jolt wrote: ↑Sun Apr 19, 2020 5:02 pm
The 2009 vibe do not have a IAC, as they are drive by wire. The idle speed is controlled by the ECM and throttle body. If components in the throttle body are worn, it can make it very hard for the ECM to control the idle speed of the engine.
If you have any uncontrolled vacuum leaks it can be impossible for the ECM to control the idle speed. Check all vacuum hose connections and the hoses them self's. Check the evap system, check the power brake booster, ect..... anything that has vacuum on the car. About the PCV valve; just because it rattles does NOT mean the valve is good. Cut a old valve apart and look close at the tapered face of the valve. You will see small grooves cut in the face. These grooves meter the amount of air that pulled from the crankcase into the intake manifold by vacuum. These small grooves gets caked up and closed over time. The only way to clean them is to replace the valve so that the proper amount of air is being feed to the intake manifold in a regulated fashion.
When you cleaned the throttle body, you took it off the engine. Did you pull the side cover off and check the play in the plastic gears, the shafts for the gears, the butterfly shaft, because there needs to be no play in any of these parts or you are going to have dead spots or delays in how the ECM controls the idle speed. Also, did you measure the resistance on the signal pot to make sure the resistance values are linear through the whole range of travel of the pot. The pot wears, especially it the idle position because that is where it spends most of its time at, and will not give accurate information back to the ECM if its signal is not consistent.
All the parts in your car have wear on them and as things wear, they degrade. The only time you get a car to run like a new car, is to replace everything so that it is all new. A car is the sum of it's parts. Is it worth trying to fix this problem, that is a whole other matter as this problem can be a lot of little things that may cost more to fix then the car is worth.
I had the PCV valve replaced (not cleaned) last week when I got the throttle body and MAF sensor cleaned. To be honest, I haven't really noticed the problem lately. I'm going to watch it over the next couple days.
Interesting note on the "IAC valve". Today I took the car in for a front end alignment, my steering wheel was cocked about 10 degrees and driving me nuts. I also asked him to clean the IAC valve and to replace all the rusty hose clamps. (the clamps were pretty bad, some were literally falling apart when they were removed). He said he'd only charge me $20 to clean the IAC valve because it was so simple to do. After his guy finished, I asked him how the IAC valve looked, he said it was dirty, but it cleaned up fine. Looking on the invoice, he charged 79.95 for the alignment, $20 for under hood labor, (IAC cleaning??), and did not charge me for a ton of clamps. I wasn't expecting a charge for the labor on the clamps because he had previously said he would do them for free, but I was expecting to pay for the clamps (but he didn't charge me for that either). He didn't do any of the work (he's the manager). I'm wondering whether the mechanic who did the work, just failed to communicate to the manager that there was no IAC to clean, and so he just assumed it was done and invoiced it anyway? It was already past closing and they were in a hurry to get out of there. I guess that could explain the IAC cleaning mystery, but that doesn't explain why he would answer my question about how dirty the IAC valve was. I'm guessing that's just his standard reply to customers even though he doesn't actually see the work done? Little bit of fibbing going on there.
I really had wanted to see the throttle body last week after they cleaned it up, but forgot to ask. I wanted to make sure they actually removed it and cleaned it properly. As soon as I get a nice day, I'll stick a flashlight in there and have a look.