4.9L stumble
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Joined: Dec 2005
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4.9L stumble
Hey guys,
I'm new to the site and I have a question about a stumble/hesitation in my friends 91 F150. The truck has the 300 (4.9L) six, the stumble/hesitation happens just off an idle if you just touch the throttle. When the truck is cold, you could make the truck stall by just touching the throttle. When the truck is warm it just stumbles as if there is a flat spot in the throttle. I'm thinking it might be the throttle position sensor or may be a dirty throttle body. Just wondering if anyone has had a similar problem. The check engine light does come on but only for a few seconds and then goes out, but only at random times. I have a diagnostic computer, but because the check engine light doesn't stay on I can't read any trouble codes. Any suggestions would be greatly appreciated.
I'm new to the site and I have a question about a stumble/hesitation in my friends 91 F150. The truck has the 300 (4.9L) six, the stumble/hesitation happens just off an idle if you just touch the throttle. When the truck is cold, you could make the truck stall by just touching the throttle. When the truck is warm it just stumbles as if there is a flat spot in the throttle. I'm thinking it might be the throttle position sensor or may be a dirty throttle body. Just wondering if anyone has had a similar problem. The check engine light does come on but only for a few seconds and then goes out, but only at random times. I have a diagnostic computer, but because the check engine light doesn't stay on I can't read any trouble codes. Any suggestions would be greatly appreciated.
Posting Guru
Joined: Jun 2004
Posts: 1,781
Likes: 1
From: Central NY
Since the CE light comes on, its time to pull the codes and see what its trying to tell you. Visit www.fordfuelinjection.com to learn how using just a paper clip and coounting CE blinks, see if your local parts store willpull them for you for free, or buy a reader for about $30.
It also could be leaking vacuum lines/canisters, bad throttle position sensor, or the Idle air controller.
A Haynes or a Chiltons manual $15 would list testing procedures for all of the sensors.
Cheers,
Tim
It also could be leaking vacuum lines/canisters, bad throttle position sensor, or the Idle air controller.
A Haynes or a Chiltons manual $15 would list testing procedures for all of the sensors.
Cheers,
Tim
