Cleaning a dirty throttle body:
The below pic shows my throttle body on the lower right, attached to the air manifold. It has that small black plastic air manifold with the two hoses going to it…which is separated from the throttle body at the moment, here’s a link to one on eBay: Throttle Body.
There’s only a couple, maybe three, bolts holding it and once the air cleaner ducting, vacuum hoses pried off the top, throttle cable removed, two electrical connections disconnected, it comes right off. I carefully and completely followed this Throttle Body Cleaning video. My symptoms that called for cleaning it were similar to what’s shown in the video. I’d start the car, and the idle would jump up over 2,000 RPM, than creep down to 1200 RPM, often taking longer than expected. While driving, and after warm up, again, it had excessively high idle. Note that these symptoms can point to a dirty TB. There are other items that can cause it as well. But…cleaning of the TB needs to be periodically done anyway, and I had the time so…
After I removed the TB, and operated the butterfly, it was obvious that the butterfly was sticking closed which would cause a lurch when accelerating, and the air passageway was slightly blocked by carbon buildup in the main body and the vacuum ports. Visual inspection showed lots of built up carbon all over in there. So those two things pretty much were what was causing some of my intermittent high idle issues. Occasionally, while sitting at a stop light, in D, the idle would jump up to 2,000 and sit there for a while before dropping down to normal.
Scraped out as much of the carbon as I could with a flatblade screwdriver, then filled a small tray with spray carb cleaner and soaked the TB for 15 minutes. Sprayed it several times and used a clean rag to wipe it off. Used an acid brush to get at hard to reach areas. Cleaned out the ports as best I could too.
When finished, it was good as new, all nice and shiny. I’m lucky this car only has 60K miles on it because everything in the engine compartment is fairly clean to start with so I don’t have to contend with built up gunk and grease.
Even with taking my time, this job only took around an hour, and the cost was just $5 for the carb cleaner.
After cleaning the TB, I didn’t really see much improvement in the intermittent over idle RPM situation. When cold starting, it would jump up over 2K RPM, but I did notice that it dropped much quicker now after cleaning. However, it now seemed to like idling at 1200 RPM. So, at least something was better, but there was more to do.