I have 2001 GT that every once in a while seems like it is misfiring.When this happens you can see in the mirror that it is billowing smoke and you can smell the raw fuel.Check engine does not come on.I pulled a pending code that said misfire in #4. Usually it's a coil gone bad ,so changed it.Same thing happened.Changed the plug .Misfire again but no pending codes.Changed the injector.Still sometimes misfires and you can smell and see the raw fuel.Changed the airflow meter to no avail.Can some one add some insight into this?With no check engine,I'm baffled.

Thanks
Mike

 

What is done to your car? How do the plugs look, do they have a lot of carbon deposits on em?

 

The plugs are new.Pulled a couple out and they look light tan as they should.I have swapped #4 coil with number 7 since #4 is new to see what happens.Could be a bad new coil.Drove it about 20 miles yesterday with this arrangement and right when I got in my driveway it started to missfire and smoke.I didnt have time to dissconnect coils or injectors to see what cylinder or cylinders were the culpret.I do alot of work on all different dars and like i said this one is baffling and irritating.

 

wow, you have changed a lot of parts for this problem. I know how irritating something can get after you try everything you can think. Some times it something not so obvious, like a crimped wire or something along the ignition or the fuel injection system. Check the singal coming into the coil with a multimeter and compare it to the others. Then do the same for the fuel injection.

 

i agree with stangalator. i had the same issue with my 01 stang and it ended up being a grounded wire in the cruddy wire bundle that ford puts under the hood. when i do my rebuild im going to clean my wires up and try to make it look like just a motor under the hood....i.e. lots of wire hiding!

 

Seems to be running OK now.I think it was a bad NEW coil.I hate when that happens.

 

i have a 1996 mustang gt that will do that seem thing. If i am driving say in town it seems like its loading up with fuel then it starts sounding like it is missfiring, but if i get on it and bring the RPMs up it seems to clear it out and then it may be ok for a bit. I have quite a few mods done to my car but there were a couple of things already on the car when i bought it so i am not sure if someone tuned it wrong or something. would i be able to buy a programmer and set it back to say more of a factory defult or at least start over and tune it to my liking. i hope it will be an easy fix like maybe they just have the fuel to air ratio off a little bit but im not 100% sure. any tips or help i would appriciate?

 

Turned out to be the wiring harness under the hood was redting on the egr pipe.Burnt thru #4 fuel injector wire and was shorting it out.Problem hasn't come back for about a year.Now it's runniing rich again.I'll have to get back into the wiring harness and see what is happening.Car is so rich it stalls out and no check engine light.

 

Failing but not yet dead front O² sensors can cause the engine to run rich, and not throw a code until they die a bit more. As the sensors fail their output voltage drops, lower O² sensor voltage = lean, and the PCM compensates by making the mix richer--which the failing sensors now report as stoichiometric (14.7:1) making the PCM happy but the mix is really too rich.

If you can log the short term fuel trims, if they are running +15% or better then it's likely to be the front O² sensors.

You can bench test the sensors with a propane torch and a multimeter. Check the heater resistance too, it should be around 3.3Ω, if not the sensors may be running cold which makes their out out low as well...

 

Hey cliffy,

I'm throwing p1152, and only p1152(and p1000) i've swapped the o2 sensor from side to side, changed nothing. So i then decided to take the car down to JBA in San Diego.

They have tested the wiring harness and even managed to hook up the o2 sensor directly to the ECU. Still acted funny. The heater core in the o2 sensor isn't heating up for what ever reason. After a full day of testing and diagnosis, they still are at a complete loss for what is going on.

It idles fine when I start it up, but when I start crusing in 3rd gear or higher it will sputter as the short term FT slowly climps to 1.250(I can watch this on my tuner)

Any ideas?