Here's a little background...

Tilley installed a full DE-K in my car over two years ago, and until recently I was pretty satisfied with the job he did. Prior to installing the PFTB the car put down 205/200, and I figured everything was dandy. However, after installing a Walbro FP and Nismo AFPR and FP gauge with the PF TB, things started to go downhill.

I now have the common idle/starting problems associated with the PF TB, but I also have a problem that I have not yet seen discussed. When the car is warmed up and idling, the AFR will stay around 14.7 for 30 seconds or so. Sooner or later the car will idle rough and the AFR will shoot up to 20 until I tap the gas. This has led me to have to continually keep my foot on the gas whenever I'm in neutral, which is not fun. This does keep the AFR from going crazy at least. I can't remember if this problem started happening only after the PF TB, or if it started after the Walbro/AFPR/gauge install.

Moving on....

I was recently referred to a new mechanic by a fellow org member, and so far I've been really impressed with his knowledge and ability to diagnose problems. Apparently Tilley didn't do the best job routing my vacuum hoses, and my mechanic had a few questions for you guys who are more familiar with the DE-K.

1. How do you reset the air bleed screw (the screw everybody uses to raise the idle)? According to his service manual computer thing, that screw is set at the factory and is never to be adjusted. Over the years, mine has been adjusted so many times to try and compensate for the PF TB problems, it's probably nowhere near correct spec. Is there a reset procedure for the screw, or do I need to buy a new unit?
Also, here's a pic of the Tilley-modified IACV:



2. When not connected, is the swirl valve open or closed? Where does the vacuum source for the swirl valve come from?



3. For the intake runner control, is there supposed to be vacuum at all times? Is it a reverse vacuum? Where does the vacuum source for the intake runner control box come from?




4. Should I make a tee in the large vacuum line and connect it to the (can't think of the name right now)?



5. Also, in another thread, someone mentioned that installing a DE-K IACV on this swap will correct the problems associated with the PF TB. I'm not sure how, but that's what I was told. According to my mechanic, the DE-K IACV doesn't have any provisions for the power steering and AC sensors. How in the world would that be installed in a 4th gen?


Basically, the mechanic is wondering if my VI is either stuck open or closed because the (IIRC) the swirl valve isn't getting any vacuum. I have Harlan RPM switch, but apparently something isn't right here.


Basically, I'm in overload at the moment, and probably got a few terms confused. I know this is a super long post, but hopefully the answer will be a little simpler than all the stuff I just posted.

Thoughts on this messy setup?

 

Ok, well lets see if this helps:

Pic 3, left nipple on VIAS. That is a breather.

Pic 4, I would recommend a breather filter. Or install a fitting in the mid pipe for a hose. I wouldn't T it, may be flaky.

Pic 1, Swirl valves are closed unless vacuum, IIRC.

IACV in 4th gen:
http://forums.maxima.org/showpost.ph...7&postcount=15
http://forums.maxima.org/showpost.ph...4&postcount=16

Also, even if the VI is closed, the swirl wouldnt get vacuum, its got another air passage above the VI. If you want, try removing the power rod, but it should not have any effect.

Hope that helps!

 

Why do you think a T would be flaky?

I removed the butterfly (power rod?) and dynoed. I gained 1 HP and lost 8 TQ. Unless we're talking about two different things.

 

Well, if the other end of that hose(IACV I assume?) and the breather need more air that the hose can hold...but I have no idea if it would or not. T would most likely work.

Power rod is the thing that the VIAS turns.

 

Can anybody shed some light on what could be causing my AFR to go crazy after the car idles for a while, then returns to normal when I blip the throttle?

 

BTW, I forgot to mention that my car stalls if I'm at idle and I turn the steering wheel all the way to one side. I think this started happening after the PF TB install.

 

Mine did this furing the 00vi swap. Turns out I had a large, unseen and unheard vacuum leak on the manifold. Same sypmtoms including dying at idle.

GL man.

 

Interesting. My mechanic pointed out what could be a potential vacuum leak on the modded IACV unit. Where was your leak? How did you find it?

 

It was on the back of the manifold between the 4th and 5th ports from the left. I took it to a mechanic and they used a smoke machine to test for vac leaks through the brake booster line. Cost me $40 and it showed me any possible leaks in the system, how big they are, etc.

 

What guys do for the power steering and a/c connectors when using the 5th gen iacv is unscrew them from the 4th gen unit and just leave them plugged in and dangling, obviously it doesn't raise the air volume during useage of those, but it gets rid of the codes.

You should just fill the swirlvalves imho.

Regarding the air-bleed screw. If you mean the one for the throttle stop, located on all VQ TB's (minus dbw obviously).............. I keep telling people not to EVER touch that, but it's usually AFTER they have touched it. However, if you mean the black plastic screw on the IACV, that CAN be adjusted, BUT you DO NOT want to adjust it without following the steps in the FSM to do so. It tells you you verify several things are in order beforehand, than it has a fairly lengthy checklist of conditions that must be met/followed before setting the idle.

 

So why do people install it? Does it solve the cold start problems?

Got any more info on why/benefits?

Yeah, mine has been touched many times already I'm hoping that when I reset it and properly adjust it it will help some of my idle problems.

 

I prefer not to comment, no first-hand experience. Ask me next weekend, or wednsday if I can get ahold of a PF TB for my 4.5 gen before then.

They are an amazingly large restrictions. I'd love to see a before/after dyno, It would show significant gains without a doubt, it sure does on the butt dyno. When they are opend they don't go full 90*, so the butterfly's themselves add even more of a restriction than just there width, then there is the rods themselves, which are pretty damn big.

Sounds like a personal problem


I could have sworn there was a spec somewhere, but I know I am wrong, but if you had access to a different TB you could measure that one with a feeler gauge and compare to yours. I'd offer to measure one for comparison, but it's a finicky process that would give some innacuracies if two different people did it.

 

Apparently he did a fine job routing the vacuum hoses if the car was fine and dandy for the 2yrs before your recent installation.

I've highlighted the something that isn't right there

 

You're right, I misspoke. Tilley, for the most part, did an excellent job on my car. There are just a few small details that weren't done quite so well.

Again, my memory failed me. I originally had a Harlan, but replaced it with a Summit RPM switch, which is still in the car now.

 

Gotta cut corners when i did a DE-K swap in 10 hrs. pull motor,swap acc to new motor and reinstall and get running.

 

I would think that if you A/F is getting too lean, then it seem that you would obviously have a vacuum leak somewhere...

 

Grab a can of brake clean and start dousing possible vacuum leaks, if you hear any fluctuation in rpm then thats where it is. Id specifically focus on the IACV/TB area, considering that the problem arouse after the PF TB. Perhaps the TB gasket is not doing its job, or the IACV adapter plate is starting to leak.

It does sound like a vacuum leak though.

 

isnt lean at idle normal? My a/f ratio used to always be off the gauge (lean) until I reinstalled my IACV and now it idles around 15. Never had a problem with cold starts until I swapped for a 5 speed ECU.