Im sorry to create another thread about this, but I figured I could get more help from the knowledgeable people in this section.
My set-up is the vq35 w/ PF TB in my 4th gen. Without the IACV my car always idled decently, steady 650-750. I SSIM'd my intake manifold one time and my idle shot up above 1k and I had to close the throttle via the throttle stop screw to bring it down. I hadnt heard of anyone elses idle shooting up like that but couldnt find an intake leak nonetheless. Using my A32 TPS on the pf tb I have to turn it all the way to the right to get the WOT spec correct (4.1k ohms) however the closed throttle is low, its down to .3Xk ohms. Possibly due to me closing the throttle after the SSIM incident? But why would I have to max out the TPS to get it in spec?

Now here's what the IACV is doing regardless of the screw position which is currently completely tightened clockwise. The idle will drop down to normal after a good 10 seconds of hanging up at 1500+ rpm after I bring the car into neutral and am trying to come to a stop. What I have noticed is that the IACV consistently allows air through at any point in time when I am in gear and the revs are below 2300~. Its as if it is trying to compensate for something but its very frustrating, it creates a sort of cruise control and fights my brakes when I am trying to slow down. I know for a fact this is whats happening as I can see my A/F gauge reading richer than its usual maxed out position when I'm off the throttle and above 2300 rpm.

Another note- I have an auto ecu, but am running the 5 speed tranny.

Hopefully more swappers running IACV's and PF TB's can chime in and tell me if they've had any similar problems.

I appreciate the help...and need it.

Oh and the FSM says to disconnect the TPS and adjust the throttle body screw to get an idle of 650. When I do this my idle goes up to 2000rpm and stays there. I would be completely closing my throttle body valve to get anywhere near 650. Is the plan to bypass the iacv by unplugging the TPS? Im fairly sure thats not what happened.

edit- solution at post #39.

 

Plug up your maf and pump your intake up with compressed air.

 

what are you telling me to do, check for leaks? I dont think thats it though honestly. The IACV engages like clockwork, right at 2300 rpms every single time. Do you have any info on the a32 tps and PF TB set up? Like is the general consensus that it should be easily in spec as it would on a normal throttle body? Maybe my TPS is screwed up....

i'm scrapin' here...for anything that could be wrong.

 

Yes, 1: symptoms match and 2: it started after you removed and installed the upper plenum.

You didn't do anything different with anything else correct? Do you have a mid-pipe and pvc set-up as normal?

The idle will drop down to normal after a good 10 seconds of hanging up at 1500+ rpm after I bring the car into neutral and am trying to come to a stop

Normal with your set-up, 5mt + at ecu, I've always owned stock 5-speeds so that drives me NUTS.

If tps is misadjusted so it say's 0% throttle past when it should the iacv kicks in while on the gas, usually just barely, and shuts itself off, causes an on - off stutter while driving at low throttle.

Its as if it is trying to compensate for something but its very frustrating, it creates a sort of cruise control and fights my brakes when I am trying to slow down.

I've seen that from a corroded terminal on the tps, one reason or another ecu is sensing more throttle than it should, and some times it was possible to dial it to 0% closed but the increased resistance still made it read incorrectly when you would begin to open it. My geuss is that the ecu was sensing that you were on the gas alot yet airflow and rpms were way low from where they should be so it opened the IACV to bring them up.

I would be completely closing my throttle body valve to get anywhere near 650

Page #, that doesn't make sense, I'll go out back and grab my fsm in a min.

Regardless though, the more I think about it, here's my advice vacuum leaks aside. Your tps is reading to much throttle from increased resistance. Considering it's swap if it's not the pins on the tps or harness right there, and you are fairly sure it's not the tps, I'd look closely at all the wiring where it had to be pulled back near the firewall, but only after confirming by seeing what the ecu is seeing.

Tip: Ditch the ohmeter for setting it, and use an obdII under the hood. Use the meter to confirm the power and ground and wires straight from tps to the ecu, it's all there in the fsm if you know how, if not let us know.

