I have been having some issues trying to get my freshly built 2005 4Runner 2UZ VVTi with Link ECU piggyback running. It has run recently: it idled well; and I could slowly raise the rpms, but if I gave it any real throttle it would cut out. I’ve made a number of adjustments to try and get it running again::
-Improved cam/crank sync signal setup
-Added a fuel pressure sensor to run modelled fuel equation
-relocated MAP sensor to unused brake vacuum boost port for shorter vacuum line and larger diameter fitting
But I'm not able to get the motor started. I'm having two symptoms that I've tried to troubleshoot, weak ignition spark and low vacuum.
Symptom: Weak spark in direct spark ignition mode
When using DSI, the spark is far weaker than when telling the ECU to fire in wasted spark mode–at least according to my timing light, which flashes in wasted spark and test modes but not in DSI
Troubleshooting actions taken:
-Removed all spark plugs, cleaned blackened tips, checked gap. Increased dwell time and compared it to dwell in wasted spark; the numbers agree–around 3.2-3.7ms at healthy battery voltage and cranking RPM. The plugs do fire, just not as strong as in WS, and not enough to trigger the timing light. I also meticulously configured crank/cam trigger sync, see this trigger scope output:
Though it’s not clear in the FSM if my mechanical timing here is correct, it does seem to align with trigger scopes I have where the engine ran. Here’s the FSM’s scope example:
-Used oscilloscope to probe coil signal and 12V supply; 5-6V, ~3ms spikes in the signal coincided with gradual discharge of coil voltage from constant 13V to 11.5-12V, as expected
-Probed DC voltage between coil ground and battery ground during cranking to verify good ground, returned mV range, as expected
-Tried cranking with base timing at 370 BTDC rather than 10 BTDC in case it was firing on the exhaust stroke, though I don’t think this would explain the strange timing light behavior
Symptom: Low vacuum during cranking:
Very little manifold vacuum during cranking; 98-99 kPa absolute, down from 101 atmospheric, with no sign of dropping further over multiple crank revolutions. The engine has Kelford 207-B cams with more intake/exhaust overlap than stock, though I don’t think this much more.
Potential causes/troubleshooting actions taken:
-Confirmed MAP sensor calibration and compared it with a dial gauge; they agree
-Ensured throttle plate was closed during cranking
-Compression confirmed qualitatively on all 8 cylinders, though I suppose it’s possible they’re compressing air from the exhaust rather than intake valve if mechanical timing were out
-Manifold tested for leaks with fog machine; a very large leak–i.e. warped head mating surface from heat cycling– would have to occur for such a lack of vacuum, though none was detected
-Moved MAP sensor reference from unused, presumably restricted (small fitting orifice) SAIS VSV fitting to factory brake booster fitting (2005 model has electronic brake booster so Toyota plugged the port)
-Ensured VVT was disabled in my map and confirmed by probing OCV voltage during cranking; 0V, as expected
I feel like I’ve covered all of my bases except for mechanical timing–I now suspect at some point after multiple failed cranking attempts one or both of the cams jumped a tooth, though I’m not convinced whether this would cause enough of a difference to have almost no vacuum, and the timing belt is brand new. Please let me know if there’s anything else I’m missing. I’m curious if I can get a good read on this either by probing the VVT cam position signals and crank signal or pulling the valve covers, which would be quicker than pulling the timing covers. Here’s a diagram from the FSM that shows proper cam angle with respect to crank angle:
Other notes:
-I tried adjusting the base timing offset to 360 degrees as well to see if it was firing on the wrong stroke. The motor slowed down during cranking in conjunction with MAP spikes ~99 kPa to ~108 kPa and dips in battery voltage; I attributed this to incorrect timing, but there was no change when I adjusted the timing back, and this symptom has now persisted.
-The inside of the intake has a noticeable layer of oil from the PCV, though I suspect this was from successful starts since vacuum is so low.
-I’m fairly certain the MAP had better cranking vacuum the few times the engine did run, though I’m not sure how much better it actually was
I attached my latest map and crank log.
Maybe at this point I just need to hire a tuner to remote access my machine and pore over my ECU map? I have a thread discussing this in the Link ECU forum that I am also keeping updated: https://forums.linkecu.com/topic/27853-ecu-not-commanding-coils-to-fire/
Thanks for any ideas.
