My initial symptoms seemed to be that I was getting gas & getting spark since the car would start when cold, run and then die. I could not test fuel pressure as I did not have the proper fitting to connect my fuel pressure gauge.
I measured the head temp sensor with a DMM, and the resistance seemed low across the board which would cause the car to run slightly lean while cold. The sensor has a reputation as a trouble spot and my car still had the old-style single wire version so I went ahead and purchased a new one to install.
The installation is a little tricky for a few reasons:
The old sensor and new are different sizes. There is a factory tool, but it is sized for the old sensor. You need to fake it or make a tool to get the new one in place.
There is a grommet that the 2 crank sensor and the temp sensor leads runs through in the rear of the tin. This is not terrible to pop out but getting it back in is no fun, and the replacement grommet did not have the cuts in it to allow routing the other leads through it so re-using the old one will be necessary.
Getting to the sensor does not require removing the driver's side rear shock, but it sure makes things better.
Basic Procedure:
Lift car securely
Remove rear DS wheel
Remove rear shock (or not, if you want to have a go)
Remove the plastic Aux hot air duct
Under the car, remove the grommet covering the temp sensor (DS rear wheel well, on engine tin)
Remove the "eye" that the 3 sensor leads route through.
Cut the lead on the old sensor and use a 13mm socket to remove it. Keep the lead long - you will need it.
Make a 14mm deep socket with a deep cut in the side to install the new sensor. Some folks on the boards use pliers since it does not need to be very tight. Suit yourself.
Once the new sensor is in place, replace the grommet over the head where the lead exits.
Using a large (preferably dull) slot head screwdriver, push the grommet into the engine bay (up and away from you as you are under the car). This is the grommet that all 3 leads pass through. Try not to damage it, you will need it. Work your way around the edge and gently push it in.
Now tape the old lead to the new lead so you can use it to pull the new lead up into the engine bay. I used electrical tape.
Remove the 3 sensor plugs in the engine compartment, and unscrew the locking plate that holds them in (2 small phillips screws)
Remove the old temp sensor plug and insert the new one. You may have to wiggle it a bit to get it all the way in so the locking plate will fit and the plug will connect well.
Re-assemble the mounting bracket for the sensor connections and connect them.
Remove the old temp sensor wire from the old grommet and feed the new one into it (there are slots)
If you can reach, push that old grommet back into the tin where it was. I was not able to, but my engine is coming out soon for top end work so I let it slide.
Re-install the DS rear shock (as needed)
Re-install the rear road wheel.
Test run the engine and make sure it runs and gets to operating temperature.
Action Pics
Get the car comfortably up in the air, and make sure it is stable. You'll be spending some time below.
Remove the Aux air vent so you can get to the engine sensors. Or really anything else on the driver's side of the engine bay.
Here is the bracket with the 3 sensor connections. Top is temp, the other two are the crank sensors. Remove the wire clips and then disconnect the plugs. Unscrew the 2 screws that hold the retaining bracket in and slide it out. This will free the end of the temp sensor plug.
Here we are behind the engine, in the driver's side wheel well. At the top is the grommet that seals the engine bay. Below it are the wire routing "eye" and behind that is the grommet that protects the head temp sensor. You can see that the rear shock is kind of in the way. How in the way is up to you...
Another view, closer up showing the grommet protecting the head temperature sensor
I opted to pop the shock out. 1 nut up top, 1 bolt down below. Stubby wrenches are your friends. It really did make things much easier under the car. (Bilstein shock)
Ok, wire routing eye is loose and we're removed the grommet over the temp sensor. To remove it, we'll cut the wire close to the sensor itself and then use a 13mm deep socket to remove it.
Old sensor is out, and you can see where you have to screw in the new one. A little tricky to start but not too bad.f
To give the wire room to not get crushed by the wrench I bought a cheap 14mm socket, ground in a nice opening and then filed it smooth enough that I did not have to worry about cutting the new lead by accident. Ugly, but effective. YMMV. The factory tool is $100, and it's the wrong size.
Here is the new sensor as it arrives, complete with its own grommet but also the bigger one that goes into the engine bay. The end cap is there because it ships with some anti-seize on it (great idea)
OK, here we have screwed the new one in with our fancy custom socket. Now we get the new grommet in place, fish the lead through the eye, re-mount the eye and then use the old lead to fish the new one up into the engine bay.
After taping the new lead to the old one, pull the new one into the engine bay with the old one. You'll need to loosen the eye between the intake runners to route the wire properly. It's a little tricky but not too bad.
Push the new plug as far through the bracket as you can and test fit the socket. Once it is connecting positively, slide in the retainer bracket and replace those 2 screws.
Replace the wire clips on the plugs, and you are just about home free. Here I was already putting the shock back in, I still needed to replace the hot air duct. But as long as the car starts and runs you're good to go once you put the other pieces back.
I was not able to replace the original grommet into the engine compartment. It is located in the tin and is down and behind the engine. Some red rubber grease and a mirror to let me see what I was doing might be enough to solve that issue, but since the engine is coming out very soon I gave myself a break. If anyone has a hot tip for that last bit, I'd love to hear about it!
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