 

hey this sounds like my car but it's hard to adjust the tps correctly when my bracket moves but my pftb just came in the mail and the adapter should be here next week and I'll adjust the tps then to get rid of that problem

I'll post next week and let you know if I am having the same problem and if not what I did to make it work correctly

 

With yours it's that tps mount flexing before the actual potentiometer starts moving, so at first it thinks it's at idle until the flex is overcome, rest assured your problem will go away once you get that pftb on for sure. Once you get it all straight don't forget about me

 

t637- PLEASE let me know how your car runs!! your set up sounds similar to mine!!

now on to address all of KRRZ's greatly appreciated help.

 

PCV set up was returned to normal as soon as I got my midpipe to do the IACV as well. But you are correct, the jump at idle was created immediately after my SSIM and IIRC that is the only thing I changed at that point that could cause such a thing. Nobody ever told me if that was normal or not except you but the car seemed to run decently and idle completely fine after I closed the TB. I'm going to see if I cant get all new gaskets for between the manifolds and heads and maybe one of those stethoscopes to listen for a leak....I HATE LEAKS.

Since you mention the A/T ecu causes some of the problems I'm mentioning I'm wondering if its not the cause of all of them...Its worth replacing anyway, so I guess that will rid one of the sources once I find one for cheap.

What do you mean get an OBD-2 for the engine bay? You mean a consult thing like the dealership has?

I did see in the FSM where it says to check the voltages at the ECU. I suppose I will try it out...I do have a vafc2 as well to show the TPS readings though, although I realize that is only based off of the parameters I set for it initially.

 

The few times I've driven with that set-up, after owning cars that came stock 5-speed, it drives me NUTS, so good call.

Any halfway decent obd-II scanner that can show data will show the ecu's actual reading of the tps, on a scale from 0% to 80-90%. I find it much easier to set the tps by plugging my scanner in, run the cable through the window and into the engine bay, and set the tps by dialing it to 0% on the money so it rises as soon as you touch the throttle.

Last time I had this similiar problem from a corroded terminal a vafc read 0-100% like it should, it's all self learning like you mentioned when you initialize it so it won't know if the voltage is incorrect.

I mainly just wanted to make sure you didn't have a massive unmetered air leak at the front valve cover, I pointed that out to someone at the nwp meet this weekend, they had an 00vi with the rear pcv line connected and the front one dangling, I think I got that out of someone in a thread recently also, running no mid-pipe and the pcv incorrectly seems to be common. Also, don't forget that with the midpipe and pcv all in place and functioning things like no oil cap or a leaking plug seal can cause a vacuum leak, that's one of the reasons why I was suggesting pressurising the intake to find leaks (+ soapy water) It's my new favorite method, I've found it pwns the stethescope hose, allthough that has it's uses also.

Yes you may have just done the SSIM, but remember that in order to do that you had to disconnect the tps and also moved around all those wires on the rear........

 

good points. I definitely appreciate the help. I could very well have a leak at the rear VC (leaks a good bit of oil) but I didnt realize that was an actual VACUUM leak. Anyway, i've got some things to take care of obviously.

As far as the ECU goes, should I have a preference as to which one to get? (obviously not the 99 one). I dont know which wires positions they switched around and I'd prefer not having to go switching around anything I've tapped into for my vafc2.

 

I suck, somewhere at my house I have a list of all of the difference's in pin locations according to the fsm's between a '99 and a '97, it's in a box with my auto wire strippers, solder, flux, soldering iron, multimeter, I am lost without that stuff, I'm going to head to the junkyard on friday, I'll see what I can come up with for ecu's since I know there is at least 2 of them there for 5-speeds.

 

i had the same issue when i had my 3.5 swap and pathy tb. It just kept on venting air out of it. Once i got the block off plate and removed the iacv the idle went to dead steady.

I'm thinking of putting it back on but im not to sure if i want to deal with all of that crap again.

 

KRRZ- thanks. let me know. I was thinking about going and trying to get one at the pick-a-part around here and just tell them it was a windsheild washer computer or something to snag it cheap haha. That could be a big problem if the pins are different.

