1994 mustang gt misfire

Tnelson-sn95

New Member
Oct 23, 2019
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Developed a misfire the other day, pulled my plugs and found a wet plug in cylinder 3 and smelled like gas not oil. Replaced all my plugs and tested spark. Had a strong blue spark on my plugs that I gapped to factory specs, what else could be causing this? I'm leaning towards a failed injector but would like some input if anybody else has run into this. Already replaced my fuel filter and tested rail pressure everything checks out and compression is 165 across all holes
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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polk county florida
Pull codes
Read through it to make sure you understand and have the tools handy. 94-5 specific stuff is highlighted.
Let us know what you find and welcome to stangnet.
 

jozsefsz

5 Year Member
Aug 11, 2013
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A failed injector is a good guess, though if one were stuck open you'd notice a rapidly falling pressure at the fuel rail. Might just be a leaking injector. You could try running the cylinder balance test to see if it points out #3. If it's the only impacted cylinder, and you have good compression, that eliminates a lot of things. Do other plugs on the same bank look ok? You can swap the injector to see if the problem moves with it, or pull the fuel rail and pressurize it to see if that one is leaking.
 

Tnelson-sn95

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Oct 23, 2019
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After pulling injectors I found debris in the nozzle of cylinder 3, replaced with new injector and found no change in idle. I'm getting really burned out on this pile
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
14,150
4,461
193
polk county florida
Ok lets play 20 questions
does it misfire all the time like it is running on seven cylinders
is it random hummmmm ta da da da hummm (no I don't have tourettes)
has there been any recent work done
what size left shoe do you wear
ok that's only four but there will be more later
 

Tnelson-sn95

New Member
Oct 23, 2019
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Its nonstop full rev range, and to my knowledge no there hasn't been. Only thing different is I added a new cap and rotor a month ago trying to chase down the rough idle and the contacts were cooked anyway. Checked last night and I'm only pulling 15-16 inches of vacuum at idle but the needles steady not bouncing around. My fuel trims are maxed out rich in bank 1. And size 11.5 but that's both feet so I don't know if that'll help much
 

Tnelson-sn95

New Member
Oct 23, 2019
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Plug wires are good, ohm checked them and they pass and they're not in bad shape. My vac gauge was indicating my timing was too far retarded on the dial but I have my doubts as I just set base time with the spout disconnected and the distributer hold down is tight not moving around. I have a picture of the cylinder 3 injector here
20191103_131204.jpg
 

jozsefsz

5 Year Member
Aug 11, 2013
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That injector looks like it wasn't flowing much, probably for quite some time. So it definitely needed replaced, even if it wasn't the immediate cause of the problem. If the left bank is being enriched, the O2's think it's not getting enough fuel (too much air). That could be caused by another dead cylinder (O2 sensors don't detect raw fuel, only the air which hasn't been used up in the combustion reaction), and it could still indicate you might have a leaking injector that wasn't #3. Did you check how they all flowed / held pressure when you had the rail disconnected?

Run the cylinder balance test, see which problem cylinder it points you to. If they're all good, then an O2 sensor might be in order since it's just one bank mis-reading.
 

Tnelson-sn95

New Member
Oct 23, 2019
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I pulled plugs and found only 1 wet plug which was cylinder three and at this point I'm not convinced it's missing on more than one cylinder. I'll try pulling codes again today to see if anything new has come about. This cars like a woman, if it would just tell me what's wrong I'd fix it but that'd be too easy
 

jozsefsz

5 Year Member
Aug 11, 2013
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I hear ya, the EEC-IV isn't the easiest thing to diagnose. The cylinder balance test is very helpful. Have you run that? It's basically part 2 of the KOER test, can be run with a paper-clip if needed (if you don't have an OBD-I scantool). Will definitively tell you if it's missing on more than one cylinder, for any reason, and which one(s).
 

jozsefsz

5 Year Member
Aug 11, 2013
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Bearings are a gold-ish color underneath the silver coating. Could be cam, rod, or main bearings. Not sure if your cloudy oil was a lot of shavings, or coolant in the oil. A blown head gasket might explain your driveability issue, as well as the wet plug (that injector probably wasn't pumping any gas). If it was getting coolant in the oil, it'd chew up the bearings pretty quickly. Or it could be some other mechanical failure or low oil pressure.

Sorry man, brighter side used 5.0's can be found relatively cheap (in the $500 range in my part of the world).