dshepp806

My '89 has always idled under the spec'd 880 RPMs, and has never had ANY hunting issues on cold starts,..idle has always been rock solid (well, that is, except for the NORMAL movement +/- that we see,..far be THAT from a bad HUNT)....So why not frick with something that isn't causing any issues, right?

I attempted the base idle ajustment today to see if would achieve what the books call for. I did not (at any time) adjust the "mixture setting" screw...only the base idle adjust). I hated to even touch anything without a wideband sensor around but hard-headed-ness-and boredom prevailed....I had been told (ALREADY), to check the mixture FIRST, THEN go through this adjustment....oh well. I figured I'd give it a go.

The ICV was removed and cleaned first (I always keep this thing cleaned frequently),..hose connections are good and tight....also checked (continuity-wise) the idle control switch,..found to be dead on: that is, the audible click was certainly coincident with the meter. Cleaned/lubed the AFM vane door(found to be very clean in there),..vane sweep resistances are nice and smooth.....cleaned/lubed the throttle arm assembly,..everything moving nicely!

(((((WOT switch data to be discussed later)))))=I've some questions there.

With jumper in place (to "center" the ICV), I made my adjustments while watching the meter attached to coil primary to render the measured RPMs...(my console gauge is pretty close to the meter readings, BTW).

Long story longer,.....I found that, if I adjusted this to ~880 RPMs,..then removed the jumper: the idle would be too low, sometimes dropping below 800 RPMs...I adjusted the jumpered RPMs upward (on several iterations), watching to see where idle would land.

I found that I had to set the jumpered idle RPM setting to about 930 RPMs to achieve a base idle (jumper removed) of ~880 RPMs...[[[curious about that,...as I think I've read where this is quite normal but will await incoming responses]]]...

As I was sweeping through the area where she was orginally setup, I started hearing a bit off hissing around a specific rotation (position) of the idle RPM adjust (and coming from that location, seemingly)...This can't be right, eh? Anybody seen this piece go south? I noticed that once I had it in a hissing position, I could rock the adjustment around and extinguish the hiss......again, this is a very small "hiss" window relative to the many turns available.....that don't "hiss"!!!!!!

Bottom line : she's set around 890 RPMs now (AC off), =/- 20 RPMS,..and it seems a bit temp dependent.....I'm quite curious to go through this again AFTER having the mixture checked....for now, she no longer idles at 810 RPMs.

I attempted this adjustment last week (actually) and found the morning"s crank up to have a bit of bouncing before she'd level out to a steady state idle RPM...I had this adjustment to where it would only bounce 1-2 times then achieve a cold idle steadiness each morning,..when warm she's steady..I'll check her tomorrow AM and see how she's doing on the NOW cool AM cranks.

Time to get a wideband sensor...sorry for the ramble....... BEST!

Doyle

dshepp806

As to the WOT switch findings.....

I conducted a continuity check on the WOT switch, manually actuating the throttle arm while watching the meter. I found that the switch is actuating a bit BEFORE the full physical travel of the throttle. This correlated with the actual gas pedal movement...I watched that WOT switch give me continuity BEFORE I had the pedal all the way down...(mmm?). I didn't touch that adjustment, for now.

Guess this means that the wide open throttle maps are being used before I'm fully down on the pedal?

Best!

Doyle

whalebird

Doyle
I think you've mastered the base idle adjustment. It's really easy. I do think you may find that sdjusting the bypass screw on the AFM may help the idle a bit. That may be why you're looking for a wideband. This AFM adj. only affects idle mixture and you may be surprised how close you can get simply by listening, or hook a vacuum gauge south of the throttle and adjust to max vacuum. IIRC, the o2 should be unplugged for this. Also, I recall that you most likely have an aftermarket chip...this may be related.
My first thoughts, we'll see what others chime in with.
Hope all is well...candidly looking toward Atlanta for the Porsche gathering thinggy posted in the other thread(most 911s in one place). We'll see

rusnak

Iirc, idle is not adjustable, per se. You're either w/in or out of spec, which is programmed in the chio.

The fact that the icv drops the rpm makes me think that something is off a small amount. Maybe your baseline might be rich, and the icv is off center to achieve 890 rpm?

dshepp806

idle, per se, is not adjustable, but I'm told the base idle can be set (I assume this to be a physical position of the ICV start point,..moreso?)

Your point makes sense, for sure,...need something to quantify it WITH!

Still curious as to the hiss sound?

Bird,..I'll certainly look into that event!!!!!!!! Hope everyone is well!

BEST (and thanks!)

Doyle

dshepp806

Thanks for your post Bird. I have thought about the chip and it just bothers me more until I find out how it's mapped. Again, it came WITH the car,..and I've often wanted to get it sent to Steve to read it out (if possible.....he may already know the maps once I get the part # to him....we'll see on that point). I would hope that none of these chip guys would muck with the idle RPMs or mix but then again: I wouldn't know without asking/mentioning.

