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What else could it be 94 bronco

923 Views 6 Replies 5 Participants Last post by  miesk5
Just replaced 302 with a new 302.

runs rough when accelerating, idles fine though, loss of power, Exhaust manifold gets red hot.

What I've tried to fix it:
Adjusted timing even took it to a shop to ensure it was right, removed cats, sprayed carb cleaner around intake while running to make sure the intake was not leaking, new plugs, wires, distributor.
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Red hot manifolds usually means lean fuel mixture and/or retarded ignition timing. I assume this engine is EFI? You may have misfire(s). You say it idles fine but is sluggish when accelerating. I would double check your timing, plug wires ran correctly according to firing order, each spark plug is firing, each injector is good, and fuel pressure is good.

If your fuel mix is lean, you could have non firing injector(s), bad O2 sensor, or maybe a bad fuel pressure regulator.

Check this - let it idle with the hood up and watch the engine. Is it shaking at all? If you manually give it slight throttle, does it stumble and shake? If so, you have a misfire and are not running on all 8 cylinders most likely.

Assuming your plug wires are routed correctly, your distributor was stabbed correctly, and you have fire to all the plugs, check timing. Pull the spout connector and set to 10° BTDC.
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double check all the sensor connections as well as ensure no vacuum leaks in intake track or distributor.
Thanks I'll check it all out tomorrow and get back with you guys
What year is your rig?

Never Mind, I see my error.
Did you happen to check your timing in relation to #1 cylinder & T.D.C.?
(Possible slipped tooth / Slack timing chain / Bad Dist Gear)
Yo 94BroncoUSMC,
WELCOME Devil Dog!

Try a Self Test for Diagnostic Trouble Codes by my pal, BroncoJoe19 @ Code Reader.....

See this Vacuum Gauge Diagnosis @ 1996 Bronco/F-Series
Includes possible Leak's in HVAC System in cab as well as underhood.
Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

Other perps are:
Fuel quality; Oxidized fuel often turns darker over time and may even smell sour. You can check stored gasoline by pouring some into a clear glass container and comparing it side-by-side with known fresh gasoline. If your old sample looks noticeably darker than the fresh gas, you have strong evidence the gas has gone bad.

Electrical connectors; inspect for corrosion, etc at firewall connectors, PCM, etc.; especially those with broken locking tabs.


Find out if speed control, if equipped, recall work completed by a dealership. Call local dealer or register and view status @; or @ Recalls Look-up by VIN (Vehicle Identification Number) ... have VIN ready.
To confirm current status, use this guide by jowens1126 @ 93 & 94-96 Cruise Control Recalls Repair
note that the 93 recall is different than 94-96

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1994 Bronco Brochure, Partial; Cover & Page 3; plus pics of EDDIE BAUER model accessories.
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