lude1888

iTrader: (3)

So I've read countless threads about hesitation in high rpm and can't quite figure out what's wrong with my 8.
Info:
Engine was professionally rebuilt by Jim's Rotary shop. Engine pulls good and strong up to 6k. hesitation/stuttering occurs after 6k. Sometimes it will stutter at 7k rpm with no power and will throw a blinking check engine. Free reving engine passed 7k can result in flashing engine light. Car does not smell rich, it smells strange; probably lean when rev high thus I'm leaning more toward maf or injectors. Engine will rev past 7k with light gas pedal pressure, but if pedal is past 75% stuttering will happen at 6-7k rpm.


Car has/things done:
new full rebuilt engine with 3k miles
bhr ignition kit (15k miles) (One coil replaced for being possibly faulty)
new fuel pump
aem intake (screens are properly placed)
stock cat (catalytic converter is excellent + passed smog easily yesterday)
Checked SSV,
20 brake stomp
brand new set of spark plugs (<300miles)

Things to check,
-Stock ignition system (per Jim's suggestion)
-I have a spare maf that I can try
-Fuel Injectors? (Do these fail often on 8's??) (Would fuel injector cleaner in gas tank work???)
-Maybe Jim forgot to reflash engine after rebuild???

Carbon Fibr

plugs & wires ~ thats the probable cause
also theres another air valve (i forget what its called) that opens up at higher RPM might be an issue there.
Spray some seafoam or carbcleaner on your maf
maybe even a seafoam job on your engine, clean the carbon build up on your rotors.

for ***** and giggles id do a full reset. Take the negative off your battery, hop in your car turn key forward and do 10 brake stomps, turn key back, put negative back on.
Than take it for a drive cuz the fuel trims must be relearned.

last resort take your car to a tuner or something maybe that bhr kit and fuel pump going to need tune of some sort.

revivo73

The 7 years old coils on my 2006 used to cause non-complete firings at high rpms, and when I replaced them with OEM Mazda ones, the problem was solved. But that problem of mine didn't cause any noticable power loss or CEL, mainly it caused explosion sound at the exhaust.

In your case, there's power loss (it will stutter at 7k rpm with no power) and that might be caused by some problem on the fuel line: The fuel pump (which you say new), injectors. I can't say anything about the MAF. But try with stock ignition system and try doing the KAM (disconnect the battery for 10+ minutes) and NVRAM (the 20 brake stomp) resets to make sure that the engine is completely reset.

lude1888

iTrader: (3)

Just for completeness to close out my thread for future reference. The issue was the bhr coils. Swapped back out to stock and car drives amazing. New engine rebuild is beautiful. Much more useful power and response and no cel or hesitation. Coils are getting sent back to Charles for some diagnostics. Can't wait to get my bhr kit back .