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Breaking up under boost

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3.2K views 21 replies 4 participants last post by  LividST  
#1 ·
Hello all, I've been battling an issue with my ST having issues under boost causing a "anti lag" sound with no power and a p0300 random miss. I have replaced spark plugs twice with gapping of 0.030 and 0.027 and get the same issue. It sounds exactly like when spark plugs go bad on these cars, and I know for a fact because i have run into that issue on 2 other STs. I've also checked the FP low side and rail pressure and both are within spec. The map sensor is reading correctly and has been cleaned. Injectors have been flushed and flow tested. I've ran 2 tanks of gas to get any contamination out. And I have checked thourgly for air leaks of any kind with a smoke tester and brake clean. I also once got a over boost code but could never get it to set again. Any advice would be great. Thanks in advance!

Mods are FBO and a built bottom end with stock turbo.
 
#2 ·
Can you post a data log with this happening to datazap.me and link it here? That might help us in diagnosing the issues.
 
#12 ·
Yeah, your FRP desired and FRP actual are WAY off several times in the pull. What's your boost look like on the run? I didn't see that PID as part of the DL?

@Dirtfiend602 may be right on the sensor and/or pump. Sure appears that there are some major discrepancies between what the computer is asking for and what the sensor is reading.
 
#13 ·
Yeah, your FRP desired and FRP actual are WAY off several times in the pull. What's your boost look like on the run? I didn't see that PID as part of the DL?

@Dirtfiend602 may be right on the sensor and/or pump. Sure appears that there are some major discrepancies between what the computer is asking for and what the sensor is reading.
I agree, and boost is going to about 18 pounds due to it being a stage 0 tune. Any suggestions on how to test the sensor and or pump?
 
#14 ·
Hopefully Dirtfiend will be along shortly to give some info on those since he had to troubleshoot his.
 
#16 ·
Not enough PID to really dig into this. RPM, MAP, TIP, high & low fuel pressure ( actual & desired), ETC.

From the 3rd csv file I'm not seeing a large enough variation in the HPFP A vs D delta.

The HPFP has been known to get flaky due to the pressures it plays at. The low not so much, but nothing is out if the realm of possibilities.

The PCM can only command the HPFP higher as the only way to reduce the rails pressure is via the injectors opening.

The LPFP has three separate parts. Sensor, control module, and pump itself.
 
#17 ·
Not enough PID to really dig into this. RPM, MAP, TIP, high & low fuel pressure ( actual & desired), ETC.

From the 3rd csv file I'm not seeing a large enough variation in the HPFP A vs D delta.

The HPFP has been known to get flaky due to the pressures it plays at. The low not so much, but nothing is out if the realm of possibilities.

The PCM can only command the HPFP higher as the only way to reduce the rails pressure is via the injectors opening.

The LPFP has three separate parts. Sensor, control module, and pump itself.
Sorry the 3rd file was just average driving gear to gear, file 2 is actually a pull when it happens l, and file 1 is just making sure it would log due to it telling me I kept having too many pics.
 
#19 ·
Make sure to add ETC & APP