I just finished my swap, and have one issue that I am working on. When first starting the car up cold, idle is horrible. For the first minute or two, I cannot give the car any throttle, or it comes close to dying, and I get a misfire code, P0300. One the car warms up a bit, idle and throttle response is fine, and no codes. My setup:

1998 Max
2002 VQ35 60k miles- 3.0 timing, 3.0 upper/lower oil pans
Revup cams w/stephanmax spacers
Full emissions equipment, upper IM tapped for EGR
IACV mounted behind the upper IM, feeding into the IM along with the PCV valve
NGK copper plugs
Pathfinder TB and adapter
Z32 MAF

Troubleshooting done: I had a vacuum line not hooked up at first, tracked that down and that fixed several codes I got at first.
Replaced all the spark plugs (again) and made sure the gap was at .042
Checked all the coils with an OHM test. All passed, but one was inconsistent with the readings, so I replaced it.
Pressure tested the intake piping/tract. Found a leak at the throttle body connection, resealed and tested good.
Fuel injectors were cleaned/tested before they were installed. I did an audio test while running and all are clicking fine, indicating that they are firing.

Thoughts? I kept all my emissions and hooked up the IACV hoping to avoid the codes and starting issues that many people have had, but here I am in the same boat with the cold start. It gets down into the 20's and 30's in the winter here, so I would like to get this solved asap. I also have an emissions test due, and we cannot have any codes in WA to pass (all they do is an OBDII scan).

On initial startup, I am at 16-17 on my Air/fuel ratio. I can't remember if I ran that lean before the swap or not on startup. My fuel pressure is currently reading 36psi, perhaps I need to go a little higher? Once it warms up, I am back to 14.7-15.X

Other thought is the Z32 MAF. I have an emanage ultimate that is wired up, however I currently have it disconnected for initial startup and troubleshooting. It is tuned for my S/C setup, and my laptop broke, so I won't be hooking it back up until the laptop is fixed. Perhaps the MAF is causing issues though, with the smaller fuel injectors, since there is no problem with 370cc injectors and the Z32 Maf on a stock ECU.

My only other thought is with the IACV. I plumbed it into the Upper IM along with the PCV valve. My other rear connection is going to the brake booster, I wanted to keep that seperate from anything else.

Any ideas welcomed. Thanks in adance.

 

I bet its the z32 MAF. You're most likely getting a random misfire due to running lean. IIRC when you start a cold motor, the ECM runs Open Loop until it warms up and then it adjusts fuel according to the O2 sensors. So if you're running a z32 MAF and the ECM is running a predetermined map for the injectors based on an a32 MAF, chances are you're going to run lean until the ECM enters Closed Loop and adjusts the injector pulse width based on the O2 sensors.

 

your AFR is not the problem, that I can say for certain. I idle at higher AFR than that on purpose. 16-17 AFR is what I use for constant throttle cruising.

it's not apples to apples because I run no emissions equipment and thus don't have to worry about a switch from open loop to closed loop, but I run the same MAF and made the same injector change as you this past weekend (from 370cc side feeds which actually flow more like 410cc, to stock VQ35 top feeds) and all I had to do was introduce more fuel (I did it the ghetto way for now since my laptop is also dead, i used the emanage ***** and increased fuel pressure.)

how long is the vacuum line you used to remote mount your IACV?

 

It had to be pretty long to reach, I'd say 2 feet from the intake pipe port to the IACV, then from the IACV to the Upper IM is approx 6-8".

I don't have a current picture, but mine is setup like Dubbya's was:

 

I got my interior all cleaned up and took it for a test drive tonight:

Startup was the same, real rough idle, sounded like it was going to die a couple times. I left the throttle pedal alone for a couple minutes until the temps started to come up.

Took it around the block a couple times. It's running pretty lean under a light load, 17-18 afr, I even saw 20 a couple times. I have a couple of moderate hills in my neighborhood, and AFR went more lean going up the hill, and I felt it stumble a few times.

Coming off throttle, AFR will go rich, 12-13.5 AFR, then steady out around 15.

I'm thinking of changing out my MAF first. If that does not work, I'll play with my fuel pressure some.

Neal, you said you had to go more rich with the stock injectors vs. your 400's, any reason why?

 

I didn't have to make my AFRs richer numerically, but switching from 400s to 270s without changing the tune at all meant that with the new injectors my old tune had the car running too lean to drive because they flow almost 1/3 less fuel. my target AFRs are the same.

 

I don't have a 3.5 yet but I had a very similar problem when I did my 00VI swap. The line going to the IACV was not big enough and it was not getting enough air. So I drilled out the fitting on the manifold and hooked up to that and I have not had any more problems. AJcool was also having a problem with this and I showed him what I had done and it fixed his problem as well. I would make sure you are getting enough air to the IACV before you go any further. Good Luck!

 

Hmm, I'm not sure how to get more air to the IACV. I used a 3/4" hose from the intake pipe to the IACV, which fit perfectly. If I used any larger, it was going to be a 1" hose, which was way too big for the inlet fitting on the IACV. From the IACV adapter to the IM, I have a 3/8 hose.

I am going to make a jumper harness to swap my MAF out, that way I don't have to rewire anything if that is not the problem. Then I'm going to play around with my fuel pressure, easy enough, since I have an AFPR.

If neither of those work, I'll try to figure out something else to do for the IACV. I think the issue is something else though, since I was having some driveability issues, when the IACV shouldn't come into play.


Thanks for the tip!

 

here you go, this is my thread that I talked about this problem.
http://forums.maxima.org/all-motor/3...e-problem.html

I was running the same size set up from the IACV to the manifold and I was having similar problems. I would try a bigger fitting and bigger hose. Goodluck with this and I hope it helps.

 

It was the MAF. Well, nothing is wrong with the MAF, but my car is not liking the Z32 MAF with stock injectors and no EU.

I made a jumper harness and put the stock MAF back in. Car starts and idles normally now. Took it for a test drive, good AFR, no hesitation. I'll do some tuning once I get my laptop fixed. For now I still have 495 miles left to break in my new clutch.

Thanks for the tips/assistance. Helps to bounce ideas sometimes.

 

Just passed WA State emissions. It's just an OBDII test, but still...

 

NICE!