Adjusting Air Fuel mixture '7747 AKDX

**57 Handyman** · 11-25-2017

OK...will check that method out tomorrow. Thanks

**stew86MCSS396** · 11-25-2017

When initially started the engine, Stuck my finger down into that hole and could feel the air bypassing. At the time, we had the key "on" engine "off," the scanner was reading 145 which is the "park" position set in the ECM. At this point, we could have jumpered pin A to pin B on the ALDL and watch the IAC close to 0 on the scanner. 2nd time running, scanner was hovering around 39. I think it's working fine, time to move onto bigger things!!!

**57 Handyman** · 11-26-2017

OK, thanks Stew. I didn't know you had already gone thru that process to verify/validate proper operation of the IAC. With that done, I agree with "time to move onto bigger things."

**57 Handyman** · 12-01-2017

Dave W: I did a re-burn of the chip and verified the settings for buffering and addressing were correct per the MOATES notes for a 4K bin file. I installed it into my ZIF-modified 7747 and it appears the initial issue of too much fuel at restart remain. If I depress pedal to the floor, I can get the engine to start and run. Once started, it idles okay. BUT, that still doesn't indicate whether my modifications to the 7747 have not damaged the ECM.

With Stew's assistance, I borrowed and ran his stock 7747 AKDW. Motor start up was good and idled smoothly. I wasn't able to run a 24-pin AKDW since they are in holders and I don't want to mess them up. Stew will burn me a 24-pin AKDW tonight which I will then test in the 28-pin ZIF (per Dave W's advice) to see if my ZIF-modified 7747 is functioning properly.

Thanks for helping!

**57 Handyman** · 12-02-2017

Update: Received the 24-pin AKDW chip (with EGR deleted) and installed it in my ZIF-modified 7747. Unfortunately, the results were the same--slightly rough idle and too much fuel during restarts. As Dave W indicated earlier, one of the symptoms of running in Limp Home Mode is too much fuel. Since I've tested several 28-pin chips in the ECM and, thereby, eliminated that the problems are with the EEPROMs, the remaining conclusion is I messed up my 7747 while installing the 28-pin ZIF socket.

Before I toss the ECM out, is there a sure-fire way of determining the ECM is indeed running in Limp Home Mode? Is there software available that will read this via the ALDL? If I removed the LHM chip and leave in only the AKDW, will a "no start" indicate that the ECM was indeed running in LHM?

**dave w** · 12-04-2017

Originally Posted by 57 Handyman

Update: Received the 24-pin AKDW chip (with EGR deleted) and installed it in my ZIF-modified 7747. Unfortunately, the results were the same--slightly rough idle and too much fuel during restarts. As Dave W indicated earlier, one of the symptoms of running in Limp Home Mode is too much fuel. Since I've tested several 28-pin chips in the ECM and, thereby, eliminated that the problems are with the EEPROMs, the remaining conclusion is I messed up my 7747 while installing the 28-pin ZIF socket.

Before I toss the ECM out, is there a sure-fire way of determining the ECM is indeed running in Limp Home Mode? Is there software available that will read this via the ALDL? If I removed the LHM chip and leave in only the AKDW, will a "no start" indicate that the ECM was indeed running in LHM?

One method of troubleshooting is to "Bookend" the problem. It seems we have one "Bookend" established, (if I'm understanding correctly) good chip / good ECM engine runs OK.

There was a day and time, my soldering skills needed improvement, likely still do for some surface mount components. Thru hole soldering, like the '7747, is about as basic a soldering project gets. I would use my OHM meter on the ZIF modified ECM that was soldered and compare those measurements with a "GOOD" ECM. I would measure resistance from pin 1 / pin 2, then pin 2 / pin 3, then pin 3 / pin 4 .... ending with pin 11 / pin 12. Then repeat the OHM measurements pin 13 / pin 14, then pin 14 / 15, then pin 15 / pin 16 .... ending with pin 23 / pin 24. I would also measure the modified ZIF pins. Ohm measurements should be within 1% from known good ECM to the ZIF modified ECM. Maybe re-solder pins that show a resistance of more than 1%, if there are any. If everything measures within 1%, I would be "STUMPTED" as to what is causing the rough idle and rich fueling.

dave w

**stew86MCSS396** · 12-04-2017

That's some sound advice. I felt a little rushed installing the 28 pin zif and wondered if I may have not clean the contacts good enough. I've done the OHM measurements on another '7747 I have here and can compare with modified ones at the shop. If yours don't check out, the offer still stands that I can try re-solder your '7747. I really need to get one of them magnifying glass with a good light. After staring at it too long, everything gets a little blurry. Based on the IDLE datalog, I'd like to pull some fuel out to see if idle improves, but if none of the initial adjustments are done/verified, I feel it's going to be an uphill battle.

**57 Handyman** · 12-05-2017

Dave W, thanks for providing a way to test the results of my soldering. I will follow the steps you outline above. Hopefully, any differences in resistance will be minimal.