Thread: Advice on Hard Cold Start

yeah last night I turned the car to IGN, pulled that plug (yeah it's brown to match the plug on the ACC) and grounded the multimeter to the car battery and tested both pins cuz I'm not sure which is the power. One side have me .001 and the other side was .13. I'll do again when I get a chance and grab a picture. That's why I wanted to double check the fuse

UMM. Did you continuity check the frickin +12V?!?! Jesus man, thats not healty. Continuity check is just for the PWM pin, not the +12V feed. Re-read the testing procedure, and report back.

No no no I didn't do the continuity check because I didn't know which was the ground. I just checked for 12v power.

Pull the brake booster hose and see if more air fixes startup. That's an easy test to see if the valve isn't opening when cold.

Brake booster thing didn't seem to help.

Swapped on another IACV, the one under the intake manifold with a 99. I noticed at the same ambient temperature my old one was a look more closed than the 99. Here are pics






Well I got it start fire up 2nd try but not strong at all so I think my issue is still there, it's pretty warm out today so that could have helped it starting. Idle was still pretty weak. One thing that bothers me, I'm getting battery voltage when testing the AAC valve plug on my NXs but I don't on this plug. There's no damage to the plug. or harness so I'm not sure what's going on with it. Perhaps that's my issue?

So it would appear swapping that sensor didnt solve my issue. Last night Josh helped me come to the conclusion my Engine Electronics B fuse wasnt seating properly because I was getting no buzzer sound with the key in the ignition (long story short because of the previous owner using a jumper on the fuse it pushed the fuse holder clips wider on one side so the fuse wasnt fully seating properly. This helped me get battery voltage at the plug for the IACV/AAC so I know thats ok. I got the idle dialed in beautifully but the cold starting issue remains. I haven't swapped that IACV/AAC mechanism yet up there on the passenger side intake manifold but I'm wondering does it even matter for cool start? Doesn't that sensor just control the idle speed...etc, not the cold starting (like the one i swapped/shown in the previous post?) At thing point I'm not sure what else to look for. Might have to take her to Nissan to get looked at cause I'm officially stumped.

**UPDATE FOR IACV/AAC**

Well I got leads on the AAC pins and i'm seeing around 11 ohms which I believe is within spec of the 10 ohm per FSM. I also tested the actuator on the battery and I can hear it clicking so I must assume that its fine. I also tested the resistance of my original IACV (under the intake manifold one) and it was also within spec so I dont think anything was wrong with it either. I'm officially out of ideas here......

You are close man!

I would reset the idle now that you have a functioning idle valve. That might fix the cold start.

So, warm up engine, enter timing/idle mode, and try to set the idle to 750+-50rpm

Nice one @lynchfourtwenty

Yeah I set the idle at about 8-850 right now. Doenst seem to have fixed the hard start issue but the car runs great when it warms up lol (as it did before but yeah). I'm pretty stumped and dont know where to go from here except (even tho resistance and specs are good) swapping the IACV/AAC, Water Temp Sender and maybe fuel rails/injectors off another one of my good running highports. It about 87 degrees out right now and it took about 4 starts to get the it to overcome whatever issue its having enough to build up to a solid idle. Takes about 6 or so seconds to get to that good idle. I'm sure the cooler it is outside, the longer it would take though. Gonna snag a water temp sender from the auto parts store and swap to a Z32 fuel filter (turbo prep for next year) just cuz i have them

OK, if pulling the brake booster line didn't help the starting, then it isn't a problem with not enough air, so the IACV isn't a cause for concern since that's what it handles. As for the two you have being open different amounts at the same temp, not a big deal, but if I remember right you can put a wrench on the electrical connector and give it a twist one way or the other, at least I could on the one I had, and you should be able to move it to where it is fully closed.

I know at the beginning of this thread you mentioned cleaning the TB and other parts. It's possible that the intake valves though may have some deposits that are causing problems. I usually use something like Seafoam and warm the engine up to temp, disconnect the brake vacuum line, and let it slurp up some of the cleaner. You'll get a ton of white smoke, so be careful if the neighbors are out. If too much gets slurped up you can kill the engine. If this happens, go ahead and let it sit for a bit to let the liquid loosen any crud, and restart after a few minutes and slurp in just a bit more and give it a few revs to clear that out.