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Toyotapro, ASE master tech
Category: Toyota
Satisfied Customers: 9974
Experience:  ASE Certified, 10+ years Lexus and Toyota Certified
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2000 toyota corolla: the temperature needle moves.Then on take

Resolved Question:

i have a 2000 toyota corolla with a weird problem.It runs fine until the temperature needle moves.Then on take off i feel like it has no power.I changed the MAF, the O2 sensor before the cat.The fuel filter and the head gasket is only 1 month old.The spark plugs are white so it runs lean but i have no lean fuel mixture code on my computer.Help me!
Submitted: 9 years ago via
Category: Toyota
Expert:  Toyotapro replied 9 years ago.
Hello and thank you for using just answer. First why was the head gasket replaced and has this problem been present since that repair? Does your scan tool read live data, I would like to know what your MAF sensor, b1s1 o2 sensor and fuel trim readings are. Also does the vehicle bog down like it has back pressure?
Toyotapro and 2 other Toyota Specialists are ready to help you
Customer: replied 9 years ago.
ok one of the exhaust valve on cyl 4 burned and i had the head rebuilt.The engine has 185 psi on each cyl.So yes this problem was there before, but not as noticable as now.I got OBD2 and can only read stored codes on computer.Back presure like i got a blocked cat converter or something?
NO it feels like that , but then if i give it full throttle, it goes normaly.And it doesnt accelerate in a linear way.Its like steps.I keep my foot steady and the cars goes like i give it a shot of NOS at evry 1000 rpm change.
Expert:  Toyotapro replied 9 years ago.
it sounds like you may have a back pressure issue from the cat. converter. If no codes are stored and compression is within 15 psi of each other then it is safe to assume compression is not the cause. Not the most conventional way to check for back pressure but you can unbolt the converter loosely or remove the front o2 sensor to see if the condition goes away. If back pressure is indeed the cause it will not always set codes for p0420. Some times you have a partially clogged cat that will still allow exhaust movement but is restricted, it would be the same thing if you were to stick a potato in the exhaust pipe. This can also cause engine damage and could have been the root cause of the burnt exhaust valve. The other scenario is that is the computer was compensating for a burnt valve the cat may have been exposed to raw fuel that "lit" the converter and partially melted it down.