Lean Spot At ~2400 RPM...What the?
06-21-2010, 12:49 PM
#61
mx594,
I just wanted you to know that I came across your thread and directed it to one of our techs. We read the thread through, and it doesn't appear to be an injector related issue. Typically, when an injector fails, it will show itself at idle and throughout the rev range.
But, since you are planning to swap the injectors out, if it does solve your lean issue we'd like to check them out to see what is up.
I just wanted you to know that I came across your thread and directed it to one of our techs. We read the thread through, and it doesn't appear to be an injector related issue. Typically, when an injector fails, it will show itself at idle and throughout the rev range.
But, since you are planning to swap the injectors out, if it does solve your lean issue we'd like to check them out to see what is up.
I take it you have never seen anything like this before? I'm completely out of ideas. I'm just going to start replacing parts until I figure it out.
06-21-2010, 01:03 PM
#62
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We haven't come across this issue before. ...and you've certainly exhausted many avenues to try explaining this phenomenon. From what we've read in this thread, we don't think this is injector related. It doesn't have typical symptoms of a faulty injector...but we'll see in a bit when you get the new ones swapped in.
It sucks when you have a unique problem and have to grab at straws to find a solution...but look at it this way, you'll be helping out those that follow behind you.
It sucks when you have a unique problem and have to grab at straws to find a solution...but look at it this way, you'll be helping out those that follow behind you.
06-22-2010, 08:29 AM
#66
Does the VDC work via fuel cut? I thought it just hit the brakes? How could it cut fuel if the Haltech is in full control of the fuel? I do have a 3.90 final drive...
I wouldn't call it a very brief instant though. I can hold the engine at 2400 rpm and it will stay lean all day long.
Thanks Chris, I figured those numbers were ok.
I wouldn't call it a very brief instant though. I can hold the engine at 2400 rpm and it will stay lean all day long.
Thanks Chris, I figured those numbers were ok.
06-22-2010, 12:50 PM
#67
I also ordered a new crank angle sensor. I have an early 2003 G, and I know there was a recall for 03 (at least there was on the Z). What are all these old posts I am reading about shielding the CAS wire? Is this still common or did it turn out to be no big deal?
06-22-2010, 01:20 PM
#68
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That was way back in the Emanage Blue days when people were losing motors left and right. They were scrambling to find the cause, but it turns out the crank sensor wiring is fine. APS even included a new sensor cable with their Unichip piggyback.
06-23-2010, 10:12 PM
#70
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hi there just read the whole thread and it sounds like an airflow issue to me. I would pull that lower plenum off and take a very close look. Also would put new gaskets in everything and torque it all back up. I think at this point it is a resonance at that certain rpm which is letting in air between that lower plenum.
06-24-2010, 03:08 AM
#71
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Hi, sorry for my english 
(I'm italian) .... I have the same problem with my 350z ...( greddy tt + haltech)...I'm trying the solution,too but at the same time,I've enabled the o2control,but disconnect the wideband....
in this way the afr oscillates at 11.0 10.0 and the lean spot disappears
(I'm italian) .... I have the same problem with my 350z ...( greddy tt + haltech)...I'm trying the solution,too but at the same time,I've enabled the o2control,but disconnect the wideband....in this way the afr oscillates at 11.0 10.0 and the lean spot disappears
06-25-2010, 07:59 AM
#72
06-28-2010, 04:36 AM
#73
More updates:
I got my new DW 600cc injectors and put them in. When I compared the new ones to the old ones I was surprised to see that the new ones have a large O-ring at the base of the injector, whereas the old ones had some other kind of seal a bit further up the body. I got excited because I thought maybe the old injectors weren’t sealing to the head and were causing a vacuum leak. After installing the injectors I went for a test drive and the lean spot is still there, just the same as before. So it’s not the injectors.
I also installed a new crank angle sensor, but that didn’t help either.
