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.

5.0 Idles rough then dies

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Old 01-12-2012, 02:39 PM
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BaltRavens
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Default 5.0 Idles rough then dies

1995 GT

When you start it up it fires up just fine no delays etc. but it will rough up and down, until it dies, unless you give it gas. It bounces back and forth between 900-1500RPMs give or take a few hundred here and there without giving it gas until it dies, it will only stay running for about 5-10secs.

When you do give it gas and attempt to hold it at say 3000RPMs it will have some issues constantly holding 3000, it won't jump up, but it will jump down, or miss, and fall to around 2400RPMs and jump back up.

If you attempt to drive it, the car has a loss of power and has a bit of a hesitate and feels like its struggling at times when you give it gas. It will also NOT go past 4000RPMs on the open highway, it stalls at 4000RPMs. I thought it could be blown head gaskets, but I am not sold on that. I haven't noticed a loss in fluids and my oil is very clean, and my car seemed to run at a pretty normal temperature.

I am in the middle of all that jazz of buying a home so my wife is leaving me no room to mess with my toys... so I am just browsing ideas/brainstorming in the mean time. I probably won't have the car looked over / fixed until late spring. I am just looking for ideas and opinions for now, thanks!


Here are some of the mods
Cobra Upper Intake
Gt40 Lower Intake
GT40P Heads
BBK 70MM TB
Professional Products FPR
Walbro 255 fuel pump
24# injectors
Scorpion 1.72 Roller Rockers
MAC CAI
MAC Shorty headers
Under Drive Pulleys
UPR X Pipe (2.5")
Mac Pro Dumps
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Old 01-12-2012, 04:30 PM
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javila2468
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Clean out your MAF sensor
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Old 01-12-2012, 04:32 PM
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javila2468
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similar issue with my 89 mustang. mine would rev perfect when in neutral but once I hit the road it would feel like if it was being held down by a school bus. i cleaned the MAF and CAI pipes, let it dry and reinstalled and it worked just fine afterwards.
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Old 01-12-2012, 10:48 PM
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BaltRavens
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Simple stuff I will try it t/m and see what happens, minor stuff like this I can do myself.

Thanks!
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Old 01-13-2012, 06:14 AM
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jojobanks
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you may also have a vacuum leak somewhere
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Old 01-13-2012, 08:11 PM
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Bubba 95SN
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Codes, fuel presure?
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Old 01-13-2012, 08:59 PM
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AdderMk2
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mods list does not show a calibrated MAF sensor... put 19# injectors back in the car, or get it tuned.
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Old 01-14-2012, 01:07 PM
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BaltRavens
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Originally Posted by AdderMk2
mods list does not show a calibrated MAF sensor... put 19# injectors back in the car, or get it tuned.
This is what I thought was the issue, the car needing a tune. I had plans to get it tuned. The issue I am having just came about, the car run fine for months then just over night this problem happened. I don't think the car will even drive to the shop for a tune its that bad. Would a issue like I am having come about over night from needing a tune?

I cleaned the MAF but that did nothing it still does the same thing.
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Old 01-14-2012, 09:05 PM
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It's a possibility that you may have a plugged fuel filter, if you have one, I know I put one in mine just to check out how clean the gas tank was when I first bought mine. The rough idle may be either fuel flow, vacuum malfunction, or even timing. Those will play a role in it. But with the mods you do have I cannot tell unless I'm actually there. That's my best hypothesis.
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Old 01-15-2012, 12:00 PM
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BaltRavens
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Originally Posted by SmallblockPower
It's a possibility that you may have a plugged fuel filter, if you have one, I know I put one in mine just to check out how clean the gas tank was when I first bought mine. The rough idle may be either fuel flow, vacuum malfunction, or even timing. Those will play a role in it. But with the mods you do have I cannot tell unless I'm actually there. That's my best hypothesis.
Yes its tough because it could be many things, its been snowing here past week. I haven't had any clean/warm weather to get under the car and change the fuel filter or to really mess with the car. I am going to give it a overlook when it warms up before I take it to the shop.
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