Created By:	FLAASH	Category:	Maintenance ECU / Computer / Diagnostics
Date Posted:	02-16-02	Views:	10953
Title:	Geo Storm Idle Problems - Random Revving/Stalling
Article:	While this can be attributed to a number of different items there are a couple of common problems that can be easily, and inexpensively, addressed on the Storm. First off I’ll assume that your tune-up components are in good working order. Meaning that you have checked the cap, rotor, ignition wires and spark plugs and replaced if necessary. The oil has been changed regularly and the timing belt has been changed on schedule right? OK, so all those things are in working order. First, the Geo Storm throttle body (TB) has a problem with excess carbon buildup on the butterfly plate and its surrounding areas. Disconnect and remove the intake hose. It is not recommend that you spray carb cleaner directly into the TB. So, liberally spray carb or TB cleaner onto a clean rag. Then, using your rag, THOROUGHLY clean the area around the throttle plate. Don’t forget to clean the throttle plate too. Use a flash or shop light to make sure that you clean everything you can see (and maybe even some things you can’t). Reinstall your air cleaner assembly Another area to check is the Idle Air Control Valve or IAC. This is the sensor located at the very front of the TB (on the side facing towards the front of the vehicle). It is held in place with two torx type screws. First unplug the wiring harness from the IAC. Then, remove the two screws holding the IAC in place. Gently remove the IAC from the TB. Using your rag, soaked in carb or TB cleaner, gentle clean the pointed end of the IAC. DO NOT PRESS THE VALVE INTO THE BODY OF THE IAC. This could cause the tiny motor and gear to strip ruining your IAC valve. Also, clean the area inside the TB itself. Again, liberally soak your rag with carb or TB cleaner. Using the blunt, or handle end, of a small screwdriver press rag into the TB and thoroughly clean the IAC port. Check the IAC o-ring for cracks and replace if necessary. Replace the IAC and connect the harness. When restarting the vehicle it may take a few moments for the computer to figure out the new settings. Last is the Electronic Control Module (ECM). It is a well documented fact that the ECM that comes in the Storm has some serious issues. Basically, because of the way it was designed, after years of being exposed to heat and cold the circuit board expands and contracts to the point that the connections are eventually broken or severely weakened. The only way to cure this problem is to acquire a used, new or re-manufactured ECM. If buying used make sure that you get the one specifically for your vehicle. Meaning if you have a ’92 base SOHC Federal Model with a manual transmission that’s the ECM you need. Anything else will not work. If buying new or re-manufactured the ECM will probably need to be programmed by the dealer. Replacing the ECM is fairly easy and not very time consuming. About 20-30mins total time needed to remove and replace the ECM. First, disconnect the battery. Then you will need to remove the lower portion of the dash on the driver’s side. Once removed, you will need to take out the vent tube that you see right in front of you. Once out you will see a shiny box about 8” X 2” square. There are two screws that hold the ECM in place. Not the 8mm nuts but the two Phillips screws. Once the screws are out, slide the ECM towards to front of the vehicle to clear the mounting bracket. Once the mounting bracket is cleared you will be able to pull the ECM straight down. Disconnect the wiring harness from the ECM. Reverse order to install your new ECM. Once the new ECM is installed it will take a little while, and some driving, for the ECM the ‘learn’ all of your vehicles specific requirements. So don’t worry if it doesn’t work perfectly right away.