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WOT problem

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Old 11-17-2009, 08:08 PM
  #41  
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Originally Posted by youguessit
fix the vacum leak and start from there... could also be an exhaust leak... if it were fuel it would get better when the car got warm...sounds like o2 sensors, exhaust leak, vacum leak, or bad maf/ maf plug. The map sensors rarely go bad but its a possibility. car has to be running very lean to throw code for it. If it is falling on its face and it were do to it running lean it would throw the code for sure. Sounds like vacum leak to me but i havnt been there to see and hear the problem in person so its a guessing game.
uh I have never seen a fuel pump get better the warmer it gets. Also it would have to be a HUGE vaccum leak for it to effect WOT. CHECK FUEL PSI UNDER WOT and see if it drops. O2's dont do anything WOT (they are in open loop) 3/4 throttle and less they can effect drivabilty. Vaccum leaks effect idle and low throttle ... not alot at highway speeds. if u cant read data or have a fuel psi gauge u can read while driving it. take it to a shop. Dont guess and start throwing parts at it.

lets us know
Old 11-17-2009, 08:32 PM
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try unplugging the maf and revving it up. see if it clears up.
Old 11-17-2009, 09:05 PM
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Well it still does it when im all the way to the floor on the gas, so if it goes into open loop when that happens, only thing that makes sense is the maf or something. Because it runs great when cold so the pump wouldnt be a factor anymore.

What spark plugs are you guys running. What would be the recommended gap for a 2004 LQ4?
Old 11-17-2009, 10:04 PM
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Originally Posted by mr spree
Well it still does it when im all the way to the floor on the gas, so if it goes into open loop when that happens, only thing that makes sense is the maf or something. Because it runs great when cold so the pump wouldnt be a factor anymore.

What spark plugs are you guys running. What would be the recommended gap for a 2004 LQ4?
quit guessing dont rules out the pump until you check it while the car is acting up. Just because it doesnt act up cold that doesnt mean it cant be the pump. MORE pump fail when hot than cold. if u known how many times i had to drive a customers car to get it to acted up. sometimes it only takes a few miles others it has took nearly 50miles before the pump started dropping(do to it getting hot) DONT ASSUME ANYTHING

Please check ur fuel psi while the car is acting up(under a load).
After that u can rule it out. If u dont have a scanner(for data not codes) use a voltmeter and tie into ur O2's and see if the car is going lean when is falls on its face.

keep us informed
Old 11-17-2009, 10:20 PM
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Originally Posted by mr spree
Well i replaced the TPS sensor and she idles great now. No more Idle surges or anything.

Still having that huge power loss when i punch it. It runs great when i first start it up if it hasnt been running for awhile. So im guessing when it goes from Open loop to closed is when it falls on its face.
A car is in open loop when cold(first cranked and under WOT) its in closed loop after a minute or so(if a 4 wire O2 is used) and under normal driving conditions. if you put it to the wood its in open loop and the O2s dont do anything. Anytime ive seen a O2 problem its been idling or cruising around.

I had a small fly disable a lexus before(no power under full throttle) the fly some how got pass the airfilter and stuck on the MAF wire. it would idle and drive ok till u stomped it. Maybe want to check that after u check fuel psi.

Had a 2004 chevy truck the other day with weak fire on all the coils..it bogged under a load. it was the bad ground on the driverside of the engine block. may want to look at that also.

let us know
Old 11-17-2009, 10:36 PM
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like i said before, easy check. unplug the maf and either drive the car and put it in the rev range where your having problems or do it at a stop if your having the problem there as well. if it clears up you most likely need a maf. sometimes it won't throw a circuit code but they can still be faulty.
Old 11-20-2009, 09:23 PM
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Originally Posted by mr spree
Well i replaced the TPS sensor and she idles great now. No more Idle surges or anything.

Still having that huge power loss when i punch it. It runs great when i first start it up if it hasnt been running for awhile. So im guessing when it goes from Open loop to closed is when it falls on its face.
would you fix your vacuum leak already??? YOU HAVE UN METERED AIR COMING INTO YOUR ENGINE.. AIR THAT THE MASS AIR DOES NOT SEE... Why not put a fuel pump ,mas air, o2's, a temperature sensor a PCM, and an egr valve while your at it.....


I got a vacuum leak so I'm gonna put a TPS on it?????? My engine is blown so I'm gonna put a new rear end in the car???? You can lead a horse to water but you cant make it drink............ I'm not trying to be a dick but you said there was a vacuum leak at the back of the intake but did nothing about it why would you ignore that??? You have more air in the engine then the mass air sees.. The mas air measures the air to see how much pulse with to give the injectors(among other inputs) So air that is not read by the mass air is not in the pcm's equation. Im not saying it will fix your problem but your chasing GHOSTS until you fix it...

Last edited by Hasstle95Z; 11-20-2009 at 09:33 PM.
Old 11-21-2009, 11:54 AM
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Originally Posted by mr spree
Whats the best way to check for a vacuum leak? Or where to find out where its coming from.

I have a suspicion its coming from the rear of the truck intake (LQ4 Motor). Theres that part on the back of the truck intake im using for my brake booster, but idk where to buy a plastic piece that fits into that to hook a hose up to it, so i found a small metal pipe that i fit into it and clamped a hose on it.

Anyone know where i could pick up a fitting for that hole on the back of the truck intake?

thanks
i said i had a suspicion of where the vacuum leak is if i had one. and i replaced the maf and no more problems.

I wouldnt think it was the maf since it only started bogging when it was on for 5 or 10 minutes. Could anyone explain that to me? thanks!
Old 11-22-2009, 07:39 AM
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Had the same problem. Posted this same issue on several forums and no body had a clue. I could do a nice burn out when cold but when it got into operating range it would just about fall on its face. I brought it to the dyno to see if he could figure out the issue but the problem really didnt show up like it did on the street. After going in and out of HPTuners and looking over everything about a 100 times, turns out that the TCS was enabled and retarding the timing big time. Look in the Engine, tourque management, there are a few tables that need to be modified. I now can do full burnouts and have the trans shifting like it was pro built without having pressures boosted to max and still have tranmission tourque managment enabled.
Old 11-22-2009, 12:21 PM
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So you deleted the TCS? what is the TCS exactly?
Old 11-22-2009, 12:22 PM
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Originally Posted by mr spree
so you deleted the tcs? What is the tcs exactly?
traction control system.



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