It's too bad you didn't get a look at what chip is in there.
No need to de-solder anything just open those black nylon standoffs and you can open up the two boards, they are hinged with a ribbon cable.
Listen to Sal, he is an expert on this.

You must confirm that the AFR is below 13 at WOT.
You made a few mods which means the stock chip may not be correct for your motor. You really need to confirm the AFR

Cold idle speed is not 800, that's why we never adjust idle speed till fully WARM.
At cold start the DME has a idle speed MAP that controls idle speed based on the CHT sensor. At initial cold start it MUST idle above 1000RPM, typically around 1100RPM.
Not until the engine is fully warm does the CHT sensor drop down to below 200ohms and then the idle speed is 800RPM in 84-85 or 880 86-89 engine.

This is why all adjustments are done fully warm.

After you figure everything out, you really should upgrade to the 87-89 chip that idles at 880RPMs. But don't worry about this yet till things are figured out.

If you plan to keep this car a while, best under $200 investment is a decent permanent WBO2 gauge in the cockpit. You can setup your mixture perfectly using it and verify everything is correct. In addition, it's amazing how many tests you can do with a WBO2 gauge. I really like the AEM 30-4110 gauge because it uses the better LSU 4.9 sensor that does not need free air calibration. But be careful as China knock-offs exist, only purchase from reputable sellers. Or better yet the AEM store directly here:

https://www.amazon.com/AEM-30-4110-UEGO-Ratio-Gauge/dp/B00N3VGPYS

Then learn all about these gauges and ideas for mounting them here:
http://forums.pelicanparts.com/porsche-911-technical-forum/895323-aem-wideband-o2-gauges.html

Again, you really need this to properly setup that Engine like the pros do.

Am at sea level... but planning drive through Rockies. Will get to 9,000 feet.

Nice vid Sal. Thank you. Am back into it.

Insides...


http://forums.pelicanparts.com/uploa...1714766068.JPG

http://forums.pelicanparts.com/uploa...1714766068.JPG

http://forums.pelicanparts.com/uploa...1714766068.JPG

Your have the '85 thru '87 4K chip (XXXXXX180).

All the mods have been returned to the original settings including the rotary fuel switch inside the ECU---so back to original status but for the disconnected Ox sensor.

Just did get the ECU open (Sal's vid for ref) and Dave posted the chip inside is '85 - 87. My engine is '85. First test runs today proofed the engine doing well without the ox connected. ECU reinstalls after I post this and tomorrow I'll test run some more.

Provided test runs tomorrow confirming today's performance, fuel tank gets filled and we'll see what comes of the mpg.

Thanks for the hole response Brian.



Sal, more thanks for your intel and recommends. I'll recheck the adjustments with the engine warm tomorrow. I've come off a long rebuild with the last bit of it being this fuel mileage puzzle. When this is sorted, am not enrolling in any other 911 project for a while. I'd like to enjoy the car for a while without a wrench in my hand. Wide band is on future list.


Thanks Dave.

If the ECU's still apart, take pics of the solder side as well, in particular where those power transistors with the big heatsinks connect to.

Might as well.

Looks like you're making good progress!

I did, post #39. ECU is back in car now. If weather looks good, will drive to Islamorada today to check mpg. If so, post results after doing so.


http://forums.pelicanparts.com/support/smileys/wat6.gif
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Great thread and diagnostics going on here. What great Pelicans we have offering up great technical support. Love this place. :)

I bought the AEM setup, made it portable with clips for power. Used it on porsche, motronic VW vanagon, one day i will install it permanently.

Ah, sorry, haven't kept up with all the posts !

Any defects, cracks in the solder where circled, look closeup ?

http://forums.pelicanparts.com/uploa...1714848515.jpg

It was poorly soldered before. When doing the soldering, bend the tabs and increase the soldering area.

P... I looked but in hindsight, I could have looked more intensely now that you raise the point. With the ECU back in the car, goal now is to get a handle on where the MPG is at. Later, and if issues persist, I'll dive back in the ECU. Thank you for the push in this regard.


Good eye Dave. Bending for increased contact area makes perfect sense. Whomever did this board obviously didn't concern themselves with this. Intel appreciated.
.

MPG check today…

First crank start. Idle begins at 1200 rpm. Can’t call idle perfectly stable—hunted for 1 cycle down to 1000 and up to 1300 then stabilized at 1200. Runs at 1200 for some seconds, then slowly settles to 800. Filled tank at Shell till pump itself cuts off. 93 oct. Background notes: Tire pressures cold: 25 F / 29 R (Found tires wear better—more evenly across width—with lower than recommended psi. I realize there is the question of which is more economical, higher tire pressure for less fuel use, or lower pressure for longer lasting tires?) Oil now and after engine’s break in: Motul 20 - 50 synthetic. (Break in was with Motul mineral.) Gearbox: 5 spd. Engine mods just done: 964 cams set to 1.45, SSI exhaust, Dansk 2 in 1 out muffler. Sound is slightly more robust than stock but no drone and not loud.


http://forums.pelicanparts.com/uploa...1714863455.jpg

Went downtown Miami to Islamorada and back. Returned to exactly the same Shell fuel pump that I filled with. Did same refill allowing pump to cut itself off so fuel used should be spot on.


http://forums.pelicanparts.com/uploa...1714863612.JPG

Miles driven.


http://forums.pelicanparts.com/uploa...1714863640.JPG

Refill gallons.


Miles put on are highway for the most part with sections of stop & go in Miami and in the Keys. Only a few heavy footed accelerations were made during this test. Highway cruise = 60-80 mph. MPG = 27. Good news (so far.) No idea what the AFR is. Am inclined to think that without an Ox sensor, there’s nothing telling the ECU what the burn status is. Am guessing the ECU must default to some set measure of fuel delivery—total guess so do not quote me. Manual check of AFR obviously needs to be made. Thinking this through, it seems sensible even with an Ox sensor installed to check the AFR.

Mission today was to drive the fuel tank down immediately to see if there is or isn't an improvement from where this fix started, that being 11 mpg (city.) Clearly things are headed in the right direction. Now, and with last fill up just made, city mpg test starts. Will take several days before next refill. Update when city number is had.

Just received the new Ox sensor. Setting it aside for the time being---not installing it.
..

Looks about right. O2 sensor will bring milage up default map is rich from what i have read. I just did a 500 mile trip and got close to 30 mpg keeping revs at 3200 mostly freeway, some stop and go traffic.

Helpful graphs;

http://forums.pelicanparts.com/uploa...1714929680.jpg

O2 sensor connected - Lambda ~ 1.0

Helpful!?!?! I'll be candid, I see abstract art Dave. Is there any explanation to enlighten those who don't make head or tail of those images?

Warm idle adjustment. Jump BC. After a few increment adjustments & rpm checks, idles at 800 after a total of 1 1/2 rotations clockwise from starting point. Must say it's a good place to be making progress... thanks to you guys.