Jump to content
HybridZ

Where does the o2 sensor go!?


SuperPickle

Recommended Posts

  • Administrators

With it running so rich, does it run better when the engine is cold, i.e. first started up and then gets worse as it warms up?

 

If the Water Temp sender becomes disconnected for any reason, the EFI will flood the engine and the symptoms you described at WOT are the result.

It is very common for the leads that go to the water temp sender to corrode and come apart or for the connector to just fall off as these connectors are pretty trashed after 19 years in service.

It is also possible while you did the gasket R&R that you swapped the Thermotime switch and water temp sender connections.

 

On the Thermostat housing itself, you will have 2 sensors that have Bosch style electrical connections. One of those sensors has much bulkier body than the other. The BIG one is the Thermotime switch, (controls the cold start injector), and if you follow its wires back approx 3-6 inches from the sensor you find a pair of bullet connectors. They SHOULD have red electrical tape wrapped around them on both sides of the bullet plug connector. The Water Temp sensor, (that is the smaller Bosch style sensor), it also has a pair of bullet plug connectors in the same area as the Thermo time switch and does NOT have the red tape.

The Water temp sensor is NOT polarity sensitive as it is just a resistor and at 70 degrees Fahrenheit, it should read between 2000-3000 ohms and at engine operating temp of 190 degrees, resistance across the EFI water temp sender should read between 200-300 ohms. With a Haynes manual, looking at the wiring diagram in the back for the ’77 car, you can trace the pin-outs for the water temp sender at the ECU plug itself and verify with and ohm meter that the ECU is in deed getting the correct resistance value, i.e. no break in the wiring. If the resistance values measure are any where close to those posted here, then that is not your issue.

 

 

Too bad you don’t live in the Pacific Northwest We’d be glad to diagnose it for you.

 

 

 

Keep us posted on your progress..

Link to comment
Share on other sites

I thought of water temp sensor as soon as I saw that picture of the plug as well Paul (great info on telling which wire is which btw).

SuperPickle: if you didn't mix up the two connections for the thermotime and water temp sensor and the connectors look OK, I'd bet money it's the water temp sensor gone bad. (and I'm not a betting man) They're cheap. I think the last one I got was 12 bucks and change.

Link to comment
Share on other sites

When I took out the spark plugs earlier, five of them looked like the one I posted before. The one in the attached pictures below is the plug closest to the front of the car. My question is what signifigance that may have. The pictures were taken after my uncle chipped at it for a bit. It was completely "clogged", and looked like a burnt lump.

 

I printed out this thread so I can go looking for the water temp sender/sensor in the morning (when it stops raining).

Link to comment
Share on other sites

Sorry I haven't replied recently. I Just got in to Boston early yesterday morning, and have been busy setting up shop, so-to-speak. I changed out the fuel filter right before I left, and I plan on changing out the fuel pump once I've had a job for a bit. So far I think I've only treated the symptoms, but I'm probably going to end up doing an overhaul next spring. Until then, I'll probably just drive it until it doesn't wanna drive anymore...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...