89 F150 problem stumps me+a team of mechanics?
#1
89 F150 problem stumps me+a team of mechanics?
I've posted before about my misfire problem and after extensive searching, checking, and replacing near every sensor in the truck I have to my witts end on what is at fault. I've got a code 31-EGR position sensor below minimum voltage. My symptoms are a rough idle, a misfire when over ~half throttle, and the engine stumbles and near dies at WOT.
So far I've changed out the EGR valve, EGR position sensor, O2 sensor, Throttle position sensor, and coolant temp sensor. I've also checked voltage to the EGR position sensor and as vacuum is applied, the voltage does change HOWEVER the voltage is not consistent with a diagram I printed off Alldata (our schools online chilton's guide to every vehicle), it is reading above what it should. I was told that this wouldn't cause the problems, but it still worries me.
I had the truck in a local shop where he suggested either the O2 sensor was faulty or the injectors were dirty. I pulled and cleaned the plenum and injectors spotlessly along with doing a ignition tune-up and replaced the 02 sensor. I'm a student at Linn state technical college and have been lucky enough to get the truck in mechanics shop where they found today that the voltage from the 02 sensor was inconsistent with normal readings and that they are going to be searching for ground issues or a break in the wire harness.
I have free time tomorrow and was hoping to get in the shop and check the ground wires and test continuity from the EEC to the sensors and grounds, however I can't find a diagram anywhere on Alldata or on the internet on where the ground wires are.
Does anyone here have any suggestions on what else to check out or have a diagram of where I can find all engine grounds?
So far I've changed out the EGR valve, EGR position sensor, O2 sensor, Throttle position sensor, and coolant temp sensor. I've also checked voltage to the EGR position sensor and as vacuum is applied, the voltage does change HOWEVER the voltage is not consistent with a diagram I printed off Alldata (our schools online chilton's guide to every vehicle), it is reading above what it should. I was told that this wouldn't cause the problems, but it still worries me.
I had the truck in a local shop where he suggested either the O2 sensor was faulty or the injectors were dirty. I pulled and cleaned the plenum and injectors spotlessly along with doing a ignition tune-up and replaced the 02 sensor. I'm a student at Linn state technical college and have been lucky enough to get the truck in mechanics shop where they found today that the voltage from the 02 sensor was inconsistent with normal readings and that they are going to be searching for ground issues or a break in the wire harness.
I have free time tomorrow and was hoping to get in the shop and check the ground wires and test continuity from the EEC to the sensors and grounds, however I can't find a diagram anywhere on Alldata or on the internet on where the ground wires are.
Does anyone here have any suggestions on what else to check out or have a diagram of where I can find all engine grounds?
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Thanks for the link adrianspeeder! I did a lot of research on that website today and it had some great data on it.
After reading through it, I wanted to test my MAP sensor but I don't have a multimeter that reads hertz. I unplugged the electrical plug from the sensor and the truck idles perfectly and the RPM's dropped much quicker when revved than when it was plugged in. It was the best the truck has run for months. Would this be a sign of a bad MAP sensor?
After reading through it, I wanted to test my MAP sensor but I don't have a multimeter that reads hertz. I unplugged the electrical plug from the sensor and the truck idles perfectly and the RPM's dropped much quicker when revved than when it was plugged in. It was the best the truck has run for months. Would this be a sign of a bad MAP sensor?
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Hmm, I've done it before, but needless to say the guys at the parts counter know me well. When I have a bucking\surging\backfiring problem I tried a new MAP sensor and it didn't do anything for it, so I took it back. Later I found out that my distributor shaft bearings were bad causing the distributor\rotor to drag.
#14
Your symptoms sound similar to mine booba5185 with the bucking and surging. Is it possible to regrease distributor bearings? Even if its temporary fix, it will single out my problem before dropping more money and pulling the dizzy.