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Old 04-19-2010, 10:34 PM   #1
KurtP
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Default cylinder 4 misfire continues to baffle me, tuners and experts?

2009 Legacy GT 13k miles

Mods: ngk 1 step colder.
header, full catless exhaust, TGV deletes, full intake (cobb/perrin inlet), phenolic spacers, perrin pulley, DW 750's, BNR turbo, perrin TMIC. Everything except the perrin pulley went on all at once during the turbo install.(perrin pulley was first mod)

Installed my BNR 20g and all parts in december and was given a gimp map by EFI logics for my tune. Blizzard of 2009/2010 hit on my appointment day and I wasnt able to get back to Connecticut and went to Akuma in NJ. They were awesome at the shop while I was there and tuned the car. Leaving I started pulling Cyl 4 misfire codes at idle or at cruise, but not at WOT and as far as myself or anyone Ive asked can tell, we dont hear a misfire. I sent logs to Akuma who said they dont see any problem and check physical stuff. Ok.

I cant find any evidence of a physical problem. I pulled and changed the plugs. The plugs showed no signs of detonation, oil consumption, and had nice conservative timing lines. The car doesnt burn oil. No smoke or oil residue from the tail pipes, no vapor from the oil filler tube. The car starts right up and idles smooth and drives smooth. I moved the coil packs around and I moved the injectors around and the code stays with Cyl 4.

How do I get this code to go away? Take the Akuma map off and put the EFI gimp map on. viola, no misfire code. The car hasnt seen boost since the day it was tuned at akuma and was in storage for the last 3 months while I was gone. Now Im back and I want this fixed so I can actually drive my car.

Needless to say I started data logging. Long term fuel trim at idle on the Akuma pro map fluctuates between 5 and 7. On the EFI gimp map has long term fuel trim thats WAY higher, but it never ever throws the code, which seems somewhat counter intuitive to me.

Ive talked with a bunch of shops and had a couple shops look at the car and no one can find evidence of a mechanical issue, and have had more than one expert tell me it seems to be a tuning/fueling issue.

Im going for another pressure/vacuum leak test this week to make sure everything is tight and selling the AP and going OS with tuning it.... and Im also working on finding a compression tester to pull the compression of cyl 4. Usually in this kind of situation the only thing you can ever get anyone to tell you at first is "Cracked ringland" but I just dont think it is, because I cant find evidence of mechanical failure. I realize that its prone to bust, but the car has been driven conservatively and hasnt ever had a very extreme set up. Coupled with the fact the issue is only on the one map(which baffles me) leads me away from the idea its a piston failure.

What else can I check in the meantime to pulling the compression? Crank/cam sensors? What about loading a regular cobb stage 2 map to see if the misfire code comes on with that map? (although not scaled to my injector, so i dunno if that would even idle at all....)

Short of a new tuner Im out of ideas....hit me. I just want to make sure there isnt anything else Im missing that I could look at.

If it ends up being the piston, then so be it, Ill rebuild the short block. Im stumped because Ive seen subie's with bad pistons and I just dont have any of the symptoms of it(short of the misfire code on the one map), and nothing has gotten worse over a few thousand miles of driving.
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Last edited by KurtP; 04-19-2010 at 11:28 PM.
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Old 04-20-2010, 12:47 AM   #2
Uncle Scotty
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cracked block at #4???
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Old 04-20-2010, 12:50 AM   #3
sokoloff36
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Going back to the Akuma pro map, can you check and see if the injector time tables for the cylinder are off compared to cylinder 1 though 3. maybe during the tune the numbers were skewed. Its a possibilty atleast. I would def check and see if you can see if your o2 sensors are reading differently too. that would be another indicator that some sort of fuel issue is present on that bank of the engine.
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Old 04-20-2010, 07:54 AM   #4
Viperguy324
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Quote:
Originally Posted by KurtP View Post
2009 Legacy GT 13k miles

Mods: ngk 1 step colder.
header, full catless exhaust, TGV deletes, full intake (cobb/perrin inlet), phenolic spacers, perrin pulley, DW 750's, BNR turbo, perrin TMIC. Everything except the perrin pulley went on all at once during the turbo install.(perrin pulley was first mod)

Installed my BNR 20g and all parts in december and was given a gimp map by EFI logics for my tune. Blizzard of 2009/2010 hit on my appointment day and I wasnt able to get back to Connecticut and went to Akuma in NJ. They were awesome at the shop while I was there and tuned the car. Leaving I started pulling Cyl 4 misfire codes at idle or at cruise, but not at WOT and as far as myself or anyone Ive asked can tell, we dont hear a misfire. I sent logs to Akuma who said they dont see any problem and check physical stuff. Ok.

