Hey guys!

I'm very new to learning how to re-program these chips here. I've gone through all of the stickies above many times, and I think I've got the general idea of what I need to do.

I went out today to collect some data logs, everything from just crawling speeds, to wide open throttle from an idle to 100 mph (I fear for my poor tranny doing that, the 700r4s arn't known for their strength, esspecially in a 6500 lb truck, lol)

However, trying to collect some idle data, the truck will not idle below 1000 rpm with the cable hooked up. Unhook the cable, and restart the truck, and it will idle at 600 rpm in gear, but not with the cable hooked up.

Is there any specific reason for this, or will I just need to figure my way around it?

 

Its in the program, whenever you enter diagnostic mode, idle is set at 1000 rpm. Really there is nothing wrong. If you don't want this to happen, look around for posts about 10k mode or diag mode. I'm not sure but you may be able to edit diag mode rpm in the chip, as I said I'm not sure.

 

Where did you get the ALDL cable from?

RBob.

 

Suppose I should have mentioned that the truck I am working on is an 89 half ton truck with a TBI 355, and 700r4. As such, it runs a 1227747 ECM.

I got the cable off ebay. I may be making a bad assumption, but I assume that the 7747 uses the same resistance to get into ALDL mode as the `165 ECM my GMC used to have (still hunting for a `730 ECM with a 350 memcal for it at a price that I am able to cough up at the moment)

Ran into a bit of another setback here. I got the chip copied onto my laptop using my programmer and did some BLM changes, and very small timing changes (my engine likes a lot of timing right off idle), then went to burn it on the AT29C256 chip I've got, when I realized that the TBI uses a different chip than the TPI (which is fine, my other truck is TPI, and will need it later)

Anyone know of what model number of flash chip I'd need for the TBI ecm? I did a bunch of hunting online, but wasn't able to come up with anything, and the sun doesn't put down nearly enough UV this time of year to just erase them outside.

I'm not too terribly concenered with not getting idle data yet. I already know that the ECM is running full enrichment due to valve overlap letting 02 by the 02 sensor, so I still need to work on adjusting what a/f ratio it goes for at an idle to try and remedy that.

This is definitely scary stuff for me though. I've got a bit of a background in computers and electronics, but I don't wanna go overboard with anything and kill my poor 355, lol

There is a good reason why I'm starting on the TBI beater truck (put a 355 from a 73 Nova with a mild cam, TBI heads, and throttle body with interceptor injectors) rather than starting with my GMC, which has a far less EFI friendly engine in it (anyone say 108 LSA )

 

Can't you ask them why your engine idles higher when their cable is attached? Seems most logical to me.

Al.

 

Your cable has a built in 10k resistor across the A and B terminals that puts the ecm into ALDL mode. Some ecms will bot spit out serial data unless this is in place. One of the side affects is a 1000rpm idle.

The '7747 is NOT one of these ecms! It will spit the data all the time, so you need to remove this 10k, or remove the B pin entirely. Some cables have a switch on the side that switches the resistor in or out.

 

There arent any flash chips for TBI unless you use one of those adaptors, I think they are from http://www.moates.net/

The TBI uses a 2732A chip, which is 24 pins. The TPI chips are 27C128 for MAF or 27C256 for MAP, which are both 28 pins.

 

Thanks for the information everyone!

I'll pull the white / black pin from the ALDL connector, and datalog that way. Also look in some local pawn shops for a UV eraser

Thanks again, and have a Merry Christmas!