kentompkins

Okay. I have that seemingly common issue of inconsistent, but frequent misses throughout my RPM range. It's most noticeable at idle probably due to less sound from the engine. Randomly, within the beautiful, typical glug, glug, glug of the exhaust there is a puuff..... puff.. puff........pufff.

While getting it dyno tuned, my tuner and others gave me the theory that I have a COP doing bad. Not bad enough to throw a code yet but bad enough to cause this.

So... I ordered two brand new Motorcraft OEM COPs. (Don't waste time telling me to buy GMS, MSD, Accel or any other COPs). I moved them around the entire engine and it had absolutely zero effect. I tried the test of unplugging each one by one while idling... all of them had the same effect. So, I eliminated the COPs as the cause in my mind.

Next I focus on the plugs. I took out all four on the passenger side bank. Three plugs looked exactly as I would have wanted. One did not. It was wet. I smelled it and it doesn't seem like gas. I tried to light it think it would just go right up if it was gas... it didn't. It's not antifreeze... Yes, I tasted it. I think it's oil.

Hoping that it wasn't I tried moving that wet plug to the next cylinder and running it again - hoping that the same plug would come out wet from a different cylinder (hoping a bad plug or something I guess). Well, now the formerly wet plug was dry in the new cylinder and a previously dry plug is now wet in the same cylinder from which I pulled the first wet plug.

This cylinder and I are not friends. It's the second one in from the front on the passenger side. It's the one that I BROKE ONE OF THOSE DAMN OEM plugs in back in my naturally aspirated days. It's the one into which I feared a small piece of ceramic from the broken OEM plug fell down into. I thought we got it all out. I fear that we didn't...

So, what exactly would be the symptoms of a piece of ceramic being down in that combustion chamber? I assume it would not be vaporized. How much damage would be caused? Am I now looking at a rebuild?

I'm all in favor of getting a new block with a forged internal setup but does this now mean I need new heads too?

Lay it on me... I can take it. Be honest.

jz

Well you narrowed the problem down to at least that one cylinder. That's a start. I would do a compression check next. You may have some oil getting by the rings and that could be where the wetness is coming from. Could also be a pin hole in a piston if your timing or tune isn't 100% correct. If the compression in that cylinder is less than the others then I'd say it's time for a rebuild.

At least you caught it now and not on the side of the road somewhere after your car died on ya.

Derf00

Porcelain is like sandpaper to aluminum in that if the piece is still stuck in there or was stuck for a short while in there it will literaly gouge the cylinder wall. Do you have any smoke (blow by) in your exhaust? The only way to be truely sure about cylinder damage is either getting a scope down there through the plug hole or fuel injector hole, or remove the head and do a complete inspection.

If the wall looks good, a compression check is in order to make sure the rings are good. If all that checks out then it could be a valve stem seal.

kentompkins

There is no smoke in the exhaust at either startup or under load. I am going to order a compression tester kit from Summit that has the 16mm adapter in it.

I'll probably end up removing the head to inspect too.

So what's the best case scenario here? Assume I did all the labor. What might I end up having to replace? Heads? Rings? Whole Block and Heads?

Shadow7874

Might could get away with a hone is its just scratches a little. Or if the cylinders are scratched you could order new pistons and bore it out a little. Really it depends on where it is damaged. Im having a similar issue with my little 2 cyl jet ski. My crank bearing in it threw out and managed to make it above the piston so my head and pistons is dinged up but the cylinder walls and rings are perfect. It all depends on what damage there is and where it is.

highline

Unfortunately, I have no ideas to help you, as your "level" or knowledge is probably greater than mine, but this quote, for the first time ever, actually and literally made me lol...sounds exacly like myself...

kentompkins

There is a God... I got to thinking... was this the cylinder that had the broken plug. Guess what? It wasn't. I found my original post from back in February 2009:

https://mustangforums.com/forum/4-6l...ml#post5916254

So.... now this goes back to being a friggin mystery BUT THANK GOD - I am not likely working with a ruined cylinder wall or valves or piston.

Here's what I've tried (Compression tester is still on its way from Summit Racing):

1) Interspersed two new COPs around every position. Nothing resulted in the infrequenty yet recurring puuff, pufff, pufff going away.

