89 Bronco Dies Under A Load

[peteinmd]

My 89 Bronco XLT slowly begins to quit when under a load ( climbing steep hills, pulling trailers or pushing snow) until it finally just dies and leaves you stranded. Driving down the highway it seems fine until you encounter a long hill. When you try to start it, it acts like it is very, very hard to turn over, almost like it has seized up. The temperature is fine, the oil pressure is great and the voltage is perfect. After about an 1/2 - 1 hour it will start right back up and purr like a kitten. It starts out hesitating and feels like something is holding it back. With your foot to the floor it just begins to die. I have just replaced the motor with a new crate engine since the old one had a lower end knock. I had the problem before the swap, so I assumed it would go away with the new engine. Not so! Here is what I have replaced so far: (engine, EGR Valve, EGR solenoid, rebuilt entire distributor, ignition module, coil, cap, rotor, plugs, wires, fuel pump in tank and new tank as well, new exhaust from motor back including cat. converter, reset timing to 10 BTDC). I can't imagine what would make a motor feel like it was practically seizing up, shut down, then purr like a kitten after it starts back up without overheating or ever losing oil pressure. I was wondering if the transmission or torque converter could fool me into thinking it was a runability issue? Any help would be greatly appreciated. I am lost for ideas.

 

[BigNasty]

The biggest ideas that come to mind is back pressure in the exhaust or a leaky vacuum line from the transmission or a clogged/partially clogged fuel filter.

I know yousaid the exhaust was replaced form the engine back, but did you use a new muffler as well?

And it is possible, but unlikely that the new cat has failed or broken up and is partially clogging the pipe.

I doubt that is the issue though.

Did you replace any or all of the vacuum lines when you installed the new engine?

Did you change the fuel filters when you changed the tank and pump?

 

[Justshootme84]

That does sound like a fuel delivery problem, so i would do a pressure test on the HP pump mounted on the framerail. Also check the relay.

 

[indoz]

Since you experienced the same problem on your old engine, just a question.Do you block off your vscuum line when you set your timing? You could also try setting your timing at 7' BTDC

 

[carlos74]

don't forget to check for clogged injectors!

 

[cjmy]

replace your fuel pump relay switch if that doesnt work replace the pcm my friends bronco had same symptoms it was the computer.