kaidenshi
New member
- Joined
- Jul 13, 2016
- Messages
- 4
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- Vehicle Year
- 1988
- Vehicle
- Ford
Hey folks, I've been having a weird issue I hope you can help with. 1988 BII with manual and 4x4, replacement 2.9L engine with 30k miles pulled from a wrecked 1986. The issue only shows up in cold weather (less than 60 degrees), in warm weather it runs fine. What's happening is it will start but immediately bog down and run rough, like it's not timed right or it's misfiring constantly. It's a steady "thrum, thrum, thrum" like a cammed big block Chevy. Eventually the truck will warm up to operating temperature and it will suddenly run fine. If I try to drive it while it's bogging like that it barely moves and backfires like mad. Once warmed up it drives like it should. In warm weather, I can start it and it never bogs down, and I can drive it immediately with no issues.
I've replaced a ton of parts over the last two years I've been restoring it, including most sensors and the IAC. Whole new exhaust system including O2 sensor and cat, new ignition system -- plugs/wires/coil/TFI/battery/starter/alternator, everything except the distributor itself and it has a new cap and rotor. In fact, I had tried replacing the distributor but the new one never worked no matter how many times I installed it, yet the old one worked fine. New cooling system including radiator, hoses, cap, thermostat, coolant temp sensor, and water pump. New fuel tank and sending unit/pump, new injectors, new fuel pressure regulator.
I'm thinking it has to be an electrical issue, two things are pointing me to that. One, the alternator is the last part I've replaced and when I replaced it, it improved but did not completely get rid of the issue. Before the new alternator, it would bog down immediately after starting and not run correctly until warmed up. With the new alternator, it starts and runs fine for a minute or two before bogging down, then running fine again after warming up. Two, when it's running rough and I turn on any power draw that runs through the chassis electrical system (headlights, turn signal, windshield wipers, heater blower) it bogs even worse and sometimes dies. Once warmed up, power draws don't affect it. Any power draw that runs directly off the battery (LED light bar) doesn't affect it at all.
I haven't yet tried the engine management computer, and I've found and fixed a couple of brittle/broken wires in the engine wiring harness with no change in performance. This gremlin has me pulling my hair out and wanting to get rid of the Bronco, but I would rather fix it and drive it than let it go. If anyone has any ideas I'd be grateful.
I've replaced a ton of parts over the last two years I've been restoring it, including most sensors and the IAC. Whole new exhaust system including O2 sensor and cat, new ignition system -- plugs/wires/coil/TFI/battery/starter/alternator, everything except the distributor itself and it has a new cap and rotor. In fact, I had tried replacing the distributor but the new one never worked no matter how many times I installed it, yet the old one worked fine. New cooling system including radiator, hoses, cap, thermostat, coolant temp sensor, and water pump. New fuel tank and sending unit/pump, new injectors, new fuel pressure regulator.
I'm thinking it has to be an electrical issue, two things are pointing me to that. One, the alternator is the last part I've replaced and when I replaced it, it improved but did not completely get rid of the issue. Before the new alternator, it would bog down immediately after starting and not run correctly until warmed up. With the new alternator, it starts and runs fine for a minute or two before bogging down, then running fine again after warming up. Two, when it's running rough and I turn on any power draw that runs through the chassis electrical system (headlights, turn signal, windshield wipers, heater blower) it bogs even worse and sometimes dies. Once warmed up, power draws don't affect it. Any power draw that runs directly off the battery (LED light bar) doesn't affect it at all.
I haven't yet tried the engine management computer, and I've found and fixed a couple of brittle/broken wires in the engine wiring harness with no change in performance. This gremlin has me pulling my hair out and wanting to get rid of the Bronco, but I would rather fix it and drive it than let it go. If anyone has any ideas I'd be grateful.