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97 Ford F150 Running lean when hot

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New User

Jul 22, 2011, 4:02 PM

Post #1 of 3 (2600 views)
97 Ford F150 Running lean when hot Sign In

I have a 97 Ford F150 that the short term fuel supply goes completely lean at 32 and the long term goes up 32 and kills the engine. There are no negative numbers on the long term. It had a crank sensor code and I changed it but now I'm having this problem. It ran fine in the garage for 30 minutes but once I did the drive cycle test and all the monitors came on I finished the cycle and started the truck to do another drive cycle the trim went to 32 and the engine stopped running. Any ideas on what would cause this would be very much appreciated!

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 22, 2011, 5:06 PM

Post #2 of 3 (2581 views)
Re: 97 Ford F150 Running lean when hot Sign In

Reaching the lean limits will not cause the engine to quit unless it's just too lean to run. It doesn't do anything automatically. You're going to have to find out if this thing is really going lean or if the PCM is just going bonkers.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Veteran / Moderator
Sidom profile image

Jul 22, 2011, 10:39 PM

Post #3 of 3 (2568 views)
Re: 97 Ford F150 Running lean when hot Sign In

What size is the engine? What do the trims look like at cruise & full engine load?

Run some propane thru it & see what your trims & 02 look like.

Going off the little info I would have to guess a big vacuum leak but you should be able to hear that if it's killing the engine at idle....

Are getting any pending lean codes?

(This post was edited by Sidom on Jul 22, 2011, 10:39 PM)

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