1988 Bronco II is bogging down.

[AlaskaBronco]

This is an odd one. I bought a Bronco II 1988 4x4. Runs great, idles great for about 10-15 minutes.
At that point, it starts to bog down. It behaves as if there is a fouled plug/gummy injector/bad gas/mixture issue. It will bog down and periodically "surge" back to normal power output. It will still run, idles fine, and never dies. It's just only getting the proper gas/spark about 60% of the time. If I shut it down and let it cool for a couple of hours, it runs perfect again..............for another 10-15 miles.

It's not a temperature thing. Temp gauge is warm and stable by 5 miles, and it still runs great at that point.

I can't figure out what would cause it to behave this way after running for a while, but not affect it at all for the first few miles. It's terribly annoying.

Is is a computer thing? Something to do with emissions?

I've replaced the plugs, wire, distributor/cap.

Something to do with the coil perhaps?

I'm flummoxed.

[bronco_lou]

Have you pulled any codes from the computer yet?

[drofman]

check the fuel pressure. have you replaced your fuel filter? if you check your fuel pressure at least you'll know it's not a fuel delivery problem and go from there.

[Daehtop]

i was gonna ask that same question. have you had any luck yet?

[Daehtop]

so my 86 fully crapped out and now it wont fire. it just turns over. i started it this morning and it idled nice for a bit then started to sputter and bog down. not it just wont fire. i know my inline pump is good. before it would run like that randomly and then clear out and run perfect. anyone out there got some help?

[Ranger Dave]

this thread is about a 1988 Bronco II is bogging down

[KRE]

If you believe the TFI is the issue, unplug the sprout connector, check base timing, with the engine hot. Reinstall the sprout and start the engine, check timing and record at idle an 2K RPM. If you don't know what it should be,(with the sprout installed) drive the truck until it acts up, recheck timing at idle and 2K RPM if theres a major change replace the TFI an trigger assy.

[AlaskaBronco]

Hey Y'all!

Dug through the forums and found someone discussing the ECT sensor. My engine temp gauge was working fine, so it simply didn't occur to me that there was a separate sensor for the computer. It was dumping a cold engine's worth of gas into a warm engine, running rich as it were.

It was a bear.........Not enough clearance to get a socket around it and very hard to get a wrench around it due to location, but replaced.
Been running well since then. Gotta love the $15 fix.

Thanks!

[swan8706]

it's not just wont fire