Hey guys,

Have a 2003 VIII with the following:
26k miles/~5k on build
2.3L stroker
Built heads with +1 valves
AMS 900X turbo fitted to a modified GT30R kit
E85
FIX Bluemax 1650 injectors
Spoolin COP
EBC
Speed density tune

This car is fairly new to me but was driving fine up until a day ago.

Issue: Car now has almost unmanagable breakup at both low RPM and under load (only usable range is above 3k under very light load), and rough idle.

I have:
-replaced spark plugs (.020)
-gapped new plugs smaller than the first set (.018)
-gapped new plugs wider than the first set (.022)
-replaced what appeared to be a bad coil pack
-checked all clamps and elbows

Have not had a boost leak test done yet but am scheduling one with comp/leak down. All clamps appear tight.

So far, no improvement....

 

the problem just appeared out of no where? have you checked the power going to the coils?

 

progressively got worse. started under full load/boost. have not checked the power there. what should i expect as "normal" when i do?

 

Are you able to see your fuel pressure? Could it be fuel pump?

 

Would a bad fuel pump only have issues at low and high rpm? Mid-range is fine.

 

I could very well be boost leak.

 

I would swap stock coils back in and see if it goes away... my spoolin up kit used to blow coils and it was very noticeable at 3000 rpm cruise...

 

3k+ is actually where it starts behaving normally until it hits boost

will try to swap OEM's back in if i can find some.

 

if all else fails check your throttle postion sensor, mine was going bad and caused miss fires like you said. i changed all the above aswell ended up being this.

 

Also, this has happened to me before as well... it appeared to be a cam position sensor that was on its way out... $60 at autoparts store, and quick swap...

 

Does it sound like a machine-gun when you hit boost? If so, that's a bad coil pack

 

Have you checked to see if your intercooler pipes are all still in place, it could have blown one off...do a boost leak test as soon as possible.

 

Its on of theses 4 problems i bet.

- Do a Boost leak test.
- Cam angle sensor "The one on the head"
- Crank angle sensor "A pain to get to so check last resort."
- Check major grounds / alternator.

 

^This

 

Boost leak test: pass (didnt have the stuff to do a smoke test, found leaks before the sensor which i covered but nothing else.) All IC piping is intact and secured with t-bolt clamps.

Compression: test looks good with consistent readings across all cylinders +/- 5 psi

Fuel pressure: 65 at idle, moves up and down with adjusting the FPR, doesnt seem to be an issue

Fuel: added more fuel from another station to help balance out would-be bad fuel

Ignition: have a buddy overnighting me a stock coil pack to check ignition. Fuse looked fine.

Will add the above suggestions to the list!

Thanks guys!