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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 07-15-2013, 02:18 PM   #1
Danielsmustang
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Default Misfire from hell

Whatsup guys. Havent been on the forums for a while but I got my stang. Her name os sandy. Shes been sweet but I have been ioing crazy trying to figure her out. So I have been having this small misfire since day one. I bought it and he said it could be a rich misfire. The car had 24lb injectors with a 19lb maf. It only misfired on idle and low throttle. So I went home, changed the plugs. It stayed the same. So I bought a used c&l 80mm maf. It ran like crap. When I fully gas it it goes away. So I said, maybe vacuum leak? Checked and I had one between upper and lower. So I replaced it. It stayed the same. So then I went back to the old maf. It drove better but the same as before. Only on idle and low throttle. Then I bought new wires and ignition coil. Same. New cap and rotor, same. then I put 19lb injectors. Same. Now when I drive it, as it warms up it gets worse. If I fully gas the car it goes away. I just bought a new tfi. As I was installing it, I took out dizzy. Now its out of timing and got to fix it. But I thought maybe, since it has roller rockers, the previous owner didnt tighten them correctly. Could that affect? Or floating valve? What do you guys think? I also cleaned the salt and pepper.
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Old 07-15-2013, 02:38 PM   #2
dawson1112
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I think valve float would manifest itself at wot or very high rpm .
Have you tried a different dizzy or replacing the pip in side the dizzy? Pretty common for the pip when it starts going bad to cause misfiring.
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Old 07-15-2013, 02:49 PM   #3
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Quote:
Originally Posted by dawson1112 View Post
I think valve float would manifest itself at wot or very high rpm .
Have you tried a different dizzy or replacing the pip in side the dizzy? Pretty common for the pip when it starts going bad to cause misfiring.
What is the pip inside dizzy?
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Old 07-15-2013, 03:19 PM   #4
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PIP or Profile Ignition Pickup sensor is responsible for telling the ignition coil to start firing. If the pip is not working at all you will achieve a no start condition , however they have been known to intermittently cause problems creating a miss fire.

This is fords name for crankshaft position sensor and is located inside the distributor.. A complete tear down of the dizzy is required to replace it, most times pple opt to replace the distributor completely rather than just tear it down and replace the pip.
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Old 07-15-2013, 03:36 PM   #5
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Hmm. Okay havent thought of that. Now, how would i be able to diagnose that? Any test i can do to see if it working properly or not? And mind you, it only misfires on idle and low throttle. not under wot. I can be cruising in 4th gear going like 50mph and if i slowly gas it, it will start misfiring, but if i step on it, it misfires for a sec then goes away.
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Old 07-15-2013, 04:08 PM   #6
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If the pip is working but intermittently cutting out you have no real way to check it, but this page has a lot of very useful tests you can perform NOTE: This test is assuming you have a no start condition.

http://easyautodiagnostics.com/ford_...d_module_1.php
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Old 07-15-2013, 04:11 PM   #7
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You will have to scroll down a bit to find the pip section
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Old 07-15-2013, 05:21 PM   #8
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Quote:
Originally Posted by Danielsmustang View Post
Hmm. Okay havent thought of that. Now, how would i be able to diagnose that? Any test i can do to see if it working properly or not? And mind you, it only misfires on idle and low throttle. not under wot. I can be cruising in 4th gear going like 50mph and if i slowly gas it, it will start misfiring, but if i step on it, it misfires for a sec then goes away.
That's an EGR misfire. Probably a bit lean, given your conundrum with the inj/maf combo.
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Old 07-15-2013, 06:16 PM   #9
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Quote:
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That's an EGR misfire. Probably a bit lean, given your conundrum with the inj/maf combo.
Alright, so I start the car up , car idles and runs good, so I drive down the road and shift at 3000rmp and its fine, then if I rev the car over 4000 when I shift the car will start to over heat after about 5 mins after being ran hard and stay hot , it has a 180degree thermostat in it , so to sum it all up, when I run the car hard the car will over heat pretty much immediately
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Old 07-15-2013, 06:22 PM   #10
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Alright, so I start the car up , car idles and runs good, so I drive down the road and shift at 3000rmp and its fine, then if I rev the car over 4000 when I shift the car will start to over heat after about 5 mins after being ran hard and stay hot , it has a 180degree thermostat in it , so to sum it all up, when I run the car hard the car will over heat pretty much immediately

Lol how did you get in this thread
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Old 07-15-2013, 06:22 PM
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