4g63t hesitating under high RPM s

[techghost]

i have a AWD colt with a 4g63t 6bolt from a VR4-RS with 510cc and B16g. recently i've started to face problem under high RPM say 5k+ where motor hesitates misfires and seems like missing power, in mid-range car pulls good which starts to sputter, misfire, brrbrrr when get passed 5k/6k rpm

Initially i thought that my plugs are fouled and also changed them but no effect what so ever. i'm running 8es

### help

 

[antilag]

Sounds like it is fuel related. First, what kind of afr's are you hitting up top. I would say your pump is on its way out and not holding pressure up top.

 

[Richrx_tsi]

New plugs never hurt.

 

[viperlp01]

He put plugs in it^^^??? But what did you gap them to??

Could defidently be fuel related. What are you using to tune the e85?? Maybe a log would be more helpful.. Are you knocking?

 

[1bad95tsi]

We did a head job on my buddys 98 gst and had simlir probs -we swapped on a used head and it had issues after chasing the issue around we ended up changing the rubber o rings for the injectors they were dryrotted and the plugs and it was ok hows afr when it sputters? sounds fuel related

 

[Drubble]

No mods in your profile, but an 8es plug may be too cold. Try a 7 and gap it a bit thinner to see if it helps (.025). It also sounds like it is time for a boost leak test. As 1bad95tsi suggested, check the injector seals. If one (or more) are leaking, that will also cause problems.

 

[viperlp01]

A proper boost leak test will tell you if the seals are bad^^^

 

[techghost]

Update:
Changed my plugs to Denso W16x, and now car is much better uptop, took it out for a run but just after accelrating a little bit, when the car reached NOT, it started to sputter again
Second gear, WOT and it seems like one or two cylinders are not working at all.

There isnt any boost leak at all, have new seals for my injectors.

 

[habitatguy187]

Wires are the next check. Sounds like you're not getting a strong enough spark.

 

[techghost]

If say i'm not getting enough spark even then my cylinders will stop working? due to flooding?

 

[habitatguy187]

If say i'm not getting enough spark even then my cylinders will stop working? due to flooding?

They won't stop working, they'll just be missing out. A backfire is usually gas igniting in your exhaust, making the noise. The reason it ignites in the exhaust is because it didn't get a complete burn inside the combustion chamber.

Good read - HowStuffWorks "How Car Engines Work"

 

[techghost]

I know they will be misfiring, i just wanted to let you know that it feels like one or two cylinders are not working. feels like i'm running 2/3 cylinders only, you know what i'm trying to say here? this is the problem i'm currently having

 

[habitatguy187]

I know they will be misfiring, i just wanted to let you know that it feels like one or two cylinders are not working. feels like i'm running 2/3 cylinders only, you know what i'm trying to say here? this is the problem i'm currently having

Well if it only does it under high load then it's probably an ignition/too much fuel problem, now if it felt like that all the time I would say it was something else, but since it's only at high rpms the first thing to start with would be plug wires.

 

[DJTanberg]

how much boost u runnin? check boost controller..had same issue no boost leak, but the boost controller was leakin causin sputtering at top end under wot. possible break up in the wires at high rpm

 

[Drubble]

Your ignition coil pack may be suspect as well if it is original. I would go back to the NGK plugs, as has been recommended countless times on this forums. And how about that "gap" question?

 

[99GST83]

check your roller rockers under the valve cover. I had the same problem, and found that I had a rocker come off. It caused a high rpm hesitation, and idle wasent as smooth as it could have been. I wound up replacing injectors, injector rings, plugs, wires, boost leak check came back ok, no vacuum leaks, and replaced coil before I found it... Just a quick 5 min. check. Good luck