problem after changing water tep sensor

[mrfixit.joe]

77z I put it back on the road after 10 yrs. it was runnig good but found it was running very rich and was only getting 14 MPG. everthing else was good.

change the water temp sensor because i believed it was not allowing engine to lean out after warm up. the engine starts great and I had to reset the idle down. it revs fine but as soon as i put a load on it it pops and bucks.

I replace the plugs and checked the timming. I can not put the old one back in because it broke.

I hope somebody has an idea.

joe D

Edited January 21, 2012 by mrfixit.joe

[mrfixit.joe]

ok I have and update if i disconnect the temp sensor the idle drops. I can turn the idle up and the car runs rough but it has the pwoer again. it is agin running rich .

I hope this helps so you can give me and idea what to check next.

[Zed Head]

1972 240Zs came with carburetors, so your post does not make sense. Do you have an EFI engine in the car now?

If you do have EFI, then you need a properly functioning temperature sensor. For starters, measure the resistance at the ECU plug and compare it to the values in the chart in the FSM.

[mrfixit.joe]

sorry for the confusion my Z is a 1977 280Z.I belive the sensor is working correctly and there is a different problem. I just checked and adjusted the TPS and need to test drive it but it is poring right now.

Joe D

Edited January 22, 2012 by mrfixit.joe

[grantf]

do you have the temp sensor and the thermotime sensor connectors switched? easy mistake to make.

[mrfixit.joe]

I checkd this by running a ohm it to the cold start valve to make sue I had them correct. If you are sure which one the green wires go to I would mind checking again.

[grantf]

Let me go outside and look.....

Green is thermotime/cold start. Black is Water temp sensor. Confirmed on my car, FSM and color wiring diagram.

Edited January 23, 2012 by grantf

[mrfixit.joe]

Ok here is what I found. The car was running with a bad water temp sensor, so it was real rich. After changing it and the it getting the proper fuel mix caused a lack of power and poping. This ended up was being caused by a bad AFM. The bad sensor was masking the problem with the AFM .

I had a spare from a parts car. Ran it through all the test and it checked out, so I put it in and she's running good and lean.

Thank you all for your help.

[ZSaint]

I have a similar concern with my '78 280Z. It sat for 7 years and I just got it running again. It also pops and backfires when I try to do a normal accel from a stop. If I hammer it, it runs great. This is my first Datsun FI system. I have aways worked with Solexes, Webers, SU's or Hitachi carbs. I have changed AFM and computers and the malady still exists. I bought a new water temp sensor and think that may be the problem. Mine is for the 80's ZX's. Will it work on my '78?

[Zed Head]

Have you tested fuel pressure, and resistance on the WTS circuit?

[ZSaint]

I have installed a new pump. I have 40# pressure. I have not done any work with an ohm meter.

[grantf]

Well there you go. One problem area in the EFI system can mask another. Glad you got it worked out.