Again, she's always been VERY predictable on cold cranks(5years) ,.and liked to (once) idle around 820'sh very solidly. I just want her at the 880 world for spec...

today's AM crank demonstrated 2 bounces of the RPM needle then stability at 1100-1200 rpms,..she then slowly came down as I drove off. A couple of trips today showed an idle around 880 RPMs,..with a different look showing ~840 RPMs......a bit of variance,...no funny "smells" whatsoever,..AGAIN: NO TOUCHO' OF MIX SCREW!!!!! I had hoped to check things again today but time doesn't allow (at least for today).....Still looking around at which hardware test piece is the best to use in this case. I've "NO WHERE" the experience as you with motors to be able to "listen" and turn that screww by listening......(pretty impressive,....) Audibly-speaking, could you describe a desirable sound (and from what) when one turns a mixture screw without instrumentation...when I think of the iterations I did yesterday, I can't help but determine the following can be done......SHOULD there be NO CHANGE when attaching or removing the jumper,..and one should be experiencing this, I assume, once the 880 RPMs is set. On the other hand, one could continue to jumper-adjust-remove over again and again,..and you'll find the setting of the idle RPM adjuster where the jumper removal doesn't change,..THEN read the RPMs. This sounds a bit more "diagnostic" than calibration and would probably speak to something that's slightly amiss,..not sure...just saying.

As to JUMPING on cold crank,..what, exactly, would be the component causing this jumping (bouncing)?



My plans are to get a fresh O2 sensor, as I think this one has over 60K on it (I'll have to check my records)....go ahead and get this piece changed out (preventatively) as a "consumable" (I know, I've NO indications that it's bad,..so, WTF, Why Not?...I would assume these are not like fine French wine over time).....Get my hands on the instrumentation so that I can measure the precat parameters, ensuring the idle mix is good-2-go. THEN attempt setting of the idle RPMs....seems right?

Thanks for everyone's inputs.

Doyle

dshepp806

Thanks Rusnak. I know I need to get a baseline idle mix read, for sure.

To rephrase: Would a baseline idle being rich (or lean for that matter) "require" the ICV to be "off-center" (results of the baseline RPM idle adjustment setting) ??????

Best to you,

Doyle

whalebird

For just listening, you should simply listen to the rpms. If you screw the afm bypass in you go rich: you will reach an abrupt drop in rpm. That would be your rich margin. Then screw out on the bypass and you will find a stabilized area that will end in the slightest, very subtle, rise in rpm...maybe around(or less than)100rpm. This is known as a "lean-rise" and will be your lean stop. A turn and a half back toward rich from this point may get you in the ball park. This is not clinical, nor factory procedure and may be refutable by some. I only offer it as a diagnostic aid, but you will not screw anything up by this. The bypass screw may have a plug covering its head(5mm allen)sometimes blue plastic, other times an aluminum plug. I suspect there may be a tutorial somewhere on the interwebs for this and I would certainly get a second opinion. Then again, this may be where your car likes to run.
While your at it, you may want to ohm the AFM just to secure it's basic function. I have found that the temp sensor inside the afm can crap out while the air "flow" part is fine. I don't know what the ohm data should be, but it only takes a minute. Again, this data should be easy to find.
If everything checks out and you've done all of your test/adjustments that you can do and you are still annoyed by this. You should locate a factory manual and go thru the DME test plan. It checks everything(most everything at least) at the DME plug where the computer views it. This can be a lengthy process if you care to nail it down. It could be something silly like your altitude sensor, or a faulty diode for the upshift indicator, but probably not. I would say you're very close with what you have and would know if you had a BIG problem. Check it all out though.

dshepp806

Very nice , Bird. I've a better sense of "it" now,..so, thanks!

As far as ICV testing (resistance), I get the expected 40 ohms on the outer terminals and 20 ohms from center terminal to each outer terminal....

As to the AFM, I can tell you that I opened this piece many years ago,..to do some resistance checks and get a visual on the conductive trace "relation".......I ended up touching NOTHING......I know better than to fuch with the spring tension (why would I?),..and studied the resistive connection to the trace,..being an electronics "kinda=guy", quite easy to check.....nothing "complex" here......I simply cleaned the trace areas with some fine Caig products,..and provided a nice burnish to the connector piece...didn't see any "wear" areas,..she sure cleaned up nicely..........simply put her back together and haven't looked back...SO: the AFM is cleaned and (still) unadulterated.....

