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Old 02-24-2013, 08:23 PM   #1
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Missing!?!?

94 gt

New MAF
IAC
WIRES
PLUGS
DIZZY
CAP
ROTOR
Timing is set
New vac line
TFI

When driving it had a miss when the car is at a constant speed. Unplug the TPS and it stops, but the TPS is ready .99 on the multimeter.
Idle is set
Reset computer
No codes
Idle is kinda jumpy but it never dies


Hope this is enough info without actually driving the car Thanks.


Suggestions?
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Old 02-24-2013, 08:42 PM   #2
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Coil?
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Old 02-24-2013, 09:23 PM   #3
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Quote:
Originally Posted by 94GT302 View Post
94 gt

New MAF
IAC
WIRES
PLUGS
DIZZY
CAP
ROTOR
Timing is set
New vac line
TFI

When driving it had a miss when the car is at a constant speed. Unplug the TPS and it stops, but the TPS is ready .99 on the multimeter.
Idle is set
Reset computer
No codes
Idle is kinda jumpy but it never dies

Hope this is enough info without actually driving the car Thanks.

Suggestions?
What's your voltage when everything is on?
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Old 02-25-2013, 06:57 AM   #4
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Coil is brand new MSD

Ill have to check the voltage. The alternator hasn't been change, pretty sure it's original.
158k miles
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Old 02-25-2013, 08:39 AM   #5
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Coil is brand new MSD

Ill have to check the voltage. The alternator hasn't been change, pretty sure it's original.
158k miles
Did you check the gap on all the new plugs to make sure one isnt squashed? I always check mine o.O
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Old 02-25-2013, 08:42 AM   #6
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Did you check the gap on all the new plugs to make sure one isnt squashed? I always check mine o.O
Not only that but are they gapped correctly and what kinda plugs
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Old 02-25-2013, 10:20 AM   #7
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There pregaped NGK's the ones right below iridium plugs. Wanting to say NGK E power?
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Old 02-25-2013, 10:26 AM   #8
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Correction: they are NGK Platium G power with a .54 gap
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Old 02-25-2013, 10:33 AM   #9
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Correction: they are NGK Platium G power with a .54 gap
Maybe take a second look at those, in my exp and the exp of many many others these push rod 5.0L's LOVE a plain old copper core AutoLite or MotorCraft plug.

I've run AutoLite 25's in 4 different 5.0's and never had a problem across more then a decade.
I hope this does not start a flame war or crazy debate just making a suggestion in hopes to help you pin point the issue.
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Old 02-25-2013, 10:33 AM   #10
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My idle is a little weird in my 94 and I have plugs (Ngk) and new wires and new cap and distributer and new alternater. 140k. A guy that owns a mustang shop around here looked at my car and said it could be because I have an after market oem maf so I will be getting one from him that he has that is for my car and ill let you know how that goes ill post a pic of what mine looks like
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Old 02-25-2013, 10:38 AM   #11
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The guy said he could tell it was aftermarket cause of the sticker on it hope this helped

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Old 02-25-2013, 01:07 PM   #12
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I wouldn't trust anything that says pregapped. All it takes is a simple bump during packaging and its out.

I also use autolites with great results.
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Old 02-25-2013, 01:11 PM   #13
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The guy said he could tell it was aftermarket cause of the sticker on it hope this helped
The one I purchased is from Orielly it's not the cheap one either. I remember the old pocket book squealing a bit after that purchase.

---------- Post added at 01:11 PM ---------- Previous post was at 01:09 PM ----------

Does anyone have any idea why it would run better with the TPS unplugged? Even if its reading .99. When it's running it jumps from .98 to 1.00
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Old 02-25-2013, 01:32 PM   #14
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The one I purchased is from Orielly it's not the cheap one either. I remember the old pocket book squealing a bit after that purchase.

