Intermittent Injectors on Rear Bank?

[DoctorDex]

I've have this issue I've been trying to solve for the past few months.

Here's whats been happening, sometimes (but not all the time) when I'm accelerating, my rear bank will just decide it wants to go really lean and then it starts to knock. My front o2 voltage will be a rock solid 0.91V and my rear o2 voltage will start out at 0.91V and then it just decides to randomly start dropping. I've seen it drop as low as 0.41V on the rear bank (whereas the front is still @ 0.91V). It seems like it wants to do it more often with hard acceleration, but it does do it sometimes while gradually accelerating. It doesn't do this at cruise.

At first, I though it was spark blow out related because it usually only happened in the higher rpm ranges @ WOT. Then it started happening while accelerating in the lower rpm ranges to (so this pretty much rules out spark blow out), so I started thinking maybe it had something to do with my fuel pressure being to low. I increased my fuel pressure back to stock, still no difference. I've been looking at switching to a dual feed system, but this seems like a lot of time and money for something that I'm not even sure is the cause of my problem.

Injectors have been cleaned and flow tested, I have new coils, plugs are gapped to 0.28, no boost leaks and I have replaced the caps.

Has anybody seen this before? I'm not sure where to even start looking for the problem.

Declan

[DoctorDex]

If one was opening long before the other would it affect the AFR/O2 voltage? Is so would it run leaner? Or would it richer?

I did have some issues in the past with one of my wastegates being stuck open. I never did figure out which one it was because when I went to test them, whichever one it was came unstuck.

Declan

[DoctorDex]

Originally Posted by magn1t

Try a different ECU. Just because you've changed the caps doesn't mean it's OK.

Finding another ECU is my problem. I can't find a single 1st gen (91) ECU within 8 hrs drive... My only alternative is to buy another one, which is a bit of an expensive experiment.

Declan

[slage]

they may not be getting enough fuel from the shitty stock fuel rail loop. I bought an ek2 fuel rail loop and now my rear bank reads slightly richer than the front, but it's still much better than before.

[DoctorDex]

I already have an ek2mfg fuel rail loop. Going to switch the direction of fuel flow later today (rear rail first --> front rail) to see if this helps.

Declan

[DoctorDex]

I haven't had time to switch the direction of flow in my fuel rail loops, as it looks like my one line is too short and I'm going to have to make another one.

I'm praying its a wastegate issue. I haven't been able to test them as I don't have an air pump handy. Will need to drive to my parents place to get one (1hr & half drive away).

I made a log of the issue. My rear bank runs very lean from 2000 rpm to ~ 6000 rpm. Above 6000 rpm my rear O2 voltage matches the front. Here is the log if anyone is interested:

