I finally have my winaldl set up and working. I can see what the engine is doing now but I have no idea if any of these readings are correct. Other than a few items that I have read about here on the forum eg the tps and iac, which by the way is not close to 20 but that's another story.
My question is: Is there someone who has a stock 86 L98 that can paste a copy of their engine parameters at idle on the site? I have searched but can not find such a post. Thanks in advance.

 

you looked in Scan and Tune?

 

PM member "Cliff Harris". He has done as much as any re: 86 setups. IIRC, Cliff has also linked a site that focuses on the 86 Bin.

Scan and tune is another place to look.

ThirdGen.org (sister site for Camaro's/Firebird's) has the most feedback/printouts of BINs.

FWIW. TPS should be set around .54v and the IAC should open about 15 steps with the motor hot and the fans not running.

 

I've search scan and tune for hours but I didn't use the word bin. Will give that a try.

 

I haven't looked in ThirdGen but will. Also I haven't used the word bin in my searches here in scan&tune.
My TPS is good @ .54 but the IAC is in the 40's with the Xtreme aldl set on 10ohms and the idle is 1000. If I set the aldl reader to 0 ohms the idle drops to 800/850 and the IAC count drops to 28. This is after the cooling fan comes on and goes off. My base tune is 425-450 on the idle and 6 degrees of timing, again with the engine warm and the IAC @.54v.
I think the readings with the Xtreme set to 0 ohms is correct because that is where the engine idles when I'm driving. The idle is quite slow to drop down to 800. It takes 5 to 7 seconds for it to happen. The slow idle return is the whole reason for getting the winaldl set up. The IAC is new but not an AC Delco model. I am wondering if that is the problem. I had a similar problem with the TPS and had to purchase a good "made in usa" one.

 

Since you have a 165 ECM, you should use Datamaster.

I'll dig up one of mine, after work.

 

It sounds like you need to open the TB set screw to let more air into the blades. Unless your year is different than mine, you want IAC counts lower than where you're at. High counts mean it's needing to let in more air than necessary -- because the blades aren't open enough.

OTOH, if everything is stock, no change should be necessary.

I think people focus on the time IAC takes to set down to idle when working on it. They forgot (never noticed) what it was like before. Still, the higher the IAC counts, the longer I think it takes to set down to idle.

Can't hurt to crank the idle screw a turn or two. Count the turns. Observe what happens to IAC counts and function. You can always restore the original setting if you count (and don't like the result).

I agree with the ohms setting comment.

 

Here are several WINALDL screen shots as follows:

1227165 chip - properly tuned L98 sensors with engine not running.

1227747 chip - properly tuned L98 sensors with the engine running.

 

The background: I had this weird miss after the car warmed up. Ran fine when cold. I spent way more time than it should have taken to find out that I had a bad plug wire (found it by looking at the running engine in a dark garage). I spent about two months really digging into what was happening with the ECM and the various sensors. I decided to put what I found in a web page so others could benefit from what I learned. It's here:

http://home.earthlink.net/~cliff_har...165/index.html

I've also spent a lot of time digging through the code that makes all the magic happen. Found some real surprises buried in there. It's on the web site too.

I had two problems when I first looked at the data stream coming out of the ECM: First, too much information. All these parameters varying all over the place. Second, no information on what the parameters SHOULD be.

Some things to look for (most of this applies to closed loop mode): The IAC count is set to 144 when you turn on the ignition. That's a "fast idle" to keep the engine running when it's cold. It will gradually drop down as the engine warms up (that's called "kickdown", like we did back in the carburetor days). What it's supposed to be when it warms up is debatable. I think anything under 50 is OK (my opinion only). I saw somewhere that somebody said it should go down to 0. I don't agree with that at all because then the ECM has no room to adjust the idle. Also note that IAC has a "throttle follower" mode, where it will increase as you press down on the gas pedal. That's to prevent the engine from stalling when you let off the gas.

The ideal INT value is 128. That's calculated from the O2 sensor readings. This is an "instantaneous" value that changes all the time. The INT is used to adjust the values in the BLM (Block Learn Multiplier) cells. The BLM values are used to adjust the fuel injector pulse widths. The ideal BLM value is 128. There are 16 BLM cells. You will probably start in cell 5 and drop into cell 0 when the engine warms up (idle). When driving, you'll spend most of the time in cells 10 and 15. The BLM values are limited to a low of 108 and a high of 160. If you see those values, you're way lean or rich.

You should see the TPS voltage vary between about .54 volts and up to 5 volts. Anything over 3.5 volts is considered by the ECM to be WOT (Wide Open Throttle).

The ideal O2 reading is .45 volts at 14.7 AFR (Air/Fuel Ratio). It varies between about .2 volts and .8 volts. My Diacom shows voltage, but it looks from the screen shots that it's converting it to binary numbers, which go from 0 to 255. Basically, the ECM monitors the O2 sensor and adjusts the injector pulse width appropriately. The O2 sensor is extremely non-linear so the output bounces back and forth between the upper and lower limits as the ECM corrects the AFR. The ECM increases the pulse width until the O2 sensor goes rich, then decreases it until it goes lean, then back. The cycle takes about one second. Each time it crosses the ideal value the ECM adds one to the O2 cross counts (O2_CNT in the pic). This value goes up to 255 and then wraps around to 0 and starts over. The main thing is that it should be constantly increasing, which shows that the ECM has the AFR under control.

The ECM uses the CTS (Coolant Temperature Sensor) to adjust the AFR and spark advance. This value should be reasonably accurate. It's usually about 5 degrees cooler than the temperature display on the dash because of the location of the two sensors.

