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Ask Amedee Your Own Question
Amedee, Former ASE Master Tech
Category: Car
Satisfied Customers: 24116
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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I have a 1999 saturn SC2. I am having idle problems. The ...

Customer Question

I have a 1999 saturn SC2. I am having idle problems. The car will idle up to 2000 and then jump back down to 1000. I have had the car put on a scan tool and nothing is helping. I have changed the TPS sensor and the intake are control modual. I have even put a whole new computer in the car to see if that was the problem with now progress. Please help
Submitted: 9 years ago.
Category: Car
Expert:  Amedee replied 9 years ago.

Greetings! U might have an air or a vacuum leak. This is very common! Open the hood and listen for a hissing sound when the engine is running. If it is hard to pinpoint take some break cleaner or starting fluid around the intake manifold and vacuum lines and see if the engine stumble or if the idle is affected. Be extremely careful when doing this! Also your throttle body may be carboned up and need to be cleaned! This can cause all sorts of idle and hesitation problems. This is caused by the throttle plate not seating properly. The First thing i would do is clean out the throttle body with some throttle plate and intake cleaner and a small brush.

Check for the following conditions:

Poor connection at PCM or IAC motor. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
Damaged harness. Inspect the wiring harness for damage.
Restricted air intake system. Check for a possible collapsed air intake duct, restricted air filter element, or foreign objects blocking the air intake system.
Throttle body. Check for objects blocking the IAC passage or throttle bore, excessive deposits in the IAC passage and on the IAC pintle, and excessive deposits in the throttle bore and on the throttle plate. Check for a sticking throttle plate. Also inspect the IAC passage for deposits or objects which will not allow the IAC pintle to fully extend.
Vacuum leak. Check for a condition that causes a vacuum leak, such as disconnected or damaged hoses, leaks at EGR valve and EGR pipe to intake manifold, leaks at throttle body, faulty or incorrectly installed PCV valve, leaks at intake manifold brake booster hose disconnected, oil filler cap, oil level indicator loose or missing, etc..

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