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6G Celicas Forums > 6th Generation Celica > Engine/Transmission/Maintenance
So I'm having a problem with my 97' Celica GT. One day started it up and got a CEL along with a very low rough idle. I was getting a code that my IAC was bad so I popped the hood and discovered that the previous owner clipped one of the wires to the IAC plug (the one that makes it open) so I reattached it and my code went away. but now the car idles at 2000rpm when cold and 1300 when warm. Before any of this, it idled perfectly at 750. I've discovered if I plug the port in the throttle body that leads to the IAC, the idle drops down to almost perfect. For some reason, the IAC is sticking open and causing this issue. I've replaced it along with my plugs and wires, ECT sensor and my O2 sensors and I can't find any vacuum leaks. I'm stumped on why the ECU is holding it open. Any ideas on what could be causing this? I've looked around for hours and can't find someone who has the same issue as I do. Any help is appreciated.
I believe there is a procedure in the FSM on how to adjust the IACV spring - the one held with two small screws on the opposite side of the solenoid/plug. Look into that, see if adjusting the plate helps any.

Check the FSM diagnostics procedures (DI section) if there's anything on it.

I've been dealing with my IAC for a while now - it idles lowish (690-720 rpm, spec is 750 +/-50), and sometimes when drops lower than that it starts jumping b/w 600 and 900 until I bleep the throttle. Replacing IACV didn't help entirely, but I did notice that the ECU behaves differently with two different IACV - one cold idles at below 1200rpm, where's the other at 1800.

I've been meaning to adjust that plate (which I believe is cold idle adjustment) but haven't gotten to it - not annoying enough, I guess. Yet.

Yea, IACVs on these engines are fun.
I've tried adjusting it both ways with little effect.
Check/adjust the TPS to spec to see if that helps.
Would check specs on the MAP sensor as well. There's also an A/C idle up solenoid that induces a vacuum leak when the A/C is on, so if it's stuck open and the A/C were off it'd idle in the low 1,000's. If you haven't reset the ECU after doing everything that might help.
Update. I ordered a new throttle body after noticing the butterfly was worn way down. I doubt this will effect my Idle issue but it was something that needed addressing. I'll be replacing my coolant temp sensor after noticing it looked different than any other ones I've seen in other celiacs, it's about a half inch shorter. I'm thinking this might fix my problem of being stuck in open loop/high idle. if this has no effect I'll look into changing the map sensor. I know my ac idle valve isn't the problem here.
Anyone know if a complete throttle body swap from a 95 to a 98 celica is gonna work? Both are 5sfe. I noticed the vac ports are a liittle diffferent.

Im having very low / not holding idle on only cold starts.

Cleaned my old iscv, helped a bit for a little while.

Update: I changed out the throttle body (Came with a used TPS and IACV) along with a different coolant temp sensor and She runs fine now. Idles down to 850-750 RPM and Idles just below 1K with the AC on. I'm guessing it was a worn Butterfly and a bad coolant temp sensor. I'll post more if anything new comes up. Thanks guys.

Also, Martin; You'll want a throttle body from a 1996-1998. They did a facelift and minor changes in 96. I don't think anything before will work but I could be wrong.
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