1991 5.0L F-150 Engine Lope: Symptom & Solution - Ford F150 Forum

Russ Trotter · 11-20-2009, 10:09 AM

Symptom: Engine began loping / missing wildly after 20 minutes of operation. Lope was so consistent after 20 minutes that you could set
your watch by it. Got progressively worse over 2-3 weeks until it would start acting up very shortly after start-up and couldn't drive truck at all.

Solution: First checked out the usual suspects (ignition, fuel, etc.)
Checked voltage to all sensors (OK). Unplugged MAP sensor and
loping immediately ceased, engine smoothed out. Replaced MAP sensor
and truck now runs great. Noted that the MAP sensor malfunction
did not trigger an error code, even though it was defective? Maybe it must completely fail first, I don't know.

Kphyle · 11-20-2009, 01:33 PM

this is good to know. I have the 5.0 but in a 93. mine has been starting to do the same kind of "loping" but it isn't very serious. it comes and goes as it pleases, and doesnt bother me that much.

but I'll give this a try.

thanks!

Kphyle · 11-20-2009, 01:41 PM

i have one question though. you said you unplugged your map sensor then replaced it.

replace meaning you got a new one, or just put the old one back in?

thanks.

(oh and i meant 1992, not like it matters)

Russ Trotter · 11-23-2009, 08:56 AM

Sorry, I was trying to give a concise description. What I meant to say was that I replaced the MAP sensor with a new one (~$60.00).