A handful of ideas and nothing concrete. I'll try to keep it short and to the point, but I'm at a loss here as to ruling out what the issue is with my car.

06 galaxy gray 6MT.
126~K miles.
Megan racing midpipe.

Approx two months ago on a drive from FL to NC up I95, cruising, I noticed when the fuel level got to roughly half a tank, if I would try to accelerate, the car would hesitate and cut out, the more I would try to give it gas it would just hit a flat spot and go nowhere, with audible backfires thrown in. This got progressively worse the lower the fuel level got.

I chocked it up to a failing fuel pump, because as soon as I would fill up the problem went away. Car would also leak gas from the fuel pump ring when filled up.

Due to short trips the issue never resurfaced until now. Less than two weeks ago the car would hit flat spots during driving at a sustained speed, When warm, stall out when in neutral, or sometimes catch itself before stalling, with an idle that would surge.
Wot acceleration is fine, car pulls.

Pulled codes. Evap leak, (surely related to the pump and loose retaining ring.)Eccentric shaft sensor. Strangely no misfire codes as I would have thought. And code for the midpipe.

*Replaced pump with new one.

No more leak, need to get codes pulled again, but car still stalls when in neutral after it gets warm. I thought compression, but it pulls hard when at Wot. Takes a few cranks to start up again though.

Thoughts? The ess was replaced months ago, the code went away, and now that this started happening it's back again.

 

"Pull hard" is not a difference between a 5 kg/cm2 motor and a 8 kg/cm2 motor, you need a test.

Have you ever had a belt fail? If you did, it could have lashed the eccentric shaft sensor wire and caused intermittent faults from then on. But this is such a long shot.

 

A compression test is on the horizon, although I guess I am partially incorrect with with what I said earlier, the idle/issue starts when the car is cold too. Also, no belt went out as long as I've owned it.

 

Did you replace the eccentric shaft position sensor?

 

The Ess was replaced, that code went away. But the idle and stalling persisted. The car was also throwing a p172. I changed out the coils and it hasn't had any issues since...so my theory is it was running way too rich, causing the idle and stalling problem.

One of the coils broke apart where the plug wire connects, and a few of them had that infamous white burn spot as well. Hopefully the car is good to go for now.

 

White burn spots do not matter. Glad to hear that the combo of ESS and coil change fixed your issues.

 

Annd it's back again. After that period of no issues, on the way to work again, same thing started repeating itself. hesitation when maintaining a consistent speed. When clutching in the rpms will fall and the engine will either stall or catch itself. surging idle, and sometimes while coasting in gear it has audible backfires.

I'm at a loss on this one. Changing the coils stopped it, now it's back. The only thing I can think of is maybe the plugs are horribly fouled, but if thats the case i'd probably be getting a misfire code? (last time I was getting a too rich code.)

Also worth mentioning is my positive battery terminal is loose where the metal part with the hole for the stud actually connects to the terminal itself, where its held on by the one nut. Not insanely loose, but with a tiny bit of effort you can move it back and forth. Maybe the loose connection could be causing that?

Any thoughts or suggestions? Plugs or that terminal the culprit maybe?

 

It's a rich code.

Tyblat, have you pulled the plugs to inspect them? That's relatively easy and should be your first move if you think your plugs are fouled.

Surging idle makes me think vacuum leak but that would give the opposite of a P0172. What about a bad/fouled front O2 sensor?

Can you pull data through the OBD2 port? I'd be curious to see what the commanded and actual AFRs are (as well as MAF, STFT, LTFT, RPM, and temp).

An ELM327 bluetooth OBD2 adapter is $10 and phone apps should be

 

No matter what you need to get those battery terminals tight and a good solid connection. I would recommend cleaning the terminals until they're shiny and add a bit of dielectric grease to the post and terminals prior to reconnecting. I've never had issues with the battery connections themselves in any of my cars when I had clean metal surfaces with dielectric grease added to all contact areas. This was one of the best pieces of advice I ever received from a mechanic that has since passed on - thanks Art.

 

A couple of your symptoms could be a MAF going. get the obd2 reader.

 

I'm about to purchase the OBDII reader online. I've been letting the car sit for about a week, not wanting to drive it to work with it behaving like it has been. I had to drive it yesterday and today though out of necessity. Zero issues.

I'm wondering what could be causing this, and why it apparently hasnt acted up the last two times I drove it.

The steering wheel shakes rather bad when I am giving the car gas and letting the clutch out while turning out of a parking space. That i'm almost certain is the power steering connectors (no light on.) Going to get some dielectric grease and contact cleaner, and take care of that tomorrow (hopefully that remedies the situation.)

Other issue thats recently been cropping up, and im not sure if its related to cold weather, but I did notice it started around the time I replaced my coils. Theres a whine that becomes audible the higher the RPM's get. Almost exactly like what you would hear from a faulty audio installation. My sound system is completely stock (bose.) It does have one of those aux in boxes thats connected, but i've never heard this noise before even with that installed. But I've had the radio completely off and I still hear it. Thoughts? Maybe the plug wires are just worn out and causing interference?

 

So I tightened down the battery terminal nice and well, Added some dielectric grease. Pulled my codes at Advance. Its saying Crankshaft sensor circuit malfunction, and running too rich, again. This is the second ESS i've put on this car. I have no idea how one could go bad so quick, let alone two. Maybe since it says circuit malfunction it means the contacts are dirty?

 

I would go back over the ESS wiring. The sensor itself is pretty simple, not much to fail there, but the wiring between the sensor and the ECU could have been damaged, causing it to short intermittently, creating intermittent problems. An electrical whine might mean that more than just ESS wires are involved.

The other thing, I'm not sure if you've done this yet, but clean and resnug as many ground connectors as you can, including the battery one. Audio whine is often associated with bad grounds. As you can imagine, anything that creates whine in the audio system also creates noise in all sensor and signal wiring, and some of them are sensitive, especially the ESS. So.. I bet all of this is a single issue.

 

Another thing to consider is a vacuum leak. Have you checked for vacuum leaks?

 

Have you checked the ESS positioning gear at all?
If that got bent or there is metal debris clinging to the gear teeth, it could throw-off the sensor reading.
That code does indicate a malfunction with the sensor itself or the wiring to/from, but you already replaced the ESS so wiring would be the next thing to troubleshoot. But while you're in there, can't hurt to peak at the positioning gear too.
Just something else to consider...