5.0 WoesI have a '94 GT with a 5.0 and a five-speed that has some driveability issues. About a year ago, the Check Engine light would come on intermittently while driving. It seemed to happen on hot days in Atlanta. When the light came on, I would get out my code scanner to see what the problem might be. Consistently, I came up with codes 181 and 189, of which the shop manual says: "HEGO sensor not switching-indicates lean during part throttle engine operation on banks one and two." This coincides with what I was doing when the Check Engine light came on-usually pulling away from a stoplight, shifting somewhere between 2,000 and 3,000 rpm. The first thing I did was change the fuel filter, since the way I read the code did not indicate a problem with the oxygen sensor. That didn't do it, and to make matters more complicated, now I occasionally get code 556, meaning "fuel pump relay-primary circuit failure."
I have talked to a few people, and no one can figure out whether it's the fuel pump going bad or the fuel-pump relay. I am hoping it's the fuel pump, as the relay, according to my service manual, is part of several switches mounted underhood; it looks like it can't be replaced by itself. Would the whole unit have to come out? It sounds expensive to me. Since no one is able to pinpoint the exact problem without me leaving my car and bank account at a stranger's disposal, I'm not sure what to do. Any ideas?Michael RingleMonroe, GA
I spoke with the guys at Xtreme Mustang Performance (949/305-6550, www.x-m-p.com) since they work on pretty much nothing but 5.0s and 4.6s. Shop proprietor Eric Cheney had this to say about your car: "Codes 181 and 189-as your manual states-means the car is running lean at part-throttle conditions. More specifically, code 556 is usually related to the fuel pump. Code 556 also means the processor is sending voltage to the pump, but the pump isn't returning that voltage.
"Simply replace the fuel pump. As the pump ages and weakens, its motor is building up too much resistance in the wire, and the lean condition also means the pump isn't really keeping up with demand, even under part-throttle conditions. Recall codes 181 and 189 refer to a lean condition.
"As far as the integrated relay control module (IRCM), it's probably fine and doesn't need to be replaced. Also known as the constant control relay module (CCRM), it's part of the electrical circuit for the fuel pump, ignition, EEC computer, fan control, and A/C circuit."
XMP also recommended that when you replace the pump, upgrade to a higher capacity unit in case you add performance upgrades later. A 155 or 190 lph unit would be the best choices. Also, remove and clean your oxygen sensors (or buy new ones). This will also help the car run better once the new fuel pump is installed.
Fox Open-TrackerI have a '90 GT that I drive at open-track events. I have the basic engine upgrades: no air silencer; K&N air filter; a 75mm mass-air meter; a 65mm throttle body; Cobra intake; 1.7:1 roller rockers; adjustable fuel-pressure regulator set at 44 psi; underdrive pulleys; and an offroad X-pipe. I also have several suspension and brake upgrades.
My question pertains to the coolant-overflow container. While running on the track, the coolant level can go about 1 inch above the hot line. This allows the coolant to splash out the vent hole. While it may not be important to some, my car is also a show car. This means after each session, I must wipe down the engine compartment. Can this vent hole be capped with duct tape while at the track? Does the system need the vent hole? Can another coolant overflow container be connected to the current overflow container via the vent hole? Are there any options other than switching out the factory radiator for a three-row aluminum radiator?Shawn HuffmanVia e-mail