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1995 mustang spark plug wire acceptable resistance

8967 Views 35 Replies 7 Participants Last post by  PANTYEATR
i have googled for an answer and looked in the haynes manual and couldn't find an answer.

the previous owner has supposedly installed new wires, plugs and distributor cap, but i wanna check his work since he has HACKED most of the rest of the car.

i wanna ohm these wires on the car before i buy some new ones.

so whats the window of acceptable resistance?
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should be 10k ohms or less per foot.
so, 20 ohms is ok for cylinders 4 and 8?

i haven't checked them yet, so i wanna know the minute i see the readings.
Totally depends on the manufacturer of the wires. Some are 40ohms per foot, some are a lot higher. So it depends. 10k ohms per foot would not be acceptable if they are supposed to be 40ohms.
well so far so good. i checked cylinders 1-4 and the wires are all under 10 ohms. the plugs on that bank were all showing signs of being too hot or the timing is too advance, lean A/F, intake manifold vacuume leaks, sticky valve or cooling system not up to par.

i also found that the plugs weren't properly gapped to .052

i'll post the exact ohms when i can finish getting them, it's raining now ;(
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here are the readings of the test i made per the haynes manual

cylinder / ohms
1 / 6.55k
2 / 5.69k
3 / 7.98k
4 / 7.64k
5 / 6.19k
6 / 6.90k
7 / 6.67k
8 / 8.21k

coil to distributor = 2.64 ohms

12v coil primary to coil post = 8.97 ohms

NEG coil secondary to coil post = 8.97 ohms

12v coil primary to case ground = 26.3 ohms

all the spark plugs were not gapped at all! so i gapped them to factroy .052

all the plugs on the passenger side bank had symptoms of lean conditions.

so, i don't whats going on. there is a slight surging, if there is a vac leak i can't find it, if its surging cause it's not getting a speed signal i don't know why cause the VSS is working, but the speedo on the dash is inop! i'm lost! ;(
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89coupe is correct - there is no universal ohms/foot magic number. you did it exactly right. take the wires and measure their length and then their resistance - divide to get ohms/foot. Any wire that deviates significantly is suspect.
a while back i cleaned the MAF sensor with brake clean off the car. it was dirty cause you can see the change in color. IDK if brake clean was a good thing to use, but i now have electric contact cleaner.
thats the one thing i didn't do, measure the wire length ;(
but either way they all are under 10 ohms. they are some regular, generic plug wires though.

i adjusted and cleaned the IAC around the time i cleaned the TB. i didn't record any voltage readings on the IAC to see how good it was working, but it was trying to keep the engine running when the RPMs dropped too low.

i also downloaded the ford TPS resetting procedures and did that a few times til it was were i liked it.

there is a vacuume line that i'm curious about thats missing. it goes from the A/C port on the vacuume tree thats on the driver's side and i guess it goes to the A/C vents in the car cause they aren't getting any vacuume to do any switching
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it goes to a vacuum resevoir in the passenger wheel well and then on to the vacuum controls for the heat/AC. There are color diagrams of the system here on this site if you search.
i have that diagram printed out already, it's just that i don't see the line that goes in there at all. maybe i'll check the passenger fender to see if the idiot previous owner left it in there. i had the glove box out and i can see the vacuume reserve tank, but i need to look more to see if there is still a supply line on it...
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upon further investigation, i found out that my car was originally a 4sp automatic car! that maybe why i'm having some of my issues.


World region:North America
Manufactured in:USA
Body style:Coupe
Transmission:4 Spd Automatic
Fuel type:Gas
Cylinders:8 Cylinders
Safety restraints:Dual Front Air Bags
Standard options:power Steering, Power Brakes, Tilt Wheel, AM/FM Stereo

i guess i need to pull the ECU and verify that it is a computer for a 4sp automatic since it's possible that they may have been smart enough to swap it out, but seeing the other work done to the car i bet they didn't. that may explain why the speedo doesn't work even though the VSS is working. could be wiring too, but i'll have to investigate that again. and that could be why i can't rev the engine past 3500 RPMs! what do ya'll think?
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Yeah an AODE computer in a manual car will give you all sorts of fits.

T4M0 is the computer for the stick. J4J1 is the Cobra computer (which is also a stick but accounts for the 24# injectors int he Cobra)

U4P0 would be the AODE computer...
thanks for that info, i'll look for numbers on my ECU and check beck here
the car has the T4M0 ECU. damn, i was hoping this would have been the source of all of my problems ;(
ok so, i fixed the empty A/C port on the vacuume tree. i had a piece of 1/4" air brake line in my garage, so i ran the line into the car to the vacuume reserve tank, then shrink wrapped the ends to seal and damn did alot of dust and foam bits blow out of them vents! :ahhhhhthe vent doors now work great.

i also unplugged the IAC and adjusted the throttle stop and IAC screws and the engine still hunts for an idle. sometimes it's a 100-300 RPM swing and as much as a 500 RPM swing. does that mean that there is a vacuume leak for sure somewhere?
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Brake cleaner won't hurt anything...

Are you getting any codes?
i get a check engine light while i'm driving sometimes, but i don't have the OBD1 cable to connect to my scan tool yet, so i can't tell you what it is yet :(and when i go to the autozone, they don't have a OBD1 connector for thier scan tools either WTF!
i get a check engine light while i'm driving sometimes, but i don't have the OBD1 cable to connect to my scan tool yet, so i can't tell you what it is yet :(and when i go to the autozone, they don't have a OBD1 connector for thier scan tools either WTF!
You just need a test light...
DIY KOEO/KOER/Cylinder Balance Self-Test Procedure
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i know you guys are gonna laugh but i'm intimidated by all this jumper wire in the scan tool port stuff. OBD2 cars are easier, just flip the ignition switch 3 times in 10 seconds and it will flash you the codes. i just don't wanna short anything out and kill the ECU.

i have the haynes manual and i read these procedures over and over to know and understand what i'm doing, but i'm not there yet :(
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i got a chance to go to my friend's shop to use his equis scan tool and here are the codes that i got:

176 - EGO not switching, lean exhaust bank 2

212 - no tachometer input to processor SPOUT ??? (the tach on the dash is working, but not smoothly)

543 - fuel pump circuit open - battery to PCM ??? (the car wouldn't run at all if this was bad right) ???

136 - no EGO (HO2S-1) switch lean exhaust bank 2

me and my friends agree that there is a "tapping" on the passenger side valve cover of the engine. it gets faster with RPMs, so we think it's a broken rocker, bad lifters or bad push rods. at teh very worst case the cam could be busted up too ;(

imma try to get back to my friend's shop to use his laser thermometer and see which exhaust ports are colder than the others, then attack the issue.
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