second one.
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Mar 13, 2004 - 7:19 PM
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Enthusiast Joined Aug 29, '02 From Dallas, Tx Currently Offline Reputation: 0 (0%) |
Interesting. So which one do you have? The one closest to the head? Or the one farther downstream?
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Mar 13, 2004 - 10:03 PM
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Enthusiast Joined Mar 2, '04 From Louisiana, USA Currently Offline Reputation: 2 (100%) |
SpeedToe;
I've got the sensor closest to the head installed. The other, I just unclipped from the connector, and have yet to reinstall it. I ran the stock 1-wire for 2 years, but I have since installed a GReddy A/F gauge, (4-wire HEGO) and am using the signal from this sensor to the ECU. (Not that that's a huge difference, other than the heated sensor) |
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Mar 14, 2004 - 12:24 PM
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Enthusiast Joined Aug 29, '02 From Dallas, Tx Currently Offline Reputation: 0 (0%) |
Sounds good. Did you ever try it with neither of them hooked up?
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Mar 14, 2004 - 2:54 PM
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Enthusiast Joined Mar 2, '04 From Louisiana, USA Currently Offline Reputation: 2 (100%) |
No, I haven't tried running without the sensor... That's something to ponder though, as I'm going to have to remove the sensor anyway to replace a broken stud. If I do run the car minus the sensor, I'll post my results. *edit* Did a quick unplug of the O2 signal wire to the ECU while I was out cleaning my air filter. Got a CEL once the water temp warmed up enough to go into closed loop. I didn't try to drive the car, but in the past when I've gotten the O2 sensor out-of-range code it felt like the car was down on power, which makes sense. Another test might be to run only the 2nd O2 int he car, and check for codes. This post has been edited by S_C_M: Mar 14, 2004 - 10:17 PM |
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