O2-R AFR MPH RPM INJP O2-F
0.12V 13.9V 43 2281 9.98ms 0.86V
0.12V 13.9V 44 2281 9.98ms 0.86V
0.12V 13.9V 44 2281 9.98ms 0.88V
0.12V 13.9V 44 2344 10.24ms 0.88V
0.12V 13.9V 44 2344 10.24ms 0.88V
0.12V 13.9V 44 2313 10.24ms 0.88V
0.12V 13.9V 44 2313 10.24ms 0.88V
0.10V 13.9V 45 2375 10.50ms 0.88V
0.12V 13.9V 45 2375 10.50ms 0.88V
0.12V 13.9V 45 2375 10.50ms 0.88V
0.10V 13.9V 45 2406 10.75ms 0.88V
0.10V 14.0V 46 2406 10.75ms 0.88V
0.10V 14.1V 46 2469 10.75ms 0.88V
0.10V 13.9V 46 2469 10.75ms 0.88V
0.10V 13.8V 47 2469 10.75ms 0.88V
0.10V 13.7V 47 2469 10.75ms 0.86V
0.08V 13.6V 47 2500 11.01ms 0.86V
0.08V 13.7V 47 2500 11.01ms 0.88V
0.08V 13.8V 48 2531 11.01ms 0.88V
0.08V 13.9V 48 2531 11.01ms 0.88V
0.08V 13.9V 48 2531 11.26ms 0.88V
0.08V 13.9V 49 2531 11.26ms 0.88V
0.08V 14.1V 49 2563 11.52ms 0.86V
0.08V 14.1V 49 2594 11.52ms 0.86V
0.08V 14.1V 49 2594 11.52ms 0.88V
0.08V 14.1V 50 2656 11.78ms 0.88V
0.08V 14.2V 50 2656 11.78ms 0.86V
0.06V 14.1V 50 2656 12.29ms 0.86V
0.08V 13.9V 51 2656 12.29ms 0.88V
0.08V 13.9V 51 2656 12.29ms 0.88V
0.08V 13.9V 51 2656 12.29ms 0.90V
0.08V 13.9V 52 2719 12.54ms 0.90V
0.10V 13.9V 52 2750 12.80ms 0.90V
0.10V 13.8V 52 2750 12.80ms 0.90V
0.10V 13.6V 52 2813 12.54ms 0.90V
0.10V 13.5V 53 2813 12.54ms 0.92V
0.16V 13.4V 53 2781 12.80ms 0.92V
0.21V 13.3V 53 2781 12.80ms 0.92V
0.21V 13.1V 54 2875 12.80ms 0.92V
0.25V 13.1V 54 2875 12.80ms 0.92V
0.25V 13.0V 54 2875 13.31ms 0.92V
0.25V 13.0V 55 2906 13.06ms 0.92V
0.25V 12.9V 55 2906 13.06ms 0.94V
0.43V 12.7V 55 2906 13.06ms 0.94V
0.43V 12.6V 55 2906 13.06ms 0.94V
0.49V 12.5V 57 2969 13.06ms 0.94V
0.47V 12.5V 57 2969 13.06ms 0.94V
0.47V 12.6V 57 3000 13.31ms 0.94V
0.43V 12.5V 58 3000 13.31ms 0.94V
0.43V 12.5V 58 3000 13.31ms 0.94V
0.49V 12.5V 58 3063 13.31ms 0.94V
0.49V 12.5V 58 3063 13.31ms 0.94V
0.53V 12.5V 59 3063 13.31ms 0.94V
0.53V 12.5V 59 3063 13.31ms 0.94V
0.47V 12.5V 59 3094 13.57ms 0.94V
0.47V 12.5V 60 3094 13.57ms 0.94V
0.45V 12.5V 60 3125 13.31ms 0.94V
0.45V 12.5V 60 3125 13.31ms 0.94V
0.49V 12.5V 60 3156 13.57ms 0.94V
0.43V 12.4V 61 3156 13.57ms 0.94V
0.43V 12.4V 61 3219 13.57ms 0.94V
0.43V 12.5V 61 3219 13.82ms 0.94V
0.43V 12.5V 62 3219 13.82ms 0.94V
0.43V 12.5V 62 3250 5.63ms 0.94V
0.43V 12.5V 62 3250 5.63ms 0.94V
0.45V 12.6V 63 3313 14.08ms 0.94V
0.45V 12.6V 63 3313 14.08ms 0.94V
