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Hitting a wall near 5500 rpms

797 Views 8 Replies 2 Participants Last post by  eschaider
Hi everyone!

It's been a while since I last posted here, but always kept reading. I haven't done much to my car (if anything at all) since I swapped a 4R70W in it in 2016. It's been running great since then. Except I now got an issue, it's like if I'm hitting the rev limiter much too soon. Here's what I have diagnosed so far:

  • At WOT, full boost, near 5500rpms, the engine sputter and stops accelerating
  • Nothing noticeable at low rpm or normal driving
  • If I accelerate slowly, it revs to 7K cleanly
  • If I put the blower in valet mode (5psi of boost instead of 18), it revs to 7K cleanly
  • I tried a set of known good coil packs, same issue
  • Compression between 150 and 175 on every cylinder. I once had a similar problem cause by faulty lash adjusters and I was able to see it on the compression test, which is not happening this time.
  • I have the J&S Vampire knock sensor, it doesn't light up or retard spark on any cylinder
  • No DTC code

My best guess for now is my valve springs. I have TFS 2V head bought in 2014, some springs may have lost some tension. The extra boost makes it harder on the springs and they can't keep up anymore at high rpms.

Car is now stored for Winter as of today so I can't test it anymore.
Any idea what it could be? Is my reasoning correct?

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It could be valve springs, Michel, but I would be betting on either the ECU or the coil packs. The EEC-IV and EEC-V ECUs. have always had a power (not volts but Mhz) issue, which effectively limited the maximum engine speed they could handle to somewhere between 6500 and 7000 rpm. The more burden you place on them and the older the electronics get, the more pronounced the problem. A software switch is accessible through the tuning software, allowing you to step the ECU clock to the top of its range. That is the good news. The bad news is the top of its range is 15Mhz if I remember correctly.

Things that draw on the ECU for processing cycles are emissions logic, PATS logic, and Ford brand automatic transmissions, etc. In addition, some transmission builders offer their own transmission controllers, so you do not need to use the OEM ECU, and also, because they provide features the OEM ECU does not / can not.

Another possibility is the coil packs. The OEM coil packs and virtually all the aftermarket replacement coil packs only have between 15 and 18 millijoules of energy. In the movie, The Untouchables, Sean Connery has many good one-liners. In one exchange, as he is looking at one of Al Capone's gangsters that has just been shot, he observes, "Isn't that just like a ***? Brings a knife to a gunfight."

It is sort of the same thing with Ford Modmotor COPS, whether OEM or aftermarket. With only 15 to 18 millijoules of spark energy, they are suitable for proletariat trips to the grocery store and taking the kids to school. Unfortunately, they fall woefully short of the mark for a supercharged application making north of 3HP per cubic inch like you.

Between the anemic clock speed and 1990s IC technology used in the OEM ECU, 7000 rpm is about the end of the line when everything is new and at peak operating efficiency. The problem is, what is the upgrade path available?

One of the better paths we have looked at, and many have chosen, is the MegaSquirt MS3Pro Plug and Play ECU that DIY Autotune offers. It will deliver crisp performance and timing up to more than 10,000 rpm and allow the use of aftermarket coil packs with 118 millijoules of spark energy and a very long spark — all atta-boys for boosted engines. There is one more big plus the MS3Pro P-n-P brings to the table — It runs your OEM dash, so you don't end up with a blank dash and a $1K to $2K aftermarket replacement.

I almost forgot, it also has transmission control and knock control. While the MS3Pro provides built-in knock control, if you already have a Vampire, you can turn off the MS3Pro's knock control and use the Vampire — avoiding the arduous knock control setup that most everyone uses except John Pizzuto's Vampire.

Here is a link to the ECUs => MS3Pro PnP and a link to the 118mj ignition coils => IGN-1 Inductive Coils BTW, these folks are the only EFI manufacturers that offer a lifetime warranty on their ECUs.

While you can have someone at a dyno shop tune the EFI system, it is decidedly to your advantage to learn how to do it yourself. If you decide to do it yourself, let me know, and I will point you to some excellent reference material to help you get the job done. BTW the SVT Cobra version comes with a pretty good base tune for an Eaton, and it will help to get you out of the blocks even though you use a turbo.
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Thanks Ed, great answer and very informative as always.

