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Old 05-12-2015, 05:39 PM   #1
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Default How to Fix Rough Idle / Slow Returning Idle

I Have been having problems with my Idle having slow returns when starting my 98 Saturn SC2. It would jump to 2000-3000 rpm then slowly return (about 5-7 seconds) to 1200-1100 rpm. So I have been researching all over the internet to find the solution. Many solutions being posted on SaturnFans. I am posting my experience with this problem so it could better assist people in the future that have the same issue. The ECTS has been replaced on my car, but you should start with that if you haven't replaced it. Here are my steps to try to fix the problem.

Steps to fix Rough / Slow Returning Idle
1. Make sure your ECTS is replaced with the new Flat Top Brass ECTS. (Engine Coolant Temperature Sensor.)
2. Inspect the PCV valve to see if it is broken. To do this you teak the PCV valve off, clean it off with some cleaner and a rag. After it is clean, blow on the larger end of the PCV valve, and if air goes through, then it is working in that direction. Now flip it over and blow in the small inlet. If you cant blow air through it, it is working correctly. Also try shaking it and if it rattles, the spring is working correctly.
3. Check all intake and exhaust hoses for cracks or leaks. There are methods of checking for vacuums leaks by spraying solution to hear engine idle changes. Do a search on the forum for that.
4. Check air filter. See if it is dirty and needs changing. If it is dirty, just change it, it only cost $10.
5. Check throttle body for carbon buildup. Look inside and if it is black, you need to take it off and clean it. This step is crucial because this is the step that finally fixed my problem. You need to take the throttle body off and there are 2 electrical ports attached to it. One is the TPS (Throttle Positioning Sensor) and the other is the IACV (Idle Air Control Valve). The TPS is usually not the one causing the issue, so I would start with the IACV. When you take it off the throttle body, it will look like a pencil tip. You need to take some brake cleaner or anything that can degrease/de carbonize and clean the hell out of it. Or go the easy route and buy a new one on ebay for $10. After it is cleaned, I put a very small amount of WD40 on the shaft to lubricate it. Also make sure the clean the hole that the IACV goes into as well as the whole throttle body. Make it clean enough to eat off it, and lubricate the pivot area with a tiny bit of wd40. After that reassemble everything.
6. Check the spark plug well for any oil. I have had experience with oil in the well which would cause shorting issues. To fix this you need to take all the oil out of the well with a paper towel. Then look for a tutorial on "How to replace Valve Cover Gasket". After the gasket is replaced, replaced the spark plugs if they are old as well as the spark plug wires if they are damaged, warped or corroded.

If all these steps failed, then you have a bigger issue with your car that cant be easily solved.

I hope these steps help someone in the future that has gone though my pain in trying to fix this stubborn issue.


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