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Old 03-24-2011, 01:50 PM   #2551
xsnapshot
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Not sure on idc. There were enough other issues going that I didn't think to log that. Should have, but I will next time. It's not true E85 in the tank either. More like E70 from my estimates.

My suspicions were also the fuel pump, but then I was thinking if it truly flows 190 l/hr then I would think that would be enough for a stock turbo on a non-aggressive tune if a walbro 255 can support near 400whp on E85. Maybe not though?
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Old 03-24-2011, 02:25 PM   #2552
99STM
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I don't believe it is the fuel pump. It will lean out at half throttle but I think that is because the map needs some work. I only did probably one WOT log last night and that was when the CEL started flashing for the Cyl. 1 misfire. On the way home last night, I would slowly give it more throttle and watch the wideband and the boost gauge. At 13psi, it will start to physically stutter and misfire. The AFR's were rich were a little rich, but not a whole lot. I am going to regap the plugs today and see what happens. This is also the first tank of gas and there was still a gallon or 2 of 91 in the tank when I filled it. I don't think that would cause the problems we are suffering though. At this point, I am fairly convinced it is a mechanical issue. If regapping does not work, I am going to pressure test the inlet. If that doesn't work, coil packs would be a good place to start and I will probably start on Cylinder 1 since that's where we got the misfire.
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Old 03-24-2011, 02:36 PM   #2553
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Quote:
Originally Posted by 99STM View Post
I don't believe it is the fuel pump. It will lean out at half throttle but I think that is because the map needs some work. I only did probably one WOT log last night and that was when the CEL started flashing for the Cyl. 1 misfire. On the way home last night, I would slowly give it more throttle and watch the wideband and the boost gauge. At 13psi, it will start to physically stutter and misfire. The AFR's were rich were a little rich, but not a whole lot. I am going to regap the plugs today and see what happens. This is also the first tank of gas and there was still a gallon or 2 of 91 in the tank when I filled it. I don't think that would cause the problems we are suffering though. At this point, I am fairly convinced it is a mechanical issue. If regapping does not work, I am going to pressure test the inlet. If that doesn't work, coil packs would be a good place to start and I will probably start on Cylinder 1 since that's where we got the misfire.
What I did was switch the ign coil from the cylinder that was misfiring to another cylinder... if that cylinder (the one you switched the coils with) has a misfire, then you know the coil is bad.
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Old 03-24-2011, 02:39 PM   #2554
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I will try that. But it wouldn't really make sense that at half throttle the car runs fine. A little lean but there is no hesitation. And RIGHT at the point of 13psi, it starts to stutter and misfire. I'm kinda thinking that 13psi is just the point where the plugs do not have the energy to jump the gap.
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Old 03-24-2011, 02:40 PM   #2555
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Fuel pump flow rates DECREASE as boost rises....
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Old 03-24-2011, 02:42 PM   #2556
99STM
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I will go log the car and I will post up the log.
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Old 03-24-2011, 02:53 PM   #2557
99STM
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Any thing in particular you would like me to log? FBKC, Throttle Position, and AF Corrected/Learned is probably what I would start with. I will watch my Wideband.
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Old 03-24-2011, 02:56 PM   #2558
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Parameters to Log - remember some of this may not be visible until hooked up to the vehicle

Engine Speed (RPM )
Engine load (g/rev)
Ignition total timing
Injector Duty Cycle (IDC)
FeedBack Knock Correction (fbkc)
Fine Learning Knock Correction (flkc)
Mass Air Flow Voltage (MAFv)
LC-1
Manifold Relative Pressure (MRP) (4 byte)(or direct if 4byte not there)
Intake Air Temperature (IAT)
Primary Wastegate Duty Cycle (WGDC)
TARGET Boost
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Old 03-24-2011, 02:58 PM   #2559
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Ok. Probably won't be able to post it until later.
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Old 03-24-2011, 04:21 PM   #2560
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Unfortunately, I couldn't get a log. However, when I did the pull, right around 3k rpms it starts to stutter and misfire. I got a cel that I haven't pulled yet but I am almost positive its a misfire code. After a out 4k it starts to lean out to 12:1 then leans out more. I quit the pull after it got to 13:1. I can admit when im wrong and I believe you were right. The symptoms sound a lot like the fuel pump isn't flowing enough. But would that cause the mid range stuttering?
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Old 03-24-2011, 04:37 PM   #2561
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Quote:
Originally Posted by sumfoo1 View Post
^ what injectors are you using?
I am using FIC Bluemax 1250cc injectors...it wasn't the injectors, it was the pump...
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Old 03-24-2011, 05:19 PM   #2562
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Quote:
Originally Posted by Phatron
Fuel pump flow rates DECREASE as boost rises....
Ron have you ever encountered a situation where the switch to E85 cleans out any gunk in the fuel system and partially clogs the fuel filter? Especially if its never been changed? Just curious if that might be restricting flow too much...
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Old 03-24-2011, 06:52 PM   #2563
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That's also a possibility that we have thought about. Would the first tank be enough to clog it though?
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Old 03-24-2011, 07:06 PM   #2564
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Quote:
Originally Posted by xsnapshot

