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.

Misfire/Hesitation that's baffling me

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Old Jul 26, 2012 | 06:43 PM
  #11  
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mattdel
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Nope. It's possible the pickup in the distributor is bad, but it would likely produce symptoms in more ways than what you've described. I stand by my original list.
Old Jul 26, 2012 | 07:08 PM
  #12  
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Mass Air sensor, have you cleaned it???
Old Jul 26, 2012 | 11:19 PM
  #13  
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Originally Posted by mattdel
Coil, EGR, and TPS are really the only possibilities here.

Coil would likely have a much wider range of failure.
EGR would likely pop the CEL until the EGR wasn't being commanded anymore(idle, decel, WOT, 4k+ RPM)
TPS would only need a very small problem in the voltage sweep to spike a little stumble. It's likely the cheapest of the 3 if you're without the means to do any testing.
Originally Posted by mattdel
Nope. It's possible the pickup in the distributor is bad, but it would likely produce symptoms in more ways than what you've described. I stand by my original list.
according to the shop the TPS was eliminated as the issue, not sure if they even got to the coil, distributor, it just has me a little baffled since it isn't what I expected, i figured it was either a) on the list or b)little pinhole in a line,

Originally Posted by joe95 gt
Mass Air sensor, have you cleaned it???
unknown if they did, but i'm going to be right by thee tomorrow i'll ask.

thanks guys, at least my concerns are validated, (although honestly if its running spot on for the next few days I probably shouldn't be losing sleep thinking something else was broken.

But to satisfy my curiosity i'm going to revisit it with the tech that did the work in person and dig a little deeper, i'm trying to avoid the possibility that this pops back up in a few days or a couple of months. Normally, i'd just brush it off and wait/see. Wouldn't bug me that much, its working...

But I'm about to send the car up to college with my daughter, so it will be 300 miles away for the next 5 months. That leaves me about 20 days to find out if it reoccurs.

granted I should be thrilled with a tiny bill for an inspection & clean but since it was intermittent before, concerns me that it might crop back up.

Last edited by Spim; Jul 26, 2012 at 11:21 PM.
Old Jul 26, 2012 | 11:32 PM
  #14  
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another brain fart here... just recalled it, when it stumbled like that, the misfire, it actually almost felt like it was shutting off for a split second then coming on again,

and i remember noting that when we first bought the car the part where you insert the key into the cylinder (on the steering column) was loose/wobbly, like maybe once the car had been jacked or something.,

if that puppy is loose or has a loose connection, could it be actually turning the car off/on like that for a 100th of a second ?
Old Jul 27, 2012 | 12:17 AM
  #15  
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I would expect the whole of the car would shutdown momentarily with it. Ignition switch controls all the electrical throughout the whole car except for continuous memory computers and radio clocks.

See if the dash and everything die too.
Old Jul 27, 2012 | 08:48 AM
  #16  
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i stopped by but the tech that worked on it had the day off, oh well, i'll just see if the problem re-occurs , they did replace a few lines along the way and did a lot of general cleaning along with the IAC, and the guy did mention that those symptoms generally would not lead them to think the IAC was the problem but he said it was stuck and not moving at all, just cleaned and lubed, and after a test ride it was working fine.

it's tough sometimes buying a car that somebody else modded, you end up with weird things like the speedo being off by about 5mph, idles a tad high, seems to shift out of 1st a little late, but its one of those things where tinkering might make it worse... not sure what the PO did to the computer and such, but since i'm not doing my own work, tinkering can get expensive. In the meantime i'm going to let it run and well see what happens.

thanks for the input guys ! much appreciated.
Old Aug 2, 2012 | 04:10 PM
  #17  
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well, its back in the shop, and worse, now i'm finally seeing the symptoms that the idle control should have caused, (stalling) its been 1.5 days back in the shop and i'm making zero progress, looking for a smarter mechanic as we speak

thanks again for your input, will forward your thoughts and suggestions off to the next tech
Old Aug 13, 2012 | 08:10 AM
  #18  
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Issue Resolved.
3 Mechanics, and $400 in labor, and in the end I fixed it in my driveway by replacing the ECU. So far its been 3 days trouble fee since the swap.

The only good news is that I got a major tuneup along the way, plugs wires, cap rotor, pickup coil, a couple of vacuum leaks, so with a little luck i'll have some trouble free time with the car
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