issues with false rpm readings lh2.2 distributor

[urielsa]

1981 244+t microsquirt lh2.2 single coil. randomly jumps to 2800 rpm randomly. only happens over 3k rpm. wondering what could be causing it. happened at the 103s mark.

 

[Meatball]

Is your trigger wire shielded? Is the shielding grounded at the ECM? Are you using a pull down resistor? What does the waveform for the trigger look like (if you have a scope or if there is a scope function in the software).

 

[bobxyz]

Can you post a log of the failure, and your tune? You need to .zip them first, and the resulting .zip file size must be under 1MByte to attach it directly here.

 

[urielsa]

1

 

[urielsa]

happens around 103s

 

[urielsa]

Is your trigger wire shielded? Is the shielding grounded at the ECM? Are you using a pull down resistor? What does the waveform for the trigger look like (if you have a scope or if there is a scope function in the software).

I'm not sure whether it is or is not shielded. I bought one of turbo dave's harnesses he used to sell. I'm leaning twoards it not being shielded however I didn't have issues with this initially its a new development.

 

[bobxyz]

I don't know what's going on. Your AFR seems broken / stuck at 7.4. Your battery is low, dropping to 10.6volts when RPM stumbles. TPS is noisy and calibration is off: -29% to +81%. The 1260cc injectors aren't helping anything.



I'm wondering if you have a misfire, instead of a LH2.2 tach problem. Can you do a Tooth Logger log and catch a stumble? Or just a log of free rev'ing the engine if you can't catch a stumble.

 

[urielsa]

I don't know what's going on. Your AFR seems broken / stuck at 7.4. Your battery is low, dropping to 10.6volts when RPM stumbles. TPS is noisy and calibration is off: -29% to +81%. The 1260cc injectors aren't helping anything.

View attachment 37158

I'm wondering if you have a misfire, instead of a LH2.2 tach problem. Can you do a Tooth Logger log and catch a stumble? Or just a log of free rev'ing the engine if you can't catch a stumble.

that is an older log I've got time to work on it this weekend. I'm pretty sure the harness has tps wired backwards as for the noise on it. fixed the voltage issue 2 weeks ago with a new main power and ground. ill take some new logs with a tooth logger. also wideband Is not hooked up for that run. will have more logs this week

 

[urielsa]

problem fixed! The harness had the the wires switched for the tps sensor. Depinned and and corrected the mistake. Installed a new sensor. Problem fixed. Didn’t think about the fact that ignition load is based on TPS.