I’m not really sure what to do next. I might measure the injector voltage again because I realize now that I should have measured the voltage across the two injector wires instead of using the battery or chassis as a ground. Other than that, maybe I should try a new lower collector gasket?
I got my new DW 600cc injectors and put them in. When I compared the new ones to the old ones I was surprised to see that the new ones have a large O-ring at the base of the injector, whereas the old ones had some other kind of seal a bit further up the body. I got excited because I thought maybe the old injectors weren’t sealing to the head and were causing a vacuum leak. After installing the injectors I went for a test drive and the lean spot is still there, just the same as before. So it’s not the injectors.
I also installed a new crank angle sensor, but that didn’t help either.
I’m not really sure what to do next. I might measure the injector voltage again because I realize now that I should have measured the voltage across the two injector wires instead of using the battery or chassis as a ground. Other than that, maybe I should try a new lower collector gasket?
06-28-2010, 05:09 AM
#74
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i would put new lower intake gaskets, new lower plenum gasket, and throttle body gaskets.
those are cheap and when having a lean spot should be the first thing replaced to make sure there isn't a leak.
those are cheap and when having a lean spot should be the first thing replaced to make sure there isn't a leak.
06-28-2010, 09:06 AM
#75
Throttle body gasket really shouldn't matter, since I am using MAP as a load reference anyway. It could be the lower plenum gasket, but I would be surprised since I am having the lean condition in both banks so it would have to have the same leak in two different ports.
06-28-2010, 07:26 PM
#76
More testing tonight:
Disconnected EVAP solenoid, plugged hole in manifold - No Change
Disconnected PCV and plugged hole in manifold - No Change
Cleaned all grounding points on engine block and grounding rings - No Change
Disconnected all stock O2 sensors (just for the hell of it) - No Change
Disconnected EVAP solenoid, plugged hole in manifold - No Change
Disconnected PCV and plugged hole in manifold - No Change
Cleaned all grounding points on engine block and grounding rings - No Change
Disconnected all stock O2 sensors (just for the hell of it) - No Change
06-29-2010, 09:25 AM
#78
Side note: in the Haltech, when using copy-through timing, it will still display data in the 3D graph except it will be white in that area. Do these "default" vales represent the Nissan low det timing map? Because according to the values that are displayed on the graph, the timing goes from 15 to 35 degrees between 2000 and 2500 rpm (if you click on a cell that has a "c" in it, then hit up and then down, it will now be a number). I saw this and thought that I had found the problem, but even when I replaced all the copy through cells with actual numbers and made the timing advance sooner and more gradually it didn't change the lean spot at all. Not to mention that it doesn't explain the other two lean spots through which the timing is constant.
About adding more fuel - I have already tried but it seems to have little effect. You can see the base fuel trace in the datalog - it jumps up ~20% in that area of the VE table and it's still lean. The problem is that the lean spot is such a narrow band of RPM that even 250 rpm increments is insufficient and I end up being rich just before and just after - I would almost need cells every 50 or 100 rpm, and even then I would have a HUGE awkward spike in the VE table in order to cancel out the lean spot. There is no way that a spike like that is "normal" in a VE table. How can the VE go from 95% at 2300 rpm, then 115%+ at 2400 rpm, then back down to 95% at 2500 rpm? It doesn't make sense.
06-29-2010, 10:50 AM
#79
it doesnt make sense, but if you can manipulate it so you dont get the lean hesitation, thats probably better than nothing. That such a low load area, it really doesnt matter too much if the map has a few whack cells.
at this point, it seems you have exhausted all other options.
at this point, it seems you have exhausted all other options.
06-29-2010, 01:00 PM
#80
it doesnt make sense, but if you can manipulate it so you dont get the lean hesitation, thats probably better than nothing. That such a low load area, it really doesnt matter too much if the map has a few whack cells.
at this point, it seems you have exhausted all other options.
at this point, it seems you have exhausted all other options.