Also on another note, I don't know if it matters but I did disconnect my battery and reset everything after the o2 sensors and honestly I thought they were my issue with how destroyed one side was but the problem persists and it even began idling bad after warming up. Started a slow knocking idle at about 500 rpms almost to the point of dying. I didn't know fixing things could make it worse.


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http://http://i180.photobucket.com/...s/x107/DJPUNK34/3A914A56-B00C-49AA-926D-D8961334A194-22824-000012A232EF9B53.mp4

 

I was going to say, those heads on that shortblock will raise the compression. If I had to guess, Id say it needs a tune from the added compression. What kind of injectors?

If the injectors and MAF arent calibrated togeather, bigger injectors will cause it to run rich. Smaller injectors will run it lean

 

what size injectors are you running? damn he beat me to it

 

My tuner who reflashed to remove a dyno tune said the stock tune has so little timing that the compression shouldn't make that much of a difference to just run 93 to cut back on detonation. He claimed that wouldn't be big enough a problem to cause my issue.

Its stock yellow/orange top 19lb? injectors and stock maf.


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If its running rich at cruise/idle too then find a new tuner. Timing isnt going to affect it at idle or cruise as much as WOT.

I would bring it to a reputable tuner. I think those injectors are smaller then what that MAF is calibrated too. Should be 21lb pink top injectors.

 

To put it into perspective my 2012 kia forte 4 banger can out run it and the stang has 4.10 gears as well. Its running horribly.


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My buddy has a 99 gt stock motor. Same 19lb injectors. Even if they were wrong they would cause me to run lean if smaller than needed not rich right? But either way thats the stock stuff.

And I shouldn't need a tune for the compression. It didn't really change that much. If anything a rich condition should lean out under WOT when the motor actually needs the extra fuel the computer is dumping right? I just can't fathom how its still running so rich now. It doesn't even throw an o2 sensor issue or rich code. Its just a damn misfire code that comes and goes in two cylinders. It randomly switches cylinders too. Originally it was 3 of them, which I corrected to 2 after the new parts and re-tune. What I did helped but still a problem persists and the only way I know its rich is because it throws fuel into the exhaust above 3k rpms whether its a rev in neutral or under a load.


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As for my tuner, he's very reputable. He was brought up before stang-hi performance and around here thats a big deal.


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if the pistons you put in are true flat tops with pi heads i think that would put you close to about 13 to 1 compression give or take a little bit im running 11 to 1 compression with an 11cc dish and my stock pi heads and according to the guys at modular mustang racing thats as high as you can go compression wise before you need to start running race fuel which doesnt really explain the whole rich thing id maybe think about replacing fuel injectors possibly leaking? i may be way off but just figured id throw some ideas at you and you could pursue checking them out. Could you maybe post a video on youtube and set up a link showing what it does.

 

I'm not sure what the compression ratio is now, but its not significant according to my tuner. The link above it the current idle video where it nearly dies with a slow loping idle. I'll post one later today on what it does under load and throttle.


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The pink 21 lb/h injectors were not introduced until the mid- to late-2002 MY production. And oddly there were no changes made to the injector settings in the stock tune.

Here are the injector parameters from a MY 2000 stock tune (RVAFA_NUX2):

and from a MY 2003 stock tune (RVAF1_XSH2):

The MAF transfer functions are the same as well. This results in the GTs with the pink 21 lb/h injectors running pig-rich at higher loads and WOT, with the AFR sometimes dropping into the high "10s" under hard acceleration. Changing the Stabilised Open Loop Fuel table to partially correct this is one of the first things done in canned tunes, though the proper way is to change the injector slope settings.


While running the 21 lb/h injectors I had settled in on these slope settings to get AFR at WOT and fuel trims under control:

Upon installing the FRPP 24 lb/h injectors here is what I found to work best:

As has been stated above the ignition timing in the stock tune is also quite boring. This is another thing canned and mail-order tunes fix right off the bat, even in an "87 octane" tune--adding 1.5° to 2.0° in the Spark Borderline table or the Global Spark Adder scalar value.


one last comment, MAFs are not calibrated to any particular injector size as there is no need to do that in the modern EFI age when a MAF's actual transfer function can be loaded into a tune. So-called "calibrated" MAFs are a left over from the old days when the tune was difficult or impossible to change; and are "calibrated" to a particular injector size AND a particular stock tune--read more about calibrated MAFs here...

 

Have you checked for any exhaust leaks?

 

try moving the injectors that are on the cylinders that are misfiring to a different cylinder see if the misfire moves

 

compression\leak down test

 

I'm not sure which injectors are misfiring now. The light is off. The only thing I know is after changing the oil and o2 sensors the idle has become worse than ever, almost stalling at times. I don't know why replacing an o2 sensor that looked like this would be an issue.

Right side is passenger side, where originally cylinder 1 and 4 misfired along with 5. Now its most recently became 1 and 2 but now that the light is reset idk which ones.



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It is idling once warm close to 500-600 rpms and the motor rocks pretty badly in my opinion and most recently when I rev it up, it has dropped below 500 and pulsated up and down several times before returning to a crappy 700 rpm idle.


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D46FCC44-CDC6-4AE9-AC49-13D912C04317-24082-000013898B6C2A09.mp4 video by DJPUNK34 - Photobucket

 

First link is a 2nd and 3rd WOT pull, and the second link is the idle after the drive which is worse than ever.

 

I agree that it is time for some mechanical tests, if for no other reason then just to rule things out--compression (dry and wet), monitor manifold vacuum and compare to this chart, and leakdown...

 

I have no idea how to test any of what your saying other than Compression. If the cylinder is fine it should be within 80-95 on each cylinder right?

I'm not sure how to test fuel pressure or the other aforementioned tests. Enlighten me friends.

 

135 psi is the lower service limit for dry compression, and the lowest cylinder should be no less than 75% of the highest.

The dry compression test is to pull all the plugs, block the throttle open and go at it. If a cylinder reads low then pour 1 oz of motor oil into it and test again. This is a "wet" test. If the compression rises then the cause of the lower reading is that the rings are not sealing as they should (the added oil helps them to seal for the test)--if it does not rise then a valve is leaking.

To observe the manifold vacuum you need a vacuum gauge (duh) which would be connected to the upper plenum with a "tee", at one of the vacuum lines coming from it. The PCV or the line to the EVAP system will work. Start the engine and when warm, at idle and while driving, compare what you see to the chart I linked earlier.

A leak down test involves using an adapter to apply compressed air, through the spark plug bore, to a cylinder positioned so that both valves are closed (TDC of the compression stroke). The cylinder is charged with compressed air, the air valve is closed, and the rate at which the pressure "leaks down" is recorded. The end result is different from the wet compression test only in that often just by listening you can determine if it is an intake or exhaust valve that is leaking.

It is a more precise test than the wet compression test, but in truth failure of either means the head is coming off and once it is off it would be silly to just rebuild the single valve indicated as bad by the leakdown test; and the wet test is much easier...

 

Wait I was told a compression test was to remove all coil on plugs, and individually remove each spark plug install the gauge and turn the engine over without igniting to build compression and it should read around 80-95. I'm assuming the number you got is indicative to the fact that my compression with flat top pistons and PI heads is higher?


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But all kidding aside, a top end rebuild should solve my problem correct? Or could I be looking at rebuilding the bottom end as well? I don't know if any of the rotating assembly or pistons would be the issue or just head and up related.


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The more I drive it the more I feel like its a timing issue. Is there a how to or a guide to follow as far as to check my timing chain/guides and the timing itself?

Almost there guys.


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