Hey Guys,
I have a new 1320 scanner that I used on my 86 c4, along with aldlDroid and my FSM. Im trying to determine if things are bad or good after the scan and any help here will be very welcomed.
First thing that was very apparent was the 45 degree difference in engine temp, and this was after I replaced the gauge sending unit. This much of a dfiff cant be OK. Harbor freight is out of hand held laser thermometers at the moment so I have to wait a few days to verify temp.
I was able to get my IAC counts down to about 22 at idle and warmed up. and the scan reported about 135 when cold and first starting in the morning. If these are good measurement please let me know.
Several things keep popping up in red on the screen and they are

1; Manifold air temp is red, its reading -40 to 122. It keeps bouncing back and forth on these two numbers.
2; The Mass Air Sensor is red as well with a idle reading of 8.73 to 9.33 at idle and warm.
3; The o2 sensor is red and reading 448.44 at idle and warm
4; Lastly the reading for the injectors turn red when I step on the gas. Dont know id this is normal. BTW the injectors and fuel pump are new.

And one last thing to add here I do not have a check engine light at all.

If someone wouldn't mind helping on these reading to advise if there ok or not I might be able to save some money by not throwing parts at it.

Thanks in advance for the help.

Tony

 

Air temperature sensor reading should be stable not bouncing. In section 6E there should be a page or 2 of scanner data both key on and when running to compare too.

 

The Coolant Temperature Sensor is a critical part of the fuel injection system and it should be as close to accurate as possible. Try cleaning the contacts on the sensor first and then if needed replace the sensor. This sensor tells the ECM how much fuel to use at the specific temperature. When they are reading improperly the fuel system will see the wrong temperature and compensate for that. If it thinks it is -40 then your fuel enrichment (Choke) will stay on until the engine warms up. This causes the Corvette to have terrible mileage.

In the closed loop mode where the Corvette engine spends most of it's time it is relying on the Coolant Temperature, Oxygen sensor and the MAF/MAP system to calculate the proper air/fuel ratio. If your CTS is bouncing it will cause trouble for the ECM. If your engine runs with an overly rich mode you risk damaging the catalytic converters.

The 1320 Scanner looks like a nice way to get the information from the Corvette in action. I have the Old Snap On MT2500 which allows me to see almost as much. Having a scanner is very handy as long as you understand what the readings mean in real time. I am still learning myself. I am finishing up the installation of a Holley Sniper EFI system and have learned a lot just doing that alone. I wish the factory software was as easy to understand as the Holley software.

Your oxygen sensor should oscillate between .1 and .9 volts very quickly (hard to see without proper tools), as they age the signal will narrow like .2-.8 and so on. Your scanner might be averaging them out for you. I have heard that before with some scanner software. The other thing that happens to O2 sensor's is that the signal is slower and slower on older units. This causes confusion for the Corvette so the ECM tends to have issues keeping up with the constantly changing conditions. The Oxygen sensor was designed to be used for 24 months or 50k miles on OBD1 vehicles. If your O2 sensor is older then just replace it. Newer OBD2 cars get twice as much out of their O2 sensors, 48 months or 100k miles.

A fresh O2 will give your Corvette the Performance and Economy it was designed for and make it more fun (and Affordable) to drive!

 

Thanks so much for this reply. Just a couple of things that I thought needed clarification.
The coolant temp sensor that you mentioned is the one that is at the front of the engine. I have already replace that and it was not the one I was referring too. I was talking about the MAT, mass air temp sensor that lies under the plenum. It was the one that was bouncing back and forth between -40 and 120. I just confirmed today that I have the right MAT part in there by checking with my Chevy dealership. What I did not have was the correct plug end for the MAT. I picked that plug end up today and spliced it in, now its reading -40 with ignition just in the on position, when I start the car it jumps to 122 and then goes up from there. Dont know if this is correct or not and I cant find anything info in the FSM.
I replaced the 02 sensor today as well. Found the old unit to be just hand tight when I removed it, go figure. Put a new AC Delco in and thouse new readings seem to be ok.

Thanks again

Tony

 

Sounds to me like a broken wire on the MAT sensor causing it to short out. You could relocate it to the air filter housing to make it easier to access too. The wire runs down the back behind the distributor.