Oh really? Did you by chance do a tranny swap as well? I'm hoping its the a/t ecu causing these problems. My car ran pretty damn good before the IACV as well. The only problems I was having was a jolting at low speeds in gears, like some serious bucking when trying to cruise in a parking lot which I'd have to take it out of gear to prevent. I dont know if its due to the IACV feeding air when it shouldnt but it pretty much eliminated the bucking from what I could tell. Again, this could be due to the fact that its feeding air when it shouldnt. Its also nice to have the a/c and power steering compensation although I never had any problems without it. Maybe some very minor loss of power steering when the idle dipped for a moment. I want to keep the iacv if I can though. I want the car to be tame until I unleash the power.

 

Oh ****, I completely wasn't thinking about the pathy tb...... It has a huge bypass for it's iacv.... oops.

Yeah that definitly won't work with the computer, lol, but as far as switching pins around it's actually kinda fun after you finally figure out how to do it, eng92 and somebody else helped me out big-time with that, I still have the instructions in my e-mail.

 

What do you mean it has a huge bypass for its iacv? I've filled that area where the ecu used to be with jb weld btw.

I dont know why switching pins doesnt sound fun to me....but it doesnt. lollll. I hope there is a way to avoid this, I didnt realize thats what people were doing when they swapped ECU's. I get super paranoid about those little pins and them being so fragile or not making a good connection...thats all it takes is some stupid little frickin electrical problem

 

will do, got the pftb just waiting on the adapter in the mail now

I think they are the same 3.5 swap, converted 3.5tb, 5-speed swap, 5-speed ecu

At 1st I did not have the iacv connected and idle was fine, installed it and my idle was like 2grand, played with the iacv and tb adjustment screw and now everything is fine

when I start the car it sits at 1500rpms for a few sec's then drops to 800

 

well I have the auto ecu and the PF TB soo those sound like the main differences.

 

nah my car has always been a manual. the pathy iacv didnt have any sort of adjustment on it that i noticed. I tried it for a few days and the idle would be set just fine but then it would shoot to 2k or so and then make its way back down. It just made driving in first gear pretty hard. I even followed the steps that someone posted in trying to get it to work but no dice.

t6378tp- what iacv are you using?

kr- do you have pics or something to go with how you set up the pathy iacv on your car? do you plug up the outlet on the iacv with something to keep it from leaking?

 

I always confuse you and goldtooth, who has two cars, so right now I'm very lost on what year your car is, but I got the feeling it was a '99. If you are '99 you should be 'bout it 'bout it when it comes to swapping in a non immobilized ecu, unless you live in a super high crime area, but even still a simple kill switch for a cam or crank sensor hidden nicely pwns all anyways. Pulling pins on a nissan is like losing your virginity, it's a little tricky and you'll have no idea what your doing and have to wiggle it around a bunch at first, but once it comes out you'll be a pro after that, just don't force anything. ok maybe that analogy isn't totally accurate bceause it takes forever at first, but destroying the pins probably won't happen, if you or me gets an ecu for you from a different year and you need to swap pins I can send you a harness connector to practice on along with eng's instructions.

 

I've never been fortunate enough to have cruise control on a fast a32 But there is several ways to do it, the way I would do it is fill it up with jb-weld from the inside so that you can also eliminate those big flow stopper edges.

 

haha nope not goldtooth, CHILLIN014!!! and I have a 95. Remotely mounted IACV just to clarify. Nice analogy haha, I'm sure I can handle it, something to practice on would be sweet if it is necessary. I'm crossing my fingers a 96 one would have identical pin outs or something.

 

at the moment i took the pathy iacv off of the car and my idle is fine. i would like to get this iacv working before really cold weather shows up and makes my cold starts very difficult.

cruise control?

 

PFTB on a 4.5 gen = cruise control.

I tried to get the pathy iacv to work on someones 00vi swap car once as well, based on the 180* switch of the connector + destroying the outer part. It caused nothing but problems, come to think of it iirc he complained of the same thing - intermittent jump to 2k rpm idle. In order for you to get a working iacv I would recommend keeping it plugged with the block off plate like it is (preferably for performance reasons fill the holes flush on the inside) and get an adaptor to run the 4g iacv.

 

yeah i felt like when the car was in 1st gear it would drive up to about 10mph on its own. I am planning to run my 4th gen iacv once i get a chance. its a shame i wasnt able to get the pathy iacv working like i wanted. it would have been such a clean look.

