Rough Surging Idle at 2k RPM
 

Nothing as fun as breaking your car doing an oil change. I started and drove my car just a little to better position it in the garage for doing an oil change. Simple oil change, done dozens on this one before. Did not disconnect anything besides the drain plug, filter, oil, oil fill cap.

This idle issue happened once I started the engine to check everything was OK, before lowering the car. First crank failed, clicking noises as if the battery wasn't enough to spin. Second struggled but turned the engine over, but now the engine won't idle below 2k rpm and its bouncing/surging around unable to stabilize even momentary blips at WOT. I turned it off, tried again a few times, same results. Once I attempted to use the accelerator to try to see if I could maintain a stable rpm for the car, but the engine surged to redline. It came back down, I turned off the car and now I am afraid I broke my engine doing an oil change.

I did get a video of the idle.




Besides the oil change, about a week ago my A/C stopped blowing cold, I was going to test a couple things after the oil change to see if it was low pressure or a frozen compressor/failed clutch, etc. About 3 years ago the compressor did seize on me and at the time I only replaced the compressor/accumulator since the condenser is so much. It wouldnt surprise me then to have another compressor failure. I have put a hundred mile or so on the car since the A/C failure without issue. Could it be coincidence the A/C clutch is now stuck and the engine can't spin the drive belt? There are no engine codes. I can't see where I could have broken anything.

Its an 09, 70k miles, manual, base with light mods (Exhaust, CAI) that have been on the car for its life almost. It did just get an inspection and service at Z1 at about 68k miles in which I had valve cover gaskets replaced and a heater line leak fixed.

I went back, disconnected the battery to force a reset, also took off the drive belt. Idled smooth, kinda high at 1.3k but it was a cold start. The A/C clutch spun freely so it was probably more the battery disconnect or just time. I'll reinstall the belt when I'm in a better mood and see what happens.

Car is back together and running fine, and also the A/C is blowing cold without issue, clutch engaging again.

Not sure if a control module just needed a reset or is starting to fail. Does anyone know which module would control the A/C clutch engagement and idle/throttle response? I don't want throttle control issues while I'm out on the roads.

To help out with idle issues. Clean your MAF sensors and throttle bodies.

If you go down the route of cleaning your throttle bodies you have to do some pedal dances. Search for motorvate on YouTube. He has the exact procedures.