Throttle body on Hagan's car
I may have mentioned in a previous post that I was going to clean the throttle body on Hagan's car. He's had some low and rough idle issues with it. So I cleaned it a few weeks back. Now, if you disconnect the TB for any length of time (more than 30 seconds, I believe), you have to go through a throttle/idle relearn process. For the life of me, I could not get the car's computer to relearn successfully. After about 40 tries (no exaggeration), I started to think that perhaps I had gotten TB cleaner in the electronics of the TB (it's drive by wire [electronic]). So I bought a new TB. It came in and I installed it. Same thing. It would not relearn the correct idle position.
One of my students who works for Firestone as a tech suggested that it may be the gasket. I had reused the old one because it still looked like it was in decent shape, but I took his advice and spent $5 for a new one (I really don't know why 1AAuto.com didn't include a gasket with the TB). It was definitely in much better shape. Nevertheless, that didn't fix it, either. So to Google and YouTube I went. After searching for some time, I came across a video made by a mechanic who was experiencing the same thing. He said that he called his friend who was a Nissan Master Technician. The tech told him that the car will not relearn if, before doing the procedure, the car idles at or above 1000 RPM. Hagan's was at about 1800!!
In order to lower the RPM, you have to unplug some number of coils. He had unplugged 3 (not sure how his car ran on a single cylinder, but...); I unplugged two. The RPMs dropped below 1000 (barely). I let it idle for about a minute, then I shut it down and performed the relearn procedure. I fired it back up, still on 2 cylinders, and let it idle for at least 30 seconds. I then plugged in one coil so that I was running on 3 of 4 cylinders. After idling for 30 seconds, I shut it down and performed the relearn procedure again. Then I started it, let it idle (below 1000 RPM) for at least 30 seconds. Then plugged in the final coil. The engine smoothed out and the idle remained at about 800 RPM. IT TOOK! I let it run at idle while I put my tools away, and then I took it for a spin. Everything seems to be back to normal!