Anyone know how to test the IAT sensor or Coolant Temp. sensor??

[DSMcrazy3]

Alright i've been having a misfire at idle, and i've read that it can be the IAT sensor or CTS. I was just wondering if anyone here could inform me on how I would go about testing these to see if they could be the culprit??

Thanks for any help

 

[huafist]

The IAT is in your MAS. If it goes bad, you'll get a CEL.

The coolant temperature sensor is a thermistor - resistance decreases as temp. increases. I don't know if either one of them would cause a misfire - I suppose it's possible.
Try this website for tests: http://www.geocities.com/MotorCity/Downs/7678/dsmtests.html

Good luck finding the problem.

 

[DSMcrazy3]

I have non turbo motor(420A) not 4G63..I believe my IAT sensor is screwed in the back of the intake plennum. I've read other threads that if it isn't plugs/wires then to check those. I don't see how the CTS could, but I could see IAT sensor being a culprit.

Josh

 

[huafist]

I have non turbo motor(420A) not 4G63..I believe my IAT sensor is screwed in the back of the intake plennum. I've read other threads that if it isn't plugs/wires then to check those. I don't see how the CTS could, but I could see IAT sensor being a culprit.

Josh

Heh. Way to go me for being an idiot and not reading vehicle profiles
I'm not sure of the location of the IAT on the 420A, I'll go look at the manual and see. You could probably find out for sure at 2gnt.com .

I hope this helps.

 

[akdsmer]

I believe my IAT sensor is screwed in the back of the intake plennum.

plenum. Yes it is. There are two wires. The Brown/Blu wire should have 5 Volts with the connector disconnected. Plug it in. The voltage will be around 2.5 Volts +/- a couple of tenths. The IAT sensor has very little fuel control and will not cause a misfire.

I don't see how the CTS could, but I could see IAT sensor being a culprit.

The CTS has much more fuel control authority, but won't really cause it to run so rich or lean as to cause a misfire. You should have about 500mV (1/2 Volt) or so when the vehicle is up to operating temperature on the Green/White wire.

If both of these are even close, they are not part of your problem.

Misfire:

Plugs, wires, coils.
Maybe cam or crank sensor breaking down sending a bad signal.
Intake leak at the manifold or bad valve guide leaning out one or more cylinders.
Bad/dirty fuel injector(s), PCM not actuating injector.
Low/poor compression.
PCM wiring issues...there are more, but the little stuff could go on and on.....

Compression test first. I would then locate the offending cylinder(s). Removing the fuel injector connector one at a time and look (listen) for the rpm changes. A cylinder that has no or little rpm change will be the one that is not contributing the combustion process properly. You can then rule out the injectors by swapping with another injector and see if the problem follows. Spray some brakeclean or such around the intake manifold to see if you find a rpm increase. This will indicate a manifold vacuum leak and will need to be repaired. This is where I would start.

 

[DSMcrazy3]

Thank you all very much. Especially you wiseman! That was very descriptive and will help me alot! Do I just spray the brake clean around where the TB meets the plenum? or all of the TB?

Thanks

 

[akdsmer]

Specifically around the manifold runners that go to the individual cylinders. Leaks around the TB or further upstream will make the vehicle run leaner as a whole (and will cause a lean misfire as well) but the leaks at the individual runners causes a misfire in the corresponding cylinder. Don't be afraid to use all $2 bucks worth of the brakeclean! A little does NOT go a long way when your trying to get a rpm change.

Let us know if it is one cylinder or more, because that change what you test...