How can a bad engine coolant temp. sensor cause hard starting. I was told that might be the problem, as I'm having hard starting issues.

 

only thing i can think of is that if the sensor tells the computer that the car is cold when it is actually hot, it will try to do a cold start and i think i will give you too much gas kind of "flooding it out" or if it is cold and the sensor tells the comp that the car is hot it might not give it enough fuel

 

Oh ok. Well that makes sense. Thanks for the reply.

 

Im not sure if the coolant sensor even passes through the computer. Its been a while since i did my wiring but i dont think it does. It is merely for your gauges. Thermostat keeps the engine cool and the wiring for the fans doesnt pass through the pcm either. I think im right, somebody please correct me if im wrong.

 

The temp sensor located on the side of the drivers head has no relation to the PCM, but the waterpump sensor does send info to the PCM. The fans are also controlled by the PCM.

 

i had the same prob awhile back when i got my new radiator put on.. some new guy at the shop busted my ects on the waterpump, car would only start if i gave it gas. and yes its because the car is getting too much fuel to burn because the engine is being told its -40C if thats the one thats messed up. thats how i was explained the problem anyway. but whatever you do.. dont let a shop change it for you, if youve got a wrench and a jack its a no prob install, save ya about $40 if not let em change it lol. my car ran a lot different though, wouldnt go into closed loop or anything. good luck with it, and i hope that helps ya.

 

Just make sure you get the correct sensor. Both sensors in the waterpump and drivers cylinder head have different part numbers.

 

Shoebox has a great website that lists the part number you want:

http://shbox.com/1/Parts.htm

 

I've posted this before but there is a later model dual GM sensor that has the gauge and the PCM sensor in one unit. That way your gauge reads the temp of the water in the block and not the head. Saves you all the anxiety of thinking your car is overheating in traffic when it isn't. I've got one. Just pull the wire off the head sensor and route to the new one.

 

Is this an LS1 coolant sensor? Your other posts refering to this sensor don't say much about it. Does it screw in without adaptions? What's the part #?

 

I got the information off of the "Herd" Lt1 Impala website. Scott Muller did a very good writeup of the LT1 cooling system. Here is a quote from him with the part numbers.

"A more elegant method of correcting this problem would be to simply replace the existing PCM sender with a new dual purpose sender that GM has recently been offering on other applications. This is a new GM 3-wire sending unit which includes both the PCM and Gauge senders in one unit, and which installs in the existing PCM sensor location.

GM has begun using a 3-wire dual purpose sender on some new engines. It combines both the PCM and gauge senders in one unit. This is ideal as no additional holes will have to be drilled or tapped, this new dual purpose sender can replace the existing PCM sender.

Here's the information on the 3 terminal coolant temperature sensor.

Part No Description Cost
10096181 PCM/Gauge sending unit $14.81
12102748 Connector pigtail (incl. terminals) $17.29

This connector pigtail is a complete connector with terminals and wires installed, which would have to be spliced to the existing wires. Alternatively, you can get just the connector shell and terminals, which you could crimp onto the existing wires. Unfortunately most dealers are not able to get Packard electric parts through GM.

Part No Description
12078090 Packard connector including the seals
12103881 Terminals (three required



Another alternative would be to get the connector and terminals plus wire from a junkyard. It's the same connector that is used on the throttle position sensor of the LT1 and many other engines.

The new sending unit is wired as follows:

Pin A = Black, PCM sensor ground
Pin B = Yellow, coolant signal to PCM
Pin C = Dark Green, to Gauge
In summary, the temperature differential in the Impala gauge vs. PCM sending units is the fault of the location of the gauge sending unit, and not the gauge or sending unit itself. I would consider this a design anomaly (nice word for bug or flaw ) which fortunately can be easily corrected, and which of course does not affect vehicle operation, just the gauge reading. "

 

Thanks, I think I'll try it.

 

So, tell me please..... your car begins to actually overheat for whatever reason, (old radiator, waterpump failure, air in system). Which sensor would warn the driver of pending overheat sooner....the cylinder head sensor or the water pump sensor?

That sensor mod is not as popular now as it was 10 years ago.

 

My Scanmaster would tell me first. I chose to dabble.

 

LOL> Your Datamaster would be looking at the water pump temp.
So I guess you'll respond to the steam raising from under the hood.