So ever since I put this engine (stock LBZ long block, LLY injectors and fueling/ECM) in my truck ~6,000 miles ago, its had a random odd misfire above 3,000rpm or so.
It only happens when its warmed up to temp. When its cold, it will rev up to the rev limiter (3,900) and smoothly hold that rpm (no misfire) with my foot on the floor. As the truck warms up, the "rev limit" (where it starts to misfire/cough and wont rev above) progressively gets lower until when its fully warmed up, it wont rev above 3,000rpm. Like when the truck is "half" warmed up, it will rev up to ~3500ish and then start to sputter/misfire.
Yes, its been doing this for 6,000 miles. No, I havent really cared to spend time diagnosing it until now because ive been too busy and I stopped beating on the truck/driving it hard two engines ago. Obviously I cant go WOT when its warmed up because the shift point is above the rpm that it starts missing/sputtering at. Ive just gotten used to lifting just enough to get it to shift at 3,000rpm right before it starts missing.
NOTHING strange/abnormal shows up in the logs, ive already logged the thing 100 times. Rail pressure is fine, main rate holds steady, pulse width stays steady, etc etc etc...
Reflashed to stock tune, still does it. Its not the tune because I ran the same exact tune on the last engine that was in it (stock LLY long block) and it never had any issues like this.
The only thing I can think of is the ECM is losing crank signal/resolution at higher RPM's for some reason. I have not tried a new CKP sensor, and I have not tried a new CPS sensor.
The only 'wild card' with this engine is its running an LBZ reluctor wheel (yes, I cut a tooth off, otherwise it wouldnt run at all. Pat did this on one engine and didnt notice any abnormal effects.
AND it has some bizarre front cover. I dont know what it is, maybe an early prototype LB7 front cover??? Schulte and I got it in the mountain of parts that we bought from Curtis (DPR) when he closed shop in wisconsin. At first glance it looks normal, but the mounting place for the CKP sensor is different. On normal production dmax's, there is a big hole in the front cover, then there is a spacer/bushing/mount thing that bolts to the front cover, and then the CKP sensor mounts to that spacer.
On this oddball front cover, there is no spacer, the mounting flange is spaced out a little differently, and the CKP sensor bolts directly to the front cover.
I suppose I could answer my own question and swap front covers, but Id rather get some input (Fingers???) on if anyone has seen a dmax do anything this, before I spend a whole afternoon swapping front covers.
The thing that baffles me is it only does it when the engine is warmed up.
I know im going to get 100 responses that say "must be in the tune, check your tune", so Ill say it again, its NOT in the tune.
In the video im slowly increasing revs to 2900-3000 where it just barely starts to miss, then as I press my foot down more and more (as if I wanted to increase RPM's further), the misfire/sputtering gets more violent/severe and it clearly wont go above ~3,000rpm.
[YOUTUBE]0Pb1dVzO4hc[/YOUTUBE]
thanks
Ben
It only happens when its warmed up to temp. When its cold, it will rev up to the rev limiter (3,900) and smoothly hold that rpm (no misfire) with my foot on the floor. As the truck warms up, the "rev limit" (where it starts to misfire/cough and wont rev above) progressively gets lower until when its fully warmed up, it wont rev above 3,000rpm. Like when the truck is "half" warmed up, it will rev up to ~3500ish and then start to sputter/misfire.
Yes, its been doing this for 6,000 miles. No, I havent really cared to spend time diagnosing it until now because ive been too busy and I stopped beating on the truck/driving it hard two engines ago. Obviously I cant go WOT when its warmed up because the shift point is above the rpm that it starts missing/sputtering at. Ive just gotten used to lifting just enough to get it to shift at 3,000rpm right before it starts missing.
NOTHING strange/abnormal shows up in the logs, ive already logged the thing 100 times. Rail pressure is fine, main rate holds steady, pulse width stays steady, etc etc etc...
Reflashed to stock tune, still does it. Its not the tune because I ran the same exact tune on the last engine that was in it (stock LLY long block) and it never had any issues like this.
The only thing I can think of is the ECM is losing crank signal/resolution at higher RPM's for some reason. I have not tried a new CKP sensor, and I have not tried a new CPS sensor.
The only 'wild card' with this engine is its running an LBZ reluctor wheel (yes, I cut a tooth off, otherwise it wouldnt run at all. Pat did this on one engine and didnt notice any abnormal effects.
AND it has some bizarre front cover. I dont know what it is, maybe an early prototype LB7 front cover??? Schulte and I got it in the mountain of parts that we bought from Curtis (DPR) when he closed shop in wisconsin. At first glance it looks normal, but the mounting place for the CKP sensor is different. On normal production dmax's, there is a big hole in the front cover, then there is a spacer/bushing/mount thing that bolts to the front cover, and then the CKP sensor mounts to that spacer.
On this oddball front cover, there is no spacer, the mounting flange is spaced out a little differently, and the CKP sensor bolts directly to the front cover.
I suppose I could answer my own question and swap front covers, but Id rather get some input (Fingers???) on if anyone has seen a dmax do anything this, before I spend a whole afternoon swapping front covers.
The thing that baffles me is it only does it when the engine is warmed up.
I know im going to get 100 responses that say "must be in the tune, check your tune", so Ill say it again, its NOT in the tune.
In the video im slowly increasing revs to 2900-3000 where it just barely starts to miss, then as I press my foot down more and more (as if I wanted to increase RPM's further), the misfire/sputtering gets more violent/severe and it clearly wont go above ~3,000rpm.
[YOUTUBE]0Pb1dVzO4hc[/YOUTUBE]
thanks
Ben
