Hunting idle, Pretty sure its the head temp sendor Options

[VaccaRabite]

Caveat: I'm using custom fuel injection (Microsquirt)

So this weekend my idle started hunting. I was pretty sure I had sprung a leak somewhere that was opening and closing a miniscule amount while the car vibrated at idle.

My idle would go from 1000 RPM (where I have it set) to about 1900 RPM for a few seconds and then settle back down again. Whatever, drove the car for 300 miles anyway. Only time when it became an issue was at stop lights and trying to get through the free bridge traffic jam between NJ and PA - and then it was just an added annoyance.

When I got home I did not find anything obviously wrong. I plugged my laptop in to see if my IAC had gone out of compliance. It was fine but I noted my "coolant" temps were all over the place.

Coolant sensor for me is the stock location head temp sensor, plugged into my ECU.

Are these things known for failing? Mine was giving readings with a 100+ degree swings every few seconds (I'm guessing cutting out), and my idle air valve was opening and closing trying to keep up, hence the idle hunting.

Zach

[JamesM]

I should already know this, but I forget, are you just running a stock d-jet single wire head temp sensor for coolant temp on your MS setup?

100 degree sensor reading swings are for sure a problem, may not be your only problem though and while it may be a bad sensor, if you are using the single wire d-jet sensor it could also be a grounding issue or something causing a lot of noise on the ground path. After setting up megasquirt just about every possible different way on 914s I find to have the most reliable/cleanest signal you want to be sure all sensors are grounded back though the MS sensor ground path and not directly to engine/battery ground. I have switched from using stock CHTs to Marios temp sensors as they are 2 wire, use a standard GM curve, and are WAY easier to install.

https://thedubshop.com/fuel-injection/sensors/


Chasing idle hunting with Megasquirt isnt always as straight forward as it is with carbs or D-jet because as your RPM and manifold vacuum change with the hunting the MS starts pulling values from various VE bins, and if your temp sensor has huge swings in its reading then it could be kicking it back into warmup enrichment mode as well.

Shoot me some logs via email and ill take a look.

Caveat: I'm using custom fuel injection (Microsquirt)

So this weekend my idle started hunting. I was pretty sure I had sprung a leak somewhere that was opening and closing a miniscule amount while the car vibrated at idle.

My idle would go from 1000 RPM (where I have it set) to about 1900 RPM for a few seconds and then settle back down again. Whatever, drove the car for 300 miles anyway. Only time when it became an issue was at stop lights and trying to get through the free bridge traffic jam between NJ and PA - and then it was just an added annoyance.

When I got home I did not find anything obviously wrong. I plugged my laptop in to see if my IAC had gone out of compliance. It was fine but I noted my "coolant" temps were all over the place.

Coolant sensor for me is the stock location head temp sensor, plugged into my ECU.

Are these things known for failing? Mine was giving readings with a 100+ degree swings every few seconds (I'm guessing cutting out), and my idle air valve was opening and closing trying to keep up, hence the idle hunting.

Zach