In preparation for my upcoming emissions test, I thought I'd take a stab at trying to lower my idle rpm today. The lower to oem spec idle the lower my emissions should be, right? Normally, it sits around the 950 mark. Adjusting the AAC did nothing to those ends as I have the idle adjust needle screwed in almost all the way. I also checked the hard idle switch on the TPS via the continuity test and found the hard idle switch wasn't engaged. I checked the voltage of the TPS and found I was sitting at 0.47V. Years ago, because of the poorly aligned butterfly shaft of the Z1 58mm throttle body, I had to file out the mounting tabs of the TPS so as to elongate them so that I could rotate the TPS enough. I wasn't happy with that 0.47V setting so I also decided to elongate the mounting tabes even further today. In doing so, I was able to rotate the TPS enough to reach 0.43V. Additionally, that extra amount of rotation also produced the continuity necessary to engage the hard idle switch as well. You would think that after doing those TPS adjustments, it would bring my idle down a bit. But no such luck. Even going back to the AAC and trying to adjust it, made no difference at all. What I have noticed is that if I leave the AAC unplugged, it lowers the idle by about 100rpm to approx 850rpm. Is it safe to drive with the AAC unplugged and will having it unplugged for emissions testing worsen my chances? I have made 2 videos using ECUTalk. One with the AAC unplugged and one with it plugged in. First off, I noticed a big % difference in the 2 AAC readings. What's got me a bit concerned is that the timing stays solid at 18* BTDC. AAC Unplugged http://www.youtube.com/watch?v=2LywMpyqxbs [YT]2LywMpyqxbs[/YT] AAC Plugged in http://www.youtube.com/watch?v=I9HgxVnv2Gk [YT]I9HgxVnv2Gk[/YT]
You have an air leak. When you fully screw the idle adjuster in. In theory there should be NO air getting into the cylinder to allow it to idle. If you did that and it still runs. There is air getting in somewhere else that is providing the air to idle. Need to find that. leaky AAC valve, orings on the balance tube. paper seal on the AAC, throttle bodies adjusted wrong. hose leak on one going to the plenum. Upper plenum gasket. Anything after the throttle bodies that can leak air basically.
Cold start assemblies are starting to get dirty & jam on these engines now, the valve stops rotating back to fully closed & hangs open a little, this prevents the ECU from being able to control the idle correctly & creates a fast(er) idle. This is the one located at the back of the engine after the idle control unit and before the balance tube if your following the idle air circuit. It actually feeds air directly from the idle air intake tube (LH turbo boost outlet tube) to the manifold if it's open. Other thing to look at is the adjustment of the butterfly stops on the throttles and make sure they are set correctly, with the larger throttles it makes a BIG difference if they are not set correctly. There is a special varnish type stuff you can buy to coat the area around the butterfly to help it seal, starting to get pretty techo doing that but you will notice the factory applies this to the OEM throttles.
Try cleaning your throttle body's. There should be a tech section post on it. Also is that the T.P.S showing 0.40 volts ?. Cheers Dave
I have seen first hand what Mungyz has posted and recommend checking this, my other suggestion is make sure someone has not tried to set the idle with the throttle cable or the throttle stop screws, ie make sure the throttle bodies are closing completely.
not that this is of much help but all the extra mods you have aren't making it easy to resolve the issue. its hard enough fixing these beasts at the best of times when standard... and as you know even with a load of information at your disposal it's still a nightmare sometimes.. so, like the guys have said... read though your info and do the basics again. it might be something simple.... temp sender... air leak... idle valve dirty... etc... best of luck..
Sorry I didn't respond earlier guys. I didn't get any email notices to my thread. The AAC, FICD and air regulator were all overhauled, cleaned, tested etc and found to be well within oem specs. No tears to the paper gasket for the AAC either. Pretty sure there's no air leaks around the plenum. Replaced balance tube o-rings a few years ago with vitton(sp) types. I did a complete throttle body sync a few years ago and actually did a write-up on it. The throttle bodies are very clean inside. The throttle body butterfly shaft arms are correctly set to their respective stoppers. My base timing was incorrect at 18* BTDC and I corrected that yesterday with a timing light by rotating the CAS clockwise to retard 3* back to the oem 15* BTDC. This still didn't help matters much. I thought perhaps that my coolant temp was preventing the idle from dropping lower as it normally sits at 162*F during normal summer ambiant temperatures. I brought the engine temp up to 162*F and then turned the air conditioning and the temps gradually went up to 184*F. Still not much of a change in idle speed. A year ago I substitued my throttle shaft for a chromed one. I assumed that they are all machined/made exactly the same but perhaps this isn't the case? Today I re-examined the throttle cable tension and it seems fine but I loosened it a tad anyway. I inspected the throttle cable shaft and noticed there was a bit of tension on the throttle body arm. I loosened it off and adjusted for a 0.2mm space between shaft and throttle body arm. I then proceeded to the other side and noticed a different type of adjuster. This puzzled me. Do all throttle shafts have this same mis-matched set-up? Then I looked on the other side of that throttle body and saw this. It looks like the head on that shaft adjuster bolt is too thick and is hanging up the throttle body and preventing it from closing all the way. I only have to apply slight finger pressure and the throttle body arm will rest against it's stopper. Now I have to figure a way to correct this. Any suggestions?
I didn't even notice that. I'll recheck again. Yesterday I sent it with my multimeter to 0.43V yet ECUTalk shows 0.40V. I know I get a 0.3V variation in battery voltage between my ECUTalk and my Apexi NEO with the NEO reading lower.
My throttle has similar setups to yours however I believe the nut in the second linkage is an extra. I still think from your comments that it may not be closing completely but you would need to pull off the hoses at the TB to check. the 2 different setups on the TBs are to allow for setting the tb's to close completely at the same time the 3rd one is the actual throttle stop to stop the shaft completely.
Set the T.P.S using e.c.u talk as that is the voltage the e.c.u is using to do it's calculations. Cheers dave
Thanks Stu. I think that unknown air source is leaking past the throttle body butterfly. I'm going to remove both throttle bodies this weekend, clean and reset them them again and then sync them to each other. Thanks Dave. I'll set the TPS based on ECUTalk this time around. Might be a dumb question here, but is the free PPC/PDA Ecutalk program the same as the ECUtalk used on laptops? I've been using only the PPC/PDA program so far.
the base idle timing should show the same with a timing light as on Conzult or ECUTalk.. etc.. (when up to temp) you might need to check it again later and re-adjust. you need to re-calibrate the TB linkage, it's easy... this guide shows how to do the correct adjustment.. http://www.300zx.co.uk/forums/showthread.php?151304-Throttle-balance-tech&highlight=throttle
