I have a very different type of misfire

BlueChappy570

New Member
Jul 22, 2020
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0
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49
Port St. Lucie
So not that long ago, I ran the tank almost empty. I did not run out of fuel but I was with 6 miles. I have a 2005 Mustang GT and it’s slightly modified, so 6 miles is probably closer to 2-3 miles.

Anyway, since that day, I’ve been having a horrible stutter on acceleration. It does happen at lower RPM’s, and slightly on straightaways, but really is accentuated after making a turn.

I did what I thought it was. I changed the fuel pump, fuel filter, and the fuel injectors. They are all brand new, and the car is still stuttering especially around corners.My coil packs are less than a year old and I changed the plugs at that time as well.

I’m thinking it’s a fouled plug. But are there any other ideas what might be causing this? I don’t want to keep sinking money into things I don’t need. It would be easy if there were an engine light to get coffees from, but no light is present.

Any ideas?
 
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08GT500

Active Member
Jul 12, 2018
858
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Massachusetts
Hi,
Sorry to hear. Good idea, throwing money at it will only make the root cause more difficult to locate. This may be related, or coincidence & unrelated. Don’t focus on only that.
A piece of crud that broke free may be inside the fuel line, e.g. sensitive on corners.
Have a decent Scantool that allows live Data viewing, drive cycles, etc?
Fuel pressure at the rail?
1) Connect and look for Codes-regardless, they don’t always throw a light.
2) Pulling plugs is a good idea, clean/regap. Add NeverSeize to the threads, install. Use electrical grease on your COP to Plug connections. Note the color of each plug & where it came from.
3) Spray the MAF sensor with CRC MAF cleaner, clean all the way up to/including the TB.
4) Fill up for fuel at the same spot, or did you change to a non typical spot for this fuel?
Few to start with, gather info.
5) Check engine light ever flash under acceleration?
Best!
-John
 

BlueChappy570

New Member
Jul 22, 2020
3
0
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49
Port St. Lucie
John,
Thanks for getting back with me. A Scantool is something I don’t have. I will bring it to AutoZone to see if it kicks a code. I did fill up at the same place. I thought maybe it’s been a bad batch of fuel myself. But I’ve had three tanks of fuel in it since it’s started. The light has never flashed or come on at all...

considering it’s really bad in a turn, do you think it’ll be electrical? Of it were electrical, would it be bad in all situations? Thank you so much for your help.
 

BlueChappy570

New Member
Jul 22, 2020
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Port St. Lucie
UPDATE!!!

So, I changed my oil yesterday and cleaned my cold air filter. ALL PROBLEMS ARE GONE. I was low on oil which probably means that I had insufficient oil pressure at low RPM's to operate the VCT system. Not sure why I was low, but I know now to keep an eye on this. We are back on the road!
 

08GT500

Active Member
Jul 12, 2018
858
133
53
49
Massachusetts
Hi,
Very good, happy to hear all is well!
Although it sounds more like air restriction, a typical dirty MAF affecting A/F ratio- when you mentioned “it’s worse on corners”, the oil level swinging away from the oil pickup in the Pan due to a restrictive pickup, leaky pickup connection, or low oil did come to mind.
But we have warning systems for this, why did they not function?
The Oil pickup is between 1/2”-3/4” off the base of the Pan, and Oil is within passages, some in a gravity fall back into the pan, some returning from filtration. The reserve is the excess that remains in the Pan while this is occurring.
I run a simple Mechanical Oil Pressure gauge on every motor I care about, and as a result of a very close call. I encourage others to do the same. They never lie, are inexpensive, require no electricity. An oil pressure transducer/ignition cutout is the ultimate.
IF the Oil level played into this or not, I’m pretty sure you’ll want to find out.
I Am truly happy to hear it’s running well, as that’s now OK, there’s a little more I’d suggest you consider prior to moving on. Where the oil is going will show up within the same simple diagnostic efforts.
The Conundrum...
A Bullet dodged if the oil was as low as described. Generally, an engine has sustained damaged by the time you hear any noise or experience oil pressure low enough to affect performance, almost always starts with noisy hydraulic Valve-train, then main & rod bearings lose pressure.

Delve a bit deeper. For instance..
1) How low was the Oil on the stick before draining?
2) How much Oil drained out into the catch basin when the drain plug was removed? (if you don’t still have it, guess..it was low, but how low....3 Quarts..3 Quarts + Full Filter, etc).
3) How much Oil did you refill with, where does the oil level show up now on the Dipstick?
4) Still have the old Oil Filter?
5) Last Oil change made in Miles back, full Synthetic, Viscosity, Mfg., Filter Mfg.?
6) A Shop do it, or personally performed?
SYSTEMATICS..
A) Why didn’t the oil pressure gauge dip.?
B) The low Oil light did not illuminate.?
C) If VVT was affected, i’d expect a few DTC’s, lash adjusters may not cause any Codes. No Codes, correct?
D) Low Pressure Chime? (Not 100% if 05’s have them). My 08’ does.
General information..
More times than not, the hydraulic lash adjusters will become louder with even “borderline” or erratic oil pressure due to lack of Oil, or barely enough oil to reach the oil pickup, causing aerated (Cavitated) oil which affects pressure.
Lash adjusters are very sensitive to oil pressure levels being low, they carry the Valve spring loads by oil pressure and are the furthest away from the Pump, have very small orfices, and become louder with lower oil pressure, then Valve lift decreases, power loss.
Oil Filters have an anti-drainback Valve (Some Filters do not) and why its crucial that OE Filters or the best aftermarket Filters for the correct engine are used.
The valve prevents complete oil drain back in the blocks upper galleries and drillings, so there’s a little oil sitting in the motor when you shutdown. Startup. Still, 70% of engine wear is a product of cold starts until pressure builds.
Certain engine blocks have these drain-back preventers installed within (which is why some Filters don’t require them).
Pressure drops off from seconds to minutes, but the unpressurized oil should remain. The Oil pump also supports this.
Best!
-John
 
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