My car has 120000 miles, and 1.6L Engine. Before cleaning my throttle body, I had three codes present for a long time: P0420, P0442, P0455. This was my first time doing anything with the engine. I got the car secondhand from my brother. Car has had some history with stalling and also had a blown head gasket (this has been repaired). Now here's the story: Car would occasionally shudder and rev on it's own while in idle, so I decided to clean the throttle body. I'm going to list what I did so that you guys can see if I messed this up somehow.


1) Removed the Intake Hose. It was stuck pretty good on both sides so I popped it off with some screwdrivers. Ended up with a small gash on the throttle body and a dent on the lip of one of the ends of the rubber Intake Hose. The gash on the throttle gets covered by the Intake Hose and the clip is higher up on the intake hose, away from the dent. I inspected the Intake hose and there are no cracks or tears in it.

2) I didn't remove the throttle body from the Intake manifold. I didn't get a maintence history from my brother but it looks like the throttle is original (I also don't know if the throttle has any special coatings on the inside). I briefly sprayed the throttle plate and the part past the plate with throttle cleaner. Wiped it all off as best I could with some paper towels. Then I took a dirty toothbrush (I washed it with some water but the brisels are stained black from previous maintence jobs), sprayed the toothbrush with throttle cleaner, scrubbed, wiped it off, and repeated until clean. I ended up using half of the bottle. I also plugged up the hole to the IAC to unsure that the cleaner didn't leak in (it could have gotten in anyways, who knows) and I made sure I unplugged the hole before I put everything back in.

3) Put the Intake hose back.


After doing this, the engine was okay for a day (shuddered+revved once though). Next day, I'm on the road and I get a P0300 Engine Misfire, which is something the car didn't have before I cleaned the throttle body. At that time, the car (while in park) idles at around 1200 rpm until it's at operating temp, it stalls, revs itself, and then gets back to normal. I could also hear a hissing sound from the engine bay which wasn't present before the cleaning (I think). While I'm at work, my dad (not a mechanic but has more experience with cars) checks the sparkplugs which turn out to be fine, and replaces the ignition coil plus the MAF sensor. He takes the car for a couple minute test drive: now the car drives rough all the time, he heard a knocking noise in the engine bay, and to top it all off he lost his brakes at one point. Apparently he also cleared the car of the P0300 error before the test drive and after the test drive two new errors pop up: P0507 and P0171. After that, we waved the white flag and are now looking to buy another car.


Now, I'm convinced that I'm the one that caused this but I'd like for someone to explain to me how the heck all of this could have resulted from me cleaning the throttle body. Or is it that my car was already on it's last legs and I just put the nail in the coffin? I want to learn from my mistakes so that something like this won't happen again if I fix my car. Any thoughts about the whole situation is much appreciated. Thanks.