I cant find any evidence of a physical problem. I pulled and changed the plugs. The plugs showed no signs of detonation, oil consumption, and had nice conservative timing lines. The car doesnt burn oil. No smoke or oil residue from the tail pipes, no vapor from the oil filler tube. The car starts right up and idles smooth and drives smooth. I moved the coil packs around and I moved the injectors around and the code stays with Cyl 4.

How do I get this code to go away? Take the Akuma map off and put the EFI gimp map on. viola, no misfire code. The car hasnt seen boost since the day it was tuned at akuma and was in storage for the last 3 months while I was gone. Now Im back and I want this fixed so I can actually drive my car.

Needless to say I started data logging. Long term fuel trim at idle on the Akuma pro map fluctuates between 5 and 7. On the EFI gimp map has long term fuel trim thats WAY higher, but it never ever throws the code, which seems somewhat counter intuitive to me.

Ive talked with a bunch of shops and had a couple shops look at the car and no one can find evidence of a mechanical issue, and have had more than one expert tell me it seems to be a tuning/fueling issue.

Im going for another pressure/vacuum leak test this week to make sure everything is tight and selling the AP and going OS with tuning it.... and Im also working on finding a compression tester to pull the compression of cyl 4. Usually in this kind of situation the only thing you can ever get anyone to tell you at first is "Cracked ringland" but I just dont think it is, because I cant find evidence of mechanical failure. I realize that its prone to bust, but the car has been driven conservatively and hasnt ever had a very extreme set up. Coupled with the fact the issue is only on the one map(which baffles me) leads me away from the idea its a piston failure.

What else can I check in the meantime to pulling the compression? Crank/cam sensors? What about loading a regular cobb stage 2 map to see if the misfire code comes on with that map? (although not scaled to my injector, so i dunno if that would even idle at all....)

Short of a new tuner Im out of ideas....hit me. I just want to make sure there isnt anything else Im missing that I could look at.

If it ends up being the piston, then so be it, Ill rebuild the short block. Im stumped because Ive seen subie's with bad pistons and I just dont have any of the symptoms of it(short of the misfire code on the one map), and nothing has gotten worse over a few thousand miles of driving.
What plugs did you change to? normal to colder?
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Old 04-20-2010, 08:06 AM   #5
KurtP
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I went to colder NGK plugs. Im changing them out for Denso stock heat range today or tomorrow.

sokoloff- how would I check those parameters with the AP?

Thanks
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Old 04-20-2010, 08:20 AM   #6
Viperguy324
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Quote:
Originally Posted by KurtP View Post
I went to colder NGK plugs. Im changing them out for Denso stock heat range today or tomorrow.

sokoloff- how would I check those parameters with the AP?

Thanks


See if you can swap your TPS with someone if the plugs dont work
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Old 04-20-2010, 12:49 PM   #7
20SilverSti05
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does the car idle a little rough....so once ur just sitting their for a while then it throws the cel? but otherwise when driving its fine....then it might be your intake tune at idle....thats what my problem was
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Old 04-20-2010, 03:35 PM   #8
sokoloff36
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Quote:
Originally Posted by 20SilverSti05 View Post
does the car idle a little rough....so once ur just sitting their for a while then it throws the cel? but otherwise when driving its fine....then it might be your intake tune at idle....thats what my problem was
i hear what your saying but for it to be just cylinder number 4 i think the problem does lie in that part of the idle but in the fuel tables in the tune. Im not sure what type of variable your program let you look at but i know that if you can look at each individual cylinders fuel table and those numbers for that cylinder are comparatively different from the others then that could be the reason. also like i was saying that if you are not able to view injector fuel tables then a basic but common parameter to view is oxygen sensor data. you may be able to see a difference in rich/lean reading compared to the other side of the motor. (since the knock is happening more at idle i would look at the data during idle.
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Old 04-20-2010, 05:45 PM   #9
arghx7
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is this a locked pro tune map? you can't see in it at all? Have them rebuild the map from a stock calibartion, the map could be corrupted. I had a problem where the DTC's kept showing up after a reflash. It turns out the map had been corrupted. I rebuilt the map by modifying a known good map and all was well.

If both the limp map and the tuned map are in an unlocked format, I would manually copy and paste the data from the tuned map into the limp map.
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Old 06-04-2010, 10:51 AM   #10
KurtP
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solved!!

Compression was even at 145psi on cold motor.

Continued searching revealed a leak at the #4 tgv and a broken air tube from the secondary air injection system that feeds cyl four causing lean burn at idle.
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