Odd higher RPM WOT behavior on a 302

[SlograbDC]

Hello everyone, making this thread to see if anyone might know what problem I'm having with my new setup on my 302 with an MSPNP2 and trickflow upper/lower intake manifold - hopefully, if anyone faces a similar problem, this will help them out as well!

Recently had my upper and lower swapped out, as well as had my old quarterhorse tuned ECU replaced with something more modern, a Megasquirt MSPNP2. Driveability is significantly improved now, especially when starting, and acceleration is significantly better now too - I'm putting down about 250WHP at 4200RPM.

The complete build at this point has:
* AFR 185cc heads
* mildly ported upper Trickflow trackheat upper and lower intake manifold
* B303 cam
* 24lb fuel injectors
* BBK 255lph fuel pump and fuel regulator
* Ford Racing fuel rails
* 1.6 roller rockers
* Professional Products throttle body
* Fluidyne Radiator
* obligatory A/C delete

However, when I'm around 4800 to 5000RPM at wide open throttle, it breaks up and my tachometer begins reporting the RPM weirdly - I had it once or twice pin itself at 7000RPM when it did that, or increase by 500RPM way too quickly for it to actually be accurate.

I'm honestly not too sure what could have caused that behavior. Bad fuel filter, dying ignition coil, bad distributor maybe? Whats quite funny to me is that there was no timing pointer on the engine before tuning started, so I have *no* clue how the previous owner had the timing set up, haha - after having bought one and setting at top dead center, seems fine now from what I've seen, though!

I do have logging functionality from my ECU, I didn't get the chance to try and recreate that behavior though, but maybe someone can see something that I don't. I'll probably get he chance to get some better logging data tomorrow.

 

[SlograbDC]

Also, hoping this is the right thread to ask this in

 

[07GtS197]

It definitely could be the pip going out. How old is the distributor? What about your other ignition components? Given the odd tach behavior, I’m leaning more towards the pip starting to go bad.

 

[SlograbDC]

It definitely could be the pip going out. How old is the distributor? What about your other ignition components? Given the odd tach behavior, I’m leaning more towards the pip starting to go bad.

That's an excellent question - I'm not sure honestly, but I wouldn't be surprised if it was mostly original at ~106,000 miles

Only non-stock part on it is the MSD cap and rotor, I think. Ignition coil is probably original as well, I got that ordered already so we'll see how that changes things. I'll probably order a motorcraft OEM distributor sometime this week if that doesn't change anything.

 

[07GtS197]

That's an excellent question - I'm not sure honestly, but I wouldn't be surprised if it was mostly original at ~106,000 miles

Only non-stock part on it is the MSD cap and rotor, I think. Ignition coil is probably original as well, I got that ordered already so we'll see how that changes things. I'll probably order a motorcraft OEM distributor sometime this week if that doesn't change anything.

I think that’s a good start.

 

[SlograbDC]

Hey everyone - as promised, I did get the chance to replace the ignition coil with an OEM Motorcraft one - seems high quality enough, it does seem to have some play on the mounting bracket itself but nothing some silicone probably wouldn't fix. Put dielectric grease on the plug insert and it works just fine!

Did some WOT pulls once the engine got warmed up while driving up north a bit and back - the ignition coil definitely seems to have helped, earlier I saw it consistently exhibiting the stumbling around 4800RPM to 5000RPM with the tachometer going crazy alongside it - now it seems to have slightly different behavior at about 5300 to 5500RPM exhibiting some kind of break-up behavior, although to a much lesser degree - I never saw timing exceed 27 degrees at the time

I did poke around in my tune and noticed that injector size is set to 240cc, when it should be 252cc (lb to cc can be calculated by multiplying by 10.5x - so 24lb should be 252cc), doubtful that would cause this behavior though.

Going to probably replace my fuel filter tomorrow and change the injector size in the tune to be correct, we'll see if there's any behavior change at that point fellas. Like before, if anyone wants to poke around in the logs I pulled off the MSPNP2, I attached them to this post

 

[Terrorist 5.0]

The tach bouncing around is a very good indicator of your issue. Whatever reads engine RPM is overwhelmingly likely what is your issue. AFAIK, the PIP sensor is responsible for that. All your symptoms fit the profile of the PIP failing.