---------- Post added at 01:11 PM ---------- Previous post was at 01:09 PM ----------

Does anyone have any idea why it would run better with the TPS unplugged? Even if its reading .99. When it's running it jumps from .98 to 1.00
Because its sending the ecu into a closed loop. Basically a fixed set of parameters. That doesn't necessarily mean its the tps that's the issue. It could be one of many of the sensors that the going into closed loop is covering up.
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Old 02-25-2013, 03:37 PM   #15
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Because its sending the ecu into a closed loop. Basically a fixed set of parameters. That doesn't necessarily mean its the tps that's the issue. It could be one of many of the sensors that the going into closed loop is covering up.
What sensors would you recommend? I've changed all but the EGR and TPS
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Old 02-25-2013, 06:39 PM   #16
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Its hard saying. I would make sure your eye valve is opening properly. Then check for vacuum leaks. Also clean your MAF sensor.
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Old 02-25-2013, 06:50 PM   #17
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Its hard saying. I would make sure your eye valve is opening properly. Then check for vacuum leaks. Also clean your MAF sensor.
Eye valve? I guessing your talking about the IAC
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Old 02-25-2013, 06:58 PM   #18
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Eye valve? I guessing your talking about the IAC
Sorry lol. Egr.
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Old 02-25-2013, 10:52 PM   #19
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Maybe take a second look at those, in my exp and the exp of many many others these push rod 5.0L's LOVE a plain old copper core AutoLite or MotorCraft plug.

I've run AutoLite 25's in 4 different 5.0's and never had a problem across more then a decade.
I hope this does not start a flame war or crazy debate just making a suggestion in hopes to help you pin point the issue.
Every old timer ive talked to say use coppers on the 5.0s unless you have nitrous. Have you checked for vac leaks ? Are you losing and coolant?

---------- Post added at 10:52 PM ---------- Previous post was at 10:50 PM ----------

Triple check to make sure your wires go to the right plugs!
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Old 02-25-2013, 11:26 PM   #20
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Every old timer ive talked to say use coppers on the 5.0s unless you have nitrous. Have you checked for vac leaks ? Are you losing and coolant?

---------- Post added at 10:52 PM ---------- Previous post was at 10:50 PM ----------

