duowing

Alright in the whole process of trying to get my car's A/F ratio to be normal, get my idle to smooth out, and determine what's causing my car to run lean I've done a few things.

My vacuum was reading lower at idle than normal, so I left the TPS unplugged to richen the mixture at idle, this brought my vacuum to about normal which told me that I was in-fact running lean.

I installed my A/F gauge to try and go from there: First off, when my car is idling should the A/F gauge be bouncing around like the ECU is richening and leaning out the mixture to keep it near Stoich? It does it every so often.

To try and figure out if the cause of my mixture being lean or not was related to a vacuum leak or some sort of internal leaking valve such as the AAC, VCV or such I ran the car under boost a bunch while watching the A/F gauge, and I noticed I'd maybe get to 2-3 bars max into rich, generally 2 which I hear is normal, so that makes me think I don't have a regular vacuum leak which would be causing a boost leak.

After a good drive today I noticed at idle in Drive or at idle in Neutral my vacuum was back to normal, but my idle was sitting higher. Closer to 1000 in D, and around 1200 in Neutral. Although with the AAC not connected to vacuum I've noticed that my idle was generally higher, but why it's sitting a bit higher than before I don't know. I checked the TPS thinking maybe it's being on but when I unplugged it the idle speed increased more, and the engine started bogging and misfiring a bit like it was running too rich. My thoughts right now are I need to get the AAC, EGR, VCV plugged, check the air regulator, and clean all my connections in hope that I can figure this all out.

NismoPick

If you're worried about a/f ratio at idle... gotta go wide band. Narrow band is only good for boost / full throttle.

duowing

I'm not so worried about the ratio at idle, as trying to figure out why it acts up, it seems like in general the car is running lean which is the source of my crappy idle, but I wanted to see what the ratio was under boost/fuel throttle to try and determine if what's causing me to run lean was a normal leak. As people have said a vacuum leak and lean condition becomes a boost leak and extra rich condition under boost. So since my car seems to drive fine under boost and not read any more rich than what I've heard is normal it seems like something else is causing it, but then again we here on Zdriver have managed to pull the running lean in boost quite a few times.

snwbrderphat540

if the idle was faster thats why the vac was reading more normal because the vac pump was working harder, u just got a leak some where.

NismoPick

I think he took off the AAC valve, so no vacuum idle assist... Speaking of which, Duowing, have you tried putting the AAC back on?

duowing

Actually I have the AAC on, as my sheet metal block-off plate wasn't working. When I don't have it connected to vacuum my idle will sit higher, but if I plug a vacuum line directly to it my idle sits alot lower. My vacuum readings would also even out. I've left it disconnected from vacuum, and just plugged up everything. Like I said I've sprayed brakleen everywhere many many times and haven't found any change in engine speed, sound, or anything.

snwbrderphat540

lemme ask you this.... where is your boost/vac guage hooked up? can i get a pic?

duowing

I've got it teed into the line that goes to the Fuel Pressure Regulator.

I also have the factory boost gauge hooked up as well.



One thought came to mind as I was out there looking at my car, there's a metal line that runs off the manifold, I never knew where it went to, so I was looking at it and it looks like it supplies vacuum for the transmission, I wonder if the metal line goes down and hooks to a rubber line onto the transmission or not. I need to get under the car and take a look at that.

snwbrderphat540

hmmm... k, thats not the prob then. cause i accidently ran another line off the same line as my vac/boost guage and caused me to get teh EXACT same reading you were getting. right around 11-12 inHG

duowing

I checked the line to my factory boost gauge, and that looked like it was leaking...again, so I fixed that and that seemed to bring my idle back down a little, and help to bring my vacuum a bit closer to normal. I really need to go buy a new hose for that factory boost gauge line. I just keep cutting and reusing the same 25 year old piece of factory vacuum hose.

duowing

Nismo, when you installed your Z31 ECU did you have to adjust your idle at all? I've heard that once you remove the VCM and crap that you'll need to adjust your idle via the idle stop screw on the throttle body.

