Fox 1990 Just Bought And Started Acting Up. Need Help.

johnny85

Member
Aug 14, 2016
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I just bought a 1990 Cobra Clone last week. It has edelbrock performer heads and intake, Moroso CAI, 24lb injectors, BBK long tubes and flowmasters. Car was running great until this past friday. I would get on it and at about 3500rpm it acts like you are feathering the gas. It pulls then its like it lets off then pulls and it keeps doing this. Just riding around the car runs great its not until you go to call for power when it acts up. Saturday I changed the fuel filter to rule that out. I have check all the wires and cleaned the MAS as well. Fuel pressure at idle is about 37lb. What am I missing here? Any help would be great.
 
Have you pulled the codes?

If it's tuned, you should see some sort of piggy back chip on the computer in the passenger side kick panel


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Well here is something new. I have never had more than 4 gallons in the tank since I had it (1 week now). This morning I filled her up with 93 octane and she ran like a raped ape. Im thinking fuel pump. I will be running the codes at work today as well. Just thought I would share that. What do you all think?
 
If it was a fuel pump, you might get some lean codes spit back at you.

But honestly, it's really not worth speculating until you have codes in hand. Really does make troubleshooting a lot easier when you can narrow it down
 
As suggested...

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
 
Well here is something new. I have never had more than 4 gallons in the tank since I had it (1 week now). This morning I filled her up with 93 octane and she ran like a raped ape. Im thinking fuel pump. I will be running the codes at work today as well. Just thought I would share that. What do you all think?
Often times when the fuel pump is going out the car won't have any power during WOT but will cruise around just fine. However, a full tank of gas wouldn't "fix" a bad fuel pump. Maybe your gas tank isn't venting properly? I'm curious to see what codes come up.
 
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