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F 150 idel issues


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taderchip
New User

Apr 26, 2014, 8:29 AM

Post #1 of 7 (1224 views)
F 150 idel issues Sign In

86 f150 EFI starts up and runs for 5 mins and starts having idle issues and dies then hard starting


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 26, 2014, 8:53 AM

Post #2 of 7 (1214 views)
Re: F 150 idel issues Sign In

Which engine? The 300 six (4.9L) was known for stretching head bolts that were early for "turn to torque" and might be just right when cold then not when warm and screwed up like a bad head gasket then show nothing wrong when/if checked cold.


There's about 1,000 other reasons too so some checking is in order of what and why it does that. Those head bolts BTW would have been done by now so unlikely that and the 5.0 V8 didn't do that,


T



Discretesignals
Ultimate Carjunky / Moderator
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Apr 26, 2014, 9:20 AM

Post #3 of 7 (1207 views)
Re: F 150 idel issues Sign In

What is the fuel pressure at when the engine stalls or doesn't want to start?





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taderchip
New User

Apr 26, 2014, 9:38 AM

Post #4 of 7 (1205 views)
Re: F 150 idel issues Sign In

I'm sorry . its a302


taderchip
New User

Apr 26, 2014, 9:45 AM

Post #5 of 7 (1198 views)
Re: F 150 idel issues Sign In

I don't have a pressure tester at this time . but it is now idling high


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 26, 2014, 9:47 AM

Post #6 of 7 (1197 views)
Re: F 150 idel issues Sign In

OK: Let the testing begin. IMO these engines didn't have super common issues mechanically so get the fuel pressure or any test observations WHILE it does this so be ready for quick testing.


1. Fuel pressure as just mentioned.


2. May want to check lash on timing chain if not known done already it's late. Just watch distributor rotor while turning engine by crank bolt back and forth and if you can still see timing marks you can see how much lash in degrees.


3. Vacuum leaks anywhere as when cold it's running richer and could be covering those or just the wrong one.


Start checking and ruling things out. Most of these engines didn't just up and croak for no reason,


T



Hammer Time
Ultimate Carjunky / Moderator
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Apr 26, 2014, 9:53 AM

Post #7 of 7 (1191 views)
Re: F 150 idel issues Sign In

You probably want to test fuel pressure and volume after the issue have started. I believe this one uses 2 fuel pumps even though you never gave us an engine size., one supply pump inside the tank and one high pressure pump on the frame rail.



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