My R53 has a 17% pulley, DDM airbox and a dyno tune. It made 175 whp stock and made 210 after the mods and tune. I know these are very optimistic numbers; I guess I'd chalk it up to the dyno. A couple months ago I was checking out the location that most people tap into for a boost gauge. This is the nipple underneath the passenger side supercharger horn on the intake manifold. It normally has a vacuum line plugged in to it that goes to the fuel pressure regulator. I noticed that this line was unplugged. I assume it has always been unplugged. I plugged it back in and test drove. Noticed no difference. A week or so later, I replaced my clutch, which entails disconnecting the ECM. When that job was finished, I began noticing an intermittent power loss condition that usually occurred at wide open throttle. The car would hesitate beginning around 3k RPM and get worse through the entire range. I think it happens in any gear, though it's less noticeable in first. One time the car simply stopped accelerating in 3rd gear by the time I reached 5k RPM with my foot still to the floor. I'm assuming I'm having this problem because disconnecting the ECM reset fuel adaptations and now the car has learned the fuel pressure regulator exists. The car has thrown no codes. In my ownership in the last 25k miles, I have replaced or upgraded a lot of the normal culprits for hesitation; spark plugs, spark plug wires, coil pack, air filter (with my DDM intake), fuel filter etc. My thought now is that my tune in combination with the additional fuel I'm now able to get is causing my stock injectors to not be able to keep up with demand and I'm leaning out at WOT. I suppose it could also be that my fuel pressure regulator is bad given that it hasn't even been plugged in in I don't know how many years. Does this make sense? I was thinking of just getting some 380cc injectors and seeing if that helped with my current tune. Just bouncing thoughts around. It's obviously a very annoying issue that I would like to get resolved as soon as possible.

 

This all depends on if the fuel regulator vacuum line was unplugged when the car was tuned.

​​​​​​First thing to note is that with the regulator vacuum line now plugged in, it wouldn't be a lean condition, but a rich one, compared to it not being plugged in, since the regulator works off lack of vacuum, in a low vacuum or boost situation the regulator allows more fuel to flow, and full flow is still full flow, no matter what RPM.
But if it was disconnected during tuning, the tune may have been "richen'd" up to compensate for lack of fuel flowing from the regulator, now that it's connected, it's flowing much more fuel at inappropriate times in the RPM range. And the injectors getting more fuel wouldn't cause it to lean out, even at redline, it would only cause them to be wide open too early in the RPM range. Replacing the current injectors with 380's would just add to an over fueling situation, if that is the issue.

"BUT" that's assuming it was disconnected, and even if it reset adaptions, those original adaptions should still come back if the car was running fine before the ECU was disconnected, so keep looking for other culprits.

The only real way to check this is with an AFR reading, either with the installation of an AFR gauge or a trip to a local dyno that can hook up a sniffer on a dyno run.

My suggestion would be to definitely find a way to get an AFR reading to know for sure what's going on, it's the only safe way to find out, but don't run the car at WOT anymore until you know for sure it's safe to do so. It sux to damage an engine on a "hunch".
Oh, and replace that vacuum line with the correct sized new one, it came off in the first place for a reason, and that vacuum line stretch's or cracks from the heat, all the time.

Good luck.

 

Thanks for the reply. I’m assuming that it was unplugged when it was tuned. Unfortunately, my tuner has since sold their dyno and no longer does tunes. I suppose I could try to get Jan to do a canned tune for me or something. Is the Innovate kit kind of the standard for R53 wideband setups? Oh, and the fuel pressure regulator line is plugged into my tee for the boost line now so I don’t think it’s coming off again.

So I did do some WOT testing after I wrote the OP. I know it’s probably not a good idea, but I wanted to see if there was a difference between having the regulator line unplugged and plugged in. With it unplugged, I couldn’t get it to hesitate. It felt like the power trailed off near the end, however. With it plugged in, I couldn’t get the hesitation to happen until I did a pull starting from low RPM, around 2k, and then it jerked and bumped around all through the rev range. It also picks up quite a bit near the top of the rev range when the hesitation isn’t happening. I don’t know if this means the fuel pressure regulator needs to be replaced or if it just needs to be retuned or what. I think it’s probably safe to say I don’t need bigger injectors since the problem seems to begin happening from low RPM. For what it’s worth, once the hesitation starts, it seems to happen more frequently beginning at higher RPM.

 

FYI, I did revise my post after rereading your OP a little closer, but the gist is still the same.

It really does sound like it's over fueling at the wrong places in the RPM range.
And any AFR gauge will do, myself, I use the Innovate kit because of the compatibility with my ByteTronik Datalogger. But also will any dyno and sniffer, if you're just looking to verify your situation.
But to fix it, yes either a canned or remote re-tune will be your only option.

Odds are, it happening more frequently, is a result of adaptions being maxed out and set to their limit, since the ECU can only adapt "so much".

 

I’ve emailed Jan. I just hope it is just a tune issue and not also a fuel pressure regulator issue.

 

Either a Scan or Ultragauge albeit no where as accurate as an A/F Gauge can give you a good idea of A/F ratios without welding in a bung or running wires all the way to the exhaust tip.

 

Delete post. Wrong thread