I have a 1995 Ford Bronco (5.7 ECC-IV) that will occasionally start (hot of cold). The trick to starting is to crank for 2 seconds and let off the key and sometimes it will catch. When it does start, it idles fine but bucks and bakfires under load. Sometimes this will clear up and it will run fine (10 miles) then start bucking again. New plugs, wires, cap, rotor, air cleaner, fuel filter. The other day, I could not even start moving from a stop sign. I then started depressing the gas pedal about 1/8 inch every 10 seconds. Got it up to about 5500 RPM and 80 mph, let off the gas, depressed the gas pedal half way and it started bucking and backfiring again. I suspect the timing advance is not functioning correctly. Is this taken care of entirly by the PCM? I can get the truck to start if I move the distributer about 1/2 inch CCW, then move back to smooth out the idle. ANY IDEAS??????

 

EEC IV has been know to have problems with high energy Ign wires transmitting to the Signal wires going into the distributor. The Dis. wires have to cross any plug wires at 90 Degrees or the energy pluse from the secondary transmits to the primary wires and scrambles the timing. I bet when you move the Dis. by 1/2 rotation you change the aspect of the wiring enough to stop the interference. Then when you move it back to get the proper base timing the wires also get too close and the interference starts. I would first check to see if your primary wires are running parallel to the secondary. If they are even close to doing this I would pull the dis, rotate it so the wiring is in a 90 degree orentation., and change the wires on the cap to compensate for the dis. change. I had an earlier EEC IV that ran fine for quite some time and then on day started having the same trouble. never touched it under the hood. just one day it decided it didn't like the way the wires were run. Finally found a TSB about it after doing all the same tune up stuff you mentioned.

 

Just to make sure, but have you checked for codes?

 

I'll look at the primary/spark plug wire orientation tonight.

The only code present is I believe a 33, EGR not responding.

 

You did install the wires in the correct firing order for 5.8l/351.(been there and done that, that is why I ask)

Like the above post says, the wires have to follow a certain path. I think on that model there is a sticker on the hood or radiator cover. Like post said. If the correct path is not followed it will have major interference.

Another thing is if your mileage is around 120K, you may want to change your timing chain.

Try and get it on a scanner, and check for codes.

Fuel pump and filter is a good thing to check too.

Good luck,

Mike

 

Since it is from your initial gut response, check for spark timing advance. Hook up a timing light and note where the timing is (should be around 10BTDC). Increase the throttle speed and see if it is advancing. If not, check to make sure the SPOUT line did not come loose.

Be sure about your codes. The EGR does not open at idle but does at part throttle, so that may be related to your problem. Check to make sure that the EGR pintle is moving up and down with a goose of the throttle.

 

OK Here it is.

Hooked up the timing light to check advance. When opening the trottle very slowly, the advance worked fine. When I would open the throttle at a rate of simulating taking off from a stop, the timing light would go dark. NO SPARK WHATSOEVER. Open throttle slow = spark, fast = no spark. Replaced the coil and everything is fine. Explain this one to me please.