-Improved cam/crank sync signal setup
-Added a fuel pressure sensor to run modelled fuel equation
-relocated MAP sensor to unused brake vacuum boost port for shorter vacuum line and larger diameter fitting
But I'm not able to get the motor started. I'm having two symptoms that I've tried to troubleshoot, weak ignition spark and low vacuum.
Symptom: Weak spark in direct spark ignition mode
When using DSI, the spark is far weaker than when telling the ECU to fire in wasted spark mode–at least according to my timing light, which flashes in wasted spark and test modes but not in DSI
Troubleshooting actions taken:
-Removed all spark plugs, cleaned blackened tips, checked gap. Increased dwell time and compared it to dwell in wasted spark; the numbers agree–around 3.2-3.7ms at healthy battery voltage and cranking RPM. The plugs do fire, just not as strong as in WS, and not enough to trigger the timing light. I also meticulously configured crank/cam trigger sync, see this trigger scope output:
Though it’s not clear in the FSM if my mechanical timing here is correct, it does seem to align with trigger scopes I have where the engine ran. Here’s the FSM’s scope example:
-Used oscilloscope to probe coil signal and 12V supply; 5-6V, ~3ms spikes in the signal coincided with gradual discharge of coil voltage from constant 13V to 11.5-12V, as expected
-Probed DC voltage between coil ground and battery ground during cranking to verify good ground, returned mV range, as expected
-Tried cranking with base timing at 370 BTDC rather than 10 BTDC in case it was firing on the exhaust stroke, though I don’t think this would explain the strange timing light behavior
Symptom: Low vacuum during cranking:
Very little manifold vacuum during cranking; 98-99 kPa absolute, down from 101 atmospheric, with no sign of dropping further over multiple crank revolutions. The engine has Kelford 207-B cams with more intake/exhaust overlap than stock, though I don’t think this much more.
Potential causes/troubleshooting actions taken:
-Confirmed MAP sensor calibration and compared it with a dial gauge; they agree
-Ensured throttle plate was closed during cranking
-Compression confirmed qualitatively on all 8 cylinders, though I suppose it’s possible they’re compressing air from the exhaust rather than intake valve if mechanical timing were out
-Manifold tested for leaks with fog machine; a very large leak–i.e. warped head mating surface from heat cycling– would have to occur for such a lack of vacuum, though none was detected
-Moved MAP sensor reference from unused, presumably restricted (small fitting orifice) SAIS VSV fitting to factory brake booster fitting (2005 model has electronic brake booster so Toyota plugged the port)
-Ensured VVT was disabled in my map and confirmed by probing OCV voltage during cranking; 0V, as expected
I feel like I’ve covered all of my bases except for mechanical timing–I now suspect at some point after multiple failed cranking attempts one or both of the cams jumped a tooth, though I’m not convinced whether this would cause enough of a difference to have almost no vacuum, and the timing belt is brand new. Please let me know if there’s anything else I’m missing. I’m curious if I can get a good read on this either by probing the VVT cam position signals and crank signal or pulling the valve covers, which would be quicker than pulling the timing covers. Here’s a diagram from the FSM that shows proper cam angle with respect to crank angle:
Other notes:
-I tried adjusting the base timing offset to 360 degrees as well to see if it was firing on the wrong stroke. The motor slowed down during cranking in conjunction with MAP spikes ~99 kPa to ~108 kPa and dips in battery voltage; I attributed this to incorrect timing, but there was no change when I adjusted the timing back, and this symptom has now persisted.
-The inside of the intake has a noticeable layer of oil from the PCV, though I suspect this was from successful starts since vacuum is so low.
-I’m fairly certain the MAP had better cranking vacuum the few times the engine did run, though I’m not sure how much better it actually was
I attached my latest map and crank log.
Maybe at this point I just need to hire a tuner to remote access my machine and pore over my ECU map? I have a thread discussing this in the Link ECU forum that I am also keeping updated: https://forums.linkecu.com/topic/27853-ecu-not-commanding-coils-to-fire/
Thanks for any ideas.