0.47V 12.6V 63 3313 14.34ms 0.94V
0.49V 12.6V 63 3313 14.34ms 0.94V
0.49V 12.5V 64 3344 14.34ms 0.94V
0.49V 12.5V 64 3344 14.34ms 0.94V
0.49V 12.5V 64 3344 14.59ms 0.94V
0.55V 12.5V 65 3344 14.59ms 0.94V
0.55V 12.4V 65 3438 14.85ms 0.94V
0.55V 12.4V 65 3500 14.85ms 0.94V
0.55V 12.3V 65 3500 14.85ms 0.94V
0.64V 12.2V 66 3469 14.85ms 0.94V
0.64V 12.2V 66 3469 14.85ms 0.94V
0.60V 12.2V 66 3563 15.10ms 0.94V
0.60V 12.2V 68 3563 15.10ms 0.94V
0.57V 12.3V 68 3563 15.36ms 0.94V
0.57V 12.3V 68 3563 15.36ms 0.94V
0.57V 12.4V 69 3625 15.36ms 0.94V
0.66V 12.3V 69 3625 15.36ms 0.94V
0.66V 12.3V 69 3563 15.62ms 0.94V
0.62V 12.3V 69 3719 15.62ms 0.94V
0.62V 12.4V 70 3719 15.62ms 0.94V
0.66V 12.3V 70 3656 15.87ms 0.94V
0.66V 12.2V 70 3656 15.87ms 0.94V
0.66V 12.2V 71 3750 16.13ms 0.94V
0.66V 12.2V 71 3750 16.13ms 0.96V
0.70V 12.2V 71 3813 16.38ms 0.96V
0.70V 12.1V 71 3844 16.38ms 0.96V
0.70V 12.0V 73 3844 16.64ms 0.96V
0.68V 12.0V 73 3875 16.64ms 0.96V
0.68V 12.0V 73 3875 16.64ms 0.96V
0.70V 12.0V 74 3781 16.38ms 0.96V
0.70V 11.9V 74 3781 16.38ms 0.94V
0.70V 11.9V 74 3938 16.64ms 0.94V
0.70V 11.9V 74 3938 16.64ms 0.96V
0.66V 11.9V 75 3938 16.90ms 0.96V
0.70V 11.9V 75 3938 16.90ms 0.96V
0.70V 11.9V 75 3875 16.90ms 0.96V
0.72V 11.9V 76 4031 16.90ms 0.96V
0.72V 12.0V 76 4031 16.90ms 0.94V
0.66V 12.0V 76 4031 17.15ms 0.94V
0.66V 11.9V 77 4031 17.15ms 0.96V
0.70V 11.9V 77 4000 16.90ms 0.96V
0.70V 11.8V 77 4000 16.90ms 0.94V
0.72V 11.8V 78 3969 16.90ms 0.94V
0.70V 11.9V 78 4188 16.90ms 0.94V
0.70V 11.8V 78 4188 17.15ms 0.96V
0.68V 11.8V 78 4219 17.15ms 0.96V
0.68V 11.8V 79 4219 17.15ms 0.96V
0.70V 11.7V 79 4250 17.41ms 0.96V
0.70V 11.7V 79 4250 17.41ms 0.96V
0.68V 11.7V 80 4063 16.90ms 0.96V
0.68V 11.7V 80 4063 16.90ms 0.96V
0.64V 11.7V 80 4125 17.41ms 0.96V
0.74V 11.6V 80 4125 17.41ms 0.96V
0.74V 11.6V 82 4344 17.15ms 0.96V
0.70V 11.7V 82 4188 17.15ms 0.96V
0.70V 11.5V 82 4188 17.15ms 0.96V
0.74V 11.4V 83 4188 17.15ms 0.96V
0.74V 11.4V 83 4188 17.15ms 0.96V
0.76V 11.4V 83 4438 25.86ms 0.96V
0.76V 11.4V 83 4438 25.86ms 0.96V
0.78V 11.2V 84 4281 17.66ms 0.96V
0.78V 11.2V 84 4281 17.66ms 0.96V
0.74V 11.2V 84 4281 17.41ms 0.96V
0.74V 11.2V 85 4281 17.41ms 0.96V
0.74V 11.2V 85 4563 17.92ms 0.96V
0.78V 11.1V 85 4563 17.92ms 0.96V
0.78V 11.1V 86 4563 17.66ms 0.96V
0.82V 11.0V 86 4375 17.66ms 0.96V
