Engine sensor specs

Can anyone point me to where I can find specifications for testing the engine electrical components, like TPS, MAP sensor, etc? My Haynes manual doesn't have these listed...

My '94 4.0 with 170K miles failed emissions and the local dealer doesn't even want to take the time to look at it. I have the usual new O2 sensor, new plugs/wires/cap/rotor, as well as a new catalytic converter, but my NOx is still high (5.2 - passing is 3.0). CO and HC are great - passed those with flying colors.

The shop that replaced the converted said that both the old and the new one weren't getting very hot - around 350 degrees F with an IR thermometer, and 600-700 is minimum to have the cat fire correctly, no? Additionally, my engine temp never seems to get over 150-160 F. I've replaced my thermostat TWICE now, just to make sure it's working, and I even tested one of the old ones in a pot of water on the stove, and it worked fine...

Anyways, I'm assuming that it has to be one of the peripheral components giving the ECU a bogus signal, so if I could find out what values these items should test at, I can start eliminating things.


Thanks for the help -

Let's start with the temperature sensors. Coolant and Manifold air temp sensors both produce the same values. Here are selected values from the chart. More if necessary, but this should give you an idea if one is actually busted:

50 degrees F = 17990-21810 ohms
68 = 11370 - 13610
86 = 7370 - 8750
122 = 3330 -3880
158 = 1630 -1870
176 = 1170 - 1340
194 = 860 -970
212 = 640 -720
248 = 310-410

Make sure you get the right coolant sensor. It's the one on the thermostat housing, not the one back on the head for the gauge.

I doubt the other sensors would affect the running temp, but for the MAP sensor, back probe the connector between terminals A and B with ignition on, engine off. Voltage should be 4-5 volts. This should drop to 1.5 - 2.1 volts at neutral hot idle.

There's something funny somewhere if it isn't running up to temp with a good thermostat.

Matt, this is exactly what I'm looking for. Thanks for your help!

Andy

A good time to test the temp sensors it after it sits over night.
Before you start up every temp sensor should be reading very close to the same temp/resistance.

Makes sense - thanks for the tip.

Heres a good reference.
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm