Hello all,
So I went searching on the forum and couldn't find anything specific to my issue, so I figured I would start a thread and see if anyone has any input/feedback.
I'll make a long story short: My dad and I rebuilt a motor that had a spun bearing/scored journal on crank. We have gotten everything back to ship shape with the exception of one issue and that is when the engine will kick into limp mode at idle after it has warmed up. It usually sits pretty at 750 rpm (with some occasional idle hunt), then it will dip to about 600, choke a little, then limp and throw engine codes. When I actually drive the car at 800-1000 rpm or more, there are no issues at all. DIS throws us the codes:
271D - VANOS control, exhaust bank 2 - actual value too low
271B - VANOS control, exhaust bank 1 - actual value too low (this one doesn't come in that often, but it still does periodically).
We also get the CEL for increased emissions.
Following a troubleshooting guide by Troy, at one point we disconnected the exhaust bank 2 camshaft position sensor. This was after six-nine bleeds and three oil changes (yes, we did get a good bit of crap out that had been left over in the system from the spun bearing as well as from the rebuild, but subsequent changes yielded nothing in the oil). When we disconnected the sensor, the only error we got was:
2719 - Camshaft sensor - exhaust bank 2 - No signals (obviously expected with a disconnected sensor).
However, when we cleared codes, drove the car, stopped it, and restarted, we would still get increased emissions. The car would still drive no problem though. No limp mode, could push it into the higher RPM range with no concern, and it drove like a champ.
We have already swapped out solenoids SEVERAL times with both Sophie Solenoids AND OEM solenoids. Even went as far as to swap out adjusters because we figured some copper flaking may have scored the inside of the adjuster piston walls and was allowing oil through when it shouldn't have. No change no matter what.
We're about to replace all the spark plugs (because it definitely needs it anyway) as well as some ignition coils that were damaged from the previous owner. While I don't believe these would be the cause, we still want to get it done just in case there is a chance they are the cause. Since we're already that far into the engine bay, we're going to look into re-timing the exhaust camshafts on both sides.
My question, however, is this: Do you think it could be camshaft exhaust timing? This is mostly in the exhaust bank 2 as well, with bank 1 rarely coming in. The engine runs great, however at idle RPM it sounds like it could be having lack of complete combustion in one cylinder. It's REALLY hard to tell though. Is it possible that a bad plug could be causing incomplete combustion and causing all this? Or does it sound like the timing could be off by a couple degrees on both exhaust banks? If timing is off, can we adjust it using the VANOS gear's 30-ish or so degree variance that it has available? We have two and a half months before our emissions test and we know that it will fail with that emissions warning/CEL light coming up, so we are looking for any input from the community that we can get!
Thanks in advance, and thanks again to Troy for the suggestions/assistance already provided! It has definitely helped with a huge chunk of our issues, but this seems like it is playing outside the realm of the VANOS.
Additionally: using a standard OBDII reader, we got readings that both exhaust banks were over-retarded timing. This was another item that we considered when we thought it might be a timing issue and not a VANOS issue anymore.
So I went searching on the forum and couldn't find anything specific to my issue, so I figured I would start a thread and see if anyone has any input/feedback.
I'll make a long story short: My dad and I rebuilt a motor that had a spun bearing/scored journal on crank. We have gotten everything back to ship shape with the exception of one issue and that is when the engine will kick into limp mode at idle after it has warmed up. It usually sits pretty at 750 rpm (with some occasional idle hunt), then it will dip to about 600, choke a little, then limp and throw engine codes. When I actually drive the car at 800-1000 rpm or more, there are no issues at all. DIS throws us the codes:
271D - VANOS control, exhaust bank 2 - actual value too low
271B - VANOS control, exhaust bank 1 - actual value too low (this one doesn't come in that often, but it still does periodically).
We also get the CEL for increased emissions.
Following a troubleshooting guide by Troy, at one point we disconnected the exhaust bank 2 camshaft position sensor. This was after six-nine bleeds and three oil changes (yes, we did get a good bit of crap out that had been left over in the system from the spun bearing as well as from the rebuild, but subsequent changes yielded nothing in the oil). When we disconnected the sensor, the only error we got was:
2719 - Camshaft sensor - exhaust bank 2 - No signals (obviously expected with a disconnected sensor).
However, when we cleared codes, drove the car, stopped it, and restarted, we would still get increased emissions. The car would still drive no problem though. No limp mode, could push it into the higher RPM range with no concern, and it drove like a champ.
We have already swapped out solenoids SEVERAL times with both Sophie Solenoids AND OEM solenoids. Even went as far as to swap out adjusters because we figured some copper flaking may have scored the inside of the adjuster piston walls and was allowing oil through when it shouldn't have. No change no matter what.
We're about to replace all the spark plugs (because it definitely needs it anyway) as well as some ignition coils that were damaged from the previous owner. While I don't believe these would be the cause, we still want to get it done just in case there is a chance they are the cause. Since we're already that far into the engine bay, we're going to look into re-timing the exhaust camshafts on both sides.
My question, however, is this: Do you think it could be camshaft exhaust timing? This is mostly in the exhaust bank 2 as well, with bank 1 rarely coming in. The engine runs great, however at idle RPM it sounds like it could be having lack of complete combustion in one cylinder. It's REALLY hard to tell though. Is it possible that a bad plug could be causing incomplete combustion and causing all this? Or does it sound like the timing could be off by a couple degrees on both exhaust banks? If timing is off, can we adjust it using the VANOS gear's 30-ish or so degree variance that it has available? We have two and a half months before our emissions test and we know that it will fail with that emissions warning/CEL light coming up, so we are looking for any input from the community that we can get!
Thanks in advance, and thanks again to Troy for the suggestions/assistance already provided! It has definitely helped with a huge chunk of our issues, but this seems like it is playing outside the realm of the VANOS.
Additionally: using a standard OBDII reader, we got readings that both exhaust banks were over-retarded timing. This was another item that we considered when we thought it might be a timing issue and not a VANOS issue anymore.