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Author
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Topic: Slight Bucking while cruising Help
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FivePTSlow
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Member # 7682
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posted
 
 
I have a 1993 Mustang 5.0. Motor mods: are Paxton SN 2000, k&n filter, upr boostmaster 4" inlet piping, MSD 6al box, MSD Blaster Coil, MSD Wires, 76mm C&L MAF 42# calibrated(green tube), 70mm bbk throttle body and spacer, bbk shorty headers, electric fan, off road h pipe a9p computer, FMS 42lb injectors
I've noticed recently a very slight bucking while cruising(driving at a steady RPM). If you didn't drive this car daily you probably wouldn't notice the bucking while cruising because it's very slight, but no hesitation under WOT.
Stuff done to try to fix the problem: cap, rotor, wires, plugs(autolite copper #24 one step colder)gapped at .038, new Fuel Pressure Regulator, new fuel filter. K&N cleaned and oiled recently, cleaned MAF sensor, T/B, and Air Idle Bypass. New EGR Valve, New EGR Position Sensor, New EGR Vacuum Solenoid, New Barometric Pressure Sensor(MAP), New Bosch o2 Sensors, New 255lph walbro in tank fuel pump, New fuel pump relay, New rubber vacuum hoses(every hose has been replaced including the ones under the upper intake plenum), tested all hard lines to 25in vacuum as well as zip tying all connection points, so I know there aren't any vacuum/boost leaks. Throttle position sensor set at .96 volts(proper base idle reset procedure was followed), timing set at 8* advance while running 91 octane from shell. I have 3 MAF Sensors it does the same thing with all of them.
Spray test with brake cleaner around all vacuum lines and intake manifold. Checked vacuum line diagram and all lines are run correctly. I have ran the suggested amount of Lucas fuel system cleaner in my past few tanks of gas.
Occasional check engine(typically only under acceleration) no codes come up in KOER, or KOEO
Tested my Ignition Control Module with my multi meter and it passed all test ranges no problem.
Tested the EGR Valve by putting 5in vacuum on it at idle and the car stumbles really bad. The EGR Valve holds that amount of vacuum as long as I leave it connected.
Tested the TPS Module with my Digital Voltage Meter. It appears to go through voltage smooth & steady, but then again since it's digital it could be reading so fast it's impossible to notice a dead spot.
My guess is either the PIP module inside the distributor, TFI, or TPS? Pretty much anything else I can think of that might cause this problem is brand new.
What are your thoughts?
[ November 01, 2011, 08:46 AM: Message edited by: FivePTSlow ]
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
No one with any similar experiences?
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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Jaejae5.0
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Member # 7958
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posted
hmmmmm..plug gap?..o2's maybe
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1987 notchback h/c/i 302 & 70mm turbo SOLD
2000 camaro ss cam only
Posts: 4890 | From: the combustion chamber | Registered: Oct 2007
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FivePTSlow
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Member # 7682
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posted
I have checked the plug gap and they all remain at .035" and with my MSD 6AL box that should be fine.
o2's have been replaced with brand new ones
[ September 30, 2011, 09:40 AM: Message edited by: FivePTSlow ]
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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Jaejae5.0
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Member # 7958
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posted
hmmm you could try cleaning the maf
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1987 notchback h/c/i 302 & 70mm turbo SOLD
2000 camaro ss cam only
Posts: 4890 | From: the combustion chamber | Registered: Oct 2007
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FivePTSlow
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Member # 7682
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posted
I just cleaned the MAF late last month, so it should be fine, but I'll clean it again just to be sure
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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JohnB
Tech Moderator
Member # 969
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posted
Fuel pump is on it's way out.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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FivePTSlow
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Member # 7682
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posted
Ya know I thought about that too. I remember my old 91 GT kind of doing the same thing then the fuel pump went out completely.
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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JohnB
Tech Moderator
Member # 969
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posted
Having to key-on, key-off a few times to get it to start is a sign the check valve in the pump is failing. This is a typical sign of a pump failing.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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FivePTSlow
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Member # 7682
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posted
quote:
Originally posted by JohnB:
Having to key-on, key-off a few times to get it to start is a sign the check valve in the pump is failing. This is a typical sign of a pump failing.
Sweet. Thanks for the info I appreciate it. More than likely I would have replaced all of the other stuff first like PIP, o2's, ICM etc
If I don't turn the key on and off a few times before I start up my car it turns over for a lot longer than normal before starting up
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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JohnB
Tech Moderator
Member # 969
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posted
Ya, dropping the tank isn't fun, but normally the sh!tty jobs are the ones that fix things. And I know the feeling, the tank is out of my 03 Cobra for the second time in two weeks. lol
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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FivePTSlow
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Member # 7682
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posted
quote:
Originally posted by JohnB:
Ya, dropping the tank isn't fun, but normally the sh!tty jobs are the ones that fix things. And I know the feeling, the tank is out of my 03 Cobra for the second time in two weeks. lol
I've had several Fox's including: 1987 GT T-Top, 1988 GT Convertible, 1989 LX Coupe, 1991 GT, Two 1992 LX Coupe's, and my current LX Coupe which is a 1993. The more I work on these cars the more I realize how easy they are to work on compared to most other cars. This plus the fact that I have lifetime warranty on so many parts now is one of the many reasons I gravitate back to the 87-93 5.0. There is nothing on these cars that is out of the scope of mostly anyone with a decent set of tools and some willingness to learn.