2) I tried individually unplugging all the COPs one by one while idling. Each one seemed to have the same effect on the engine.

3) Measured the Ohms on all the COPs. All were with a tight tolerance somewhere in the high 5.X range.

4) Put a little dielectric grease on all the COP connections.

After those four things I am pretty close to saying it's not the COPs.

I also:

5) Pulled every plug. Regapped them to 0.300. Cleaned the all off and reinserted.

After running the engine and pulling all the plugs again - every plug was perfectly worn except that same cylinder (2nd from the front on passenger side). HOWEVER, it seemed to have less liquid on it. The liquid is definitely not gas and not antifreeze. It has to be oil.

6) I swapped the injectors (39.5 lbs) between the front cylinder and the second cylinder on the passenger side thinking maybe I had a spray problem. No dice. It had no effect.

So, after all this tinkering, I might be fooling myself but I think the miss seems less frequent. It's probably my mind failing me after breathing in so many fumes while kneeling behind the exhaust to listen. I have noticed that it is much more noticeable when I apply just a tiny bit of gas. So, between idle around 800 - 850 and under 1,000 rpms - this seems to be when it's most noticeable.

Next week holds the following to do's when I get back on Wednesday:

1) Bought two new upstream O2 sensors (Bosch OEM replacements). I will replace the originals and run it for a while to see if that has any effect.

2) Compression test when I get the tool in from Summit.

3) Look around for someone who can loan me a leak-down tester kit.

4) Oil change - just for the hell of it.

5) Maybe put a fuel pressure gauge on the rail... although I can't believe that my GT500 fuel pump setup isn't delivering enough fuel. I mention this one because, in the last few months, I DID replace the original fuel filter with a new Puralator OEM replacement. Maybe it's defective???

6) Recalibrate the throttle position sensor.

I know that numbers help so I should say that I have the SCT Livewire tuner. I noticed that both Short Term Fuel Trims seem to bounce around between 1.02ish and 1.10ish. Bank 1 seems to usually be lower than bank 2. Is that trying to tell me something?

Maybe I'm making too much of this? It almost makes it sound like I have aftermarket cams.... and she did dyno at 453 rwhp last week....

Should I just accept this as part of her personality?

Simon1

I doubt it has anything to do with any of things you are trying to correct. My car has done that on different occasions with the turbo. Exact same symptoms. Your procharger flows air thru the intake at idle similar to what the turbo does. I spoke with my tuner about and he told me to not worry about it. No check engine light and no driveability issues while driving or at WOT means it's it's some quirck that may or may not be able to be fixed.

Here's a good example. I just switched from my turbo set up to a Kenne Bell. Same fuel injectors, same pumps, sam BAP, vacuum lines and tune. Yes I still have the tune on there from the turbo. Before when the vehicle diled with the turbo it had a slight miss exactly how you described. Now with the KB, no misses, no miss steps nothing.

I could disconnect the trubo from the car before and just run NA. The car would idle great with no miss fires.

I could switch tunes. One made alot more power than the other. Both from the same tuner. One missed at idle, the other didn't.



Alot of of us (myself included) freak out at crazy strange noises and expect our car to behave the same as they did when they were stock. Talk to your tuner, talk to another tuner and see what they say. Don't worry about it for now and don't throw parts at it unless you know whats wrong.

Best of luck.

Simon1

Yes.

Also, your rear O2 sensors are probably turned off. If you need new ones, I think you can use those.

kentompkins

Ok. So the Compression test told me nothing but it at least made me feel really good about the likely condition of the cylinders, rings, piston, etc...

Cylinder

1 = 190
2 = 190
3 = 188
4 = 190
5 = 191
6 = 190
7 = 190
8 = 189

I also verified that all of the spark plugs are sparking.... sooooo....

Next stops include:

2 new o2 sensors for the front. Already bought so I might as well try it.

1 new Motorcraft Fuel Filter to replace the Purolator filter. Already bought so I might as well try it.

After that I plan to:

Test fuel pressure at the rail.


If that shows me nothing the I plan to forget about it because I am not buying new cats to see if that's it.