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Discussion Starter #1
Hey Everyone,

I originally had an issue with my engine on my 1988 mustang lx 5.0 because it was randomly misfiring yesterday randomly even though while i was driving it all day yesterday it was fine until later on last night(heres my original thread: http://www.allfordmustangs.com/forums/5-0l-tech/589922-mustang-misfiring.html)

Now today I went to advanced auto and I bought and replaced the Distributor cap and rotor(MSD brand), sparkplugs(motorcraft), and ignition wires(autolite). I also purchased a Fuel filter but DID NOT put it in(will most likely do it tomorrow after work). After I replaced all those parts I drove the car around a bit and brought it up to 45mph to 55mph which is the speed limit it was misfiring yesterday, and no misfire! The car actually felt a little faster and nothing was wrong! I have drove the entire car around the entire day and now when i went to the store about 30minutes ago and the car began to misfire again, although the situation was different. After starting the car i put the heat on and drove. When I reached 40-50mph which was around 1500-2000rpms the car began to misfire again. Although besides noticing that, i noticed that when the heat was on the battery level indicator located on the dash board was only a little above the "8" mark. When i turned the heat off the battery indicator went from the "8ish" back up to the normal level which was about half way and i also noticed the rpms drop a small amount and go back to a normal rpm(battery and rpm situations both happened when as soon as i turned off the heat). I left the heat off the last block and a half home and when i got to around 40-45 mph there didnt seem to be a misfire although there seemed to maybe be a loss of power(when i pushed the pedal down more the car caught up and went faster(could be because i was in 4th while doing 30-35ish). The previous owner only put in regular gasoline (87 octane) and i filled it with premium (93 octane) yesterday.

Could this be because of the different gas i put in? I really dont understand what the issue is, maybe when i put in the fuel filter in tomorrow it might go away? I could only hope. Sorry the post is so long to read! just trying to give as much information to help as possible...

Thanks,
-Velez confused013.gif
 

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A large voltage drop will cause issues with the engine running right.
The heater/Fan draws a lot of power and with headlights on.

So I would go to auto store and have them check the Alternator and Battery.
It's free.

Also having bad grounds with the wire loom can cause problems with the TPS
not getting the correct volts. Will cause car to run rough, maybe backfire especially
when there are electrical loads. My car had this issue and after i cleaned those
grounds the car ran great again with headlights and heater on.
 

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Discussion Starter #3
A large voltage drop will cause issues with the engine running right.
The heater/Fan draws a lot of power and with headlights on.

So I would go to auto store and have them check the Alternator and Battery.
It's free.

Also having bad grounds with the wire loom can cause problems with the TPS
not getting the correct volts. Will cause car to run rough, maybe backfire especially
when there are electrical loads. My car had this issue and after i cleaned those
grounds the car ran great again with headlights and heater on.
The alternator is brand new and that battery is less than a year old.. makes sense though because when i drive the car during the day with no heat or lights on the cars a monster but the past two nights with the lights and heat on it was backfiring and running rough. What grounds do i need to clean? Which ones did you clean? Do you have a picture and a location? Thank you.
 

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On my year '85 the grounds are located under the hood, on top of the fenders towards
the front. You should see them coming from the wire looms. It is a single skinny wire
and in my opinion too small to handle ground for the computer, headlights, tps, etc.., but it works if you keep it clean and sealed.

unscrew/unbolt them both and clean all surfaces down to the metal.
Then tighten down good and seal with some paint, preferably matching your car.
 

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Discussion Starter #5
On my year '85 the grounds are located under the hood, on top of the fenders towards
the front. You should see them coming from the wire looms. It is a single skinny wire
and in my opinion too small to handle ground for the computer, headlights, tps, etc.., but it works if you keep it clean and sealed.

unscrew/unbolt them both and clean all surfaces down to the metal.
Then tighten down good and seal with some paint, preferably matching your car.
Is there any sealant that i can put over the ground after i clean it? Maybe something I could buy from autozone or something that is made for the car? Instead of just red paint? lol I'm gonna go check the grounds now, see if that works. Ill probably buy a better battery next week too. Probably a Die Hard because the one I have in the car right now is a "Plus Start"?
 

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touch up paint from autozone is fine. if you really want to get detailed then use primer first but not really necessary.

The idea is to seal it from oxidation again.

If it is rusty like mine was use sandpaper and get it really clean then wipe it all off with alcohol. tighten snug with good contacts then seal in.

Diehard gold is the best I have found if you can still get them.
 

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Discussion Starter #7
touch up paint from autozone is fine. if you really want to get detailed then use primer first but not really necessary.

The idea is to seal it from oxidation again.

If it is rusty like mine was use sandpaper and get it really clean then wipe it all off with alcohol. tighten snug with good contacts then seal in.

Diehard gold is the best I have found if you can still get them.
well... i cleaned the ground that was skinny. Infact I cleaned 3 grounds, the two skinny ones on each side and the one ground that was wired to the positive battery wire(for the terminal)... and nothing... still the same. I started the car and was driving down the road and when i slowed down at an intersection(stop sign, there was a car in front of me) and then my rpms dropped to 0 and my car died... i started it up again and the battery indicator on the dash read low and died again about two more times when i could finally drive home. So is it either the battery or alternator? the alternator has to be okay because i've been driving the car since sunday without it dying..

thanks,
 
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