Hesitation/Misfire under boost

[mcrane]

Originally Posted by sid94

Put oem plugs in it. They’re good for pretty high hp. I had a random cylinder misfire code when I was breaking in my engine cause I had put a set of ngk “for break in” and it would throw me that code and hesitated like a old man before farting. Swapped oem plugs and car ran great after that


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I ran new OEM Plugs and had the same issue.

[Kodename47]

Originally Posted by mcrane

DI and PI are always running. Plus, it doesn't do this with the stock tune and injectors/MAP

They are, but the PI ratio combined with a larger port injector setting may make the DI take on a longer injector pulse width and with no change in injector timing it will go too close to the spark event and you will end up with a misfire type event. If you're using a later version of EcuTek you can log this. Otherwise I would have a go at calculating it.

[mcrane]

Originally Posted by Kodename47

They are, but the PI ratio combined with a larger port injector setting may make the DI take on a longer injector pulse width and with no change in injector timing it will go too close to the spark event and you will end up with a misfire type event. If you're using a later version of EcuTek you can log this. Otherwise I would have a go at calculating it.

This is a good point. I spoke to my tuner and he said that he adjusted that timing so that the DI would phase in later.

Back to the drawing board.

[mcrane]

Going to be tearing down and diagnosing tomorrow. Will update with results...

[Drakiv]

I had similar issues, turned out to be my map sensor. Although I also had issues getting the car to hot start as well. Cold starts were fine, but once warmed up the car wanted to die and then would be almost impossible to get started again until it cooled back down.

[mcrane]

Originally Posted by Drakiv

I had similar issues, turned out to be my map sensor. Although I also had issues getting the car to hot start as well. Cold starts were fine, but once warmed up the car wanted to die and then would be almost impossible to get started again until it cooled back down.

I never have issues starting or having the car die. I replaced the MAP Sensor and it didn't make a difference.

[86 South Africa]

Dunno who the tuner is - but isn’t this why you pay them? To help find and fix these issues. I’ve had a couple of tunes from delicious and never an issue.
True I’m supercharged, not urbocharged, but wondering if you’d find a better and a faster solution going to someone better at tuning this car?

[mcrane]

Update

Found a large exhaust leak post Turbo. This may have caused the tuner to be tuning on false information (AFR). Repaired the leaks and installed a wideband. Car is still having the issue. AFR is fine when cruising around. As soon as I hit 4,000 RPM the AFR pegs below a 10 (super rich). Going to have the tune adjusted with the fixed exhaust leak. See what that does.

[Fred E]

Originally Posted by mcrane

Update

Found a large exhaust leak post Turbo. This may have caused the tuner to be tuning on false information (AFR). Repaired the leaks and installed a wideband. Car is still having the issue. AFR is fine when cruising around. As soon as I hit 4,000 RPM the AFR pegs below a 10 (super rich). Going to have the tune adjusted with the fixed exhaust leak. See what that does.

Was the leak before or after the O2 sensors? If after, there's likely to be no change even after tuning adjustments. See if you can get any datalogs during the re-tune and share them here. Is the tune locked? If not, can you share that too? Given all the pieces that you've already replaced in your testing, it's quite likely this could be a tuning issue, especially since it's happening at a specific point in the rev range.

[mcrane]

Originally Posted by Fred E

Was the leak before or after the O2 sensors? If after, there's likely to be no change even after tuning adjustments. See if you can get any datalogs during the re-tune and share them here. Is the tune locked? If not, can you share that too? Given all the pieces that you've already replaced in your testing, it's quite likely this could be a tuning issue, especially since it's happening at a specific point in the rev range.

I should have mentioned that the tuner used a sniffer on the tailpipe to read AFR since I did not have a Wideband at the time. He had a hell of a time getting an accurate reading. So, by tuning off a sniffer in an exhaust system with a massive leak could lead to the wrong tune.

[Fred E]

Originally Posted by mcrane

I should have mentioned that the tuner used a sniffer on the tailpipe to read AFR since I did not have a Wideband at the time. He had a hell of a time getting an accurate reading. So, by tuning off a sniffer in an exhaust system with a massive leak could lead to the wrong tune.

I think you did mention that in the first post, but the ECU would still be using the OEM O2 sensors to make fueling adjustments as you're driving. A standard default parameter Ecutek datalog would show the O2 sensor reading and subsequent fueling adjustments as well to show what's really going on.

[mcrane]

UPDATE

Fixed exhaust leaks and brought it out for a Street Tune. Found that under WOT, the car would go super rich at about 4000 RPM. Fixed this by taking out some fuel. The car was running okay, but would lean out on the top end now. Fixed this by making some adjustments. Also added and tested Launch Control. The car seemed to finally be pulling clean and running healthy.

A few days later, the car started going super rich again, this time at 5,000 RPM. The hesitation isn't as bad this time however. Disconnected the Battery for 15 minutes in an attempt to resolve. Reconnected and problem persists. However, Launch Control is now gone.

As dumb as it seems, it almost seems as if the car is "forgetting" or disregarding the tune and doing its own thing. Both tuners cannot figure this out.

Any more ideas at this point?

[Dru670]

Sounds like the same issues I'm having (I have a jrsc c38, dw700cc and dw65c). AFR would read 11 around 4k rpm aand my car would sputter and I would have to go WOT or let off the accelerator for it to stop sputtering. It happens in 2nd and 3th gear and 6th gear around 3500rpm cruising at about 70mph. I reinstalled the OEM injectors but it still does it. And sometimes my car would idle like crap afr around 11. Moto-east has been trying to figure it out but no luck. I cleaned my upstream sensor and at first it would idle lean around 19-20 but the next day it ran normal and seemed like it was all good no sputter issues for about over a week but it started happening again. I wonder if MAP or hybrid tuning could fix this. Might it have something to do with DI/PI...

[BrightSlide]

I have been suffering a similar problem,
Built motor 10.0:1 compression
SBD 500x turbo kit 1050x injectors and walbro 485 fuel pump
Previously had a terrible idle hunting and stall problem while at rest of when lifting throttle
Switched from 1300cc injectors to the 1050x’s and deleted the BOV now idle is more stable but intermittently leaning out under load most commonly above 4K rpm WOT which basically 10lbs+ strangely it also leans under partial throttle while in low vacuum but not nearly as much if ever with light boost like 50% throttle and under 10lbs boost but more than 2-3lbs
Tuner is suggesting that the car is not taking the timing that it should for its compression questioning if the spark plugs r just fucked bc of the previous idle issue etc and previous tuner thought there was an issue with a cam gear, current tuner completely disagrees
Thanks in advance for help hope maybe something i said helps someone else definitely will share my experience and solution when i find it too