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88 ford f250 5.0 rough idle


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tim88f250
User
tim88f250 profile image

Oct 10, 2011, 11:09 AM

Post #1 of 10 (2884 views)
  post locked   88 ford f250 5.0 rough idle  

truck runs rough when gas gets under 1/4 tank!!! why???? i have seen this question on lots of different post but never saw an answer,,, Any ideas!!??? oh truck has two tanks! the back tank i have never used was told not to by previous owner not sure why but dont need back tank anyway


Blulakr
User

Oct 11, 2011, 12:05 AM

Post #2 of 10 (2851 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

Fuel gauge accurate??

Maybe running out of fuel while gauge reads 1\4.

I've also seen cracks in fuel pickup tubes cause air to enter the fuel when crack is exposed as fuel level drops.


nickwarner
Veteran / Moderator
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Oct 11, 2011, 3:17 PM

Post #3 of 10 (2844 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

If you're anywhere near the rustbelt its rare to see the rear tank usable on anything this vintage. They rust out and leak. If it hasn't been used for a while the tank gets condensation built up that covers the inside of it with rust scale. Try to use it and it will plug up the system with rust. I would recommend making sure the tank straps aren't rusted out badly on it. Even if you don't use it you don't want it to drag under the truck when you hit a bump. Had a few of these trucks and live in WI so had it happen to me when I was in high school. That noise will make you jump.


Discretesignals
Ultimate Carjunky / Moderator
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Oct 11, 2011, 4:46 PM

Post #4 of 10 (2839 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

Ya, half the gas gauges on those don't work or don't read accurately.

Make sure your canister purge valve isn't stuck open. Possible that when the tank is 1/4 there are a lot more fumes for the engine to take in if the purge valve is sticking open. Also make sure you vacuum lines from the purge to the canister aren't rotted out.

Don't use regular vacuum line on those, they have to be PCV/Emissions rated hose.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Oct 11, 2011, 4:47 PM)


tim88f250
User
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Oct 12, 2011, 6:11 AM

Post #5 of 10 (2830 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

yeah i have been thinking about just removing it completely,, and yes i live near detroit and the city's use allot of salt on the roads my truck has its shair or bondo and fiberglass covered rust lol


tim88f250
User
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Oct 12, 2011, 6:16 AM

Post #6 of 10 (2829 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

i replaced the pump in the tank last year but was wondering if pump has a crack in the pick up tubes in the tank,,,, like sucking on a straw with a crack in it;;;; far as i know the gauge is accurate because i can drive it till it get to E but it has ran out on me twice when i thought i had enough gas to not run out


tim88f250
User
tim88f250 profile image

Oct 12, 2011, 6:19 AM

Post #7 of 10 (2828 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

ahhhh good suggestion i am going to check that today and post what i find thanks for the advice


dr.donut
User

Oct 12, 2011, 6:50 AM

Post #8 of 10 (2824 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

vapor lock? make surre the tank is vented so that when fuel is used air can replace the volume


tim88f250
User
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Oct 12, 2011, 5:20 PM

Post #9 of 10 (2804 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

ok!! i have looked all over for the purge valve i cant find it i found the charcoal canister near the battery and i found a plastic canister on the frame near tank it has a few hoses but not sure if its the purge valve
(did not see any wires on it),,,, any help would be appreciated


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 12, 2011, 5:34 PM

Post #10 of 10 (2803 views)
  post locked   Re: 88 ford f250 5.0 rough idle  

You need to stop with duplicate threads. I'm locking this one so you can stay with the other one.



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