Whats wrong with my Idling?

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Aug 31, 2011 | 12:44 AM

93sprucesc

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From: CA

Whats wrong with my Idling?

Hello,

I have a 93 SC300 and I just had the engine rebuilt. Basically overhauled the car. But now when I start my car in the morning it is perfectly fine until 5 minutes later. The idle starts going up and down then after another 5 minutes it goes back to normal. There was a day when my car just did not start til I messed with the intake and the mass air flow sensor. I took it to a place and was told it was the sensor so I replaced the sensor today but the problem is still there. If anyone knows what is wrong with my car please let me know. Thanks!

Aug 31, 2011 | 01:14 AM

NaturalJZ

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From: MN

Well i dealt with a bad MAF recently so i'll say to try to find another sc300 that runs, and swap maf to see if thats the problem.

Aug 31, 2011 | 01:17 AM

V8drummer

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Could be the Throttle position sensor

Aug 31, 2011 | 09:09 AM

Tabaka

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From: Dale City, VA

If it goes up above your normal idle speed, then drops down well below your typical idle speed, and repeats in that scenario than it's most likely your TPS. If it simply falls below your normal idle speed and never raises high, go low, high, go low, and gets dangerously low to the point of stalling, then it's probably your IACV.

Has your car ever thrown a CEL?

Aug 31, 2011 | 09:56 AM

Nova

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if you do have a CEL on take it to autozone or advanced and they will run it for free and print out possible causes. best place to start instead of throwing parts at it

Aug 31, 2011 | 10:28 AM

blacksc4

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if its not throwing a cel, i would start with a little cleaning (cheapest possible fix) clean up the TB, and IACV, even possibly sea foam the car if you want, if that doesnt fix it then start going with parts like the tps,

one thing it might also, since you said the engine was rebuilt, who ever rebuilt it, did they tune your tps back to the correct spot? you can try adjusting the tps to level out the idling, it probably idles normal wen start because the engines not as hot, as it heats to running temp, the idle drops so when you adjust it youd be able to have run corrrect, just a thought

there is a DIY on here on how to check the tps for functionality so do that before you buy one, make sure its bad first

Aug 31, 2011 | 10:47 AM

Tabaka

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From: Dale City, VA

Quote:

Originally Posted by Nova

if you do have a CEL on take it to autozone or advanced and they will run it for free and print out possible causes. best place to start instead of throwing parts at it

if it's OBD1 most of them won't check it

There is a DIY on how to check a code for free along with the code listings in one of our stickies.

OP, try cleaning the throttle body and IACV a little bit and see if that helps.

Aug 31, 2011 | 03:21 PM

93sprucesc

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From: CA

Thanks everyone. I will check those things out and let yall know.

lexdud: The ECU was rebuilt as well

Aug 31, 2011 | 03:35 PM

#10

93sprucesc

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From: CA

oh yeah and there is no CEL on

Aug 31, 2011 | 06:32 PM

#11

Tabaka

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From: Dale City, VA

Quote:

Originally Posted by 93sprucesc

Thanks everyone. I will check those things out and let yall know.

lexdud: The ECU was rebuilt as well

What do you mean by rebuilt? You shipped it away and had capacitors replaced or something?

Aug 31, 2011 | 06:54 PM

#12

JDMmuscle

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From: State College, PA

Check all your vacume lines. Mine did the same thing, Bought a new maf, refurbed ECU, TPS, the works.... turned out one of my vacume lines had a small tear in it.

Aug 31, 2011 | 10:12 PM

#13

blacksc4

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From: ohio

^ to check your vac line run the car and spray a mist of brake cleaner or water and if it sputters then theres a leak in the line

thot id fill in if you didnt know how to check

Sep 1, 2011 | 07:15 AM

#14

Nova

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From: NJ

Quote:

Originally Posted by Tabaka

if it's OBD1 most of them won't check it

There is a DIY on how to check a code for free along with the code listings in one of our stickies.

OP, try cleaning the throttle body and IACV a little bit and see if that helps.

your right sorry op I forgot ur car was obd1 when I was writing that post so scratch my other post about autozone

Sep 1, 2011 | 12:14 PM

#15

Tabaka

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From: Dale City, VA

Quote:

Originally Posted by blacksc4

^ to check your vac line run the car and spray a mist of brake cleaner or water and if it sputters then theres a leak in the line

thot id fill in if you didnt know how to check

Where are you asking the OP to spray this brake cleaner?