I just bought a used Honda Civic EX. Very nice car, just what I was looking for. After getting the car raised up to where it doesn't bottom out everytime I drive into or out of a parking lot, I now am wondering about this afc controller the car is connected to.

First off, the car runs just fine. I don't know a single thing about what this controller does except the little I have read about it online. I haven't touched any settings and from what I read, thats a good thing : ) To be honest, the thing makes me nervous.

I'm wondering if:

1- it is still beneficial to keep this thing connected if I am only using the car as a normal commuter car - like, will I get better gas mileage with it connected?

2 - will this thing make me fail emissions when I need to get that done? I live in the Seattle area if that helps.

3 - if I just unplugged it (if it is serving me no purpose) will it screw my car up - basically does it need to be professionally uninstalled?
Thanks

 

What year Civic?

Ok...

The VAFC is a "piggy back" tuning option for those who cannot chip their existing ECU. Usually done on OBD2 Civics (96 and up) as they cannot be chipped like their OBD1 versions (92-95 Civics).

Anyways, the only reason you would NEED it is if there are extensive modifications done to the vehicle. An aftermarket camshaft, turbo, or nitrous injection would be a few examples.

Onto the answers for your questions...

1. If the vehicle is basically stock (basically stock means bolts ons like intake, header, exhaust), it is not needed, but may be beneficial if tuned correctly. Beneficial as in allowing you to make more power. If the vehicle has extensive modifications, removing that VAFC will destroy your motor as the vehicle's fuel maps and ignition tables need to be altered for the vehicle to run correctly.

2. Check your local emissions laws. In PA, you will not fail emissions for it I believe. People use VAFC on OBD2 vehicles for this reason.

3. Same answer as #1.

Are there any other modifications done that you can see? More specifically, is there a wideband o2 sensor with a Air/Fuel Ratio gauge? If so, the previous owner was monitoring the AF ratio and tuning accordingly. If not, and he did everything himself (without gauges), he was just blindly messing with the fuel maps etc (not good IMO).

There is the possibility of the previous owner having the vehicle 100% stock and still installing this for the sake of gas mileage. However, it is extremely doubtful. The previous owner would have been leaning out the motor (removing fuel from the maps). Without an AFR gauge, he/she could have been removing too much and potentially damaging the motor.

More or less, we need to know what modifications are done to the vehicle/motor before telling you if you can or cannot just yank this out. If you deem the VAFC unnecessary, you should be able to cut it off. Be sure to locate your ECU (passenger side kick panel) and cut the connections made there. You should be able to turn around and sell the VAFC & harness for somewhere around $75-$100.

 

Thanks for the reply. Here is the complete text of the ad:

"This is a 2000 Honda Civic Ex coupe. It has 115k miles. It has a stock ex d16 engine with 5 speed manual transmission. It is silver exterior with dark grey interior. It is in great condition in and out and also runs and drives great. It is fully loaded with all power windows, locks, sunroof, ac, and much more. Aftermarket upgrades include tinted windows, Python alarm, si grill, factory si front lip, si rear lip, thin jdm moldings, si alloy wheels, si shifter, si leather wrapped steering wheel, Apexi V-AFC controler, jdm carbon fiber mirrors and more."

So it appears the engine was not modified. I had the car inspected by my mechanic and he would have told me if something had been missing or added out of the ordinary I would think. The car was also very low to the ground and had racing tires on it (which were bald). I corrected both of these problems.

Thanks for your help. I do appreciate it and welcome any more expertise you can provide.

 

Sounds like a nice find! By the sound of it, the previous owner installed some tasteful mods.

I would unplug the VAFC, turn the car on, and see how everything operates. If anything seems wrong at all, shut the car off and plug the VAFC back in. Unplugging it should allow the ECU to operate as it "should" when it was in stock form.

If nothing happens, you should be fine to cut the wires off and continue moving along.

 

Thanks - the car looks awesome too. The silver paint job is only 3 yrs old according to Carfax. My mechanic was impressed & said it was a great deal.
Got it off of Craigslist.

I'll try what you said. I found the plug connection under the floor mat today. I'll wait until I finish the tank of gas to see if there is any difference in gas mileage without it hooked up. Thanks for your help : )

 

Do not pull the plugs out from your ECU which would be around that area.

Is there a plug in the back of the VAFC which can remove? Or is there some sort of adaptor harness that was plugged directly into the VAFC and the ECU?

If you are unsure of this, pull off your kick panel on the passenger side, take a picture and post it up here so we can tell you.

 

There is a wire coming out of the VAFC which has a connector on it, connected into another wire, which I assume goes to the ECU. Thats what I plan to disconnect - just the connector in the middle of the wire.

I assume if I disconnect this and the car runs fine, I can then safely disconnect the other side of the wire (now dead) from the ECU?

The car isn't getting the greatest mileage anyway (looks like about 26 mpg), so I gather this thing is not providing any benefit.