Truck specs: 1990 Bronco, 5.8L EFI, E4OD. When I drive the truck down the road if I'm cruising and accelerate it back fires. Then the check engine light comes on. I went to hook up the scanner and the scanner says unable to read data from the vehicle. I tried it on both tests and no luck. I have another computer and installed that thinking the computer was bad and the scanner wouldn't read it. Same problem. I will check the base timing and see if there is power on the EEC plug. Anyone have any idea of where to start on this? Thanks in advance, James.

 

ok well sounds to me like your scanner might not be working properly. go to Ford Fuel Injection has instructions to pull codes with out using a code reader.

the backfire sounds like a timing issue. make sure the engine is warmed up, pull spout connector and check base timing with a light. it should be at 10* btdc. if that checks out reinsert the spout connector. I would then look at a bad coil, plugs, plug wires, cap/rotor. so if a tune up hasnt been done in awhile now would be a good time. I would then do a fuel pressure test.

 

If it isn't the scanner, maybe it's the plug for the scanner (actually i think this is a more possible culprit, as it's always on the "under the hood" harsh enviroment).

 

The wire for the dash check engine light passes through the under-hood connector so at least some of it is working.

 

Try the "paperclip" method of running the tests. This way you don't need any external devices to get the codes. Sounds like the STI connector lost negative (ground) connection. If the paperclip trick fails, the problem is most likely at or near the STI connector.

 

Ok, as far as the tune up. It's an engine I installed a few months back fresh from a running bronco. When I installed the engine I warrantied the cap, rotor, wires, distributor, and base. I also installed some new motocraft copper resistor plugs. The cap is brass and all is borg warner. Plus I installed a new coil since the original was rusty. After the bronco sat for a few months I discovered the fuel pump had failed. I removed the tank and replaced the sending unit, fuel pump, and tank. I think I checked the timing back then, but will double check it. I will also set the engine at tdc and make sure the piston is there in case the balancer has slipped. As for the EEC plug I had to replace it because the EEC in wire was bare and figured the best course of action was to replace the connector. I did do the self test tonight and the check engine light is flashing with the test. So that indicates my scanner is not working. So checklist tomorrow is 1.Check harmonic balancer and verify it hasn't slipped. 2. Check base timing with spout connector unhooked 3. Try the new scanner I ordered in for testing at my store. Thanks for all the suggestions. Everyone on this forum is always a real help. I hope to have my bronco legal by the end of the week.

 

Make sure you have the engine at normal operating temperature when you set base timing! Sounds like you are on the right track. Let us now what happens.

 

The timing was 10 degrees off. I set it at 10 btdc, but I am still having problems reading the computer. The ground on the EEC connector is good. There is a wire that is dead on the connector though. Does anyone have the pin out for the EEC IV connector?

 

There are several of them available... I haven't done one of my own and everything else is copyrighted. I suggest an image search for "EEC-IV self test connector". This yields quite a bit of information.

 

I talked to a mechanic today and he said that the pin with no voltage is not used. Although, I did find a figure that indicates it is the pin that a test light can be hooked to to test for codes if the check engine light is burnt out. I am going to put my fan clutch on and drive her down to a friends shop where he will let me use his snap on scanner. If that fails I may just have him help me look at it, but first I will get a refurb computer. It is sitting at work and would only take a few minutes to plug up. Then I will be sure that the computer is good and it is a wiring issue, both computers are 20 years old after all.