Ok I did all the tests I can think of today and no problems found. My problem is I get only about 9.8 mpg, there's a strong gas smell when I start the Bronco and the tail pipes are black and sooty. I have an 86 302 EFI I just rebuilt a year ago, it is bored 60 over, I have an AOD, headers and dual exhaust, no cats and series 40 Flowmasters, there is a 3.55 posi and I run 10.50x32 15's. There is no cross over, x-pipe it is totally separate dual exhaust. O2 sensor is on the passenger side on the header collector. The only other mod is I have an MSD super coil. I have disconnected the EGR and plugged the whole, bypassed the water going thru the throttle body, and I have taken the air pump out and closed up all the ports on the head and the intake. I have run the truck with the EGR off but connected to the wires and unconnected no difference. I did an engine off and engine-running test to day with a friends code scanner one that only blinks the code. I got both a 31 and a 34 which said EGR, either a 14 or 41, 14 pip circuit, 41 hego which is O2 lean, 25 no anti-knock sensor which mine does not have so this is ok I guess, and a 77 I guess I did not do the engine throttle up part right. That's it no other codes I check the fuel pressure: engine off with pump on about 35 to 37 psi, engine running 30 psi, engine running and vacuum pulled off the regulator 40 psi. I am going crazy trying to figure this one out . I think I gave you all the info if you need more just ask, thanks for any help,

Rick
86 302 EFI, bored 60 over, AOD,
Headman Headers, Flowmaster 40 series,
2 inch dual exhaust, MSD ignition

 

Hmm, you should have an anti-knock sensor. My '88 F-150 w/ 302 had one. It's located at the rear-center of the engine, just past the lower intake manifold. Hard to see and hard to get at.

Other things to check, I would first check your timing and see where that lies. I wouldn't suspect the EGR, but why did you bypass the cooling lines to the throttle body? Air pump removal and plugging shouldn't be a problem either. You may have a bad O2 sensor, which can cause bad mileage. Could also be a fuel pressure regulator.

I would further investigate the O2 sensor and the timing as a starting point, then check the fuel pressure while driving the Bronco.

 

I don't think mine came with an anti-knock in 86. Did not see anything where your talking about when I rebuilt the motor. Might have been removed before I got truck don't know, there aren't any wires in that area either. Timing has been checked and is dead on 10 degrees before tdc with the one computer wire disconnected. I disconnected the cooling lines because it did not make sense here in Florida to be running 195 degree radiator water thru the throttle body. I may be wrong in my thinking if I am please let me know. I did all the tests the book said to do for the fuel regulator. Do you really think a road test would be different than the parked tests with the engine running? I will see if I can clean the O2 sensor if not I will see about a new one. Thanks for your input adelyser, hope this other info gives you some more to go on. Thanks for any more help,

Rick
86 302 EFI, bored 60 over, AOD,
Headman Headers, Flowmaster 40 series,
2 inch dual exhaust, MSD ignition

 

You should be fine bypassing the coolant lines on the throttle body, especially living in Florida. This is a pretty common free "horsepower gain." I see people do it on corvettes all the time.

 

You may very well not have a knock sensor. As for the coolant lines to the throttle body, I'm not sure if they would cause any problem or not, but they should help cool the TB when it's very hot out. I have never heard of anyone disconnecting them before.

I have seen and heard of others finding that the fuel pressure readings were corret when parked, but when driving, it all becomes another story. When you start driving, you start moving the fuel around in the tank, and if there is any debris at all, it an stir up and collect around the pickup screen. When you stop, it settles down to the bottom of the tank again, unless it stick or jams at the screen. You also very the load conditions of the motor as well as the rpm's, which can show problems that testing while parked won't show, even if revving the engine.

Good luck with your troubleshooting and let us know what you find.