7427 install, first impressions

[JeepsAndGuns]

Well, yesterday I finally got brave enough to try the 7427 pcm. I wasnt brave enough to jump in feet first and go all out. So I spent a couple hours and built a adapter from the plug from a junk 7747 ecm and some spare pigtails from a 7427. That way if it ran bad, or needed lots of tuning, I could simply unplug it and plug back in my old 7747 and drive it when I needed.
First lesson learned, dont get in a rush and install the eeprom in backwards! I bought the moates G1 adapter, and I was so used to pin 1 being at the handle end of my zif socket like I have on my 7747, I just threw it in the same way. Turns out, pin 1 goes in away from the handle on the G1.
After I turned on the key, and the fuel pump never shut off, and I couldnt get aldl connection, I figured out the problem. I dont know if I corrupted the bin on the chip, but I didnt want to risk it. So I threw it back in the autoprom, erased it then re programmed it. I installed it and it works fine, so I didnt fry the eeprom.
Started the datalog and went for a small test drive.
After the drive, my first impression is wow. What a vast improvement. It idles smoother and better, acceration is smoother and more crisp, steady cruise is smoother, throttle response is better, and even decel is smoother and better. Light accel is better/smoother, wot accel is better/smoother. Even seems to have just a tiny bit more power. Seems pretty much all rpm ranges are better.
All this from a mildly modded stock bin. I imported my timing table from my old 7747 tune, and then just did some smoothing of the fuel maps. I also followed the steps and disabled all the trans controlls and turned off all the trans trouble codes, also disabled egr and turned off that code.
Going by the datalog, seems all cells from about map 50-20 I was rich, map 60-80 were pretty close, and map 90-100 was a touch lean. So just a few logs and tuning and I think it will be all set.

Now for the one and only problem I am having---the knock sensor. I made a small jumper wire to go in the plug for the esc to connect the knock sensor to the correct input on the pcm (using the old esc signal wire) but I am getting the knock sensor or circuit error code. So the check engine light is staying on. Its the only error code I get.
I looked up on advance autos website and looked up a 89 and a 95 chevy 1500. The knock sensor I am using is for the 89 350. When I look up the 95 1500 truck, it shows two knock sensors. One for a auto, one for a manual trans. The one it lists for the manual trans is the same part number of the one it lists for the 89 truck. The memcal I am using is of corse from a auto truck. So do I need to use the knock sensor it lists for the auto trans models? I'm thinking mabey the esc in the memcal is not seeing the knock sensor I am currently using.

[JeepsAndGuns]

Ok, the update this thread about the above issue. I finally had some time to do some more tuning. I figured first I would try timing. So I fired up the emlator and did a little tweeking. I higlighed the high map areas and simply raised the timing just a little and it has now went away. It just simply wanted more timing!
I also tweeked my idle timing table and pulling out has now improved. Having two timing tables is pretty sweet. Best of both worlds!

[EagleMark]

Glad you got it tweaked!

The throttle kicker may be in Govenor TBI pictured earlier, maybe not? But there is another one that is a solinoid just like old days bolted onto TBI and kicks the throttle linkage. It's activated by another control box simalar to one that controls EGR. If the guy sends pictures I'll post them up.

One of these days since you worked out the issue with timing, you should turn it off again and see if it does do something else in PCM other than activate soliniod.

[gregs78cam]

I just got my truck up and running on a '7427 with a TH350 and thought I would add a tip, Pin B6 on this PCM is listed as "not used" but it is infact a 5V reference output. So don't mix it up with the CTS sensor input that goes in pin B8, it causes some issues.

[JeepsAndGuns]

Dont guess we need to ask you how you know this....

[EagleMark]

Dave W just found another pin mistake when using the 16197427 with the 700r4, so we are going to have to redo that write up properly...

[EagleMark]

I just got my truck up and running on a '7427 with a TH350 and thought I would add a tip, Pin B6 on this PCM is listed as "not used" but it is infact a 5V reference output. So don't mix it up with the CTS sensor input that goes in pin B8, it causes some issues.

I just looked at the 16197427 wiring diagram and it has nothing from B6... so the directions we have in the 7747 to 97427 are correct, right? You just misplaced a wire?


Just checking because Dave W is making the change he found in the write up.