[alexsvt]

Hi Guys !

I working on a fox 302 , GT40P head , cobra intake , 24lb blue top , 70mm cobra maf . Symptom is like a missfire , big power loss in gear. On a fast neutral rev , it sound like a miss fire on 2-3 cyl.

Tested another coil , another distributor , inpected plug wire .

I suspect a clogged injector but the symptom is no power , black smoke on the back and wideband show very lean.

Datalog attach doesnt show any major change in reading

[cgrey8]

It's possible there's a problem in your tune. With tables or functions misconfigured to allow over-runs of the bounds of the function or table, you can run into issues like this. Being it is happening sharply as you approach 4000 RPMs, I'm thinking it's quite possible you've created a problem in the tune that causes erratic or undesired behavior at specific RPM conditions near 4000.

Post up your tune and let some of the tuning guys here to take a look-over it and determine if, perhaps, it is something in the tune. It might not be the tune at all. But it's a good place to start looking based on the description. So either confirm or eliminate the tune as the cause...

[alexsvt]

I drove back from a little road test , I burn a x3z tune , and over half throttle engine is bugging , shut and restart as i left the throttle , smooth driving is good , no stall . I found that when the engine is going very bad , the rpm needle is dropping and go back normal as the engine run better . I was able to go up to 5000 in a very light acceleration in second gear.

So far I the base a9l2 tune is not good , another similar tune for another customer does the same , and the stock cobra tune is not good . Open the pcm and no burn circuit or leaked capacitor.

Spark plug are brown black and should be more tan or coffee , wideband is 14.7-15.2 at idle.

Thanks

[alexsvt]

Here is the cobra tune and log , scroll to 100sec before see the free rev and 3 wot in neutral .

It like a rev limiter but physically there is no limiter, tested another pcm , same

[Chucko]

Is the TFI module Motorcraft or off-brand? When my original TFI died (thermal intermittent), I got an off brand, and my car had a bad stumble under heavy load, right when it got into the heart of the torque curve. Replaced it with OEM Motorcraft, no more stumble.

[alexsvt]

Both distributor I tested had motorcraft TFI . I have one only for test like this and I know its good .

[alexsvt]

This morning Humidity is 80% and temp 90 , car was very hard to start , like flooded . I checked the spark and in my memory a ford have a strong spark even w/o a msd box , what can cause the fire to be weak ?

All ground have been cleaned and buffed , main at the timing cover , both aside the battery , behind the bloc and firewall , and at the pcm . Salt n pepper connector re-tight and cleaned.


Thanks !

[EDS50]

Just looking at the log you provided, there is no kg/hr being logged which is important and load is over 90 and perload is over 100 in the 4000 rpm area.Stay away from that a9l2 garbage. Ill look at your x3z tune and see what I find.

[EDS50]

Looking at your x3z.bin you are using, it is 100% stock with no changes made. When you switched from the a9l2 to the stock x3z; did you clear the kamrfs? Did you check your plugs to see if any of them have a cracked porcelain which would create a misfire? Check stupid simple things like firing order, distributor installed correctly and not a tooth off, bad meter?...etc etc.

[cgrey8]

Pulling the coil wire off the center of the dizzy and watching it spark to ground using a nail or some other piece of metal is a good technique for determining spark strength. There should be no question as to whether the spark is "healthy" or not. If you have an ignition box, the spark should be able to jump well over an inch and still look good. I've seen GM ignitions jump 2 inches on the stock system. So if you think the spark looks weak jumping an arc from the coil plug to ground, it probably is.

Assuming the problem is an ignition component (and not the tune), the two most likely suspects are the coil and the TFI module. If this were any other brand of vehicle, I'd probably replace the coil first. However Ford TFIs have a long history of causing ignition problems, and I can't think of a single Ford TFI coil that I've actually had to replace because it was bad. So I tend to start with the TFI module. When TFIs go bad, the presentation of failure isn't consistent. If you are lucky, they out-right die with no ignition and the only way to get the spark back is to replace the module. Other times, they act flaky or operate intermittently making them particularly annoying to confirm as the source of the problem.

