misfire under full throttle

[DearDoger]

In every gear around 4-5.5 rpms my car misfires only under heavy throttle 80% or more. I replaced my spark plugs didnt help. When it "misfires" it is only a slight jerk an exhaust pop then it picks right back up.

 

[Chrispy0530]

I have this very same exact problem so I'm looking forward to the reply's here. I've never been able to hit full throttle all the way to 7k cause of this problem at WOT.

First thing most people will tell you is to check for boost leaks.

 

[DearDoger]

I have this very same exact problem so I'm looking forward to the reply's here. I've never been able to hit full throttle all the way to 7k cause of this problem at WOT.

First thing most people will tell you is to check for boost leaks.

just fixed my only leak in the bov (WOT?)

 

[Cat]

have you done any mods to your rides

 

[DearDoger]

16g,walbro 255, greddy bov, K&N intake,cat back with hollow cat that passed emmisions , mbc,boost gauge.

 

[banshee04]

In every gear around 4-5.5 rpms my car misfires only under heavy throttle 80% or more. I replaced my spark plugs didnt help. When it "misfires" it is only a slight jerk an exhaust pop then it picks right back up.

What's your gap on your plugs?

 

[DearDoger]

.028

 

[Cat]

how about feul regulator you might need more fuel pressure

 

[banshee04]

Sounds like its running a lil rich up top and giving you that misfire for that slight second

 

[jdombrow]

same problem was on mine, full throttle and felt like complete loss of power. guy before me had plugs at .040 i regapped to .025 and fixed it. I'd double check the gap. plugs will be your cheapest/easiest piece to replace.

 

[DearDoger]

I litterally just replaced and gapped my plugs before posting this thread if your right and i am runnin rich would it really help that much to close the gap from .028 to .025. And i dont loose power under full throttle. Just get a quick lil misfire.
(Could this misfire be harming the engine?)

 

[Chrispy0530]

Your lucky then. I miss fire the whole way till I go into the next gear. Wideband reads straight 10 when under full throttle.

Idle is also super lean, like 15ish or so. Not sure if thats normal.

 

[DearDoger]

A wideband would really help me figure this out. I got one guy telling me not enough fuel pressure. and another telling me i am runnin too rich. i could really use an experianced opinion.

 

[DearDoger]

Well i g2g if anyone has a real good idea of what this problem could be please send me a private message

 

[vanilla gorilla]

It could be an electrical problem. See if it gets progressively worse day by day. If it does, you know its electrical.

 

[misphit]

Misfires are so annoying to diagnose... you're really going to have to narrow it down bit by bit. If you've done all the free stuff like a boost leak test, regapping your spark plugs, making sure your TPS is adjusted correctly (.5v with the key in on position), you can also look at: spark arcing off the coil pack, power transistor going bad, plug wires arcing, running rich/lean...
As mentioned by the other posters here, do yourself a favor and invest in an afpr. This will save you the trouble of guessing your fuel pressure, not to mention it can be a helpful tool when tuning if used correctly.

 

[meliketoball]

Look into changing your plugs, plug wires, maybe your coil pack as well.

 

[cjridert1]

What for boost and and what for plug are you using?

 

[BulletShiftTSi]

like everyone else states check your spark plugs gaps and make sure they are all in spec for your motor. if your not 100% sure look up the exact gap size.

Something like that happend to my car before and it was my TPS (throttle position sensor) its on the side of the throttle body its the black sensor on the right side of the throttle body in the pic shown below, just make sure its clean and working right and tight. it fixed my problem.

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I hope this helped you.

Good luck on fixing it!

 

[Chrispy0530]

^
This will be the next thing I do after I replace my spark plug wires with the stock NGK's. Granted, they're not old, but they're an aftermarket brand.

 

[habitatguy187]

Something like that happend to my car before and it was my TPS (throttle position sensor), just make sure its clean and working right and tight. it fixed my problem.

Why/how would the TPS cause a misfire?

 

[BulletShiftTSi]

I wasn't really sure why but when I was looking at my SAFC-II it wasn't reading the right throttle in comparsion to what my foot was doing and the car would sputter under heavier accel. I had an extra throttle body from my spare motor and swapped it and it stopped happening.

again I'm not sure how it fixed it I'm just glad it did and not going to ask questions before i jinx it

 

[Robert503]

In every gear around 4-5.5 rpms my car misfires only under heavy throttle 80% or more. I replaced my spark plugs didnt help. When it "misfires" it is only a slight jerk an exhaust pop then it picks right back up.

plug wires?