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
Well my car finally wouldn't start at all the other day, so I thought the fuel pump went out, but it wound up being that some water got into the fuel pump relay under the hood, so I replaced it and it fired right up. Kind of odd is that this made my hard starting go away comlpletely, so now I'm just left with the slight hesitation when at a steady MPH/Cruising.
Still think it's the fuel pump...?
[ May 22, 2011, 05:13 PM: Message edited by: FivePTSlow ]
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
I've also noticed that I only get 10-13mpg city driving. Any other ideas?
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
quote:
Originally posted by JohnB:
Fuel pump is on it's way out.
Well today I finally replaced my fuel pump with a walbro 255lph in tank pump. I found that the in tank filter was clogged as well as the base of the pump, so it was probably caused by that. I replaced the pump with the walbro and everything looks good so far. Hopefully I'll get better MPG as well. The car starts up so much faster too.
[ August 21, 2011, 03:30 PM: Message edited by: FivePTSlow ]
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
Time for a necropost... My car has had this slight bucking problem all of this time and it really bugs me. Today I replaced both o2 sensors and the slight bucking while cruising is still there. Very irritating. I've been through just about everything I could think of and the problem still remains.
I'm going to purchase one of the Mityvac tools, so that I can put vacuum into the system without the car actually having to be on which should make it much easier to test for vacuum leaks.
I have updated the OP to show what all I have covered.
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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BackwardSnake
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Member # 10857
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posted
What kind of MAF do you have?
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Hi, my name is Jimmy Herrera aka 91Trunkster (510)375-1589 and I got snitched out by my friend or friends. Ain't that a bitch, some one or some people would rat out my fake account here to keep their own secret fake account? If you all forgot, I'm an old ass 30 something year old "man" that likes to make internet friends with boys fresh out of highschool. I like to post "bruh" a lot just like the annoying immature and ghetto CAFords kids do. I like to talk shit about this website, make it look bad, all the while trying to make and save money off of other members here. Some may call me a selfish immature bitch. Deep down I know they are correct, it's not like I have anything else going on in my life or anything but negativity to offer this community. This is a free site. Suckers spend good time and money to keep this website going. They're suckers for doing so, so fuck them, I'm going to take them for all they got. It's all about me in this world.
Who is the next troll or just plain annoying post whore to get the boot???
http://i202.photobucket.com/albums/aa91/megamallard/guaposheep.jpg
Posts: 326 | Registered: Apr 2011
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FivePTSlow
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Member # 7682
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posted
quote:
Originally posted by BackwardSnake:
What kind of MAF do you have?
I have 3 separate MAF's and it does the same thing with all of them. I have a stock MAF Housing, A 70mm MAF Housing from a 94 T-Bird, and a 73mm C&L MAF Housing with proper calibration tube for 19# injectors. I also have two different MAF Sensors and it does the same with both of them. I have basically played musical MAF's with all of them... on a couple of occasions
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
Think it could be IAB, or TPS?
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
Yesterday I did the base idle reset procedure and it seemed to help the problem out a little bit, but it's still there. I noticed the problem becomes considerably more noticeable if I just change the idle with the set screw and not go through the idle reset process.
I also did a quick test on my TPS. I left my DVM hooked up to it and open/closed the throttle body. The voltage went up and down smooth. I also would open it up a little bit and hold it there and the voltage stayed steady, so the TPS appears to still be in good working order. I also removed the IAB. It wasn't that dirty(I already cleaned it about 1,000 miles ago) and replaced the gasket.
I checked the voltage at the orange wire on the TPS and it read a steady 4.97/4.98v.
I'm starting to wonder if this problem might be caused by non motorcraft products? I bought my EGR Valve and EGR Position Sensor from Kragen, and I have no idea which brand of TPS is in my car, but it surely doesn't look factory.
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
anyone else?
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
Today just for the heck of it I removed my MSD 6AL box from my car just to test if it may be related to the problem and it seems to have went away. I'm going to start a new thread relating specifically to the MSD box.
Thank all of you guys for helping me out
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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turbo50
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Member # 6700
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posted
Lemme know if it comes back because a failing EGR will cause this too.
Dan
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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FivePTSlow
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Member # 7682
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posted
my EGR and EGR position sensor were brand new as of May of this year. Lifetime warranty from kragen/oreilly. My car still pops a CEL often for EGR position sensor out of range. Think I should go swap them out?
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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FivePTSlow
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Member # 7682
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posted
Ya know what I think it's being caused by my electric fan. I'm using one of the coil wires as the switched power source for the fan and I think the fan just might be messing with my ignition a little. What would be a better 12v switched source wire to use?
[ September 13, 2011, 11:00 AM: Message edited by: FivePTSlow ]
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2011 GT/CS 5.0 + Boost(Procharger)
90 Bronco 5.8 Lifted
05 SRT-4 24PSI E-85 at least 50 million hp
07 Harley VROD NRS Stage 1
Posts: 1857 | From: Sacramento | Registered: May 2007
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