0.82V 11.1V 86 4375 17.66ms 0.96V
0.72V 11.1V 86 4438 17.92ms 0.96V
0.72V 11.1V 87 4438 17.92ms 0.96V
0.82V 11.1V 87 4719 18.18ms 0.96V
0.80V 11.1V 87 4719 18.18ms 0.96V
0.80V 11.1V 88 4469 17.92ms 0.96V
0.82V 11.1V 88 4469 17.92ms 0.96V
0.82V 11.0V 88 4438 17.66ms 0.96V
0.82V 11.1V 88 4594 17.66ms 0.96V
0.82V 11.1V 89 4594 17.92ms 0.96V
0.82V 11.1V 89 4594 17.66ms 0.96V
0.82V 11.1V 89 4594 17.66ms 0.96V
0.84V 11.1V 90 4844 17.66ms 0.96V
0.84V 11.1V 90 4844 17.92ms 0.96V
0.84V 11.1V 90 4563 17.92ms 0.96V
0.84V 11.0V 90 4563 17.92ms 0.96V
0.86V 11.0V 91 4844 17.92ms 0.96V
0.86V 11.1V 91 4844 17.92ms 0.96V
0.86V 11.1V 91 4906 17.92ms 0.96V
0.86V 11.1V 92 4906 17.92ms 0.96V
0.86V 11.1V 92 4938 17.92ms 0.96V
0.88V 11.0V 92 4938 17.92ms 0.96V
0.88V 11.0V 94 4750 17.41ms 0.96V
0.86V 11.1V 94 5063 17.41ms 0.96V
0.86V 11.1V 94 5063 17.66ms 0.96V
0.90V 11.1V 94 4813 17.66ms 0.96V
0.90V 11.1V 95 4813 17.66ms 0.96V
0.90V 11.1V 95 5094 18.18ms 0.96V
0.90V 11.1V 95 5094 18.18ms 0.96V
0.92V 11.1V 96 5063 17.92ms 0.96V
0.92V 11.0V 96 5063 17.92ms 0.96V
0.92V 10.9V 96 4906 17.92ms 0.96V
0.92V 10.9V 96 4906 17.92ms 0.96V
0.92V 11.0V 97 5156 17.92ms 0.96V
0.94V 11.1V 97 5156 17.92ms 0.96V
0.94V 11.1V 97 5031 18.18ms 0.96V
0.94V 11.1V 98 5031 18.18ms 0.96V
0.90V 11.1V 98 4938 18.18ms 0.96V
0.94V 11.1V 98 4938 18.18ms 0.96V
0.94V 11.1V 98 5188 17.92ms 0.96V
0.92V 11.1V 99 5063 18.18ms 0.96V
0.92V 11.1V 99 5063 18.18ms 0.96V
0.92V 11.1V 99 5031 18.18ms 0.96V
0.92V 11.1V 100 5031 17.92ms 0.96V
0.92V 11.1V 100 5094 17.92ms 0.96V
0.92V 11.1V 100 5094 17.92ms 0.96V
0.92V 11.1V 101 5375 17.92ms 0.96V
0.92V 11.1V 101 5375 17.92ms 0.96V
0.92V 11.1V 101 5188 17.41ms 0.96V
0.92V 11.1V 101 5188 17.41ms 0.96V
0.92V 11.2V 102 5406 17.66ms 0.96V
0.92V 11.3V 102 5406 17.66ms 0.96V
0.92V 11.2V 102 5469 17.66ms 0.96V
0.92V 11.2V 103 5219 17.66ms 0.96V
0.92V 11.3V 103 5219 17.41ms 0.94V
0.92V 11.3V 103 5531 17.66ms 0.94V
0.92V 11.3V 103 5531 17.66ms 0.96V
0.92V 11.2V 104 5250 17.15ms 0.96V
0.92V 11.1V 104 5250 17.15ms 0.96V
0.92V 11.1V 104 5313 17.15ms 0.96V
0.92V 11.1V 105 5313 17.15ms 0.96V
0.92V 11.3V 105 5563 17.15ms 0.94V
0.92V 11.3V 105 5563 17.15ms 0.94V
0.92V 11.3V 105 5375 17.15ms 0.94V
0.92V 11.3V 106 5438 17.15ms 0.96V
0.92V 11.3V 106 5438 17.15ms 0.96V
0.94V 11.4V 106 5469 17.15ms 0.96V
0.94V 11.4V 107 5469 17.15ms 0.94V
