Full Throttle Misfire Trouble

[JBird]

I bought a car from out of state and it's got a bad hesitation/misfire when going WOT. It'll sputter ~4 times before finally going. '19 Whipple, DW400 and Deatschwerks 78 lbs, Stainless Power headers, etc. It's PBD tuned from the previous owner.

There are no codes so is there a good order to troubleshoot? I've replaced the plugs and air filter and planned on the O2's next. I'm taking the car in next month for E85 (new fuel system and injectors) so that may fix it. Just hoping to grab advice from others who may know better in the meantime so I'm not just throwing money at random things. Thanks

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[HKusp]

No codes? If it is O2's it should be showing in the fuel trims. Do you have a way of data logging?

 

[robvas]

I've replaced the plugs and air filter and planned on the O2's next.

I'm taking the car in next month for E85 (new fuel system and injectors) so that may fix it.

Don't throw a new fuel system on it before fixing the existing problem.

Datalog the shit out of it and see what looks funky. I'd think coils before O2's but don't just throw parts at it.

 

[sabtaj1]

How long the injectors and dw400 been in the car? Maybe throw some injection cleaner through it, maybe fuel filter.

 

[JBird]

How long the injectors and dw400 been in the car? Maybe throw some injection cleaner through it, maybe fuel filter.

The seller has had those things on for a couple years. During the process he mentioned tune up/spark plugs a few times so this may have been a known issue.

It seems like the only real option to diagnose it is to datalog and pay PBD $75 to read it?

 

[JBird]

Don't throw a new fuel system on it before fixing the existing problem.

Datalog the shit out of it and see what looks funky. I'd think coils before O2's but don't just throw parts at it.

Why coils first? I'm asking to learn, thanks

 

[robvas]

Why coils first? I'm asking to learn, thanks

Because they are known to fail or cause this

but if you aren't getting a misfire code with a specific cylinder you'd have to do a power balance test or something to try to isolate it

i wouldn't replace the O2 sensors without at least seeing what they are reading when you drive it

 

[JBird]

Everything I checked seemed fine. If the gas tank is full it runs wonderful. ~1/2 tank it hesitates for a second at WOT. Any lower and it runs like garbage. Straight highway roads and it would barely accelerate at 1/4 tank with the A/F shooting way up when I tried it once. Assuming it's a fuel pump/DW400 issue which will be fixed in a few weeks when the return system goes in. Anything else I should consider before then? Thanks.

 

[SH!FT]

Battery test. Had a similar issue on my Roushcharged 2020 due to a failing battery.

Check for loose ground wires.

See if your car has a fuel pump voltage booster installed. Some units are adjustable.

 

[cbrtrx]

Everything I checked seemed fine. If the gas tank is full it runs wonderful. ~1/2 tank it hesitates for a second at WOT. Any lower and it runs like garbage. Straight highway roads and it would barely accelerate at 1/4 tank with the A/F shooting way up when I tried it once. Assuming it's a fuel pump/DW400 issue which will be fixed in a few weeks when the return system goes in. Anything else I should consider before then? Thanks.

Check the nipple and the venturi hose on the dw400. Sounds like it failed.

 

[schmeky]

What plugs did you install?

There are lots of "fake" NGK 6510's on the market.

 

[Ortiz]

Check your fuel pressure. You mentioning having a DW pump and how we've seen many of them have bursted hoses could explain it. If you were tuned with SCT or HPT, you can log it all in real time and see what its doing.

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