So my 94 accord, f22b2, has had a weird issue for a long time now. Start it up and it runs great! Drive for a minute, closed loop, starts to chug and surge. Have to give a pretty decent amount of throttle just to keep from pissing off everyone behind me. Then all of a sudden... It snaps out of it, and runs great again. No codes. Never happens again until engine has cooled back down. I've pulled the EGR plate, and cleaned all the passages. Pulled the EGR valve, and cleaned it all up. All of which was extremely built up and clogged full of carbon, and the EGR valve gasket had also been leaking, so I replaced the gasket. To no avail. Pulled the IAC motor and cleaned it out, also very full of carbon. Cleaned the throttle body, and pulled each injector and manually cleaned them with carb cleaner, tapping power to them while injecting carb cleaner. Replaced fuel filter. Still, NO GOOD! It does have the idle surge in closed loop also, which is pure laziness to clean FITV. Could FITV cause this? Coolant temp sensor? Oxygen sensor? PCM? I am a technician by trade, and not only am I baffled, but all of my master techs are also lost. Previous job was actually at a large Honda dealer, and even the shop foreman, master diag tech for 28 years could not figure it out. Sh!tty obd1, so not even my shops fancy "snap-on verus" scan tool can monitor a damn thing. Had the car for four years, and over 60,000 miles. Racked my brain on this countless times, and have also given up countless times because it doesn't seem to harm anything by leaving it alone, and doesn't tend to get worse, considering outside temp, which should be expected when below freezing. Really hoping for some answers. Thanks for reading, and any ideas would be appreciated

 

Anybody?

 

1. Have anyone tried unplugging the MAP sensor to see if the surge disappears? It won't run that well; but, see what happens if that hasn't been tried yet.

2. What about did anyone try a known good ECM at the shop?

 

I'd avoid just replacing a sensor unless you get a code or it tests bad.

I can't tell if you did anything to the FITV. Here is a simple test, pull the snorkel off the throttle body. Start the car and let it warm to closed loop mode. Cover the lower port on the inside of the throttle body in front of the throttle plate with your finger. Does the idle stabilize?

 

So I had a little extra time today at work, and decided to finally pull the FITV. Before I did that, I pulled the MAP, and it looked to be in pretty good shape. Although it's a MAP sensor, so looking ok doesn't mean much. I proceeded to pull the FITV. As I was doing that, I noticed the coolant hose had a very small chunk of crusted coolant, and was also bulging in that spot. So I pulled it off, and sure enough it was completely clogged. I tried to blow through it just to see how bad it was, and I couldn't blow through it at all. Debris had built up, and the FITV hasn't been getting ANY flow for who knows how long. Long enough that there was still green coolant in it, and changing to Honda coolant was one of the first things I did when I bought the car 60,000 miles ago. So I pulled it all apart, and cleaned it. Put it back together, replaced the hose. Fired it up, and took it for a drive. Been on three test drives now, and so far not a single sputter when going Ito closed loop. I am pretty positive that fixed my problem. Pretty shocked to say the least. All my techs in the shop asked, "what the hell is that?" As I was cleaning it. I explained what it was, and none of them thought it would fix the problem. But I'm pretty confident that it did. Thanks for your input guys.

 

Sure, that makes sense.

If the FITV isn't getting coolant, then it doesn't heat up correctly. In that case, it is letting extra air past the throttle, JUST LIKE a vacuum leak. And a vacuum leak can be a cause for your surging.

 

Absolutely. Only problem is that I hadn't ever learned about these FITV on the Honda. So I had spent a decent amount of time trying to find a vacuum leak, and of course came up with nothing.