Brand new motor runs but bogs down after driving a mile.

Asked by Oct 12, 2016 at 03:52 PM

Question type: Maintenance & Repair

I have an 88 bronco 2 with the 2.9 liter. It runs
great for a mile and then starts to bog down and
runs rich. I have replaced both fuel pumps, fuel
filter, distributor cap, rotor button, plugs, and wires.  
All vacuum lines are new. What else could it be?

6 Answers

Is the distance concurrent with thr speed you get to? Perhaps the carb needs adjusting to handle more fuel as youre getting up to speed. Could be as simple as the choke....

It is efi no carb


Have it scanned for codes. Could be a problem with the O2 sensor(s).


MAP sensor can cause issues also.

Funny thing is no codes are set . That's what I've been told is those 2 sensors by a couple people. Might as well change them everything else is brand new. Thanks.


It could be in the KOER test, and yes the MAP and O2 sensors are high fail on these, you may also want to check the resistance readings of the ACT and ECT sensors just to make sure they are not out of specs, I've seen these go wacky but set a trouble code or light.

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Maintenance & Repair Experts

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    Tom Demyan
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