302 missing under load
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Elder User
Joined: Jul 2012
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From: Poplar Bluff, MO
302 missing under load
96' f150 302 4x4, only mods are headers and cold air intake. I have replaced plugs, wires, cap, rotor, and coil. has new alternator too. I can have it in park and neutral and rev it all day long and it wont miss.. But under load especially going up hill it will miss.. Any ideas?
Moderator
Joined: Aug 2002
Posts: 6,104
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From: Southern California
1. check plugs, wires, cap, rotor, and coil...even if new they can be bad...especially the wires
2. remove the cai....and you might even have to replace the intake sensor due to contamination
2. remove the cai....and you might even have to replace the intake sensor due to contamination
Lead Driver
Joined: Sep 2003
Posts: 7,018
Likes: 210
From: SoCal
Did you run an EEC diagnostic to see what kind of error conditions it may have detected?
Some other things that can cause missing under load:
A vacuum leak. If your engine compartment has lots of those thin plastic vacuum lines like my 87 Mustang, a lot of them could have cracked due to heat and age.
A faulty throttle position sensor. I came across one of these when the owner complained of the car missing and stumbling while trying to climb a hill; the same hill every time would cause the problem. The EEC diagnostic showed a couple of symptoms, and we went with the cheaper fix. The TP sensor was like $30, and it fixed the problem.
Some other things that can cause missing under load:
A vacuum leak. If your engine compartment has lots of those thin plastic vacuum lines like my 87 Mustang, a lot of them could have cracked due to heat and age.
A faulty throttle position sensor. I came across one of these when the owner complained of the car missing and stumbling while trying to climb a hill; the same hill every time would cause the problem. The EEC diagnostic showed a couple of symptoms, and we went with the cheaper fix. The TP sensor was like $30, and it fixed the problem.
Moderator
Joined: Aug 2002
Posts: 6,104
Likes: 384
From: Southern California
Did you run an EEC diagnostic to see what kind of error conditions it may have detected?
Some other things that can cause missing under load:
A vacuum leak. If your engine compartment has lots of those thin plastic vacuum lines like my 87 Mustang, a lot of them could have cracked due to heat and age.
A faulty throttle position sensor. I came across one of these when the owner complained of the car missing and stumbling while trying to climb a hill; the same hill every time would cause the problem. The EEC diagnostic showed a couple of symptoms, and we went with the cheaper fix. The TP sensor was like $30, and it fixed the problem.
Some other things that can cause missing under load:
A vacuum leak. If your engine compartment has lots of those thin plastic vacuum lines like my 87 Mustang, a lot of them could have cracked due to heat and age.
A faulty throttle position sensor. I came across one of these when the owner complained of the car missing and stumbling while trying to climb a hill; the same hill every time would cause the problem. The EEC diagnostic showed a couple of symptoms, and we went with the cheaper fix. The TP sensor was like $30, and it fixed the problem.
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
Another possibility could be a malfunctioning EGR. If the EGR vacuum solenoid is allowing vacuum to pull the EGR valve open at wrong time, it could also cause a miss.
Just another possibility...but none of this is relevelant if codes haven't been pulled to pinpoint the problem.
Just another possibility...but none of this is relevelant if codes haven't been pulled to pinpoint the problem.
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Joined: Jul 2012
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From: Poplar Bluff, MO
thanks fellas, the truck is parked/wrecked.. goto the 87-96 f150 forum and search f150 w/blackeye.. That's my project thread. Im rebuilding it and am doing all labor my self so you guys would really help me!! so this is me begging for y'alls input in that thread..
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Elder User
Joined: Jul 2012
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From: Poplar Bluff, MO
well I wish you woulda said that yesterday lol I've already dropped the tank, I bought this from oriellys Spectra Premium F1G1FA - Fuel Tank | O'Reilly Auto Parts
Guy offered me 100$ for my tank and pump as it sits, should I take that $ and run?
Im hoping once I get that installed it will run better.. any other ideas?
Guy offered me 100$ for my tank and pump as it sits, should I take that $ and run?
Im hoping once I get that installed it will run better.. any other ideas?
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Joined: Apr 2013
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id be willing to bet your timing is off. my 351 was missing under load right at around 2k rpms. i was going to replace my ignition components anyway with MSD so i put in the MSD coil, cap,rotor, and 9mm ford racing plug wires, and new spark plugs. it was a little better but still there. checked my timing and BAM! it was at 3 degrees btdc and stock on the 5.0 and 5.8 is 10 degrees btdc. so check that out cuz once i set it back to 10 it felt like a whole new truck. tons more power. SO CHECK YOUR TIMING YOULL BE AMAZED LOL
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