Random Limp Mode From Misfires

[arlisscm]

Back at the end of May at Pocono Raceway about halfway through session 3 on day one my car randomly went into limp mode (blinking CEL) and had cleared by the time I got back into the pits. Let it cool down and restarted and everything seemed fine. Didn't have any issues for session 4 or the next four sessions the next day. So, I thought it was a hiccup and moved on.

Now, Monday and Tuesday this week at Watkins Glen, no issues in session one, then about 7 laps into session two i got limp mode again and it cleared itself by the time I got back in. Again on session three, but after about 5 laps, this time limp mode cleared itself again but left on the CEL, misfires on cylinders 1+4. Cleared the codes before session 4, got limp mode again after only two laps, once again cleared itself and no hard CEL.

Swapped out the spark plugs for a new set, and swapped 1+2 coils and 3+4 coils. Session one day two, no limp mode (session was kind of a mess so I wasn't really getting after it). Session two finally got a bit of open track, then about 6 laps in limp mode, once again cleared itself.

Any thoughts? Evap purge valve/harness? Swapping the plugs and coils didn't change anything.

 

[Switchback]

Hey this is the exact same problem I'm currently having! Happens only on high-load, but I could also get the car to misfire when revving it to 3k RPM when the engine is hot but in neutral.

Since you're on a brand new built block I take it you have clean intake valves, which is the only thing I haven't checked on my car yet. Did you also get a P0316 code by chance? Diagnostics says that's a misfire within first 1000 Revs, but I get it after driving hard.

So far what I've done is swap plugs (brand new set of colder plugs), move coil packs around, and even moved the Fuel Injectors in Cyl 1 and 2 around to see if it was a fueling problem (It wasn't). Also, swapped tunes from the Dizzy stage 2 shelf tune to a Cobb stage 2 without any change.

 

[arlisscm]

Hey this is the exact same problem I'm currently having! Happens only on high-load, but I could also get the car to misfire when revving it to 3k RPM when the engine is hot but in neutral.

Since you're on a brand new built block I take it you have clean intake valves, which is the only thing I haven't checked on my car yet. Did you also get a P0316 code by chance? Diagnostics says that's a misfire within first 1000 Revs, but I get it after driving hard.

So far what I've done is swap plugs (brand new set of colder plugs), move coil packs around, and even moved the Fuel Injectors in Cyl 1 and 2 around to see if it was a fueling problem (It wasn't). Also, swapped tunes from the Dizzy stage 2 shelf tune to a Cobb stage 2 without any change.

Yeah, I for sure know the valves are clean (only about 1500 miles on them). And, the spark plug and coil swap/shuffle didn't change anything.

My codes are P0300, P0301, P0304 (random misfires, misfire cylinder 1, misfire cylinder 4 respectively).

 

[Switchback]

Yeah, those are the same codes I get, with P0316 coming up every once in a while. With an accessport set to misfires, if you rev your engine to 3k and hold it there does your misfire count start to go flying? I'm curious to see if you can replicate the issue without hammering on the car at track/canyon speeds.

I have a new purge valve on order, should be here tomorrow. Going to splice it in so I don't have to pay for the whole assembly.

 

[arlisscm]

Yeah, those are the same codes I get, with P0316 coming up every once in a while. With an accessport set to misfires, if you rev your engine to 3k and hold it there does your misfire count start to go flying? I'm curious to see if you can replicate the issue without hammering on the car at track/canyon speeds.

I have a new purge valve on order, should be here tomorrow. Going to splice it in so I don't have to pay for the whole assembly.

Went and checked, monitored knock on cylinders 1+4 and misfire count. None of which changed at all free revving at, and above 3000 rpm.

Seems like P0316 is detected within the first 1,000 rpm, i haven't popped that one. Mine pops up at least 10 minutes after starting, usually a few laps (sometimes many) in after sitting in the staging lanes for 5-10 minutes. Then clears itself after ~30 seconds and everything is good again. I still hop off track as being hamstringed that bad in traffic isn't fun (or safe).