 

4gen

 

yeah thats what mine is doing, its feeding air and the car will accelerate itself. I know its hard on the brakes too, so I take it out of gear when I start to brake and thats when the rpms stick at wherever they were out before I took it out of gear.

 

I have been following the discussion on the IACV problems with the 3.5 engine swaps. This is what I did on my 98 I30/3.5 swap with the A32 IACV..........






You may notice that I blocked off the IACV passage on the PF throttle body. I also grafted the A32 cold idle assembly on the TB so that I could have trouble free start-ups. Cruise control is also functional.

 

hmm its hard to see exactly how the iacv is mounted to the IM. Someone has some welding skills!

I never had cold start issues, so my problems may be different from what some of yall experience. Old, do you have a 5 speed? and was it swapped? what ecu do you have?

 

It's an original 5 speed car with stock ECU. The IACV is mounted on an aluminum plate, then adapted to the intake collector with a brass pipe nipple.

The cold start feature, I could probably done without, like most others have. I figured since I had the idea and skill to make it work, I did.

 

ahhhh okay i see, very nice. How did you manage to thread that nipple into the coupler and the adaptor as well?

Also, your tps was very easy to get into the correct specs I'm assuming? looks like its sitting right in the middle of its adjustment area.

 

As for the IACV mounting, I just kept threading in the nipple & adapter until I achieved the proper orientation. The TPS, well honestly I never even touched it. It is still adjusted like it was on whatever Pathfinder it came from. I thought about messing with it, but it ain't broke, so I left it alone. I did confirm with Consult II the open/close throttle position was correct, but that's it.

 

oh I'm not sure if you understood what I was asking. The adaptor is threaded into the plate and the manifold, but they are so close I dont see how you threaded it into both without turning the plate in circles. Unless you didnt have to thread it into the manifold and you have a nut on the other side of that or something.

I tried using the PF TPS but the values were wayyyy different from what my a32 one read. Not sure the cause of that.

 

omg that setup is sooooooooooooooooooooooooooooooooooooooooo nice

 

Well actually I did have to do that, but it worked out fine. I suppose if you could see it in person, it would be really clear. It's not that complicated. The adapter and the collector are indeed both threaded.

You may have noticed that bolt/bracket under the PCV hose. That was welded in place to maintain the IACV placement.

Yeah, I was bored one day.........

 

ah i gotcha, threaded it before installing the elbow. Looks really good, TIG welder I'm guessing?

 

Alright, I was trying to find an ECU online and checked the sticky in this subforum for the ecu pin outs. Apparently 96-98 are all the same? Its just 95 and 99 that got screwed. It looks like its only a matter of 5 wires at most but its not THAT clear.



Wires 24, 31, and 42 are in the same place on both ECU's (in that rectangular box above the word "maf"). But on the 96+ ecu there is a 43 wire on the bottom and on the '95 there is a 25 on the top....are those the same wire with diff numbers?

And then everything else is the same except the CKPS POS has 2 wire spots in the 95 as opposed to the 96+ which only has one and then a "45" wire in the spot where the 2nd CKPS POS wire was on the 95.

if those two things could be explained, I could jump on some ECU's of those years. Otherwise I'm going to find a hell of a time trying to find a 95 MT ecu.

 

installed the pftb and 4gen iacv and the car runs fine, idle was alittle low around 600-650range at 1st the car did not want to stay running on a cold start without feathering the gas.

so I raise it to around 950 and everything is ok but I am going to play with it alittle more tomorrow and lower it to 800-850

tps it fine and the throttle problem at 2500rpms is gone

 

according to the 96 ECU thing I'm reading...wires 25 and 43 are grounds....and I'm guessing they are the same between the two ECU's even though each wire only shows up on one of those diagrams I posted above.
here's what I'm looking at to make my comparison -http://www.jimwolftechnology.com/wol...ORENGSWAPS.PDF

.I want to buy a 98 ECU I see for sale but the only wire in question right now is 45 which is unidentified in the 96 pinout chart.

 

I thought I'd update this thread for anyone who came across it in the future. I bought a 5 speed ECU and the problem is now gone. No more air flowing through the iacv under 2400 RPM and etc. thanks everyone

 

so which iacv did you end up using?