Bucking only under WOT at 5000 rpm...

[Porkchop-wrx]

Need help with this. I have tried everything. Car drives fine besides this. Pulls hard in every gear except when I hot 5000 rpm it hits a wall. I have the stock 14b as soon as it spools up I see 10 psi..no more no less. The weird part is if I'm not under WOT i can take it to redline. Can some one help me out with this I'm getting stumped. I have new plugs gapped to .28 (NGK 7es) Checked for leaks. Not sure what else to do. I have a logger I can use to dignose just not sure how. I did do some logging in it and I do see some knock around 5000 not sure if that would keep it from reving past 5000 or not. Maybe i just need a better fuel pump or a re-wire or something. Using the TMO dat logging software. Any suggestions to help me with this? Thanks for looking.

 

[SpeedFreak03]

Sounds like fuel injectors are either too small or just clogged, try some injector cleaner.

 

[tt281gt]

If it feels like your hitting a brick wall then its fuel cut.

You said you changed your plugs, try your wires too.

I had a similar problem last week. When not under WOT I could take it to redline and the car drove fine around town. As soon as I tried to get boost (10psi is where the problems started) the car would loose power, buck, and misfire alot. I changed the plugs and viola(I did not change the wires because they were brand new)!

-Jesse

 

[awd4g63]

How are your fuel trims?

 

[Porkchop-wrx]

Changed the wires to...forgot to mention. Accel wires. As far as fuel trims....I'm on the stock fuel system. I have a small leak from the valve cover where that half moon thing is. I was told that the valve cover doesn't see boost at all so It should't effect this problem, or does it? is that what you meant by fuel trims? If not how can i check it with the logger I'm assuming.

 

[SpeedFreak03]

Fuel trims are the "modifications" that the ECU does to your A/F ratio to get it where it wants (in closed loop only). For example if your running too lean, the ECU will add fuel, which means your fuel trim is over 100%. If you run too rich, the ECU will take away fuel, which means your fuel trim will be under 100%. And 100% is dead on to the ECU fuel maps with no modifications. Heres a good site to understand it better: http://www.pocketlogger.com/index.php?pid=1gtech_trims

BTW Fuel trims aren't used during WOT (open loop mode) so I dont think this has to do with his problem.

 

[Porkchop-wrx]

Thanks for the explanation. I definitly get it. Is it a possibility that my 02 sensor is bad and it would cause this?

 

[awd4g63]

BTW Fuel trims aren't used during WOT (open loop mode) so I dont think this has to do with his problem.

He may be just more likely to be experiencing fuel cut.

 

[Porkchop-wrx]

TTT need a solution. These are things that it could be from various sources.

CLogged injectors and/or fuel pump (need new)
Bad MAF
Bad coil

Please help me track down which one it is.

 

[Porkchop-wrx]

I just got a CEL code from the crank angle sensor. Do you think that could cause this. I just had the timing belt done by turbotrix do you think that could have something to do with it?

 

[Porkchop-wrx]

I did some logs and I check the 02 sensor voltage and it seems fine. I saw it go as high as 1.0 Before I thought the car was running lean but now its running really rich. Is there any particular reason why it would be running so rich? Maybe the MAF is bad. Any insight would be good. I also need some help checking the high level fuel trims. What exactly am i looking for?

 

[MattnGsx]

TTT need a solution. These are things that it could be from various sources.

CLogged injectors and/or fuel pump (need new)
Bad MAF
Bad coil

Please help me track down which one it is.

I had the same problem in my 2g

check you fuel filter, has it been replaced?
I doubt its the maf, I havn't heard of many cases of bad mafs, but who knows.

Do a voltage check on the coil pack. If you don't know how, do a search on here, thats how I did mine.

My coilpack went bad in my car and when ever I was wot it would just back fire when I hit about 5,000 rpms; I could also smell gas sometimes too when it happend.

Tell us how it goes

-Matt

 

[Logue]

Sorry to don't mean to highjack but i'm having the same prob right know,

i figured it was just fuel cut, i installed a b16g, set to 13 pounds on stock fuel it would backfire at about 4,000-^rpm only in 2nd gear and above, i thought it was fuel cut. but i just got done installing 190lph fuel pump and 550cc injectors, the car has a different tone but it still bucks at 4,000-^ in 2nd when i get wot.

i have a 6 bolt head swap and a logger, the logger isn't showing anything unusual.
my plug wires are accel the pretty used up i think i'll get some new one and i'm running autolite plugs. the only plugs the autoparts store had. i'm going to go back to my car and install the afcII right now. anybody have a clue.

thanks,

JJ

 

[sqhopeful]

I am having this exact same problem....I have done the plugs (ngk @ .28), Wires (ngk) and presure tested the system. I am convinced this a not fuel cut since I can trun the boost all way down to 8-9 psi and still does it (just less violently) and the highest hz readign i saw on the afc (while it was bucking) was 1400hz.

I am convinced it is ignition related. Up next is the coil, but i have yet to get to checking it.

KC