I've run the AFM vane through several tests for smooth resistance measurements,..I even broke out my frikin analog TUBE Voltmeter, as well as looking at it (the full sweep) on the frikin' o-scope......VERY SMOOTH.....no issues there, insofar as contact arm and resistance sweeps......good on......AGAIN: these are resistance measurements, NOT voltage conditions....(sometimes there can be a difference on the circuits, when LOADED.......)....

As far as the Intake Air Temp (IAT) sensor measurements,..I've only read the resistance while in the spec'd 60 degree F to 85 degree F spec: 1.4 - 3.6 Kohms...mine clocked in at 2.8 Kohms.....(which, I guess, is OK?) I may consider dismounting and inspecting,...maybe they can gather "dust"? In need of cleaning? I'll, at least, LOOK! I certainly can't get 32 degrees these days and 105 degrees is "fading" to the back, as well....

dshepp806

On to Wide Open Throttle,....(WOT)

I've notive a few reads that refer to this switch setting,.......

I've noticed some very respected threads on the web regarding this adjustment.....even Wong's site refers to "seeing" this switch SWITCH at 3/4 of the "THROTTLE BUTTERFLY POSITION"......mmm...what does this buterfly relate to in terms of pulling on the throttle body arm>? I can say, for sure, that my WOT switch, as is, will activate (resistance-wise) BEFORE THE THROTTLE BODY IS FULLY PULLED BACK.....is there "slop" here, as to adjustments? I noted that the Bentley states to pull throttle full on, then adjust switch to actuate.........however, I didn't do that....in fact it wasn't touched.....my WOT seems to actuate at ~85-90% of throttle......she's running great, BTW.......just curious on this specific setting of WOT switch....


BEST!

Doyle

dshepp806

Tell me more of the "listening" thang,......I like listening,...for sure...

BEST!

rusnak

Somewhere I have an picture of a Porsche factory mechanic with a plastic tube in one ear, and the other poked into the venturi stack of a Weber triple choke carb. I think that is PURELY for the tech savy -- advanced class, for sure!!

Once the O2 sensor reaches operating temp, all attempts to adjust the fuel air mixture are fought by the DME. It's really interesting to watch on the output window if you have a fuel air gauge. You have to disconnect the O2 sensor to set baseline mixture. Some guys say set it a bit rich, because the DME likes to lean out the fuel pulses to get .98 to 1.02 lambda. I just dont know if this is correct or not.

I think that it's interesting that your idle has to be set high with the ICV jumpered. Maybe one of the ICV servos are bad?

whalebird

Thinking this through, It occured to me that someone may have monkeyed with the throttle stop screw at some point in the past...

dshepp806

Bird,..what may be the "throttle stop screw"? And what would be considered "monkeying"?

As to the actual base-RPM adjustnment (piece), this would be my "hisser" I mentioned earlier,....just doesn't sound right at a few points, yet I'm not a Pro at this to know. I suspect the integrity of this adjustment piece has been (everso) compromised/worn...not sure on the internals just yet. She's running well,..cold starts are single to 2 (max bounces, then she levels in to solid RPMs.

Still looking to get the proper instrumentation to check the base idle mix......later to look into the chip's programming.....THAT's another discussion, of course. As to THAT particular endeavor (investigation) , I may want to get a stock Porsche chip (or Stock-mapped) chip in my employ.....for comparisions, down the road). Of quick assessment needs would be the present chip's programming....NOT to get WAY the frick sidetracked here on the chip discussion piece of this thread, but could be a degree of variance,..and one would be welcomed (and warranted) to check this.....I'll say this: my car has always been very easy to rev,..the response is certainly quick,..yet I've not measured timing advances (nor would I know the chip's maps just yet)...anywaze,..back on track here:

Driving her for a few days, at my present settings (and having NOT measured the mixture at idle), I'll notice various idle RPMs throughout the day when out on the roads...sometimes she clocks at 820 (with the slow +/- variances,..then later show 890 RPMs......most of the time settling in around 850-860 RPMs, as noted on the tach (hard to get visual resolution on the tach, so these are "bestimates")...

I need to get the base mix verified.....

Neat info there , Rusnak. I'll have to review the PET to where these "servos" are,..could be time for a fresh ICV? They aren't like fine wine,..and I'm a preventive kinda' guy,..far be it from "throwing" parts at something,...even though she's measuring fine,....I've no problems with fresh hardware,..especially when replacing 22-23 year old parts ..........or any other (considered) consumables,..'tis the cost of doing business......

I'll keep you guys posted on this,..

THANKS for all inputs...might there be a technique to test this idle adjustment valve? That is, spraying something at it while hissing at me? Can this piece be replaced? On to PET...

BEST!

Doyle

dshepp806

BTW: for the record;;;;; My base idle adjustment/RPMs (hex) was covered with the yellow protector,..very brittle,..looked to be quite original (best I could tell). Wonder if it had ever been touched....

Doyle