hey guys, I remember a while ago someone helped me with a problem and said it is air intake temp sensor heatsoak. I searched a few pages but couldnt find it. What is the solution to intake temp sensoor heatsoak? Is it the sensor before the throttle body?

Here is my issue. I have a 13bt s4 with megasquirt ecu, greddy fmic setup, etc etc.

When my engine is cold and I do a cold start, everything is fine, my wideband is pretty much awake and get decent readings on my gauge.

If I let my car sit, after being driven full operating temp, when I go start it, it runs really rough, to a point where I have to give it a little throttle to stay running. My sensor reads really lean A/F ratios like 15:1 or leaner. After Idrove for 3 minutes, my car drives fine and a/f ratios go back to normal.

 

your car may still be running off of the coolant temp sensor and be stuck in closed loop insted of open loop when it should be running off of the o2 sensors. if its a full operating temp and the car is in open loop the coolant temp sensor will cause the car to lean out very bad and it won't get a enough fuel. i would give it a check.

 

I was thinking about that, but when I start my car when its cold, I get a correct a/f reading, shouldn't it be in closed loop then?

Once everything is warmed up and sits for about15-20 minutes, my engine runs and dies out. If I keep my foot ever so slightly on the gas pedal, it barely idles. if I give it too much throttle, it will either die out, or stumble and rpms raise.

When everything is warm, and it doesnt sit for very long, 5 min or less, i can start it and have very minimal if none stumbling. That is why I think it could have to do with heat soak.

MY idle control valve is starting to go out too, ive been too lazy to change it. But when my idle control valve was working good, I sitll had this warm start problem. Thanks

 

GM sensor threaded right into the BAC hole in the intake boot.

Driving down the highway I was showing 40deg intake temps with coolant temps in the 180-185 range. Given that the air filter is an open element unit drawing from the engine bay and it was a 35 degree day I think that's pretty good

Under racing conditions I was getting coolant temps into the scary hot range but air temps never went over 90F. No heatsoak here!

 

No. I forget if the temp is hardwired in but you don't want it to run closed loop when cold. With a rotary you don't want it running closed loop at idle or real low RPM, either, even when fully warmed up.

 

Does the Wideband need heat to work? I know for normal cars with a o2 sensor, it has to run open loop because it's waiting for the o2 to warm up so it can get some feeedback?

I dont think so, I have a few buddies running ms, and its fine. I'll post in the MS section

 

I used a GM temp sensor in the intake tube but I mounted it further away from the engine. I put it right behind the air filter within my cold air box so engine temps wouldn't influence the readings.

 

I was wondering though, I always thought the ecu regarded more on the o2 sensor and the map sensor mainly. Other lil sensors were mainly for engine warm up. How does teh engien regard the intake sensor?

 

Yes. At least, the ones I've dealt with have.

Most cars with heated O2s (which is all of them nowadays) start reading before you're a block away from home. Running open loop when cold is more so the engine stays happy.

On a cold start I watch my gamma correction run in the 150-160% range, and it's not even rich enough to misfire yet.





I dont think so, I have a few buddies running ms, and its fine. I'll post in the MS section[/QUOTE]

 

The intake air temperature sensor is used in the fuel equations based on the formula PV=nRT (ideal gas law). The problem is when it heat-soaks, it's not really measuring actual air temperature anymore, and so the fuel mixture gets leaned out a bit too much... the fuel formula also doesn't take account for the fact that a hotter manifold means that the fuel will vaporize better...

Because of these, there's a MAT air density correction curve in the MS that can be used to combat heat-soak issues.

I've used it on several installs to get rid of warm-start issues.

Ken

 

... man i've been so tied up recently .. matt are you on that same msq from thurs nite months back? ... but anyhow I'd relocate sensor or try Ken's suggestion ...

 

cool, thanks guys

 

I was looking for the mat air density correction but couldn't find it. Can you lead me to it, I'm having warm start issues also.

 

I'll look around and see if I can find it... it might not be in older firmwares either...

The manual for that feature is here:

http://www.msextra.com/manuals/MS_Ex...l.htm#cooldens

Basically you can set it to be based on CLT or MAT.

Ken