4.6L General Discussion This section is for non-tech specific information pertaining to 4.6L (Modular) Mustangs built from 1996 to 2004.

running weak hot

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Old Aug 6, 2009 | 09:24 PM
  #1  
stangalator's Avatar
stangalator
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From: New York
Default running weak hot

I noticed its been like this for a while. When its cold/cool the engine pulls awesome, but as it warms up its... ok, not bad, but i can notice a change. I figured it was heat, so i did a 180 stat and regap the plugs to .40 ( pi swap= higher compression, heard this was a good idea). I also thought maybe i advanced the timing too much that the temperature really hurts it and throws the timing or soemthing. still the same.

I made a ram air using 5 inch smooth ducting and when going to work at 6 am it was awesome, it was a real cold morning, it pulled great. Then driving home at 2 pm on the back road it felt sluggish however.

anything i should be looking for, maybe something leaking only when hot? doesn't make since, generally things leak when cold and seal when hot. I'm puzzled, any ideas would be great.


EDIT:
how about relocating the temperature sensor closer to the mouth fo the ram air? <-- good idea?

Last edited by stangalator; Aug 6, 2009 at 09:33 PM.
Old Aug 7, 2009 | 08:01 AM
  #2  
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devongarver
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First thing, it is normal to notice a difference between cold moring and hot afternoon in performance. Every n/a motor is affected like that. Now, if there is a really large power difference, then maybe you have a problem.

Maybe I'm remembering incorrectly, but I thought the compression actually went up a bit when you did a PI swap. Either way, your plugs should be between .052-.056" gap.

Ram air is useless and if your problems started after yo installed the "ram air" just take it off and go back to what you had. Intake air is flowing relative to the speed of sound(1300fps) and you will never be driving that fast, therefore "ram air" is and always will be nothing but a gimmick. Regardless, how close is the IAT to your MAF sensor? If I remember right I believe the IAT should be like 4-6 after the MAF housing(i.e.-in between MAF and TB)
hope this helps.
Old Aug 7, 2009 | 08:39 AM
  #3  
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MJH78
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It goes something like..hot and humid air is less dense, contains less oxygen (I think). either way, I can tell you it's normal to notice even somewhat substantial losses in power when running your car in 100 degree humid weather versus a nice dry 65 degrees. I asked a question once about timing and temperature and I believe the consensus was that you would actually retard timing a little in hotter weather, to prevent pinging.
Old Aug 7, 2009 | 09:15 AM
  #4  
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Roush2002
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From: GA
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this same problem exists on even supercharged/ intercooled cars. Its not as bad once you intercool but it is still noticeable. The heat will actually cause the computer to retard timing if it gets too hot. Thats why its best to intercool s/c vehicles because the s/c just adds more heat to the equation.
Old Aug 7, 2009 | 03:19 PM
  #5  
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stangalator
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i figured the ram air wasn't doing much. im going to keep it on for a tank of gas and see how it does on gas mileage. i dont like having no fog lights, even if they are dim and are cosmedic only.

as for the gap, i heard from a few people that since the compression ratio is higher that you need to gap the plugs smaller so the spark wont get "blown out" or something "similar to supercharged cars"


Ill update later on tomorrow, i should fill up and see how it goes on gas.

Last edited by stangalator; Aug 7, 2009 at 03:40 PM.
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