As I discovered recently by looking at the code, the IAT (Intake Air Temperature - also known as MAT for Manifold Air Temp) sensor only determines when the EGR valve is enabled, so it's not really important, but ought to be a reasonable value.

The MAF (Mass Air Flow) voltage ranges from 0 to 5 volts (0 to 255 in binary). It tells the ECM how much air is entering the engine so it can calculate the AFR and adjust the injector pulse width. I don't see pulse width in the pics, but Diacom displays it.

The knock count should be low. The ECM advances the ignition by 20 degrees while it's cranking to cause knocks, so you will see 2 or 3 when the engine first starts. After that you might see some when accelerating. Knocks are bad. The ECM takes out a bunch of advance when it sees a knock (and then gradually returns it to the normal value), so you lose power while the spark is retarded.

'86s don't have a MAP (Manifold Absolute Pressure) sensor, so no need to worry about that.

The rest of the values are mostly status values, like TCC (Torque Converter Clutch) lockup, A.I.R. (Air Injector Reactor) divert/switch and CCP (Charcoal Cannister Purge). Battery (actually it measure ignition) voltage and fuel pump voltage are just informational. They should be around 12 to 14 volts, depending on RPM.

One thing to watch for is that the car switches back and forth from open loop to closed loop while you drive. It starts out in open loop mode when the engine is cold. That means that the ECM is using the CTS to determine spark and fuel injector pulse width. When the engine reaches some temperature (that I don't recall offhand) and sees a reasonable O2 sensor reading it switches to closed loop mode and also uses the O2 sensor to determine the fuel injector pulse width. It switches to open loop mode when you go to WOT.

The MALFLGs in the pics are Malfunction Flags. They are bitmapped (each binary bit is one flag). Anything other than zero means there is a problem. The ECM is not very sophisticated when it comes to seeing problems. Usually a sensor connection has to be either completely open or shorted to set a code.

I tried to give enough information to explain what's going on without overwhelming y'all with details. Hope this gets the concepts across.

 

WOW ! You did a fine job pulling all this together, Cliff. Your research will prove extremely valuable to all of us as we continue to try to keep our C4s running in the future.

THANKS MUCH

 

Agree with everything Cliff has stated.

need the 10ohm resistor to connect to the ecm but you can take it out once its running. With the ALDL connected the ecm may advance timing 10 deg as there is an aldl adder in the bin thats usually 10 deg. This may cause idle rpm to vary. Thats normal.

And 40 counts at 1000 rpm is good. 28 at 800 is fine too. I wouldnt worry about it too much. Need SOME margin from zero to allow the IAC to do its job.

BLM/INT's, I generally shoot for +- 5. If you are near that, you should be good to go. Wideband o2 sensors will verify that air fuel is in an acceptable margin if your +- 5

 

http://eagle-mark.com/pictures/thumb...bum=34&page=29

this album has stock .bins for basically every gm vehicle of your rough year...

there 600 odd .bins there though so going to ahve to look through em.

 

Even easier

You can open and play back a Diacom .GDF file in Datamaster exactly the same as a Datamaster log
Allows graphing up to 4 selected items against each other at one time and ability to zoom in down to a couple of secs of a full Diacom log to identify exactly what is happening.
http://powertuneplus.com/syclone/tunersguide_dm.shtm

Much easier than scrolling through a spreadsheet looking for a " hiccup"
Can also adjust playback speed for easier identification of problems

As you are only playing back a file ,there no need to purchase.

Sample shows 5 seconds of a Diacom log ('730 8D ) hi-lighting knock retard at that point

 

WOW............you guys rock. Thank you so much!
A special thank you to Cliff and pmihaltian. I now have a much better understanding of what I am looking at during the scan.
From all of the information you guys have given me it seems I have a "normal" car. The only oddity being the slow return to idle.
I read in one of Cliffs' articles that the computer commands the IAC to control the idle to 1050rpm at -40c and gradually lowers the idle to 550 at +80c and above coolant temperature. My car never does this. My cold idle is 1400 and the warm idle never gets below 750.
I have no problem setting the base idle per the FSM and I can get the engine to idle even lower than 450 so I'm assuming that there are no extraneous vacuum leaks.
UPDATE:
After following the instructions in this article - http://www.docstoc.com/docs/25331704...-thru-1992-Not
I now have a correctly running engine.
Step 14 in the article is not in the FSM under setting of the base idle so I have never fully set the base idle and so my continuing problem never went away.
Again, THANK YOU. Now perhaps I can concentrate on a few rattles.

 

My 86 Vette has idled at 700 rpm's (warm) since it was new. In my view, this is normal.

If your Vette is seemingly slow to return to the 700 rpm range, I would suspect that your IAC and throttle body may have carbon deposit buildup. My recommendation is that you remove the throttle body and thoroughly clean it with a good designated TB cleaner. Also remove and clean or replace the IAC if necessary.

Once you have it all cleaned up, reassemble and install the clean TB and reset the TPS using the attached guide. (you might want to invest in the Mid American TPS test cables. The tester is cheap and WELL worth the small expense.)

Following this maintenance outline should solve your idle problems for several years.

http://www.mamotorworks.com/corvette?frame=3.900

 

pmihaltian, Thanks for the info on the TPS and cleaning. All of that has been done. I was missing a step in the base idle adjustment that is not in the fsm. Resetting of the IAC pintle position. I now have it all sorted and the engine returns to idle (550-600rpm) every time now.