Tpx

So I'm getting into tuning my own ECM rather than having Kevin (great guy btw) tune it for me every few months.My engine has recently become very strange, lost 75% (most) of it's power in all rpm ranges yet idles and drives enough that I am still driving it daily. Sputters, surges, can't seem to run smoothly at all no matter what I'm doing, part throttle or wide open.

I believe there may be a sensor causing all this mischief. I'll read that too much engine timing or lack of timing can make your car run like crap just like mine's doing (bad knock sensor). So because my car's running poorly and I'm about to get into data logging/chip burning I want to make sure all my sensors are giving me accurate, reliable information.

Where are these sensor locations?
Which are critical for engine operation?
How do I check for a bad sensor?
Which are likely to go out often?

-CTS Coolant Temp Sensor
-MAF Mass Air Flow Sensor
-MAF Relay
-Knock Sensor
-MAT(IAT) Manifold Air Temperature Sensor
-MAP Manifold Air Pressure Sensor
-TPS Throttle Position Sensor
-IAC Idle Air Control Valve
-VSS Vehicle Speed Sensor

Any help is greatly appreciated!
(Mods, if this should be in PROM section feel free to move it)

vetteoz

iTrader: (13)

Min to run engine
CTS Coolant temp (on intake under TB)
MAF air flow to engine (on ducting from air cleaner to TB)
You don't have a MAP sensor on a '88
MAF relay (supplies power to MAF)
TPS indicates how open the throttle is ( pass side of TB )
........................
The engine will "run" without the following but the computer is setup to use these inputs
Knock Sensor ( pass side bottom of block )
IAT ( under plenum at rear ) shows the intake air temp
VSS ( drv side rear of trans ) lets the computer know what speed the car is doing
..........
IAC ( under TB ) is not a " sensor" .Is a computer operated air valve that controls the idle speed and there is no feedback to the computer

Pull the codes;
all the above ( except IAC ) will put a code up if the signal is not within the range expected to be seen by the computer.

Tpx

Excellent, this was exactly what I needed to know. Many thanks for sharing your knowledge! I noticed the 1 wire going from pass side sensor under the exhaust headers was sitting on my headers, and had melted insulation (bare wire on headers). From what you said this is the knock sensor. Could a grounded out knock sensor be telling the ECM to reduce timing because it's "detecting" a high level of knock, or what voltage is given under "no knock" conditions?

My ALDL cable and Burn2 arrive on Friday, so I'll pull the codes as soon as I am able. I believe all you need is an ALDL cable and tunerpro RT to pull codes.

I did a check and I did find all the sensors you located for me, except for the IAT and VSS. My car has a T56 and cable driven speedo, and a HSR for the intake. This below is what the IAT looks like correct? It should be plugged into the back of my upper plenum?

Tpx

Just an update for future readers of this thread (if any) After using the given info in this thread and answering my question, I came across this webpage (linked in the Prom Tuning Guide also) detailing - with pictures - standard TPI sensors and locations. Great help to someone like me who is only used to carbs and vacuum lines