Triple check to make sure your wires go to the right plugs!
New vac lines and sprayed carb cleaner while it was running so no leaks. No loss coolant. Wires are all in the right place. Next thing I can only think is the O2 sensors?
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Old 02-26-2013, 06:18 AM   #21
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New vac lines and sprayed carb cleaner while it was running so no leaks. No loss coolant. Wires are all in the right place. Next thing I can only think is the O2 sensors?
I'd try cooper plugs next, cheap and easy.. Before you start throwing more serious $$$ at it.
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Old 02-26-2013, 04:18 PM   #22
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U still didn't mention if u checked the egr?
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Old 02-28-2013, 07:01 AM   #23
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U still didn't mention if u checked the egr?
Gonna do a EGR delete so that cancels the factor. Would the O2 sensors be a problem? Correct me if I'm wrong but on heavy throttle the O2's go into an open loop right? All heavy throttle the car doesn't miss, just after a min or two of idle and then at a constant throttle when underlies driving.
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Old 02-28-2013, 03:53 PM   #24
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Could the alternator be a possibility? Because when when it cuts out the needle moves at time
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Old 02-28-2013, 04:18 PM   #25
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Could the alternator be a possibility? Because when when it cuts out the needle moves at time
No its not the alt. The needle will probably move if you turn your headlights on, its just because of a drop in the engine rmps casued the alt to slow down the charge. With a miss on most cars Its usually super hard to pinpoint the issue. Best thing I would do is see if you can check the codes. There is a way to do it (google it) and there can be codes even if there isnt a CEL on. And foremost dont throw parts at the problem. But I think that goes without saying. Wish I could give you more help, and I wish you good luck. I had a similar issue on my car (turns out it was a bad fuel pump, but it did it consistently for me) and it is annoying!
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Old 03-01-2013, 08:56 AM   #26
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No its not the alt. The needle will probably move if you turn your headlights on, its just because of a drop in the engine rmps casued the alt to slow down the charge. With a miss on most cars Its usually super hard to pinpoint the issue. Best thing I would do is see if you can check the codes. There is a way to do it (google it) and there can be codes even if there isnt a CEL on. And foremost dont throw parts at the problem. But I think that goes without saying. Wish I could give you more help, and I wish you good luck. I had a similar issue on my car (turns out it was a bad fuel pump, but it did it consistently for me) and it is annoying!
This miss is consistent now. It will idle perfect for about 5min and then will miss ever few seconds. Put it in gear (automatic) will sit there for a good few min and then miss and pulse for a few second and then hit the throttle and it will clear out. Now when driving it will run perfect on heavy acceleration but at a constant throttle position it will miss for as long as you have the throttle held. When you give it more throttle it will stop missing but as soon as you go back to a constant throttle position it will miss again. There is a sweet slot in the throttle though and it won't miss idk why but I found it on accident. Sorry this is so lengthy but I hope this thread helps others as well. Thanks
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Old 03-01-2013, 09:13 AM   #27
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It sounds ignition related to me. Maybe a wire it arching, a ground is bad, if your can get your hands an some oem parts you know are good ( that mustang guy you mentioned) maybe try swapping some stuff out and see if you can trace the issue. But dont go buying new parts again. Lol I have heard of people having issues with MSD ignition parts for our cars. Im not saying it the case, but it cant hurt to check it out. I bought a brand new dizzy and it had a bad pick up coil in it. Returned it, and the TFI was bad. So I went with a diffrrent brand after that
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Old 03-01-2013, 06:26 PM   #28
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So I have a resolution. Went to Oriellys today to order some parts. Checked the cap on my dizzy and it was black. So I got some cleaner and cleaned. While I was there I figured I'd do a seafoam treatment and in the process broke the EGR vacuum line. Not wanting to buy any hose because I have some at home I just decided of wait to fix it. Drove a mile and the check engine light came on and the car ran perfect if not better then it ever has. So tell me do you believe that the EGR is the problem???
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Old 03-01-2013, 06:36 PM   #29
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So I have a resolution. Went to Oriellys today to order some parts. Checked the cap on my dizzy and it was black. So I got some cleaner and cleaned. While I was there I figured I'd do a seafoam treatment and in the process broke the EGR vacuum line. Not wanting to buy any hose because I have some at home I just decided of wait to fix it. Drove a mile and the check engine light came on and the car ran perfect if not better then it ever has. So tell me do you believe that the EGR is the problem???
It's very possible. Sometimes even the lines to the egr get backed up.
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Old 03-01-2013, 07:04 PM   #30
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Because its sending the ecu into a closed loop. Basically a fixed set of parameters. That doesn't necessarily mean its the tps that's the issue. It could be one of many of the sensors that the going into closed loop is covering up.
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Old 03-01-2013, 08:07 PM   #31
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So I have a resolution. Went to Oriellys today to order some parts. Checked the cap on my dizzy and it was black. So I got some cleaner and cleaned. While I was there I figured I'd do a seafoam treatment and in the process broke the EGR vacuum line. Not wanting to buy any hose because I have some at home I just decided of wait to fix it. Drove a mile and the check engine light came on and the car ran perfect if not better then it ever has. So tell me do you believe that the EGR is the problem???
The egr diaphragm could be screwed up causing a vacuum leak when there is a vacuum to open it up.
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Old 03-01-2013, 08:10 PM   #32
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I'd try cooper plugs next, cheap and easy.. Before you start throwing more serious $$$ at it.
+1,They can definitely change the way a car behaves. I went from iridium ix plugs to NGK standard platinums with a .48 gap and my car runs a lot better. No more miss, hesitating throttle response and it feels like it pulls harder as well.
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Old 03-01-2013, 08:48 PM   #33
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Yeah it is very possible. Fix it and see if it happens. You can always unplug it too
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Old 03-01-2013, 09:50 PM   #34
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Yeah it is very possible. Fix it and see if it happens. You can always unplug it too
Unplugging will cause a CEL light right? Now if I did a delete would that help as well? I plan on doing a GT40 H & I swap soon.
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Old 03-01-2013, 10:15 PM   #35
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Yeah it will throw a code. Sorry, I should have elaborated on what I was saying. If you fix your egr and you have the problem come back, well I think you probably found the issue. But sometimes unplugging the egr and driving it may clear the issue too (basically what you did when you broke a line). The car will probably want to die, so keep on the throttle so she doesnt stall. This is just a ghetto way of checking if its the egr or not.lol Dont drive around that way; either fix it, or delete it.
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