Hi all

I am in the process of re-assembling my motor and need to know the following:

1. What is the LARGE sensor for?
2. Can I do without it?
3. If I can do without it, what do I do with the wire that connects to it?
4. If i do need it, OR if it is advisable to have it, where can i get either a new one OR a good used one?



Thanks in advance
Nick
Cape Town
South Africa

 

the big honker is your EGR valve, and yes, it is best to keep it on. It is used for Exhaust Gas Recirculation :
The EGR valve is opened to allow exhaust gasses to enter the combustion chamber with the air and fuel. This reduces the combustion temperatures, and reduces the formation of oxides of nitrogen, a pollutant - not to be confused with nitrous oxide (N2O) which is an aphrodisiac to the bottle-fed types among us….The EGR valve is the big black donut shaped device on the back of the intake manifold. Exhaust gas flows from a tube on the #8 exhaust manifold runner, to the back of the intake manifold. The EGR valve controls how much, if any, exhaust gas it admitted to the intake manifold. The solenoid that activates the vacuum is located on the drivers side of the intake manifold, on a clip near the back. The source of vacuum is a port on the drivers side of the intake manifold, near the middle by the PCV valve.

The EGR system typically does not work at idle, and does not work at WOT. So it has little impact on performance. If the system is leaking, it will hurt performance though, and it tends to heat up the back corner of the intake manifold, but that is not of interest to the ScanMaster.


The other 2 are coolant temp. sensors and you need these as well :
This is the temperature of the coolant, in degrees Fahrenheit. It is measured by a sensor in the water pump housing. This is NOT the same sensor that supplies the temperature to your dash mounted temperature gauge. The gauge sensor is located in the driver's side head, between #1 and #3 cylinders (under the exhaust manifold).

 

Gosh Mike that is one heck of a detailed answer, thank you very much, wish i understood more it, but this will get me on the right track with the help of a local mechanic friend.

I have now looked up the EGR valve at Corvette Central and they list one for 1986-1991 Part#: 304780 for $75-50, which looks exactly like my one, i have also emailed them to find out if they have the electrical wire which attaches to it, as mine is so rusted that I'm sure when I try to unscrew it, it will fall apart.

Thanks again, what would I do without the knowledge of this forum?

BTW, just love Yellow on a Vert.

 

I think having 2 sensors not related to the dashboard is not good at all.

For instance, the dash oil pressure sensor is wild and sometimes get crazy! not giving the certitude oil pressure is really ok or not.

Is it possible to plug only one ECM sensor per dashboard gauge?
This would show accurate reading.

 

Nick,
the wire screwed into the egr valve is the egr sensor. Without it, your car will throw a egr code. It's about $22 U.S.
it senses the temp difference between the valve being open or closed.
The first sensor is the one screwed into the front of the engine intake manifold, and it is the computer's sensor. It tells the computer the temp is up, and it's time to go into closed loop mode.
The second, middle sensor looks like the MAT sensor screwed into the bottom of the plenum to determine intake air.

 

I agree with the first response except for these two sentences. The on a 84-91 (vin p) is located in the front of the intake manifold. 92-96 (vin p) is located in the bottom of the water pump housing.

The coolant temp guage sender on a '88 is located between#6 and #8 spark plugs. Has a single green wire and a spade connector.

 

There is no VIN "P" in 1984 - 1991. The 1984 L83 engine and the 1985 through 1991 L98 engines are VIN code "8". All ('84-'91), have the ECT sensor (the sensor that feeds the ECM) in the front of the intake manifold, facing forward. In 1984 and '85, the IP gauge sending unit is in the left head between the #1 and #3 spark plugs. In 1986 - 1989 the gauge sender switched sides of the engine and is in the corresponding cylinder head hole which is between the #6 and #8 plug on the right side of the engine. In 1986 - 1989, the aux fan switch, if equipped with RPO B4P, is in the hole, in the left head, vacated by the ECT sensor. If no aux fan, that hole is plugged. In 1990 and 1991 both fans are ECM controlled, therefore, no aux fan switch.

RACE ON!!!

 

The man does know his fan switches!!

 

He is a wealth of knowledge!!

 

I asked Corvette Central if the had the "wire" and they said no they do not have it, I don't know if they understand that I meant the Sensor.

Do you know where I can purchase the sensor?

 

I think you are probably looking for the the EGR valve temperature indicator switch. A FSM would help you in identifying parts, such as the EGR, as a valve, rather than a sensor. The switch I am referring to is the tattle tale that squeals to the ECM that you have disconnected your EGR valve or that it isn't working. If I am right it looks like THIS. It is part number 14087415. It may be easier to find if you ask for it by it's correct name. Assuming, of course, that is really what you're looking for.

RACE ON!!!