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2000 GT-S 6 Speed TRD LSD Fidanza Flywheel MWR Oil Pump Gear BC Coilovers
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Discussion Starter · #1 ·
Today I finally started up my Celica after putting a new engine in it and I noticed this. I let it run for a minute and it warmed up fine and everything but once I rev'ed it a little it started doing this


It seems like the engine is going to die then the idle bumps up a bit then falls again and it just keep doing it over and over. Does anyone have any ideas what could be causing this? I just installed a new fuel pump but it was doing the same thing with the old pump. When I first got the car it had a code for a oxygen sensor so I think it could be something with that. I have a Autel tablet I've been using on it but I'm still a little new at it.
 

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... if its a upstream o2 sensor then replace it thats ur air fuel ratio sensor. Also could be maf and or IAC valve. Could also be a vacuum leak.... more information is key.

2000 GTS Turbo
 

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2000 GT-S 6 Speed TRD LSD Fidanza Flywheel MWR Oil Pump Gear BC Coilovers
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Discussion Starter · #3 ·
I tried a different MAF and it worked better for a second but once the engine warmed up more it started doing it again
 

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Electromagnetic Wave :-h
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Not uncommon. Shutting off & restarting should clear it. Sometimes the ECU gets in a funky loop where it ramps the IACV up & down. Get a fairly stable idle & let it learn parameters.
 

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2000 GT-S 6 Speed TRD LSD Fidanza Flywheel MWR Oil Pump Gear BC Coilovers
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Discussion Starter · #8 ·
I checked the 2 black wires on the upstream o2 sensor and I could not get any ohms so I'm gonna ordered a new one.
 

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2000 GT-S 6 Speed TRD LSD Fidanza Flywheel MWR Oil Pump Gear BC Coilovers
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Discussion Starter · #9 ·
I replaced the upstream sensor today. I started the car and let it get to CL and it started doing it again then I remembered I had the battery connected the whole time so I disconnected it for a second and when the car got into CL again it seemed to idle alot smoother. I rev'ed it a few times and it went nicely back to ~850 rpms and stabilized. So I think I fixed it. I'm gonna test it out more tomorrow and maybe do a smoke test just to be sure
 

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2000 GT-S 6 Speed TRD LSD Fidanza Flywheel MWR Oil Pump Gear BC Coilovers
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Discussion Starter · #10 · (Edited)
Ok so I put everything back and it seems like its still doing it just its a little less extreme and eventually it settles down but eventually it starts doing it again too. While I was testing it out I decided to bleed the coolant as well and I discovered the fans turn on as they normally should, once the engine warms up some, but then after they've been running for a bit they shut off for 1-2 sec. then shut right back on and never turn off. Also the temperature needle moves around a little past the middle sometimes just while its idling.
anyways sorry to trauma dump on this thread here's another video of it doing it since I replaced the sensor and a screenshot of my fuel trims right after recording that

Font Gas Display device Electronic device Signage

My dad thinks its all being caused by the radiator not working properly, so I might replace that next. I took the entire airbox apart to make sure there was nothing loose then played around with the smoke machine and couldn't see any obvious leaks
 

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Is your a/c switched on and operating with low or no refrigerant in the system?
This will give you a 100-200 rpm drop as the compressor tries to cut in. It will also kick on the evap fans
 

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Discussion Starter · #12 ·
Is your a/c switched on and operating with low or no refrigerant in the system?
This will give you a 100-200 rpm drop as the compressor tries to cut in. It will also kick on the evap fans
Thank you for the insight. That actually would make a lot of sense because when I finished installing the engine and first started it, one of the AC hoses was too close to the belt and got a slit in it from the belt turning. I've already bought a new one and replaced it but I haven't bothered to refill it with refrigerant yet because I hardly use AC. I'll refill it tomorrow and see what that does
 

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Electromagnetic Wave :-h
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Good catch, Sheik.

grip, the AC also runs in the 2 defrost modes. Fuel trims look good. It takes close to a tank of gas and driving for the fuel trims to be learned.
 

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Thank you for the insight. That actually would make a lot of sense because when I finished installing the engine and first started it, one of the AC hoses was too close to the belt and got a slit in it from the belt turning. I've already bought a new one and replaced it but I haven't bothered to refill it with refrigerant yet because I hardly use AC. I'll refill it tomorrow and see what that does
You know you don’t just refill it. You need to back it down for 1/2 hour at least.

it’s not like adding coolant.

here in OZ you need a special licence to touch AC
 

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Discussion Starter · #15 ·
You know you don’t just refill it. You need to back it down for 1/2 hour at least.

it’s not like adding coolant.

here in OZ you need a special licence to touch AC
I know that now what I meant to say was I'll tell my dad to do it haha. I guess that was all it needed because I drove it around alot today and the idle was nice and the temperature gauge didn't move once it got to the middle
 

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And I tried to write VAC it down. Need to pull a good deep vacuum on the a/c system to remove any moisture, identify any leaks and draw the refrigerants in.
 
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