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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 03-27-2014, 01:41 PM   #1
Siggy88
 
Join Date: Mar 2014
Vehicle: 1994, Ford, Mustang GT
Location: IL
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Exclamation Computer Problems?

Hey guys, been using this site for a long time now and usually can find some related articles to solve any issues I'm having but today is the day I need help.. So I have a 94 GT with about 175xxx on it. Has BBK shortys, pypes high flow cat mid-pipe, flomasters, newer dizzy, coil, plugs, and wires. CAI with K&N filter, new egr valve, and a new MAF sensor. I have converted it from auto to a borg warner world class 5-speed and also replaced the computer when doing so. I also recently took all the smog pump related stuff out as well and replaced any vacuum lines that were involved with the FPR and EGR. I believe that is everything aftermarket I have done.

Now, I am having horrible timing issues and backfiring through the intake. I have checked the tps and it is putting out around ~1V at idle and a smooth curve with throttle increase. New EGR appears to be working correctly with the throttle as well. I just took the throttle body out and cleaned it along with the IAC and its ports.

I have adjusted timing to anywhere between 8-16 degrees advanced with the spout out doing the correct steps I have read everywhere. When the spout goes back in the timing is all screwy but seems to come back to the setting with throttle.

It runs fast as s*** for about 10 seconds after the first start in the morning or after letting it sit for 2+hours. After that its dead on its face. Also it will run even worse every couple minutes to where it will die unless I keep the RPM's above 1000 and has no power under load. If I'm moving at that point ill rev the hell out of it and clutch it.

I'm looking into getting an off road h-pipe since I took the smog crap out I just don't think that would be throwing it off this bad and it was doing all this before I did that. Any tips on where to go or check would be great. Im really looking at replacing the computer because I believe I got it off ebay when I did the trans swap. Hope this isn't too long of a post! Thanks fellas!
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Old 03-27-2014, 04:36 PM   #2
dawson1112
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You really should see if the computer is storing any codes first.
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Old 03-27-2014, 04:46 PM   #3
mongolchuck
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Its not your cats. Plugged cats will allow an engine to idle but not rev. What is your timing light showing the timing is when its running rough?
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Old 03-27-2014, 05:15 PM   #4
Siggy88
 
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I do notice the CEL flah every now and then but it does not stay. I have pulled em before and if I remember correctly it was an egr low voltage code. I will pull em again when I get a chance. It is my daily driver and I work a lot so its hard to find time to dig into it. As for the timing. it seems to go to almost 30-40? advanced when at idle and the spout in but then drops back to around what I set it at when I throttle it.
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Old 03-30-2014, 12:59 PM   #5
Siggy88
 
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So I dug out the manual for this beast and just checked the CEL codes, its giving 172, 176 which are left and right o2 sensor lean condition. 112 and 113 which are IAT circuit grounded/open above 245 and below 40 respectively. would not run for the KOER test. I just replaced the fuel pump last year along with the filter soooo... I just purchased a fuel pressure tester and should be here this week. Any suggestions on what else to check would be great!
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Old 04-02-2014, 07:03 PM   #6
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So i got a fuel pressure tester today. When I turn the key to on there is a slight bump up in pressure but nothing really noticeable and am reading a steady 20psi while running. Goes down a little with the throttle as well. I replaced the fuel pump last year to a 255lph unit along with the filter. I have removed the vacuum line from the FPR and it does nothing. Any ideas??
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Old 04-02-2014, 07:55 PM   #7
mongolchuck
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That is too low. It should be around 40psi without vacuum and somewhere around 30 at idle with vacuum. I'd say your regulator is bad, letting a lot of fuel return to the tank.
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Old 04-02-2014, 08:04 PM   #8
dawson1112
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Quote:
Originally Posted by Siggy88 View Post
So i got a fuel pressure tester today. When I turn the key to on there is a slight bump up in pressure but nothing really noticeable and am reading a steady 20psi while running. Goes down a little with the throttle as well. I replaced the fuel pump last year to a 255lph unit along with the filter. I have removed the vacuum line from the FPR and it does nothing. Any ideas??
There is your lean codes. Im surprised it runs at all. Presure should hit between 32-36 psi koeo and run at 30-34 psi at idle .

Sounds like your fpr is stuck or you have a blockage in the line or filter, or the pump is bad.
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Old 04-07-2014, 10:50 AM   #9
Siggy88
 
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I appreciate the help guys I know there's not much to the fuel system but I just wanted to make sure I wasn't missing anything stupid. I was always taught to Keep It Simple Stupid. I just bought a $400 camry to get me around while I keep this thing in the garage. I think its time for a few bigger upgrades. Maybe heads and intake. It'll be a slow process. Thanks for the help guys!
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Old 04-07-2014, 02:39 PM   #10
mjr46
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Quote:
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. Im surprised it runs at all. Presure
I'm not.............20 psi will make it run fine at idle most of the time......my 85 when it was efi ran fine with only 20 psi, however under load, it ran **** poor and forget about a full throttle romp
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Old 04-07-2014, 02:39 PM
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