twentyeight
Veteran Member
I have had two different engines now, both 1Z blocks, that have exhibited a temporary stumble issue and I'd like to figure out why. The first was a B4 with RC2 in a GQ ecu (max pump voltage ~3.8v at 3500 vs 3.6v stock). The second is my T4 running GL programming with an 11mm ALH pump. I just so happen to also be running about 3.8v at 3500, although at what I'm telling it is 64 mg/s. Both engines were running .205 nozzles. I never get a code. The B4 had a rebuilt pump (but exhibited this issue far worse).
Symptoms: It loses 99% of power and smokes like a tire fire. It stumbles terribly. If i push in the clutch (which I initially did in the B4) it would die and be very difficult to restart. If I floor it and let the engine spin in gear, it eventually clears up and runs just as before. The 1Z (smooth body) pump cleared up much slower. The ALH pump has only done it once and it was very brief and seemed more like a switch was flipped when it came back on. It also didn't smoke as badly, which I attribute to higher pressures atomizing better.
Causes: The only two conditions that I have been able to identify are a fairly heavy throttle on a somewhat cold engine, such as the first time pulling onto the freeway in the morning. When hot I can flog the bus without issue. I seem to remember the B4 would do it even when hot, but I think it had a bad thermostat so I can't say for sure.
The T4 did it a few mornings ago after I upped the pump voltage slightly on the high end of the map, which is why I mention it above. I am fairly certain that the two engines ran completely different sets of nozzles; the only things they shared would be unrelated (like a power steering pump) and the ECU. However, the B4 exhibited the issue with a different ECU as well.
Is this a QA getting stuck wide open? That's the only idea I can come up with. I need to reseal the 11mm pump so as soon as that seal gets here I'll have a look inside. Any other ideas?
Symptoms: It loses 99% of power and smokes like a tire fire. It stumbles terribly. If i push in the clutch (which I initially did in the B4) it would die and be very difficult to restart. If I floor it and let the engine spin in gear, it eventually clears up and runs just as before. The 1Z (smooth body) pump cleared up much slower. The ALH pump has only done it once and it was very brief and seemed more like a switch was flipped when it came back on. It also didn't smoke as badly, which I attribute to higher pressures atomizing better.
Causes: The only two conditions that I have been able to identify are a fairly heavy throttle on a somewhat cold engine, such as the first time pulling onto the freeway in the morning. When hot I can flog the bus without issue. I seem to remember the B4 would do it even when hot, but I think it had a bad thermostat so I can't say for sure.
The T4 did it a few mornings ago after I upped the pump voltage slightly on the high end of the map, which is why I mention it above. I am fairly certain that the two engines ran completely different sets of nozzles; the only things they shared would be unrelated (like a power steering pump) and the ECU. However, the B4 exhibited the issue with a different ECU as well.
Is this a QA getting stuck wide open? That's the only idea I can come up with. I need to reseal the 11mm pump so as soon as that seal gets here I'll have a look inside. Any other ideas?