Rep Power: 0

I wanted to know if anyone has any input for me. I have a 01 Civic LX with a 05 EX D17a2 in it. I have the vafcII installed also. I have recently been having some idle issues when its hot outside and only if im over 25% throttle. What happens is when I come to a stop my idle drops to about 520rpms the creeps back up to around 630 while in gear. If I put it into second the rpms jump up about 30 more rpms.
I checked my car and of course no trouble codes or anything. I did notice that my IAT and my ECT were both reading -40 degrees. If it was one of them I would just replace the sensor but now with both of them reading the same temp and not changing at all makes me think there is another issue.
Has anyone heard of this or come across this? I think its causing my car to run rich and now i have an intermittent misfire. Let me know if anyone has any ideas!

Thanks!!!

 
Rep Power: 217

The ECT shouldn't be reading that low of a temp. I worked on a truck which had the same issue. In return, it ended up throwing the MIL on for bad o2 sensors. We replaced the ECT and the truck ran like a champ. You will want to test the sensors to be sure. If they're reading that low all the time, you're right. It's gonna run hella rich, which can lead to all types of issues. Hard starting after long drives(turn the car off for a few minutes, restart and it stalls), fouled o2 sensors, or worse, a toasted cat.

 
Rep Power: 0

I just think its odd that my IAT and ECT are both at -40 and dont change at all. Im going to try to change the IAT and see if it changes. If it doesnt im lost lol.

 
Rep Power: 518

Are you reading PCM data on a real scantool?
You will need a real scanner to do some of these steps.


The PCM gives that reading (-40) in the datalist when the sensors are open circuit (as in unplugged). It is a default value.

You can't trust that yet. You already know that, judging by this post.
If the PCM really saw open circuits, it would have set codes for both.

Jumper (bent paper clip?) across both of the terminals in each connector (the ECT and the IAT) and read the temp value in the datalist.
Each should read higher than 240 when jumpered (I think it is around 288 with a jumper, but I don't remember for sure).

Still reading -40?

Next I would remove the aftermarket controller, return the original PCM and wiring to the way the factory designed it, then recheck your datalist (using a real scanner). Maybe the aftermarket controller is screwing with stuff. This step would tell you that.

If there is still no change, I bet you have a software glitch in the scanner.

The PCM should have set codes for both sensors being open circuit.
If there are no codes for the sensors, I would suspect a scanner problem and check on a different brand of scanner.

Or check the scanner you have on an identical car.




IF you were dealing with ONLY the stock PCM and it had set codes for both ECT and IAT, I would tell you to get a voltmeter and a wiring diagram.
Unplug both sensors.
Test each connector for 5v and ground. Ground circuit would probably be missing from both sensors. Then follow the wiring diagram to find the common denominator.

 
Rep Power: 0

Yes I am using a real scanner. Im using the snap on Modis. The sensors are plugged in and as soon as I did unplug them the engine light came on and set a code for it. Im going to put a jumper in and try that to see if it changes. I know its not the VAFCII. Ill let you know how it goes. Thanks alot for your help!!

 
Rep Power: 518

So it set codes when unplugged. You have false data displayed.

Has this scanner worked on YOUR car in the past?
Has this scanner been updated SINCE it last worked on your car?

If your add-on controller can tap into and display parameters from the datastream, it can mess with data. Eliminate that possibility by taking it out of the picture. You can't know it isn't the problem until you do this. (I also don't know what all it is capable of.)

I bet it will be a scanner problem.

 
Rep Power: 0

You were dead on. It was a scanner issue. My car is just fine. I know im a bit delayed but thank you for your input. Nothing better than this site!!!