SeanR

So, people seem to trust me to work on their cars and I tell them all that I'm learning every day. Well, someone needs to teach me something here.

My car has had some odd running issues over the years and while it's nothing that keeps it from performing like I want it to, there are a couple of things that just annoy me.

Colin (Lizard Beard Man) was helping me do some tuning back in November and some odd things kept happening which led him to think that I've got an engine harness issue. I figured as well but a cabinet maker has a bare kitchen, I've not been able to make my own harness (doing too many others and trying to catch up). Well over the last few times I've been able to play with my car I've not found any fault in the harness, none. While old I've replaced all the connectors and everything tests out good. Yes, I'm going to put a new one in anyway but that will be after I build the other 4 that customers are waiting on.

So I hook the Shark Tuner up today to goof around after a couple of people left and one oddity that keeps popping up is on the Ignition Map screen it says "Cruise Map (98 octane no cat). I should be running on the 91 octane with cats correct? Idle map is on the 98 octane cat map.


I thought my coding plug may be causing this but it is fine for 87-88 plugs.

Thoughts?

One issue I've been fighting since I got the car is when the A/C is clicked on, there is no idle up impulse sent which makes idling fun in the summer, and odd cut stumbles while cruising where the AFR goes to 18 then bounces back with an adjustment with the foot.

SeanR

Could an '87-88 coding plug combined with later computers cause this?

jcorenman

Sean,

The octane numbers that are quoted in the WSM and in Sharktuner are RON octane, used in Europe. ROM octane is 4-5 points higher than the so-called anti-knock index (AKI) used in the states (which is an average of RON and MON ratings).

So your 98-octane map selection is correct for US 92-93 octane. The 91-octane (RON) map shown in Sharktuner is for 87-octane, the gasoline equivalent of Coors Light and for a while was the only choice in Australia-- hence the 91-octane selection in the coding plug (and Sharktuner).

What is odd is the selection of the no-cat map for cruise and cat map for idle-- those are controlled by the same jumper in the coding plug. I suspect you might be getting fooled, because at idle the cruise map is not in use.

Check this: With engine running, select Sharktuner's ignition monitor page, find the idle/cruise/wot indicator, and verify that it shows "idle" with the throttle closed. Then advance the throttle slightly, and verify that it changes to "cruise", then back to idle when the throttle is lifted. Now go to the ignition maps page and step through the three idle maps, and verify that you see the cursor on the "98-octane cat" idle map, and the "98 no-cat" and "91-octane" maps show "map not in use". Now advance the throttle and do the same thing for the cruise maps-- you should see the cursor on the 98-cat map, and "not in use" for the other two.

On idling with AC on/off, make sure the ISV is working properly-- does the ISV% number on the fuel-mon page move up and down a few points as the car idles? Does it go up a few percent with AC on?

You can also manually adjust the ISV from the fuel-param page, lower-right: Disable idle loop and select an ISV setting. If you run the setting up to 70% then the idle should be around 1500-1800, and if you drop it down the the idle speed should drop accordingly. Normal idle is in the 50-55% range, 35% is fully closed and 70% is fully open.

Could the momentary cutout be fuel pump or fuse/relay? The only time I've experienced that was a single hiccup about 15 minutes before the fuel pump quit altogether, brushes were fully toasted. Look also for burned contacts on the fuse or relay that might indicate a poor contact.

Cheers, Jim

Hilton

No idea, but I can tell you that an 89-95 coding plug in an 87/88 will burn the crap out of the ground wire (and worse if its left more than a few seconds) all the way from the coding plug up to the engine grounds under the intake. (I made a thread about it somewhere, I did it four or so years ago)

docmirror

Your coding plug doesn't match anything in the chart. So, add the 150 ohm resistor and a pin in hole 8, also add a jumpered pin in hole 5 which is what your car is. Or if you have changed the LH EZK, you'll need to find the right jumper for that set. You should be using the very bottom example in the chart.

As for the AC idle up, that's controlled by the ISV for any loads on the engine, such as AC, lights, rad fans, wipers, etc. The EZK determines the idle speed, and will advance the ISV opening to maintain 675(or whatever you have it set for). Don't you have some obscure chips in the car? If so, it may not have a idle stabilization circuit that is robust enough to handle large changes in idle loads. I just don't know...

PorKen

Have you checked terminal #15 on the LH plug for voltage when the A/C is on? (#14, A/C compressor, is shown but #15, A/C on, is blank in the WSM.)

#14 and #15 provoke separate branches in the LH code. One disables injector cutoff on decel, IIRC. The other changes to a different (higher rpm) max idle speed map.

https://rennlist.com/forums/928-foru...ding-plug.html

The later plug's resistor shorts/bridges the CO pot circuit.

PorKen

I looked through my commented disassembly file again to be sure...

#14 - A/C clutch
Immediately adds ~125 rpm to target idle speed. (And flags to do something else which I did not follow.)

#15 - A/C on
Inhibits the idle speed drop when selecting a gear, IE. moving from P/N to R/D.

Hilton

I just checked the charts on pages 28-69 and 28-70.

Agree with adding pin 8 and the resistor. Not sure why he should add pin 5? Pin 5 is only for countries with lower-grade fuel.. 91 RON.

Hilton

Here's the page in the WSM

docmirror

Because of this line in Seans post: "I should be running on the 91 octane with cats correct?" If he is referring to the RON octane, then pin 5 is called for. If he is running 91 R+M/2, which I suspect is correct in the US, he can leave it out, however last I heard he was running a blower on the engine, and some modified fuel maps which got us to this point. Frankly, I would add pin 5, drive the car, see if there is any indication of detonation, and if not then remove it later. It would be messy to leave it off and find out later the map was too aggressive when there are bits of upper engine laying in the oil pan.

AO

Sean,
Your assumption that the STer is reading the wrong map is incorrect. You want the 99 octane setting. Cat vs. no-cats, is a different question, but that is what the coding plug is saying. You should be able to override those settings in the STer anyway without touching the coding plug. Another good practice, is to copy the final tune to all version of the same map to ensure consistent behavior.

RedPanda

Woah I didn't know this existed, is there one on the older 86.5 and prior?

Rob Edwards

A sharktuner for 85-86 32V US. cars and most 84-86 16V Euros? Yes:

http://jdsporsche.com/NEW%20Mk%201%20sharktuner.html

PorKen

No coding plug for pre-S4 brains.

There is one coding feature on 85-86 built into the LH code (and wired to the plug) but it is unused. It disables injector cutoff on decel. (This is used for automatics on other makes. Keeps the converter spooled up for better throttle-back-on response.)

RedPanda

So no real use much to shark tune a 1986.5?