I need to test some things on my car but I can't do it untill I know what to test for. I am having a starting problem and I would like to be able to test some of the sensors but I don't know any of the values for them so it does me no good to test them. I want to test my MAF, TPS, IAT and others. I know I could just get a scan tool and test them but it still does me no good because I don't know how they should read on the scan tool if they are working properly or not. Does someone here know this kind of info or is there a book I can buy to tell me.

Phil

 

You can't test the MAF easily (without expensive instruments), sorry.

But you can test the TPS and IAT:
- with the key on, TPS blue wire should show 0.5 volts when closed and close to 4.0V when open. If you have an analog voltmeter, you can slowly open the throttle and you should see the needle go up, smooth, without jerking and then close the throttle and the needle should go smoothly down
- IAT is a reverset thermistor so it has high resistance when cold and low resistance when hot - put it in the freezer for an hour and measure resistance, then boil it for a minute and measure resistance. Compare resistance to this value table: https://www.thirdgen.org/forums/atta...ase-ctsmat.gif

Hope this helps.
Lou

 

Great info on the IAT sensor. Here is what I have found so far. The TPS was reading about .70 volts when it is closed so I adjusted it to the .54 volts recomended. This did not cure my problem. I checked the timming and found it to be a little off so I disconected the advance and adjusted it to 6*. I checked the IAT sensor and got a little confused. I was not using my multimeter and I really have no idea what I was reading. It showed 0.729k and I figure the sensor was about 130 degrees or so. Is the 0.729k actually 7290 ohms? At any rate, I found 5.1 volts going to the IAT. When I try to start the car it acts like it is flooded and all I can smell is fuel, It won't start unless I unplug one of the injector banks. I was told today that either the IAT or the coolant tempature sensor will cause mass amounts of fuel to be dumped into the motor when you try to start due to the fact that the ECM thinks it is very cold outside. I am ready to set this car on fire and call it a day.

Phil

 

0.729 kOhms = 0.729 * 1000 Ohms = 729 Ohms. Yes, that would be in the ballpark of 130 degrees. So now we know that the IAT shows good resistance at THIS temperature at least. Of course, if you're asking "why is it showing that the AIR temperature is 130 degrees F when it's 70 degrees outside today?", I can tell you that GM engineers aren't one of the smartest cookies in the world. They took a CTS and stuck it in the bottom of the upper intake manifold. The CTS is a SOLID piece of brass with a sensor inside. To it measures the temperature of the MASS around it, i.e the temperature of the heatsoaked intake manifold. The real IAT would be located in/by the air filter, away from heat. V6 cars are configured like that.

As for the TPS, that's a good catch. How much did it show at WOT? 4.0V? More? Less?

If you suspect the CTS to be causing the flooding, you can disconnect it. The ECM will detect that and just assume standard operating temperature, thus not trying to flood the engine. If that doesn't help, it's not the CTS. (you can test the resistance the same way as with the IAT, the same table applies - because these two sensors are identical)

FPR can leak extra fuel into the intake manifold if it's ruptured inside.
Injectors are also often overlooked. They tend to wear out, especially after 20 years.

Lou

 

I ran the car for a wile and then it sat for about 10 minunts. I figured that 130 degrees was pretty close to what the it should be just sitting there after being ran. I will check the CTS tonight. Someone has had the FPR appart at some point because there is red RTV all around where the two halfs come together. I was going to replace it even if it was working fune due to the fact that I don't trust it. I also see RTV around

 

I guess it didn't post the whole thing. As I was saying, I also see RTV around all of the injectors where they go into the intake. I will just keep trying different things untill I get it. Thank's for the help so far.

Phil

 

Update!!!!!

I tested the CTS and it was about 3200 ohms. The car was cold. The only thing it did when I unpluged it was make my fans run all the time. I noticed something tonight that I have never noticed before. When I turn the key on and the fuel pump runs I can hear fuel spraying. It has to be out of the injectors. I tested the injectors wile I was at it and they all read 12.2-12.5 ohms. I don't know if this is good or bad but I was looking for one that was way off from the rest. I am going to replace the injectors and FPR. I don't know if they are the problem but I don't like the fact that someone has put RTV all over everything. Keep the ideas comming guys. Thank's for the help.

Phil