breaking up above 5K RPM only when hot

[SOAB_465]

I have been having a new issue with my mustang. It's a forged bottom end, stock heads and cam 9.0:1 on about 12-14lbs of boost from a 2.3L Whipple. Original Coil Packs, TR6 plugs gapped at .026". Walbro 255LPH pump with aeromotive regulator and billet rails, deka 60lbs, BA2800. It used to run perfect, but lately it falls on its face for a half second at a time somewhere between 5-6K RPM. It never does it on the first pass, but if I hot lap it will do it at the end of 3rd gear, and if I go around again it sometimes will even do it at the end of 2nd. The first hiccup is about 1/10th of a second, and then it cuts out longer, sometimes 1/2 to to 3/4 of a second if I stay in it.

It shows a little bit of a lean blip, (going from 0.82 to 0.90) but if I richen the MAF at those points it only goes up about the same amount (from 0.75 to 0.81). That makes me think it's maybe not the fuel pump. What else could cause it to stumble and show lean?

Here's a couple datalogs, the CSVs are from livelink (i just changed the extensions to xls for upload), that's how I have my Wideband and MAP sensor logged. I also have an xdl from a different run, but I don't have the Wideband hooked up to the EGR pin

[red5.0fogger]

sounds like fuel pump. Without double checking i think the 255LPH is on the small side for your power if at all. The tune shouldn't suddenly change.

[BOOSTEDEVERYTHING]

Sounds like Fuel pump or the plugs are too hot. I would be running TR7 plugs with that engine and boost level with about a .024' gap. Can you monitor fuel pressure when it is happening? That would tell you all you need to know.

[SOAB_465]

I'm thinking fuel pump too. I have a FRPS from a crown Vic I want to use to log ∆P I just need to build an adapter to connect it to my regulator. I thought it might be a bad coil, because it seemed to be related to under hood temps, but new OEM coils didn't make any difference

[BOOSTEDEVERYTHING]

You may just put a manual gauge on it for now and see what it's doing. Should be enough to see if fuel pressure drops out. Also, I would at least try and close the gap a little on the plugs to about 0.024" and see if that helps any. I run TR7's on most boosted Fords at about that boost level. If it were 5-10 psi I would say TR6. Also may want to double check the MAF sensor to make sure it is clean and didn't suck something in or just accumulate a bit too much crap on it. Clean it with some electronics cleaner or MAF cleaner and stick it back in and clear the KAM to see if that may also help.

[SOAB_465]

That was damn good advice. I Chased my tail for over a year... closing the spark plug gap to 0.024, and Bob's your uncle, it runs perfect. I guess they had opened up a little, the old ones were at almost. 030. If anyone needs coils, wires, plugs, injectors, or a MAF, I have some that are perfectly good sitting on a shelf 🤦

[BOOSTEDEVERYTHING]

Glad I could help. Sometimes it is always the simplest things. I have chased my tail on quite a few occasions for very simple things that should have been the first thing I checked. LOL