wheres_waldy Posted February 22 Report Share Posted February 22 Hello everyone, first time posting but I have been looking through for a while, i just got my car tuned and everything was fine but towards the end the car started to randomly drop the rpm reading to 0, ive noticed it does it when under a load but not when free reving, also once the car is warmed up and running for a while ill attach a log here, if you need the tune i can attach it as well. info on the car what is done to it relating to the trigger, it has a stock Nissan CAS with an AEM trigger wheel 24-1 and a link G4X plug in ecu trigger offset is set to 352 in case that matters, prior the car was running nistune with stock CAS and stock trigger wheel and did not have this issue, ive tried swapping CAS and same thing, i dont have a log of the trigger scope but my tuner was looking at it when he was tunin and it completly looses signal for a second and comes back he thought it might possibly be a strecthing belt but i dont think i agree, can it possibly be heat soaking and causing it to cut out? or do i have a setting messed up. If i need to switch to a diffrent trigger kit i will (PRP or NZwiring) but want to make sure im dotting all my I's and crossing all my T's, thank you in advance. trigger_loss 2024-02-22 2;48;38 pm.llgx Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 23 Report Share Posted February 23 It would be a good idea to do a trigger scope, even though it is unlikely to capture the event occurring it will still allow us to rule out some possibilities such as clashing edges and ground offsets etc. Do one at about 3000RPM would be my suggestion. The RPM dropping to zero doesnt mean the trigger signal has been lost, it just means the ecu has received a pattern of "teeth" that doesnt match the expected pattern, when this occurs it sets RPM to zero and does a full re-sync. Quote Link to comment Share on other sites More sharing options...
wheres_waldy Posted February 23 Author Report Share Posted February 23 I will try and record it again today but may not get to it until Sunday, I thought it was loosing rpm signal because gauge would also hit zero, but the way you describe it makes sense it feels like it stops and than recalculates, I can prob duplicate it on the scope if I can record the scope while driving because once it’s warmed up it does it almost every time when I go full throttle and it reaches around 3k under a load, thank you again Quote Link to comment Share on other sites More sharing options...
wheres_waldy Posted February 24 Author Report Share Posted February 24 im not sure if im capturing correctly i was able to see it on the pc while i was connected to ecu, but when i try to load it up to see it just looks like its flashing where you see the regular logs, ill attach and see if this is what you needed, i did a bunch of captures but dont think i was able to capture it happening, i thought the capture on the scope worked the same way as the log as in hit record and go drive, thank you in advance for the help. Trigger Scope6 - 2024-02-23 7;03;26 pm.llgx TriggerScopeLog.llg5 PC Datalog - 2024-02-23 6;59;52 pm.llgx Trigger Scope -3 2024-02-23 6;58;41 pm.llgx Trigger 4Scope - 2024-02-23 7;00;05 pm.llgx Quote Link to comment Share on other sites More sharing options...
wheres_waldy Posted February 25 Author Report Share Posted February 25 were the scopes helpful by any chance? i may end up grabbing the PRP street trigger kit and hopefully that solves the issue, im sure it doesnt hurt to upgrade the stock CAS so i can add a crank trigger down the road. Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 25 Report Share Posted February 25 The most likely cause I see in those scopes is there are some rather large voltage spikes present in the trigger 1 waveform. Although none are big enough in these scopes to be interpreted as an edge and cause a problem, they are pretty significant and there are a couple that would probably cause an issue if there occurred in the right place. My usual suspicion when I see something like this is there is a bad ground which is making it easier for the spark current to return through the ecu wiring rather than chassis wiring, but oddly in this case there arent many spikes on trigger 2, so Im not convinced that is the problem in this case. Possibly a bad connection somewhere along the trigger 1 path. Changing the trigger system to something that uses the same ground and signal wiring is unlikely to fix the actual cause, but often connectors and wiring etc needs to be modified as part of the upgrade so that may solve it at the same time. Quote Link to comment Share on other sites More sharing options...
wheres_waldy Posted February 26 Author Report Share Posted February 26 Hmm thank you for the help, the only thing i can think of is looking at the wiring diagram the AFM used to be grounded straight to the chassis but when i upgraded the ecu and went with the map sensor the ground for the AFM is no longer grounded, i can try hooking that up again see if it helps, worse comes to worse can i just run wiring straight from the ecu and battery voltage/ground to the other wires? am i looking for smooth square waves on the scope that way i can test again and come back with findings. Quote Link to comment Share on other sites More sharing options...
wheres_waldy Posted February 29 Author Report Share Posted February 29 So back with a quick update ive ran new power and ground wires still had the same result, i than installed the prp kit, entered new offset so the car is running again and timing is spot on, but now when i check there seems to be way more spikes on the scope attaching down below. I did take it for a ride and everything was good i thought that was it but after the car warmed up rpm signal started to drop again a bit more than before . Trigger Scope - 2024-02-29 3;56;44 pm.llgx Quote Link to comment Share on other sites More sharing options...
wheres_waldy Posted March 1 Author Report Share Posted March 1 sorry for bombarding but i just checked out the scopes and noticed the trigger looks diffrent with the prp kit i just added a shim to the single tooth sensor and it seems to have have gotten closer to how the old one looked, in theory i would assume the AEM trigger wheel and the prp kit both being 24 tooth would look the same or very close, this is the scope with a spacer on the home sensor. Trigger Scope -1spaceron1 2024-02-29 6;59;03 pm.llgx Quote Link to comment Share on other sites More sharing options...
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