I have been having this problem for the last couple of years. I have a 89 f150 with a 302. It keeps flooding out the plugs. I have replaced both the colant temp sensor and the air vane sensor and still have the problem. When I pull the codes it gives me 21 & 24, which is the for the sensors I replaced. Could a bad MAP sensor cause the other sensors to send a bag signal. I am at my witts end with this I don't know what else to do..

 

Have you tested the wiring to the ECT, and I'm assuming the air temp sensor, since the truck doesn't have a vane sensor? Are you pulling the codes when the truck is warmed up, or when it is cold? Those codes can come up even if the sensors are good if the truck is not warmed up. MAP sensor can cause it to run rich for sure, but be certain that it is bad before you replace it since they are about $120 for a new one. On the MAP sensor, the middle wire (blue) should have 2.5V between it and the black wire when it is plugged into the sensor. There should be ~5V between the orange wire and the black wire, both those readings with the key on, engine off. I would check the fuel pressure and the fuel pressure regulator too, the diaphragm in the regulator could have burst and the vacuum line is pulling in unmetered gasoline into the intake.

 

I have checked the MAP sensor and I am getting the voltage reading that you stated I should have. Does that mean the sensor is good? If it is what else should I look at, do you know the what voltage I should have for the coolant sensor and air temp sensor?

 

If you have a vacuum pump, I'd check the MAP sensor to see how the voltage (or frequency, depending on the type of MAP sensor) varies with different amounts of vacuum. A Haynes manual should have the voltage values for different amounts of vacuum to the sensor. Just be aware, that they Haynes says the MAP signal wire (blue) should have 5V, which is incorrect - it should be 2.5V. I can't remember the voltage for the ECT and ACT, but the Haynes has resistance values for those sensors with corresponding temps. Also check the wiring to those two sensors to make sure you don't have a short somewhere.

 

how do i check my o2 sensors. They can be bad with out sending a code, I have always herd that if a engine runs rich all the time it can damage the o2's. i did replace in 1998 and they have about 20,000 miles on them.

 

You can backprobe the signal wire and check the voltage on it. The O2 sensor should switch between .4V and .7V when it's warmed up and functioning.

 

Is there a way to test the fuel presure regulator. I do not have fuel in the vacuum but could it still be bad. It doesn't tell how to test it in the manual only how to replace. Also I have narrowed down my fouling only to the passenger side cylinders. I had it started on thursday reved it up to clean it out was running on 8. Sunday morning started it and within 3 seconds it was fouled out. Only running on drivers side. pulled out passenger side plugs all fouled.. Motor only ran for 20 seconds and I shut it down. Could I have leaking injectors?

 

Could be. You can test for this and a bad fuel pressure regulator at the same time. Test the fuel pressure, both while the engine is running (if you can get it to run), and when the truck is off. For the engine off test, cycle the key on and off a few times to get the pumps to pressurize the system. Then monitor the fuel pressure and see how fast the pressure drops off after the truck is turned off. If it drops really fast, then there is a leak somewhere in the system - either injectors, or possibly fuel pressure regulator.

 

I tested the fuel presure, it droped 5 pounds in the first 10minutes then it started to tapper off to 10 pounds after 30 minutes to a total of 20 pounds after 2 1/2 hours. i would think that is a little excessive. How long should it hold presure? Now is it the injectors or the regulator. I guess I will replace the regulator any how I just will like to pin point if I could. How do you know which injector is leaking. Could pull them off the intake but keep the atached to the rail and presurize the system to see which one is leaking?

 

The pressure definitely falls off too fast. I'm not sure exactly how to pinpoint a leaking injector. I would not pressurize the system with the fuel rail dangling in mid air - I think that would be dangerous, and you could have fuel going everywhere.