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Discussion Starter #1
Hi i have a problem with A heavy surging idle when engine is cold and major bucking when giving a little throttle. If i give it half or more throttle it runs great, but driving around town it bucks and hesitates bad. I did a complete tuneup and tried swapping out the idle air control and tps with used ones that i know were good(the motor ran great). This is after I swapped motors. New gaskets thruout and cant find any vacuum leaks. Im about ready to just put a carb setup on it if i can find a used one. Thanks in advance for the Help.:banghead
 

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Discussion Starter #4
I think i have codes 118 and 18 or 81. I got 11-11-11-8-1-8 then it would stop. I have also cleaned the TB and idle air control and set the tps the best i could to 1 volt. changed the fuel filters and ran 3 bottles of fuel system cleaner with fresh fuel.
 

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Discussion Starter #5
Going to disconnect the battery and recheck codes now because i had such a hard time getting them.
 

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Discussion Starter #7
Cleared the codes and ran it up to temp. Rechecked codes and only got 11 11. when I start it cold it idles up then surges from 200 to 1200 rpm till it warms up then it will stay around 700 rpm. slight throttle under load or not hesitates and runs rough till I give it a little more throttle. Could it be my TPS or MAP sensor?
 

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I am certainly a strong advocate of pulling codes. However, this certainly sounds like a vacuum leak.

Other than the typical vacuum hoses, check the PCV and the grommet... nice tight and snug.
Check the vacuum hose to the MAP.
 

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Discussion Starter #10
Test drove it for 10 to 12 miles and rechecked codes. only got 11 11. Im going to go recheck for vacuum leaks now. I will check those area's BroncoJoe
 

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Discussion Starter #11
Checked for vac leaks and found slight one at pvc gromet. So after hours of reading other posts Im going to replace all my vacuum lines and that gromet and go from there.
 

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I'm curious to see your solution.. The issue you're explaining is very similar to the problem I'm having on a 7.3L diesel motor.. No codes, and tested/replaced TPS.. fargin sucks.. :banghead
 

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I'm curious to see your solution.. The issue you're explaining is very similar to the problem I'm having on a 7.3L diesel motor.. No codes, and tested/replaced TPS.. fargin sucks.. :banghead
You should start your own thread.
A diesel does not have vacuum... therefore no vacuum leak.
 

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Discussion Starter #16
Ok changed almost all my vacuum lines and capped the port going to pvc (due to napa not having part till tommorow) and it seems to be running a little better. But it is still bucking under light throttle. going to check for more leaks tommorow. Any other ideas other than throwing parts at it?
 

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Just a thought.. I'm wondering if you're in the beginning of having an exhaust back preassure issue.. Maybe the signs of a cat starting to clog? :shrug They have testers that you plug into the 02 sensor port to test that..


You should start your own thread.
A diesel does not have vacuum... therefore no vacuum leak.
:twak

1) I doubt I'll get much help from my own thread here because this isn't a "desiel" specific site.. Sure there are knowledgable people here but not enough to help me..

2) I didn't say anything about vacuum.. I'm curious to see what his solution is so I may get some ideas to try on my issues.
 

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Discussion Starter #19
Checked fuel pressure allready and it was good and it dosent have a cat on it.
Its been off for a long time and was gutted long before I bought the truck.

Does anyone know where the vacuum hose that comes off the cruise control, and goes thru the firewall goes to?
I think I might have a leak there also but I cant get to it.

Im going to replace the upper Manifold gasket and check it out real good. Because I can hear what I think is a vacuum leak toward the rear of the engine,But cant find it.
 

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Checked fuel pressure allready and it was good
What was it?

Does anyone know where the vacuum hose that comes off the cruise control, and goes thru the firewall goes to?
I think I might have a leak there also but I cant get to it.
Vacuum switch that the top of the brake peddle touch's
 
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