Over the past week, Nismo3112 and I swapped a VQ35 into my 96. I chose to use a Pathfinder TB with this swap. My car idles at 3,000rpms right now with the 4th gen IACV disconnected. Will reconnecting the 4th gen IACV and installing a block plate over where the PF IACV is restore my normal idle?

 

A block plate will take care of the problem. I tried to install the PF TB without a plate and I had the same problem.

 

It SHOULD, anyway. Lots of people have had the same issue with the DEK throttlebody. Those unblocked passages let far too much air into the manifold.

 

Well a block off plate will work... Instead what I did was pull the IACV and put enough JB Weld around the plunger of the valve and reinsert the valve. This sealed the air passage and took less time than making a plate. No leaks here.

 

ya tht-

you're going to have to block off the air that's going through the PF tb iacv somehow. is there anyway to utilize the PF iacv so you won't have to use your 4g one? i haven't been reading much on this stuff, but i'm using a 5g TB and iacv on my 4g. just wondering if the PF one is different. that would be pimp, and a much cleaner install.

 

I don't think the 4th gen ECU can properly control the PF IACV.

 

It looks just like the 5G TB, but bigger. IACV motor looks the same too.

 

I'm going to give this a try. Do you have your 4th gen IACV installed as well?

 

yep. i installed it on the manifold. So you will have 2 iacv's on your motor and still have a slight cold start problem!

 

Yes!

My idle was 2.5k -> 3K when I still had the pathy IACV still attached at the bottom.

Once I block off that plate, my idle went to 652 instantly. This is with the iACV connected also

 

Please define "slight cold start problem"

 

When it is cold out, you will probably give it gas to help get the motor started. I have to touch the gas for a couple seconds when the engine is cold(like for 6-7hr) is temps below 32 degrees. Right now I do not have to touch the gas at all.

This is going to happen with any setup. I do not recall anyone not having this issue, but if there is, I want to know what they did.

 

I have no such issue. My car starts right up despite outside temps. When mornings were around 34 degrees my car started right up, idled high but started right up without a touch of the gas peddle.

Pathfinder throttle body plus adapters.

 

I also have PF + Stephen Max adaptor. I thought about the problem after I posted the last message and I checked stuff out on my cold engine. I think I know why I'm having the cold start is because the first priming of the fuel pump when I turn the key shoots up to 75psi. I start the car and it stays at 75 then drops to 51. I have to hold the gas during that time.
Possible a crappy FPR has something to do with this???

 

It really also has to do with the location of your IACV. With it externally mounted my car wouldnt even attempt to stay running. It would start and immediatly shut off. Not even a thought of starting. Once I had a TB/IACV block made and installed, cold starts are perfect now. Right up to 2000 then slowly down to normal.

-matt

 

IACV ~1.5ft away from normal location, still starts up fine, idles great. had to adjust the IACV screw to accomidate the new distance, but all is fine.

 

How well do you think this setup would work?

 

that is a mighty long tube. Mine is a little less then half that length and I get no problems from it. I could see problems with such a lengthy tube, but then you might not.

starting the car up, and going for a drive would let you know.

 

That will probably work ok but is hella ugly. The ID is big enough as long as the back of the IACV is going right to the manifold.

-matt

 

thats tilleys setup and he did have cold start problums with it.

my conclusion is what matt said . and with a 3.5 and pathy TB my starts where always perfect like a stock 3.0 even if it was 10 below outside.

BUT when i took my IACV 100% off i get the problums you guys are having . it sounds funny but in order to have any problums i had to take the IACV off.

so what does this say about som e of your setups

 

So what is your setup?

 

Actually I have the IACV installed and tapped into the UIM.
I know it is working because it does not allow the RPMs to dip under idle speed when I let off the gas.

I'm thinking that my AFR is choking the motor with 75 psi fuel on start up could this be it?

My other thought is it could be a base idle problem. Not sure.

 

Filled the IACV passage in the TB w/ JB Weld and all is well...kinda. My idle is a bit low at 650rpm with the IACV screw all the way out. On startup, my ebay FPR spikes to 75psi. While the car is running, the gauge shows 35-44psi...the needle keeps moving. I think the FPR is a POS (you get what you pay for) and I'm replacing it with a Nismo unit next week; hopefully I can get a 900rpm idle and consistent fuel pressure.

 

650rpm idle sounds fine? my idle goes that low sometimes.
900rpm idle i think is too high for a 5spd.

 

Car may stall out with an idle below 900 (remember, it's a cammed motor)

 

It has one crazy lope though at 650...

 

Hehe, just wait till you hear it in person.