Fast idle that CANNOT be fixed - MustangForums.com


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Old 08-23-2015, 08:56 PM   #1  
mtxplod
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Angry Fast idle that CANNOT be fixed

Well I will make this as painless as possible for you to read so without further ado.
I have been working on this project for months and finally It was time to chase a "vacuum" leak. A bottle of carb cleaner and five minutes later The leak was found on the passenger side between the carb and the intake. A few gaskets and a new spacer later and no change, so I assumed worst case scenario, My intake was warped. I mean it had a new carb and spacer.so by using process of elimination that was my conclusion. Today I spent a few hours putting on the new intake and after all was said and done I fired up the engine and had a fast idle after barley wanting to idle. Well that's weird, that is exatly what it did before. I replaced everything and was thorough in the process. So I took my handy carb cleaner and sprayed a little around the intake where it meets the spacer and it sped up when it was sprayed on the passenger side... the EXACT same place that it was before. ?!?
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Old 08-23-2015, 09:04 PM   #2  
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I forgot to mention. I tried a few things for giggles.
No spacer
Two gaskets on bottom with spacer
Gas "resistant" sealer on that one side between every gasket and also between intake and carb. so basically sealer between everything...
Ummm
302 explorer motor
4 barrel carb
Pretty stockish
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Old 08-24-2015, 07:14 AM   #3  
88 orangepeel notch
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Pull carb off and check intake / carb mounting surface for flatness with a straight edge. Something is not flat or not sealing up in that area. Then check the bottom off the carb for flatness, dings, dents, or gouges.
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Old 08-24-2015, 11:29 AM   #4  
mjr46
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check your carb adjustment as well as setting base timing to spec, the two go hand in hand
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Old 08-24-2015, 09:11 PM   #5  
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Ok so I have tried checking everything with a straight edge. the carb had a little bow to it so I decided to swap carbs with the one on my dad's old truck and ill be darned if my bowed carb made his truck run better and also made a tight seal. His super straight not bowed carb did the same thing on my 302 as my bowed carb did. Can I eliminate the carb as the issue?
The intake seems to be fairly straight with a a teeny tiny bit of unevenness from left to right but that very well could be the separator in the middle.. right?
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Old 08-26-2015, 06:51 AM   #6  
88 orangepeel notch
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How much of a bow are you seeing ? It would have to be quit a bit for the gasket not to seal it up.

And your dad's good flat carb did not help your issues at all ?

Did you do what mjr said above. You just can't throw a different carb on and expect it to be set up for your motor.

Good luck
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Old 08-26-2015, 02:13 PM   #7  
mtxplod
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Quote:
Originally Posted by 88 orangepeel notch View Post
How much of a bow are you seeing ? It would have to be quit a bit for the gasket not to seal it up.

And your dad's good flat carb did not help your issues at all ?

Did you do what mjr said above. You just can't throw a different carb on and expect it to be set up for your motor.

Good luck
Dont shoot me but i never really set the timing.
Did i mention that at first this thing will not stay running? It has to get hot before it will stay running. That's pretty annoying.
Even with the flat carb on it. Sprayed passenger side With carb cleaner and... i still had the same issue. Maybe a need a better set of eyes.
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Old 08-27-2015, 07:50 AM   #8  
88 orangepeel notch
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Might be time for a smoke check. Google " Vacuum leak smoke check" and you'll see how to do this. It's the most accurate way for chasing down vacuum leaks. Sounds like you may have more than one.

And just to clarify, when your spraying for vacuum leaks, your air cleaner is on ? Not that the overspray is giving a false rev.
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Old 08-29-2015, 01:43 AM   #9  
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All right I just installed another new carburetor. The car runs better. The sporadic idle has pretty much seized but I needed conformation. I checked everything with carb cleaner again and this time i have found a much more serious issue. The intake has a gap between it and the passenger side head that is so large I can easily scout it with a razor blade.When I was testing for leaks earlier It was probably getting sucked in there instead of the top of the intake.
What Could possibly be wrong? the engine never gets hot and I don't leak coolant or spit smoke from the exhaust These are signs of a warped head (So I have been told) but this thing has like a monster gap.
Oh yeah by the was this is a reman engine that I have only put about 2000 miles on.....
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