Ron have you ever encountered a situation where the switch to E85 cleans out any gunk in the fuel system and partially clogs the fuel filter? Especially if its never been changed? Just curious if that might be restricting flow too much...
I've read quite a bit about this happening to others. How many miles were on the car before switching to E85?
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Old 03-24-2011, 07:15 PM   #2565
99STM
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135k. It may have been changed before me but I can't say for sure.
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Old 03-25-2011, 06:09 AM   #2566
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should be changed even if that doesn't fix the issue. it would be nice to put a fuel pressure gauge on your car and go drive the thing so see what happens. Ron is an awesome tuner. These mechanical issues are hard to diagnose over the internet though
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Old 03-25-2011, 06:46 AM   #2567
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Originally Posted by STiled_04 View Post
Gonna need hundredths of a second to see if you are fifth. There are three of us at 11.7xx.
more than that i suppose
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Old 03-25-2011, 08:01 AM   #2568
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Quote:
Originally Posted by MattPersman
should be changed even if that doesn't fix the issue. it would be nice to put a fuel pressure gauge on your car and go drive the thing so see what happens. Ron is an awesome tuner. These mechanical issues are hard to diagnose over the internet though
You can rent a fuel pressure gauge and tape it to the windshield, its kind of goofy looking, but in a pinch it works.
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Old 03-25-2011, 08:44 AM   #2569
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i shouldn't say anything cause i havce not been able to work on my car recently, but looking forward to the results.

i love diagnosing mechanical problems with ron over the phone!

"i don't know dood, i'm a tuner not a mechanic!"
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Old 03-25-2011, 08:59 AM   #2570
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Possibilities:

Injector scaler too high
MAF scaling too low
Fuel pump can't keep up
Clogged fuel filter
Failing injector(s)
Massive vacuum leak
Failing MAF sensor

As others have said, the appropriate things need to be logged. Do not do anymore WOT without logging the right stuff. Log, log, log!

It could be knocking like crazy because of the lean condition. I had a very similar issue a few years ago and it turned out to be a fairly large vacuum leak and a faulty MAF sensor.
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Old 03-25-2011, 09:06 AM   #2571
99STM
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We are going to run wastegate pressure today. If we still encounter lean AFR's up top, the problem lies elsewhere. If it hits the target AFR's, it is most likely the fuel pump. I do not think the stuttering is being caused by the fuel pump, that could be blowout or possibly the fuel filter clogged up. But then again, I don't know.
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Old 03-25-2011, 09:08 AM   #2572
99STM
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Btw, the injector scalor is set pretty low. We checked for leaks the other night and couldn't see anything. All those others are definitely possibilities but I am going to put my money on the fuel pump.
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Old 03-25-2011, 09:10 AM   #2573
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do the easy stuff first, and start taking things out of the equation. in my experiences that last thing i touched is usually the last thing i ucked up.

def don't do anymore wot pulls till you get a hold on the issues. at the very least ease into it till a problem develops. i remember mikey calling it "babysteps".

have one of these tuning gurus at least look at the rom...
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Old 03-25-2011, 09:15 AM   #2574
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Quote:
Originally Posted by SVT_WRX View Post
Possibilities:

Injector scaler too high
MAF scaling too low
Fuel pump can't keep up
Clogged fuel filter
Failing injector(s)
Massive vacuum leak
Failing MAF sensor

As others have said, the appropriate things need to be logged. Do not do anymore WOT without logging the right stuff. Log, log, log!

It could be knocking like crazy because of the lean condition. I had a very similar issue a few years ago and it turned out to be a fairly large vacuum leak and a faulty MAF sensor.
+1
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Old 03-25-2011, 09:35 AM   #2575
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Quote:
Originally Posted by 99STM View Post
Btw, the injector scalor is set pretty low. We checked for leaks the other night and couldn't see anything. All those others are definitely possibilities but I am going to put my money on the fuel pump.

D0000d....just be careful....and make sure you log the appropriate stuff.

I've been able to diagnose every single one of my mechanical issues by reading on these forums.....and I do my own work. Tuning and everything else. Nobody touches my car but me.

If it were me, I would do the following in this order:

1. Clean MAF sensor
2. Change fuel filter
3. Boost leak test
4. Then log it and see what happens
5. What do IDC's look like? AFR's? Knocking? If IDC's and AFR's are good then it's probably not your injector scaling, fuel filter or fuel pump. If they don't look good then...
6. Borrow somebody elses MAF sensor
7. Log
8. Still happening? Change fuel pump
9. Log
10. Still happening? Check all exhaust bolts to make sure everything is nice and tight.
11. Still happening? Something else in the tune??? Primary open loop fueling??? Clogged up-pipe??? Jacked up turbo? Other sensor failing? TGV's not opening up???
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