4.6 won't rev past 2500 and has NO power - MustangForums.com


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Old 03-02-2009, 09:26 AM   #1
my77stang
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Default 4.6 won't rev past 2500 and has NO power

just installed a 4.6 into a 96 cougar, motor starts and idles just fine. trying to drive the car it has NO power and will not rev up past about 2500 rpms in gear driving or while in park.

it sat for about 6 months before i got it with a 1/4 tank of gas. we put 15 bucks in the tank last night to thin out the old gas but it made no difference at all. i've checked the spark plug wires and firing order and i had #7 and #8 crossed, fixed that but it made no change. i've unhooked each fuel injector to make sure they were working and i noticed a change each time so they appear to be ok. i've checked over all vacuum lines and sensor plugs and didn't find anything unhooked. tried unplugging MAF sensor to make sure its working and it definitely is, tried unhooking TPS sensor and it seemed like it was workign as well.

im going to grab a fuel filter and fuel pressure gauge now, any idea what the idle pressure should be? any other ideas what could be wrong?

also it looked like 3 of the 4 water jackets where the intake meets the head were weeping last night, but today they look dry. the gaskets were in perfect shape when i installed them and i torqued everything to 18 lbs and used the sequence as listed on the intake manifold.

input would be great
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Old 03-02-2009, 10:04 AM   #2
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have ya checked the headlight fluid?
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Old 03-02-2009, 12:03 PM   #3
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sounds like it needs a tune. my supra did the same thing, i put different injectors into it and also a different ignition and the car wouldnt rev past about 1700 rpms. just my .02
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Old 03-02-2009, 12:47 PM   #4
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it has new plugs, wires, and air filter. im going to replace the fuel filter here in a few minutes.

right now fuel pressure gauge shows about 37 @ idle and jumps to mid 40's when i give the throttle a quick rev.

i have other injectors i can use if i have to swap em over, and a couple people have mentioned loosening the cat's to see if they are clogged.
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Old 03-02-2009, 02:41 PM   #5
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does it stall out if you try to rev it up? if so, sounds like a MAF sensor problem, make sure its clean and plugged in and try it again.
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Old 03-02-2009, 02:55 PM   #6
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replaced all the injectors and it still ran like crap. loosened up the cats where they bolt to the ex manifold and problem solved.

onto my new thread, how to eliminate rear o2 sensors for cheap.
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Old 03-02-2009, 03:33 PM   #7
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http://www.paladinmicro.com/PalMFrame00.htm?wks=mil

i have also heard of people just taking them out, plugging the holes, and zip tying the sensors up under the car so they are reading the outside air, and giving a reading that says the cats are working. i havent tried it, but sounds like it might work
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