78 280z Rough Idle When Hot!

[Bored_Rice]

Oh thanks for the suggestions guys, will keep you posted

[Bored_Rice]

Sorry to be a newbie, but where is the coolant sensor and how do i replace it?

[ransomnotes]

Temp sensor is located on the thermostat housing. Check your service manual. You'll need a deep socket...can't remember what size. I had to sand the plastic edges of the new connector to be more rounded so the socket would fit over the top of it. Definitely take your old sensor into the parts store to compare.

Easy stuff, but make sure you drain some of your coolant first or you'll have a mess. Check and clean your connectors before you buy another sensor though. Could just be dirty connections.

I replaced my temp sensor and connector but that didn't fix my low idle when warm problem. I removed the connector to my cold start valve and now my idle is right where it should be. I haven't been driving the car much since it's been snowing, so we'll eventually see if that valve or connection is the culprit. So far so good though. Starts right up even in below freezing weather.

[scotts pearl]

My 78 280z had the same issue.. Found that it was a cracked vacumn hose,,,

[TDatsun280Z]

This sounds like ours it runs smoothly for a minute or few and then we try to drive it away and it just turns off. It shakes the whole car (the engine). And we're about to look at the thermostat. Every other part works, but I am sure the rings are worn out.

[Friar-Tuck]

I am by no means an expert, and I would think the state of all these cars are different.

http://www.xenons30.com/reference.html

This link goes to several downloadable service manuals.

I just started going through one item at a time when we got

our ZX.

1st thing I did was common tune-up and rule out any simple things.

2nd on the agenda was cleaning ALL the connections in the enginebay with needle files, electronic connection cleaner/protector (Deoxit, http://www.caig.com/ ) etc.

3rd was checking all the wiring I could without completely dis-assembling the harnesses. I did untape alot of splices

and re-tape where there was an suspicious bends or scrapes and nicks.

4th replacing all the vacuum lines.

Tape and label Everything!!

(I lost alot of time figuring out where all the vacuum lines should go.)

Oh.. I know..."I can remember a few vac. lines.."

WRONG!! I regret that one...

5th was trying to verify all the sensors and "controllers" with the fsm and multimeter.

I realize this doesn't sound like much help.. but thats what I did to finally get ours running pretty dern good.

I did end up replacing a head gasket and re-building the head. I hate to admit it.... but I lost at least a week when I didn't tape and mark the CHTS connection and sensor when I stripped the head and sent it out to be resurfaced and valve grind. :stupid:

When I got it back and re-installed the head and went to fire it up we were Heartbroke...but thats another story...

If the car runs good cold, and worse as it warms up.

I think I would go with Mr. Blake, Check -- temp sensor, thermotime, e.g.r., vacc advance, fpr, fuel pressure,filter...

methodically one system at a time...

You can spend quite a bit of cash throwing new parts at her, but time and patience will verify somethings actually bad or not.

Hang in there, Tuck\o/

[FilipeA]

Hi

I had a friend that has this same problem (blue 240z), when the car is cold and it runs at idle it runs good, but when we goes to the road it runs really bad and sometimes it stop at road.

I must tell you that engine was rebuilt too, but not many new parts were apllied.

Can you tell me what is the vacuum lines? i think i know, but just checking, they are the air hoses that engines has, all of them??

We get toghether last saturday, 3 240z, to help each other. My car didin`t suffer for that problem now, but once he did that, but i didn`t do nothing because engine was all rebuilt and i changed all parts.

Does he need to change

- spark cables;

- fuel pump;

- distributor;

- vacuum hoses;

any advice would be just great

Edited March 5, 2009 by FilipeA