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engine problems

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Old Apr 12, 2009 | 09:29 PM
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engine problems

i have a 88 f150 with a 300 straight 6. i had just recently locked the motor in it so bought another motor and put it in. it cranks up great everytime. sometimes it idles up and down and other times it idles perfect. when driving down the road sometimes it runs flawless and other times it will cut out and miss to the point it almost feels like it died out and came back. it has a new coil, plugs, wires, rotor, cap, internal fuel pump, booster fuel pump, fuel filter, tps, and ignition control module. was wondering if somebody might have any ideas. i have also blocked the egr off and bypassed the a.i.r. injection system. im kind of leaning towards the computer but not sure.
 
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Old Apr 13, 2009 | 04:03 AM
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I would check for vacuum leaks. Check the vacuum pipes around the engine for breaks and cracks. Check the crankcase vent system for leaking pipes. Might be worth checking the fuel pressure. And finally I would pull any stored error codes, ignore any due to the EGR valve.
For instructions go to fordfuelinjection.com and click on OBD1 self test.
Lots of other good info on there also. Hope this helps.
 
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Old Apr 13, 2009 | 04:23 AM
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every vaccum has been eliminated from the motor except for four and i traced it all and have no leaks and the fuel pressure is to factory spec at the rail.
 
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Old Apr 13, 2009 | 04:30 AM
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check vaccume to your map sensor. make sure your vaccume to your heater is not hooked in the same line, if it is the truck will run as you discribe every time you use the heat/a/c
 
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Old Apr 13, 2009 | 04:43 AM
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Originally Posted by dustybumpers
check vaccume to your map sensor. make sure your vaccume to your heater is not hooked in the same line, if it is the truck will run as you discribe every time you use the heat/a/c
Very good point.
Did you pull the codes yet?
 
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Old Apr 13, 2009 | 03:41 PM
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i just went and checked and the vaccums are separate. i havnt been able to pull the codes yet since the guy that has the computer hasnt answered me back on when to bring the truck to his house. can the idle air control valve or the knock sensor cause any of this?
 
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Old Apr 14, 2009 | 07:32 AM
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Originally Posted by cooney89
i just went and checked and the vaccums are separate. i havnt been able to pull the codes yet since the guy that has the computer hasnt answered me back on when to bring the truck to his house. can the idle air control valve or the knock sensor cause any of this?
You don`t need a computer. Go to fordfuelinjection.com for instructions on pulling codes using the check engine light. Plenty of good info there on sensors also.
 
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Old Apr 14, 2009 | 10:51 AM
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i know how to do the self test and when i try it starts to give a code and goes blank or the engine light will stay on so i know i either have a grounding problem or the computer itself is bad
 
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Old Apr 14, 2009 | 02:37 PM
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I think you found the problem then, if you can't access the computer, it can't function proprely.go over your grounds, especially the one on top of left fender, that one goes right to the computer
 
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