Sc400 Not Running Right

[lexus082]

I read up on this through the forums, but wanted to ask owners what they think it may be. Its a 94 SC400 with 130,000 miles. The idle speed is around 300-400rpm and sometimes lower making the engine stall out. While in park the engine seems to struggle to run. In park the rpm needle goes up a little and then it moves back down a little never at a constant rpm speed. It used to stay at a certain rpm while idling. I have replaced the rotors and caps, fuel filter, spark plugs, plug wires, and air filter, pcv valve. I think it could either be the fuel pump computer going faulty or the idle speed needs to be adjusted back up to 700+/- 50 RPM. The car drives ok while the rpms are up, but once the car comes to a stop and is idling thats when I notice problems. Although while driving acceleration seems to be sluggish and the rpm's don't rise like they should as I accelerate. I would appreciate any ideas on what is causing this.

[DomLee]

Just thought I would ask, have you cleaned out the throttle body?

[jzz30]

if you smell fuel and see smoke out the exhaust then it could be the coils, if not then try bypassing the fuel computer and runn with full fuel pressure, by connecting two of the check connectors, im not sure which ones but maybe someone with a manual at hand could tell you which terminals to short.

[lexus082]

I read up on this through the forums, but wanted to ask owners what they think it may be.  Its a 94 SC400 with 130,000 miles.  The idle speed is around 300-400rpm and sometimes lower making the engine stall out.  While in park the engine seems to struggle to run.  In park the rpm needle goes up a little and then it moves back down a little never at a constant rpm speed.  It used to stay at a certain rpm while idling.  I have replaced the rotors and caps, fuel filter, spark plugs, plug wires, and air filter, pcv valve.  I think it could either be the fuel pump computer going faulty or the idle speed needs to be adjusted back up to 700+/- 50 RPM.  The car drives ok while the rpms are up, but once the car comes to a stop and is idling thats when I notice problems.  Although while driving acceleration seems to be sluggish and the rpm's don't rise like they should as I accelerate.  I would appreciate any ideas on what is causing this.

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No, one of the things I put on the back burner. I will keep that in mine. If its not too much trouble how would you recommend cleaning it? Do you just remove the intake hose and use a cleaner and towel to wipe the inside of it out? Thanks

[lexus082]

Just thought I would ask, have you cleaned out the throttle body?

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I do smell something but I cant put my finger on it. It smells familiar but just cant think of what it is. Thank you for the response. I just thought of something that goes with your idea. I have a pretty starter thats been going bad for a while. It takes longer than it should to start. Sometimes its a really quick start almost instant as soon as you turn the key and then some times its a 3 second crank to start. Back to my question, if I have a semi-bad starter is that going to reduce the life of my ignition coils? Thanks!

[lexus082]

Just thought I would ask, have you cleaned out the throttle body?

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I do smell something but I cant put my finger on it. It smells familiar but just cant think of what it is. Thank you for the response. I just thought of something that goes with your idea. I have a pretty starter thats been going bad for a while. It takes longer than it should to start. Sometimes its a really quick start almost instant as soon as you turn the key and then some times its a 3 second crank to start. Back to my question, if I have a semi-bad starter is that going to reduce the life of my ignition coils? Thanks!

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In addition to everything (symptoms) my check engine light comes on along with the TRAC light but as soon as I accelerate from idle that both turn off. They only come on when the car is struggling to idle. But then they turn themselves off. They only stay on for less than 30 seconds. If I take it to the dealer what would be the best approach to fixing this problem. Also, its not the gas just got a fresh tank and I only use Exxon 93.

[lexus082]

Just thought I would ask, have you cleaned out the throttle body?

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I do smell something but I cant put my finger on it. It smells familiar but just cant think of what it is. Thank you for the response. I just thought of something that goes with your idea. I have a pretty starter thats been going bad for a while. It takes longer than it should to start. Sometimes its a really quick start almost instant as soon as you turn the key and then some times its a 3 second crank to start. Back to my question, if I have a semi-bad starter is that going to reduce the life of my ignition coils? Thanks!

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In addition to everything (symptoms) my check engine light comes on along with the TRAC light but as soon as I accelerate from idle that both turn off. They only come on when the car is struggling to idle. But then they turn themselves off. They only stay on for less than 30 seconds. If I take it to the dealer what would be the best approach to fixing this problem. Also, its not the gas just got a fresh tank and I only use Exxon 93.

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Just to let anyone know who has been following this thread. I took the car to the Toyota dealer and they found the Mass Air flow Meter Assembly was bad (Mass Air flow sensor). Just thought I'd follow up as so many people never do.

[Tbear]

I am having similiar problems with my 94 SC400 and it turned out to be the Air Tempature Sesor which is build inside the Air Mass Meter. Check your engine code, cause no check lights come on.

[lexus082]

I am having similiar problems with my 94 SC400 and it turned out to be the Air Tempature Sesor which is build inside the Air Mass Meter. Check your engine code, cause no check lights come on.

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I think the Toyota dealership was trying to make a quick buck by tring to sell me a new MAF meter assy. After finding that was the cause, i tested the resistance and it checked out ok. So I cleaned it and hopefully soon I can find out if it was just dirty. Never had a sensor go bad so I didn't know that most of the time they are just dirty I guess...

[lexus082]

I am having similiar problems with my 94 SC400 and it turned out to be the Air Tempature Sesor which is build inside the Air Mass Meter. Check your engine code, cause no check lights come on.

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I think the Toyota dealership was trying to make a quick buck by tring to sell me a new MAF meter assy. After finding that was the cause, i tested the resistance and it checked out ok. So I cleaned it and hopefully soon I can find out if it was just dirty. Never had a sensor go bad so I didn't know that most of the time they are just dirty I guess...

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Question concerning the rubber gasket. I know your supposed to replace the gaskets when something is removed which I did when I installed a replacement MAF while I cleaned my original. That was about a week ago, can I still use that rubber gasket or should I go buy a new one, its only about a week old. What do you guys think. (MAF meter box gasket)

[jzz30]

starter motor and coils have nothing to do with each other. someone else said that their timing jumped a tooth take off the cam gear covers and see if everything lines up. then you can eliminate the possibility of timing being off.