new to me, 98 M3
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Thanks Snap for that offer, hopefully don't need to take you up on that, but maybe. Here's an update.
Picked up a fuel pressure guage, if you remember I couldn't get the one from Orileys to work. Grabbed one at Harbor Freight, hooked it up to the schrader valve at the fuel rail. Here's my results, im not 100% sure I did this properly.
First, i put ignition on but didn't start the car. Pressure went up to 42ish psi, and started dropping reasoably quick, down to about 30 psi after 2 or 3 mins with ignition still on. This is probably a clue for something. Did this each time with the vacuum line going into the fuel pressure regulator on or off.
Another test, started car this time. Pressure with vacuum line attached at FPR 41/42 ish. Took vacuum line off it jumps to 51/52 psi. I believe that is spec for the S52 engine. I also gave it solid rpm of 2500 and held steady at 41/42 with FPR attached. When giving quick bursts of gas it did just a quick spike.
I also noticed while FPR was plugged and unplugged with car running it would bog down a bit, so I believe that is working properly.
What has me concerned is i read I should be holding steady pressure with just the ignition on, correct? It's definitely dropping. Injectors or something with fuel pump? Again I'm running a bit rich it appears from my fuel trim numbers.
Thanks again experts!
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51 psi is 3.5 BAR which is correct.
The pressure bleeding off with the engine off means either your top injector o-ring leaks, or the injectors themselves leak.
It would be in your best interests to pull the rail and injectors and see which ones are leaking since an injector that bleeds fuel into a cylinder during a high rpm shift or at the rev limiter can cause detonation
Your injectors are firing against 14.7psi of ambient air pressure,
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probably a stupid question. Can I pull the rail with injectors attached and pressurize the system (not start car) to see if any leak? Not sure if there's a side effect that could harm anything I'm not thinking of.
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Yep, that would be the way to go.
You dont need the electrical connectors attached so that gives you a little more flexibility to work with. Put something down to catch any fuel that may leak then just prime the fuel pump by turning the key to "On" You can also jumper the fuel pump relay to let it run continuously. This doesnt hurt anything.
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Hey again. Sorry to keep pestering, really wish i didnt have to. You all just respond so quick
Update: Unplugged injectors, turned on fuel pump watched injectors, no leaking.....but pressure still drops. So, car runs steady at 51 psi with FRP unplugged, 41 psi with it plugged in. When I start the pump FPR plugged in (not starting the car) the gauge instantly goes to 51 but immediately drops to 41 psi then pressure bleeds off somewhat quickly.
I started the car and turned it all the way off and pressure holds, doesn't drop off. Tells me it doesn't appear to be siphoning back when car is off, I've never had a hard start problem so it's not a check valve. When I pinched the fuel lines at the back of the rail the pressure on the gauge would go up and down, doubt that means anything.
So, still maybe a partially functioning FPR if there's such a thing? Hate to throw $90 at one not truly knowing. Or maybe it really is tune related. Out of ideas.
I promise to get some nice pictures up to have something fun to talk about. New rims are on, look great!
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Hi everyone,
I'm going back at this issue tonight. I did replace the FPR, no change there. I'm going to try to use http://bimmersoftware.com/bmwlogger tonight to record some live data and post it on here. Never used this program before, are there any specific things I should be trying to log for you all to look over? Just from what I see online it doesn't seem like it records much more than the scan tool I was posting in previous posts. But it's free so we'll give it a shot. It also says the free version clears DME adaptations. What would that do to my car? Whip the code for the supercharger? Don't want that I don't think.
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The tuning changes made to accomodate the supercharger are written onto the ecu chip / the base fuel and spark advance tables. This is the base tune file.
Once the car is driven it establishes a long term fuel trim (adaptation) which, once established, stays permanent until reset. This adaptation adds a fudge factor to the base fuel table to compensate for environmental factors/engine wear/ etc. since the base tune established on the dyno at the BMW factory or at the supercharger supplier's dyno is only good for the conditions present during the dyno tune.
So everytime you start the car you have the long term fuel trim (adaptation) running on top of the base fuel map as standard. Then the short term fuel trim is one more factor to add/subtract fuel in real-time while the car is running. This value is only stored for a few hundred milliseconds or so as it resets for every injection cycle.
If that was too technical:
Your parents send you to college with what they think you need. (Laptop, basic furniture)
You add what YOU think you need on top of that. (MSOE lava lamp)
Then you go shopping periodically to get other things you need.(beef jerky)
Clearing adaptations is like tossing out all the things YOU brought to college and getting new ones (toss MSOE lava lamp and acquire MATC lava lamp because you sucked at MSOE and had to transfer to an easier school)
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I ran home at lunch to mess with that program. It pulled codes that I haven't seen before with the Carly App. Thoughts?
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SNAP - this program allows for clearing DME adaptations. I get what you're saying about the short and long term fuel trims. If I reset the DME adaptations it resets those to stock then, correct? I just don't want to overwrite any tuning, but it appears thats on the ECU which is separate from the DME stuff. Anything else I should be worried about if I clear them?
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How does the car feel now? Is it that you are just chasing the check engine light or is it actually not running well?
Car feels like it's running fine. But something is clearly tripping the CEL. There's just one weird slight dip in rpm coming out of gear into neutral at stop sign. doesn't stall or anything and recovers quick. perhaps vacuum leak still? I just didn't have enough butt time in the car to know if that was normal. I'm taking in for a real smoke test tomorrow just to verify finally one way or another its not a vac leak.
Other signs seem to point to it running rich. High STFT numbers, Gas mileage is about 18-19 mpg when driving pretty easily (ie not laying into supercharger) I would think that could be better, black carbon buildup in exhaust. Car does have highflow cats though.
Lets say the DME and fuel trims worked their way down to those low negative numbers over time -8.6% LTFT and peaks above -20% STFT. I'm wondering if all the "buttoning" up that I've done changed how the car would be reading those and tripping the CEL. I guess I can clear them and see if it return closer to 0's.
I'll probably wait to do that until after the smoke test.
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yes, both 02 sensors are new (pre cat) I was throwing the CEL before I changed those.
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Gotcha. I would attribute this to some sort of vacuum leak. My coupe also drops idle and comes back when thrown into neutral at stop signs on occasion.
Yeah, at this point I'm hoping it's that. Should hopefully find out tomorrow with the smoke test. If they don't find anything I think I'm going to have to pull the valve cover and make sure my CAMs are still perpendicular from my vanos job. That's really the only other thing I can think of which could have been just a degree or two wrong that I haven't checked.
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Update after smoke test. Smoke test showed smoke. One point on intake boot elbow. Previous owner did some weird gluing thing to allow for the asc delete and tried to glue the extra nipple thing needed together with the stock elbow. I had previously discovered this one on my own and tried to jb weld the crap out of it. Honestly surprised it still leaked. Gonna order one of these bad boys and be done with it.
Second area is on the supercharger body. Not a part where there's a gasket to fix. I'll get a picture later. Tech and I agreed the only fix will be to try some RTV sealant and hope it holds. This was a much smaller leak.
Leaks seemed small to me but he claimed these would definitely be big enough on any car to trip the CEL. So, I'll hope it's that.
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I know you said you JB welded that boot really well but do yourself a favor and replace the boot if it's been torn at all. This may or may not be your issue but the boot is already weak if it's torn where you could see it.
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