Help, odd revving when engine starts. - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 9 (permalink) Old Dec 15th, 01, 02:07 PM Thread Starter
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Join Date: Jun 2001
Location: Oakville
Posts: 67

Hey all I just finished re-assembling the front end of the TPI and the runners and I cranked it up about a half hour ago. First as soon as it started the revvs climbed to 2500RPM even though the throttle body was fully closed, then it slowly dropped to a 1400-1500RPM idle. Not exactly normal. So I was thinking, the bottom portion of the throttlebody gasket between the throttle body and plenum was cracked and may have fallen off while re-install. I havent had the time to check but could this be the problem of the odd events that are taking place?

1990 Camaro IROC-Z 305 TPI.
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post #2 of 9 (permalink) Old Dec 15th, 01, 02:13 PM
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You more than likely have a vacuum leak somewhere , check for a slipped gasket or the cracked one You mentioned......Billy
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post #3 of 9 (permalink) Old Dec 15th, 01, 02:59 PM
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If you had the battery disc. the computor might have lost it's memory. On some newer cars it takes about ten min. for computor to relearn itself after it is running or after car has been started a certain number of times it relearns. This may be your problem.
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post #4 of 9 (permalink) Old Dec 15th, 01, 04:00 PM
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Greetings, orion_uv.

Just out of curiosity, when you re-installed the front end of your throttle body, did you reset the "TV" (kick down or detent)cable. If you didn't, the ECM might think the car is in a higher gear even though it is in park. Had this happen to me the first time I changed out a throttle body. It is simple to adjust. Just push in the button or tab on the side and pull the insulated cable back until the front of the cable is flush with the mount. Release the tab or button, next take and slowly open the throttle all the way until it stops. You will hear a ratcheting sound from the cable as it resets itself. Hope this helps!!!!!!!!!!!!!!!!!!!!!!!!!
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post #5 of 9 (permalink) Old Dec 15th, 01, 04:26 PM
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Your not starting it with your foot on the gas or pumping it a few first are you? I understand this can mess with the computer causing high idle...

"The '69, the '96 & the club"
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post #6 of 9 (permalink) Old Dec 15th, 01, 06:54 PM Thread Starter
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Nah not touching the gas. I dont think its the "TV" either cause again, everything looks as it should and the throttle body is fully closed so I'm wondering where its getting the air from to produce 2500RPM cleanly without any rough sounds./

1990 Camaro IROC-Z 305 TPI.
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post #7 of 9 (permalink) Old Dec 16th, 01, 06:16 AM
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Ok....lets start over.....the engine starts and idles at approx 2500 rpm.....then drops to approx 1400-1500 rpm....That tells Me that the IAC (idle air control motor) is working because of the rpm drop from startup.
This motor moves a pintle (valve) in and out that meters the proper amount of air by for proper idle (actually inducing an internal "air leak").....if an external vacuum leak is present the valve will go into the seated position not allowing any air cannot make up for an external leak somewhere else...if there is an external leak the computer adds extra fuel to this extra "air" and gives a high idle...
Check for a leak by letting the idle stabilize at the 14-1500 rpm...then spray around all the intake gasket areas with some wd40 or equivalent...if a leak is present the idle will change as You spray over the bad area....Good Luck.....Billy
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post #8 of 9 (permalink) Old Dec 17th, 01, 03:16 AM
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Propane is a good finder for leaks,

if its leaking the propane will increase the idle of the car as its getting fuel, (of course dont light the propane torch, just use a little flow of the propane gas)

and if you smoke, Dont while doing that. and only do it in a well ventilated area. otherwise its quick , and easy and less messy than squirting wd40 all over your clean engine.

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check out another site once in a while!
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post #9 of 9 (permalink) Old Dec 19th, 01, 04:40 PM
Join Date: Dec 2001
Location: Crossville,TN.,US
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Did you check the TPS if you moved it at all the ECM will resort to a factory setting and won't use the TPS voltage.There are 3 wires coming off of the TPS one is is the hot about 5 volts the other is a ground and one sends a signal to the ECM should be .525 volts at idle and increase upto 5 volts as you open the throttle. To adjust just loosen the two bolts on the TPS and turn while monitoring voltage set at .525 @ idle. You'll be suprised how little it has to move to change the voltage.
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