I haven't yet looked at your tune. I'm at work and likely won't until tonight at the earliest. Although it appears EDS50 has looked at your X3Z and determined it's bone-stock which would eliminate it as a source of this.

[alexsvt]

Looking at your x3z.bin you are using, it is 100% stock with no changes made. When you switched from the a9l2 to the stock x3z; did you clear the kamrfs? Did you check your plugs to see if any of them have a cracked porcelain which would create a misfire? Check stupid simple things like firing order, distributor installed correctly and not a tooth off, bad meter?...etc etc.

No not stock completly , mainly mtf , idle rpm neutral and drive, and shut couple of switch . I did load a tune with kamrfs clear and switch back normal. I changed the plug Autolite 104 to ford oem for GT40 iron head .

I mention that I tested another ignition coil , but did not test the spark . I just did and barely 1/8in to jump and more than that no spark . Check the connection at the coil , strong and tight . I have a stock coil and same gap to have a spark .

In the wiring diagram there is a 22k resistor , can be an issues ?

Re-attach the Test X3Z tune , maybe i just copy the stock one.

[EDS50]

You are obviously doing something wrong because both of the x3z 302.bin tunes you posted are stock as verified by the calibration differences in Binary Editor between your x3z.302 bin you posted and a factory .x3z.bin.

You mentioned a 22kohm resistor...What wiring diagram are you referring too?

[alexsvt]

Here in the Tan/yel wire to pin 4

[EDS50]

I wouldn't be concerned with that as much as loading the correct tune.

[EDS50]

You need to resolve this issue first:

x3z compare.jpg

[alexsvt]

You need to resolve this issue first:

x3z compare.jpg

Look just below the .gif , the compare.csv of the change made.

That tune is anyway just another test to unrule that is a tune issues . tends to be more electrical than electronic .

[EDS50]

You need to resolve this issue first:

x3z compare.jpg

Look just below the .gif , the compare.csv of the change made.

That tune is anyway just another test to unrule that is a tune issues . tends to be more electrical than electronic .

There are no changes made physically to the tune between what you are posting and a stock .bin.

[EDS50]

Had any changes been made or loaded to the hardware the checksum would be different between your tune and a stock .bin. What tuning hardware/software are you trying to use?

checksum.png

[EDS50]

I closed BE and reopened it and I can see your tune and calibration differences now. I apologize for the error on my end. Moving forward, you are correct there is nothing in your tune changes that "should" be causing a cylinder misfire as you are reporting. I would be curious to see what your maf kg/hr values are at 4000 rpm as you may be pegging the meter if all other mechanicals are sound. If this were a power adder combo I would be concerned about spark blowout but that does not appear to be the case here. Has fuel pressure been verified?

[EDS50]

Seeing your mafv is 4.26 at only 3700 rpm is an indication that you are pegging the meter or have a faulty meter.

dash.png

[alexsvt]

I appreciate all the help and hint everyones is giving me. Look like I made a mistake by loading the test tune I have posted here , but the point is even with the X3Z Test tune ( with the good MTF ) Or the main tune I have made so far or any chip in the J3 port , the engine is not starting . I even delete the GUFB def and redownloaded from the updater . Back in the days we just swap 24lb injector , clock the maf and bump the timing and it was starting ;)

That engine is pretty basic and normally i take 2hour on the dyno to make the car run great. But that one is a tough one to fix .

And last , have to close BE and reopen to change tune file should be fix in the next update , before i found that trick I turned in round couple of time to understand what happend .

[EDS50]

I also apologize for the issue I experienced on my end as well not being able to read your calibration correctly. I had BE open from a previous session and though it loaded your tune it did not show the calibration difference until I closed BE and reopened a new session. I am leaning towards a maf issue of some sort from what I see in the log. The hard start issue could be resolved by decreasing the msec values in fn348.