Thread: Low Stumbling/hunting idle thread (Auxilary Bypass Valve). Was Coolant Temp thread.

I am chasing down a hard cold start issue and I am hot on its ass. Threw every tune up part at it and nada. OK, searching the forum(s) lead me to the CST. Went to the Zone and got a new one. Swapped on my break and it fires up to 1500. Great. No. Fans kick in and wont go off. Went to put the old sensor back in and it fell somewhere. Had to go back to work. What may have happened? Bad CST or did I loose a wire? I have no DVM here.

well the hard start issue could be from the IACV, i have had a problem there, had to give it gas in the winter when starting it to keep it running for about a minute, then it would idle, sprayed the hose goin to the IACV with carb cleaner while running not letting it die, and that worked wonders maybe, put the old sensor back in and try that, go from there, check fuses as well, ive seen a fuse blow for like a/c or something like that and the fans stay on as a safety precaution

1. Find the old sensor (so you dont loose it).
2. If you want the fans to go off:
. . Pull both fan relays next to the battery.
3. Drive the car to the zone and get another CST..
4. Install the CST and go home.
5. Clean the harness connections to the CST.
6. Get your DVM (from your baby hehe) and figure out whats out of place.

Lunch time fixes always leave you stranded... For me too...
Good Luck ! !

OK, it was the sensor. I put a new one in there and it works as normal. Just can't find the old one and brass is not magnetic. Still have the hard start so it is not the CST. I am beginning to think an injector is leaking and i am flooding. I just do not smell gas. I am trying hard not to take off the IACV. It starts up and then after like 30 seconds, the rpms tank unless I keep the throttle open. Typical scenario

Great.. I thought it was a bad CST..

I cant blame you for avoiding the IACV. If its clogged, I have found it causes rough & high idle issues; not impacting the starting. Have you tested the fuel pressure. Im thinking your fuel regulator or fuel filter maybe the culprit. Some has had better results with the larger 300ZX fuel filter.

The fuel filter was the first thing I changed.

It's not too bad to pull the IACV out and clean it up a bit. Maybe 30 minutes of work there. Although, being that I have an oil filter relocator, it might be easier for me

You may also want to check your air regulator valve.

Also, this may seem stupid haha, but you were talking about the coolant temp sensor right (CTS), not CST?

Yeah CTS like the Cadilliac.

You are Correct.. I was typing CST too...
I do the same thing with the PCV sometimes too. We just want the Caddy.

The IACV in a NX with AC & Power Steering a royal PITA to remove AND to install. You cant see the bottom screws and must feel around to access them. With large hands, you only have 1-2 inches of room. An Oil filter relocator helps but its still a bear to access b/c of the lines above it. Using Stubby or narrow offset wrenches helps alot..

^Who has? I think this is what bgreen used on that funny HOW TO vid he made.