So...my car has 8,000 miles on it. I bought it with 5,000 a few months ago. It is a 2007 Mustang GT. Once, on the way to work it was running rough. I restarted it and then it seemed fine so I figured it was a fluke. I was on my way home from a trip to MI this morning and noticed the car seemed to be vibrating more up the mountains. I figured it was my tires. Well, when I finally came to a stop, the car was running really rough. I made it to my garage, popped the hood and got out a long screwdriver to listen to the injectors to see if they were all working. #8 was not. I played with the connector, removed and re-inserted with no change. I decided to shut the car down and restart. Of course, #8 injector was firing normally and the car was smooth. WTH? I would have said injector problem, but maybe not now. Anyone heard of this one??

I have only owned the car a few months and it has happened twice. Will pull codes and call the dealer, I guess. I am glad it wasn't the coil, as I would have fuel dumped down the cylinder for all those miles. Unless the computer determines a misfire long enough and kills the injector...?? Hmmmm...

 

I by accident got a coil wet once thus xausing a spark plug not to get its juice, the bugger must have got a drop of water on it & the car ran like crap, Ford had it flat decked to a dealer & I had to pay like $6.00 for that litle coil pack , there is one on every plug and it was good.
Sounds kind of similar

 

This acts just like a coil pack but I have determined that the fuel injector was not working. No codes were stored. WTH. Also, it was dry out both times, so no water related issues.

I called the dealer and they want $90 to diagnose and will only cover engine/transmission and nothing else, so I am on my own with this one. I could swap the #8 and #7 injectors to see if the problem moves if it happens again, I guess. Then the coil. Almost better to shotgun something like this than pay a dealer, especially here. I hate the Knoxville dealers and the one we had in my town shut down.

If the computer shut it down, it would have stored a code, I would think. No codes though. Very strange. I had a Lincoln LS with a bad injector, but even that would throw a misfire code. Heck...I swapped coil packs forever before I figured out it was a fuel injector and is why I thought to check that first on the Mustang. Geez....8,000 miles and already a problem. It may have sat too long by the previous owner.

 

According to my wiring diagram, inj#8 is feed power from #30 term of fuel pump relay, through splice109 to inj, then grounded by pcm pin#38. The relay should be ok since it feeds all injectors. Unless the splice is bad only to inj #8 the inj connector could also have a bad terminal. I would however disconnect the lower PCM harness connector and check pin#38 for corrosion, bent, crimp,etc. You should be able to check from pin 38 to inj connector terminal with an ohm meter for high resistance.

 

That's what I'd do. It's either spark or fuel. As for water and your driving dry, don't count out condensation...

The other question is, are you blowing this thing out? Taking it up to redline? With that low of miles it may have idled excessively, been in traffic, etc. Give it an Italian tune up*. I swear by it - at least once a day! Keeps your engine carbon free.

*(With maybe a bottle of injector cleaner and fresh tank of good gas?)

 

I agree with that low mlieage the car sat. Hopefully they took care storage wise.

 

Thanks all. The strange thing is, when I shutdown and restarted the car, everything was fine. I swapped the injector around the other day, so if it happens again, I will see if the problem moved. The injector was not ticking at all and then upon restart, ticking normally, so I assumed a circuit issue. Unplugging and replugging the injector connector did not restart the injector. Only rebooting the car did.

Also, the first time this happened, it was in the morning on the way to work. This time it was near the end of a 560 mile drive. I don't get on it too often as where I live, everybody is sloooowww. I flogged it a few times though, to keep it clean. I bought it with 5100 miles and now it has 8700.

The car still looks and smells new. The seats have some wear (I would say the driver and passenger were heavy set). My 2006 had shy of 30k on her and the seats still looked pretty new and this one has about the same, if not, more wear than my 2006. The paint and body show almost no driving though, along with the tires and such.

Lime GT, thanks for the detail. I am going to do nothing else yet(other than the Italian tune-up mentioned), just to see if it will act up again first as to not introduce too many variables in it. Very good to know the circuit. That is what I am going to need if the problem stays with #8.

 

Do you use a tuner and if so were there any changes made while a tune was installed, I have a tuner and left my 91 perf in place when I cleaned my throttle body so it idles high after any rev but stock and 91 torq & 93 race are fine so I think one has to set to stock before any engine service, as if the ECM adjusts for fuel grade I'd guess other things as well .

 

Other than a K&N square filter in the stock box...b b b bone stock...