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Feedback Carb

Posted: Fri Jul 22, 2005 9:05 am
by plowboy
Anybody know how to lean out a feedback carb out a little (besides chucking it in the can). It's running very rich and when I get out of I smell gas. It's not leaking. I suppose it could be the float, but it was just rebuilt a couple of months ago. Or could it be the sensors. I have no check engine light on. BTW it's an 85 2.8L (POC).

Posted: Fri Jul 22, 2005 9:27 am
by Nobody
I believe it's tied into the EGR and O2 sensors. In short there isn't much you can do about it. On the back of the carb, there is a plug that controls a big 'ol needle valve. If something is wrong, it defaults to fully open causing a rich condition.

Make sure your choke is opening all the way and the air filter is clean. Also make sure that hot air valve on the air filter housing opens.

Posted: Fri Jul 22, 2005 12:11 pm
by ranger5.0
A Major vacuum leak will also create a overly rich condition. I just dealt with that issue on a rig of mine. I went to change the carb out on it and noticed that the base gasket was broken in the back and was sucking air. The carb you have has a slightly larger base than a regular motorcraft 2-barrel so you have to be careful in what base gasket you use. I did that also with my ranger motor.

Posted: Fri Jul 22, 2005 6:36 pm
by plowboy
Vacum could be an issue. I have replaced the brake booster a while back. I have not been sure the new (reman) works properly. Brake performance has slowly degraded. The pedal has to be pumped. Brakes have been completly rebuilt front and rear as well as thoroughly bled. However the pedal goes to the floor. A couple of pumps and there is pedal, but ocasionaly goes to the floor. My first thought was that the master cyl. needs replaced. (not been done yet) However when the pedal goes down, at times pressure comes back it pushes my foot back up. It will fluctuate up an down. So could the booster be leaking vacum, or is it possible that both need replacing?

I have checked the choke, air filter, and hot air valve. All are OK. I suppose that the O2 could be bad and the check engine light is burnt out, I haven't checked that. I simple resistance test will check the 02.

Something that just came to mind. Last fall I put a new thermostat in it. The guy at the counter aske me if I wanted the hotter or cooler stat. I took the cooler. The temp guage never hardly moves. Last winter I wasn't sure if my heater was even working. Could a low temp effect the carb?
I thought that the EGR was good when I put the motor in, but I don't have a vacum pump to test it.

Posted: Sun Jul 24, 2005 9:31 pm
by ranger5.0
As cold of winters you get back there, I could see why a cooler thermostat would hardly make the heater work. The computer is design to run at the 192* or 195*. When you lower the engine temp to 180*, you need to advance the timing a few degrees to help burn more of the fuel since the extra heat of the engine is to help the fast burn desired. You will notice that most stage two chips and programmers require the use of the 180* thermostat because they extensively advance the timing to get their desired effect.