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offrdmania 01-25-2016 03:19 PM

Heavy Miss When Warm
92 F150, 5.0 automatic. When the truck is cold first thing in the morning it runs fine. Once it gets up to temp it gets a really bad miss no matter what the temp is outside. It has yet to die though, just runs super rough and doesnt smooth out when accelerating. I dont find any vac leaks and no CEL. Recently got new plugs, wires, cap, coil and the EGR was recently cleaned. Ran fine after parts replacement and then one day it started running rough out of the blue. Any ideas?

Lead Head 01-25-2016 06:55 PM

I'd check what your fuel pressure is doing when it's warmed up. Smooth cold starts, but rough when warm make me think coolant temperature sensor, however. Oxygen sensor is another possibility too.

88XLTLariat 01-25-2016 07:14 PM

Like Lead Head said, change your O2 sensor. My 88 with 5.0 had the exact symptoms of your truck. I found a Denso O2 sensor on EBay for $19 with free shipping. Removed, replaced, and truck is running good again.

offrdmania 01-25-2016 09:55 PM

Was your truck missing with the bad o2 sensor? Im smelling raw fuel out the pipe so I know all cylinders arent firing

88XLTLariat 01-25-2016 11:53 PM

Yes, more of a surge. Faulty O2 sensor can cause truck to run too lean or too rich.

offrdmania 01-26-2016 09:19 AM

Mine doesnt surge, it is a definite miss. I can watch the tach jumping up and down when sitting at idle

88XLTLariat 01-26-2016 05:10 PM

You might check the PIP sensor (stator) in the distributor for faults or the ECM for leaking capacitors. What brand name cap did you install?

phnguyk 01-26-2016 06:13 PM

TPS sensor.

Failing Injector, my '92 was driving me nuts. It was a handful of things. TPS, manifold temp sensor, and two bad injectors.

88XLTLariat 01-26-2016 06:38 PM

Good call. TPS & IAC would be a good place to start. Easy to test or replace.

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