I noticed the MS3 PnP for 96-98 finally got released in June and it's definitely something I want to buy at some point. For now I'm using the Quarterhorse & BinaryEditor.
My car is a 97 GT and use the 4 tower wasted spark coil packs and not the coil-on-plugs, are these good? => IGN-4

My car originaly had a manual transmission, I swapped a 4R70W in 2016 and use the Quick4 controller, no transmission logic in the ECU. Emissions and other stuff also disabled since many years.

I also want to point out that for many years, I was able to rev to 7K without issue, so I know the ECU despite being weak, is able to do it, and still does at lower boost. This leads me to coil packs, but I already tried another set and had the same issue, hence why I'm left with faulty valve springs as the mose likely cause of my issue. Coils & ECU are something I had planned to upgrade for a long time, but I'm fairly sure they are not the issue right now.
With the additional information, the valve springs become a high probable contributor. I am dragging my feet on the springs because even bad springs should get you to 6500 rpm.

The IGN-4 coil packs provide the same 118 mj energy at the plug that the IGN-1 coils do, so it is not a coil issue. However, increasingly I think the ECU has become a little long in the tooth and a little less spry than it was when it was younger.

Have you data logged any of the events to check the AFR, fuel pressure and other stuff like that?
My bad if I worded it badly, English not being my first language, but I use OEM coils. I had a spare set that I tried and I have the same issue with both. Both worked correctly previously so I ruled the coils pack out. An upgrade to the IGN-4 (or IGN-1) is still planned for the future.

I understand it could be ECU related if 6K+ rpm would always be an issue, but I when set the Kenne Bell in valet mode (5psi), the issue is gone, it revs cleanly to 7K at WOT. I don't see how the ECU can be a culprit but I'll be glad to learn something.

I sadly don't have datalog, my laptop broke and since the car was running perfectly for many years I just went to the track and had fun with friends. I have a video of a pass when we can see and hear the problem, that's the best I got.
It happens at the end of second gear right when I shift to 3rd, and also near the finish line. You can see a smal bump in boost presure when it happens, at 0:36
I can see it start running leaner when the issue happens, but I think that's a symptom and not the cause.
I will also add that on this pass, I shredded 2 ribs off my belt. I had no belt issue for the pass 5 or 6 years.

References of the gauges:
Sky Wheel Vehicle Car Motor vehicle
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I take back my comments about coils. The OEM coils in brand-new condition are at best marginal. Used it is anybody's guess. My list of high probable culprits would now be the ECU and also the coils. The 5psi good performance vs the higher boost poor performance is simply the additional energy required to light the fire, energy which the OEM coils and the OEM ECU are going to have a progressively more difficult time doing.

Just in case the communication is better in French I used the Google translator to say the same thing. I hope it worked as intended.

Juste au cas où la communication serait meilleure en français, j'ai utilisé le traducteur Google pour dire la même chose. J'espère que cela a fonctionné comme prévu.

Je retire mes commentaires sur les bobines. Les bobines OEM à l'état neuf sont au mieux marginales. Utilisé, c'est quelqu'un devine. Ma liste de coupables les plus probables serait maintenant l'ECU ainsi que les bobines. La bonne performance de 5 psi par rapport à la mauvaise performance de boost plus élevée est simplement l'énergie supplémentaire nécessaire pour allumer le feu, énergie que les bobines OEM et l'ECU OEM auront de plus en plus de mal à faire.
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No need to Google translate, I have no problem reading or understanding, it's my writing that leave a lot to be desired. I do appreciate the effort.

I get what you mean. Coils were ok but just enough for many years, and now they are just a bit less performing, and it shows. Hence why they stopped working and the spare set too.

I already removed the driver side valve cover tonight. Changing the springs with the engine in the car is possible but will be a PITA. They are cheap, might as well be sure and change them, but you make me doubt a lot about the coil packs, plus I've been waiting for a long time for the 96-98 MS3PnP to be released, I may do all that this winter. Sadly I won't know what solved the issue if I do everything, and won't be able to post results until next Summer.

If you can send me the reference material for the tuning, I would appreciate that.

Thanks a lot Ed, I read all of your post on this site and learned so much from you, you are a gift to this community.
Bringing this one back up for posterity. It's not a huge surprise anymore, but Ed was right again. I'm the proud owner of an MS3 Pro PnP and IGN-4 coil pack since December. I was able to do my first clean WOT pull up to 6600 RPM today and the issue I was having is now gone.
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Congrats, Michel! I knew you would win the war in the end. Sometimes those conundrums are stunningly imposing. Until you have lived the solution like you have, the idea that the OEM unit is the bad boy is really hard to come to grips with. I could not be happier for you. Great job, well done!!
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