Crazy stuff

uniqsc4

Registered User
I just bought my 89sc a couple weeks ago and am very pleased with it except for a few problems. my first problem is and idling problem. The car will idle perfectly fine around 900-1000 rpms for about 1 min and then the rpms will drop off to about 500 with an extremly rough idle. my second problem is with the check engine light. It comes on at random and shuts off quickly. I have pulled the codes and they are for both the o2 sensors and the maf, all of which are new. i have tried clearing the codes but they return. any advice would be greatly appreciated.

Thanks
 
Before you start investing in new sensors, modules, and various parts, always start with the basic stuff.
First, start with vacuum leaks. Get a can of propane (like you use to refill cig lighters) and spray it around all the intercooler connections and vacuum lines while the engine is idling. If the RPM's fluctuate while spraying the propane on a connection, you have a leak at that location.
These cars are notorius for "springing leaks" around the intercooler pipes. There are numerous ways to reseal the connections, I have used a thin coating of RTV gasket sealer (sensor safe) around the threads and fitting connectors.
If that doesn't do it, then you might check to see if there is dirt on the MAF sensor. Wires and plugs would be my next guess (unless you know they are good) then possibly the Idle Controller on the throttlebody.

Most likely a vacuum leak somewhere...........
 
i agree with LJGriggs. but also i had a thought, maybe your idling problem is due to the alternator. when you are sitting at idle for a while the car gets hotter and hotter until the electric fan comes on. and when that happens (at least in my car) alot of power is needed to run it. my rps move a bit when this happens but return to normal after a few seconds. but this is just a guess though.
 
get this one

Ok i tried checking for vacuum leaks with the propane and no luck. i checked my alternator and still no luck. today my friend and i were taking out my air silencer and when we put it back together we forgot to put on the maf wires. IT IDLED PERFECT! then when i hooked it back up..... back to rough idle
 
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