uraceulose

Hey fellas this is my first post here so to give a little background the car is a 2000 3.8 coupe 5 speed.

Car has run fine for the last few years with zero check engine lights or engine issues.

All of the sudden last week I went to drive off to go grab some lunch and noticed it fired up a little rough, then ran a little sputtery/rough as I pulled out of the parking lot. By the time I got to the first stop light, the check engine light (CEL) was flashing and it was still obviously running rough. My drive from work to home is about 5 miles so as I drove the light went from either a constant ON to flashing ON/OFF the whole time.
Grabbed the scan tool from a buddy of mine, scanned the car and go a misfire code for cylinder #3...I noticed a worn spot on 2 of the passenger side bank plug wires (where I thought it could have been arcing) and it had been a few years since the last plug/wire change so I bought a new set of plugs/wires and threw them on...no change. Went down to LKQ and bought a coil pack...no change still running rough albeit a little bit better.

Did another google search and came up with everything from check the balancer bolt to the fuel injector(s) or even disconnect the battery...

Tried disconnecting the battery for 15 minutes to reset the ECM/PCM and see if the code went away/came back the same or different.

Fired it up and drove about a mile or 2, still running rough but the CEL is now gone. When I say rough, I mean immediately after firing it up it won't idle very smooth and a few days ago it did...it will hunt for the right idle rpm between 500-1000 anytime I'm sitting at idle whether warmed up or cooled down. It also has a noise now that sounds like a rattle coming from the exhaust or something...not coming from the engine. All fluids look fresh and full, oil pressure/temp and coolant temps are all good.

Now this morning I tried driving it the 5 miles to work to see if the CEL would come back to point me in the right direction. Just driving with the scan tool on the passenger seat to see..the scan tool has live scanning data capability but I don't really know what to look for and the CEL still has not come back on..

One of the mechanics at my work said look at the crank sensor or a fuel injector. I don't want to throw parts at it if I don't have to. It seems as though this car doesn't have a crank sensor and it'll be waiting for shipping plus a little bit of work to swap a random injector so what do you guys think?

Any advice would be much appreciated.

Thanks and Happy Easter weekend to all,

Donnie

Derf00

99-01 v6 mustangs usually get passenger side leaky exhaust manifolds where the manifold meets the exhaust flange on the manifold side. If that is cracked it will throw throw the air/fuel ratio off because it is upstream of the first O2 sensor. That crack will also cause a rattle or machine gun sound if it gets worse.

The hunting idle is probably the idle air control (iac) getting oil in it (clogging it). Take it off and clean it. 99-01 valve covers tend to allow excessive blow-by in the pcv system that runs back into the intake and past the iac.
After you address those two, then see where you are at with the rough idle....

uraceulose

Thank you, I cleaned out the IAC a minute ago and it idles smoother but still fluctuations in the RPM. Took a quick look at the manifold/exhaust connection and it didn't show anything visible from the top of the engine looking down. Will check again more closely later.
Just to clarify, it more sounds like the muffler is blown out or there isn't even a muffler on it. The sound has gotten progressively all though slightly louder and more severe in the 20 or so miles I've driven the car since these issues started.

Daehawk

Two years ago or more my CEL came on and the engine missed a lot. After a few months it went away. The CEL went off and the engine hasn't missed since.