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Discussion Starter · #1 ·
I have a 2001 toyota celica gts. Just had timing chain replaced 4 months ago along with valve cover gaskets, and many other gaskets. When i first start it after it sat for a little bit it idles really high then will idle so low it will stall if i dont give it gas. Took it to advance and it read that all four cylinders were misfiring and i believe it had a o2 sensor reading acouple months ago. The guy there said to replace maf so i did. Got better gas mileage but problem didnt stop. but last time i tried to get it read they couldnt get it to work. It runs fine after its warmed up. Replaced exhaust manifold when i got it. Does have a crack on cold air intake. Any suggestions. I have new cold air intake and plugs on the way
 

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Do you know exactly what the code reader said was causing the misfire? Mine specifically tells me which part is bad. Aside from spark plugs, it could also be the coil packs. Unless they weren't charging anything, I'd suggest buying a cheap OBD2 coder reader and reading the error codes yourself so no one can swindle you. Our cars are pretty **** good at self-diagnosing. There's also a chance it could be a bad throttle body control valve....but a reader will tell you if that is bad too.
 

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Well turns out the previous owner put 1zz plugs in my 2zz engine so the misfire has been solved but the idle still starts high then drops really low and stalls if i dont give it gas. Mechanic says the engine could just be worn out. Going to get a different mechanic to look at it. Any suggestions. Not sure what codes it reads now if any. Mechanic still has it till tomorrow. The previous owner did put an cold air intake on it. I heard somehwere that the computer would have to be reset when you install a cold air intake?
 

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A good OBD2 reader tells you the code and a quick explanation of what the code means, so no need to look the code up to know what's going on. I'd say look for a bad idle air control valve code.

A CAI can cause problems if it isn't engineered right. If it's from Injen or AEM, it will work out of the box. If it's from a shady company, maybe not.
 

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I think its an injen. Mechanic says the engine is just worn that it reads no codes that would cause it to idle like that. But it was reading o2 sensor. Been busy havent been able to check engine light since i got it back. But if the the previous owner put wrong plugs on im sure if he did the cold air intake it could of been done wrong also. Also can you adjust the idle or is it controlled by the computer? Gonna have codes read this weekend. Really appreciate all the help. Driving me nuts trying to figure it out. Just recently had a new timing chain replaced acouple months ago i really dont believe its just the engine being worn.
 

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On a cable driven throttle body, you can adjust the tension of the cable and therefore adjust the idle. Stock it shouldn't have anything more than neutral tension on it though, so you can only raise idle RPM with this method, not lower it. To adjust the idle air control valve of the throttle body, you need an aftermarket ECU like my PowerFC. They are very expensive though and that isn't an option for a fix like this. My car does the same thing with RPM variation, going up and and down rapidly. I get intermittent 'Idle Air Control Valve Malfunction' codes on my reader, but it isn't bad enough for me to replace the IACV yet. This may very well be your problem too. It's a $150 part, fairly easy to replace.
 

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Appreciate all the help. Took it today and the code its reading now is p0420. Looking for a different mechanic. Mine doesnt seem to want to try to find the problem. Was in the car today for first time in awhile. When he starts it up idle starts high then drops and tries to shut off unless you give it gas and keep giving it gas but after its warmed up its fine. Could smell gas havent notice it do it before. Doesnt have black smoke from ehaust doesnt smell like rotten eggs.
 

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You might have to take it Toyota. I was having issues with my engine running rough at low idle and then not going over 4000 Rpms in any gear but first and second. My issue turned out to be a dirty throttle body and bad spark plugs. It hurt the pocket book, but no one else was able to pin point the issue.
 

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P0420 Catalytic converter low efficiency can be solved by adding an extension tube to the rear O2 sensor behind the CAT, which fools the O2 sensor into thinking there is less Oxygen left after exhaust gas is catalyzed in the CAT, therefore the CAT must be working properly.

Sold in eBay for about $2 a piece:

O2 oxygen sensor test pipe extension extender adapter spacer M18 X 1.5 Bung

You should buy a cheap OBDII scanner, about $25 in Home Depot, and read out all codes to trouble shoot the erratic idle problem.


Appreciate all the help. Took it today and the code its reading now is p0420. Looking for a different mechanic. Mine doesnt seem to want to try to find the problem. Was in the car today for first time in awhile. When he starts it up idle starts high then drops and tries to shut off unless you give it gas and keep giving it gas but after its warmed up its fine. Could smell gas havent notice it do it before. Doesnt have black smoke from ehaust doesnt smell like rotten eggs.
 

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Appreciate all the help. Took it today and the code its reading now is p0420. Looking for a different mechanic. Mine doesnt seem to want to try to find the problem. Was in the car today for first time in awhile. When he starts it up idle starts high then drops and tries to shut off unless you give it gas and keep giving it gas but after its warmed up its fine. Could smell gas havent notice it do it before. Doesnt have black smoke from ehaust doesnt smell like rotten eggs.
Hey shot in the dark i know as its been nearly 5 years and you may not even have the car anymore, but did you ever find a fix to your issue? i just purchased an 2002 gts and have the same problem and dont want to break the bank chasing the problem if you have a solution;-;.
 
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