aaronvincent

Hello there Maximites (or something along those lines) lol. I was recently given a 2000 Nissan Maxima SE (1 owner, 223k, automatic) because the previous owner said it was "nickel and diming him to death", when I got it the car wouldn't even run so I used my scan tool and it had a code for the crankshaft position sensor. 1 new OEM sensor later and the car runs and drives but I have a further issue. When starting it after sitting overnight (or when it's somewhat cold outside) the car will start right up and immediately the idle will drop to 300rpm and then it will stall. After it warms up the car runs incredibly well and is surprisingly fast. There are NO check engine codes/lights. Over the last few weeks I have done the following after reading up on the issue:

NEW OEM Nissan MAF sensor

Cleaned IAC/Throttle Body (by removing the whole assembly and cleaning it and the IAC with throttle cleaner)

NEW coolant temp sensor

Replaced all 6 coils (previous owner just did this, they all look fine)

Replaced all 6 spark plugs (previous owner also did this, they are NGK)

Adjusted TPS

Cleaned IAT sensor and tested the ohms, tested good

Still the vehicle has this freaking cold start issue, my next plan is to get an oem TPS from the junkyard and try that before I push it off a nearby cliff (jk I'm going to take it to a local shop). But I'd really prefer to figure this out on my own before I go that route. I've always fixed all my cars so this one is really got me confused. The car itself was beautifully maintained and looks spotless but this issue is...irritating. Any help is greatly appreciated!

maxiiiboy

From my own experience, this looks like an ECTS, or IACV, or perhaps a MAF problem. With this in mind, I would suggest:

• Start by replacing/rechecking the ECTS (Engine Coolant Temperature Sensor). There are two them - one provides input to the ECU, and the other provides input to the instrument cluster. You want to check/replace the one providing input to the ECU. Have you replaced the correct one ??? (The FSM has a picture showing the location of both sensors).
• If the above does not help, re-check the MAF. Does the car start with the MAF disconnected? (it should; if not, the problem is elsewhere)
• Last, check the IACV. It may need cleaning. If it was never replaced, replace it! (there are good reasons to do this - see the document about ECU Failures; link in my signature below).

aaronvincent

So I've just been poking at it the last few days, adjusting things here and there. The coolant temp sensor I replaced is the larger two-wire one (there appears to be a smaller one wire sensor below it) I imagine that's for the temp gauge. The car does start with the MAF unplugged. The IACV was cleaned (I spent like 3 hours scrubbing every little port and even removed the spring/pindle assembly and scrubbed that too).

So yesterday I replaced the throttle position sensor with an oem Nissan unisia-jecs unit and adjusted it, that seemed to help a little because when I started it in the morning it idled funny but this time didn't immediately die, just idled funny for about 2 minutes. I also replaced both the camshaft and crankshaft position sensors with oem Nissan units because the ones that were on the car were some weird aftermarket no-name junk. Not sure if this helped the idle situation but it doesn't idle anywhere near as bad in the morning now. Still after letting it sit overnight it does the weird idle/loop thing (just not as bad) so I'm thinking either I need to have the idle reprogrammed or maybe I have a fuel system issue. Either way it's going to a local shop that I'm very friendly with tomorrow morning and I'm going to let them poke at it for a few days and see what they say because this has me completely stumped