Electrical Issue? Solved

[DonTheMan]

Good Morning
96 mustang gt full PI swap aftermarket radiator/fan. Only code is for fan temp sensor. Been trying to fix an issue with car stalling when running for about 5-15min and not starting back up, about to put on a new IAC but the most recent time the car stalled it I tried to restart it and the car lost power when I turned the key, now somedays it cranks real slow then others theres no power when i turn key. I didn’t start changing the IAC yet so I haven’t touched anything

Started diagnosing and checked grounds (moved wires a little and visual) still only engine code is coolant temp sensor. The battery was charged about 3 weeks before. What is there to diagnose next?

 

[Terrorist 5.0]

I had a similar issue in that I would have the car running, and it would shut off. If I turned the key, a crank, then clicks, then nothing. No electricity. I checked the battery and my cable ends were not clean on the inside. I also found a dirty ground but I don't think that was the issue. After cleaning them with some abrasive pad, the car started right up and was perfect.

I would check your battery cable ends and the cables themselves first. This may seem obvious but you didn't mention checking it, and it is easy to get ahead of ourselves when stuff like this happens. Also, the fact that you lost power when you stalled out and turned the key most likely means the battery is no longer part of the cars electrical circuit, due to a bad connection.

 

[ttocs]

any chance the problems seem to vary according to temp/how long it has ran? Does it start right up and 10-15 mins later starts to have problems of just the opposite? I had a problem where my TPS sensor was starting to show 5-8% throttle when no throttle was being applied so I thought the sensor was bad. You could see it change if you tapped on the sensor while it was running so I I swapped it out. The car fired back up and it held solid so I thought it was good. 10 mins later though I looked down and it was again showing 5-8% and would change when I tapped on it. The harness was the only other part in question so I swapped it out(it was factory original 25 yrs old) an then it worked fine after that, I kept the old sensor as a spare because of this. When the motor heats up it causes a lot of parts to expand and over time if it expands to much then resistance will start to show up and that is how most of the sensors read. The throttle body never actually moved but as the harness heated up, the contacts were not as tight and that slight change in the resistance was read as a slightly open throttle. That slightly open throttle but no change in rpms/afr can confuse an ecu and make it try to correct the problem.

 

[DonTheMan]

My bad forgot to mention I cleaned the battery post from suggestion in other posts, I will try cleaning cable ends again.

The stall out was pretty random in between the 5-15min mark, but it does start right again like nothing happened hours later. So I’m looking at a wire harness replacement?

May the two issues be connected like no ground/positive when hot with the stalling, and no ground/positive at all now due to repeatedly losing it?

 

[ttocs]

it could be. Try starting it up and then pop the hood and look for any wire harness/connection you can find. Testing them is pretty easy, I described the technical tap method above where I just used the back of the screwdriver to tap on the part/harness. If you don't see/hear the engine make any changes then grab the harness and push it/pull it, don't be afraid to get a little rough with it as it should be able to take a fairly solid pull/tug and not have any fall off or just lose contact. IF there is a harness that has two clips that hold it on(such as the TPS sensor) it is not uncommon that the clips become brittle over the years and one has snapped off at some point. That was the problem with my tps harness, if you see any with broken tabs I would just start there as it will eventually go bad if it has not already. They have two tabs on those because the it is critical to keep the connection clean/tight for the reasons I said above. If you can't find any problems right after it starts, then wait till it does start to sputter and then repeat the above procedure and again just see if the idle changes for a sec or what happens.

 

[Terrorist 5.0]

If you are losing all electricity like you mentioned earlier, and then it starts back up hours later, I would check to make sure the cables aren't rubbing anywhere that gets hot, like exhaust for example. It is not likely, but easy to check. If that passes, then I would check the engine block ground strap. There are important circuits grounded there, and if your car is like mine, the grounds is attached to an exhaust stud, which corrodes over the years. I mainly say this because on my car it is a really easy replacement and good insurance.

If you aren't losing ALL electricity, then start checking the rest of the harness. When you say you lose ALL electricity though, battery cables are the first thing that come to mind.

 

[DonTheMan]

Thanks guys didn't expect help so fast. Right now the car isnt even responding electrically to start the car. The “door open” bell chimes but sounds glitched and code reader is dim, lights dim, and instrument cluster doesnt show anything, until I turn key to “run” everything turns off.

I checked the chassis block ground strap (to dirty to see if its connected good but there) thats on the Driver side motor mount. Is there other important ground I need to recheck?

 

[ttocs]

have you checked battery voltage both running and off?

 

[DonTheMan]

No I didn’t thought it was good because it got charged not to long ago, I also tried using a jumper pack still didn’t change so I assumed the battery was ok atleast. Might a battery still be an issue

 

[cobrajeff96]

Might be the alternator not charging the battery.

 

[ttocs]

exactly! I somehow missed we had not checked it and thought the same thing.

 

[DonTheMan]

Do i check resistance to test alternator?

Got the battery charged power still isnt getting anywhere with key on

 

[ttocs]

The fastest, but not the best way is you can do a quick test yourself to see what the voltage is at idle. Now the easiest and slightly better way is to go to vatozone and tell them you want to test it. They have a machine they hook up, they will tell you to rev to a certain rpm and in short time it will tell you if it is good or bad. Now the absolute best way, but the most difficult is to remove the alternator, find an alternator shop and they can bench test it and that is probably the best way as it takes out variables the car can throw in.

 

[cobrajeff96]

Could be a dead cell in the battery too.

If the car can be jumped either by a lithium pack or another car, it's very easy to test if the alternator is working correctly. Just put a voltmeter/multimeter on the battery terminals. It should read anywhere from 13.5 to 14.2 volts, give or take a few tenths (without any jumping apparatus installed). So get the car jump started, give it a few revs, dismantle the jumping setup, and take the reading.

 

[Terrorist 5.0]

exactly! I somehow missed we had not checked it and thought the same thing.

That is exactly what I meant earlier about getting ahead of ourselves on things like this. Crazy huh?

 

[DonTheMan]

I tried a jumper pack already, still no electricity at all in the car. Know any diagnoses for the power to get in the car first?

 

[ttocs]

If you have a bad cell in the battery can cause problems to chargers/jumper boxes. Grab a meter and check the voltage, we need to start simple/stupid or we feel stupid in the end.

 

[96blak54]

"Aint got no gas in it"

I loved that movie

 

[ttocs]

hmmmmm mmmmmm..........

 

[cobrajeff96]

Check connection from battery + to high current fuse panel.