0.92V 11.4V 107 5375 16.64ms 0.94V
0.92V 11.4V 107 5375 16.64ms 0.94V
0.92V 11.4V 108 5656 17.15ms 0.94V
0.92V 11.4V 108 5656 17.15ms 0.94V
0.92V 11.4V 108 5469 16.64ms 0.94V
0.92V 11.4V 108 5563 16.64ms 0.94V
0.92V 11.3V 109 5563 16.90ms 0.94V
0.94V 11.3V 109 5500 16.90ms 0.94V
0.94V 11.2V 109 5500 16.64ms 0.94V
0.92V 11.2V 110 5594 16.38ms 0.94V
0.92V 11.2V 110 5594 16.38ms 0.94V
0.92V 11.3V 110 5625 16.64ms 0.94V
0.92V 11.3V 111 5625 16.64ms 0.94V
0.92V 11.3V 111 5875 16.64ms 0.94V
0.94V 11.4V 111 5875 16.64ms 0.94V
0.94V 11.4V 111 5969 16.38ms 0.94V
0.92V 11.3V 111 5969 16.38ms 0.94V
0.92V 11.3V 111 5906 16.38ms 0.94V
0.92V 11.3V 111 5719 16.38ms 0.94V
0.92V 11.3V 112 5719 16.38ms 0.94V
0.94V 11.2V 112 6000 16.38ms 0.94V
0.94V 11.2V 112 6000 16.38ms 0.94V
0.94V 11.2V 112 6000 16.38ms 0.94V
0.94V 11.1V 113 6000 16.38ms 0.94V
0.92V 11.1V 113 6000 16.38ms 0.94V
0.92V 11.1V 113 6000 16.38ms 0.94V
0.94V 11.1V 114 5781 16.38ms 0.94V
0.94V 11.1V 114 5781 16.38ms 0.94V
0.94V 11.1V 114 6000 16.38ms 0.94V
0.94V 11.1V 114 6000 16.38ms 0.94V
0.92V 11.1V 115 5875 16.13ms 0.94V
0.92V 11.1V 115 5875 16.13ms 0.94V
0.94V 11.1V 115 5813 16.13ms 0.94V
0.94V 11.1V 115 5813 16.13ms 0.94V
0.94V 11.1V 115 5969 16.38ms 0.94V
0.94V 11.1V 115 6188 16.38ms 0.94V
0.94V 11.1V 115 6188 16.38ms 0.94V
0.94V 11.1V 116 5938 16.38ms 0.94V
0.94V 11.1V 116 5938 16.13ms 0.94V
0.94V 11.1V 116 5875 15.87ms 0.94V
0.94V 11.1V 117 5875 15.87ms 0.94V
0.94V 11.2V 117 6000 16.13ms 0.94V
0.94V 11.2V 117 6000 16.13ms 0.94V
0.94V 11.2V 117 6000 15.87ms 0.94V
0.94V 11.1V 117 6000 15.87ms 0.94V
0.94V 11.1V 117 6313 16.13ms 0.94V
0.94V 11.1V 117 6313 16.13ms 0.94V
0.94V 11.2V 118 6188 15.87ms 0.94V
0.94V 11.1V 118 6188 15.87ms 0.94V
0.94V 11.1V 118 6250 10.24ms 0.94V
0.92V 11.7V 118 6250 10.24ms 0.92V

Do you guys still think wastegate? Or is it possible that I have bad rings on the rear? Would bad rings cause other symptoms too? Any ideas why my RPM readings jump around?

Any help or suggestions would be greatly appreciated.

Declan

[DoctorDex]

Front or rear? I just replaced the rear ~ 1000 miles ago because it was "lazy". I a actually replaced it twice as the 1st one the dealer gave was lazy too. The sensor seems to work fine @ idle and cruise. It oscillates in the same pattern as the front.

Declan