NismoPick

Nope. When starting cold, my Z idles @ about 1100rpm. After about 30-45 sec it drops to about 800rpm (I assume that's when the air regulator opens/closes).

The only time you'd need to adjust the stop screw is if the car will die when you let off the throttle.


EDIT... I just noticed you have no clamps on the air regulator hoses. Are they on there now?

duowing

no, that pic is from yesterday. I was trying to get the VCV out to plug it off one day, and I was in a hurry and just put everything back on like that without clamps. I didn't notice any difference without the clamps so I just kind of left it like that. I figured once I finally got rid of the AAC, VCV, etc then I'd clamp everything down.

Also look at how beautiful that red over spray on the intake is, courtesy of the previous owner.

duowing

Ok quick question about the AAC, basically how does it work exactly? When it's open would the idle speed increase or decrease? I'd think it would increase, similar to the air regulator, but I'm not sure.

Also as far as the air regulator goes, does the heater wiring for the air regulator only heat the regulator while the car is running, or should it start heating the air regulator once the key is turned to the on position?

NismoPick

When the AAC is open the idle should go up. It's allowing more air into the intake (just like a disconnected vac line would increase idle).

About the air reg... It's prolly only when the engine is on that the air reg is being warmed. Tho it seems to me that the air reg temp is also affected by engine coolant (from the thermostat to tb passage)??? I'll have to check on that.

duowing

One more question, since the ECU switches to batch fire mode once the head reaches 140*F. Well it would get that signal from the CHTS, and I'd assume the coolant would take longer to warm up anyway. So head temperature would go up a good bit quicker than the Water Temp Sensor, right? I'm wondering how long it would take the head to warm up to 140. Because my hesitation issue doesn't happen right from cold start, the car is actually fine right from the start, and then it takes maybe about a minute or two and generally it's more noticeable when I come to a stop, you really won't have a problem if you're already moving, then I'll get hesitation, and it's only generally another minute or less before the O2 sensor comes on and everything runs fine.

So with the car's lean condition the mixture would burn a bit hotter, maybe it's warming the head up so that it reaches batch fire, so I'm running less fuel because it's detecting that the head is warmer, so it runs lean and hesitates bad until the O2 comes on and can fix the mixture. It seems to me the car only runs odd when the O2 sensor generally isn't doing anything, when cold, at idle, and after it's been turned off, then you go into the store or whatever and come out, maybe the O2 has cooled down enough. Because my idle will be bouncy, but the second the O2 seems to warm back up my car goes back to running good again.


Ok final edit: I went back out and checked the wiring one more time, I stabbed the positive cable for the voltmeter right into the pin 16 wire right as it comes out of the ECU, and then put the other wire from the voltmeter to a ground. It's reading 1 volt, up at the connector to the air regulator I'm getting nothing, so it looks like I need to recheck my wiring from my pin 16 wire to the black Air Regulator wire. This could definitely be part of my cold problem, the air regulator may be staying open far longer than it should, in which case it's not closing until the coolant starts flowing through it.

duowing

Alright, I know I'm bringing this back, hopefully for the last time.

I went up to Home Depot and got a 1/4" ball valve and removed the hoses from the air regulator and put that in line of the air regulator and left the valve closed. This seems to have for the most part taken care of my real lean hesitation issue when the car is cold, as my vacuum no longer drastically drops. Probably due to the air regulator taking alot longer to close than it should.

Once I got to work I checked the air regulator as soon as I shut off the car. It was closed, but the thing isn't sealed as I was able to blow air through it. So as far as I can tell one of the biggest causes of my problems was all due to a faulty air regulator that was supposed to be "new" and good. Also I finally got some good steel block-off plates, so I'll block off the AAC and EGR.

Now the only other real problem that seems to arise from this is the fact that my car has a little bit of bogging vs. lean hesitation due to running more rich, since I don't have the Air Regulator, although this is a lot more tolerable, but if anyone happens to have a good working air regulator let me know.