I've been having an issue with cold starts (surging) that randomly popped up when it began getting colder...last winter i didnt have this issue and it was the same bin...

Today i decided I would log the cold start from start until closed loop.

I began my log when everything was off, cranked and got going. The car doesnt reach closed loop for about 5 minutes or so...but my BLMs were moving already. In the past, my BLMs and INTs had stayed at 128 where they were supposed to be for open loop operation, while today the INT stayed but the BLM switched from 139 to 126, just using those 2 values. The flag stated I was still in open loop.

Can anyone lend a hand as to why? It didn't make any sense to see something other than 128 on there...I'm wondering if it has something to do with whatever is wrong or if 139 (the intial value) was what was left over from the day of driving before.

 

A good possibility is that the ECM is changing which cell it is in. There are 16 BLM cells for a range of load and engine speeds. See if the ALDL stream reports which cell is in use.

RBob.

 

The BLM cell is at cell 1 immediately after startup, then will switch between 1 and 0 a couple times, then stay at 0.

I did notice however, that the IAC is staying at 160 steps the entire time the car is surging, and as soon as the IAC steps begin to move the surging begins to stop. Any ideas as to how to make it move from 160 steps sooner, or do I have a mechanical problem with the IAC itself?

 

Surging is typically from a lean condition. As for mechanical issues, probably not with the IAC. There may be a small air leak after the MAF, that will cause a lean issue. And contributing to the 160 IAC at cold start, seems a little high.

The surging probably goes away as things steady down enough to stay in the one cell. Switching between 126 and 139 BLM will cause the injector PW to jump. And can contribute to the surging. If the BLMs were bascially 128 last year and now one is 139, that points to something has changed.

It may be worth setting the cal to set all BLM cells to 128 at key-on. Out of the 16 cells it looks like only 2 cells will be retained. The others get set to 128 at key-on. This is both the $32 and $6E mask's. Then go from there.

RBob.

 

I dont have a clue how to set it up like that with tunerpro.

 

Well, you were right but I still am confused as to why this is...

I reburned a new chip and installed it, and it started up and idled beautifully just the way it should, i assume because everything was reset to 128.

Is the 139 I was seeing a keep alive memory so to speak from the last time i drove, and it just carries over for the next startup? Meaning, the last time I drove it, it was lean, so at startup it is now starting in a lean cell?

If you could give me some info on cells, what they mean/do and what I can do to mess with them I would appreciate it.

 

The BLM cells are the long term fuel trim. In the $32 and $6E ($8D also?) there are two cells that are further slow filtered as a longer term fuel trim. These cells are also held at key-off, and at key-on are checked for upper & lower limits. The other 14 cells are set to 128 at key-on.

My preference is to have all BLM cells reset to 128 at key-on. This is required when doing tuning, and when not tuning seems to work out better.

Can also move the cell boundries around to better match the engine operating range. Typically this is only required with a modified engine.

RBob.

 

But how would I achieve moving all BLM cells to 128 at key on?

How do I move cell boundaries around?

In tunerpro, I only see 6 cell boundary options, 3 are for RPM and 3 are for airflow. I can't find anything that says "set all BLMs to 128 at key on."

Do you happen to have any threads on hand that relate specifically to how to do this, or just explain it in general?

Edit:

I looked through the hack, and unless I am wrong, I believe i needed to change addresses 4D8-4DB to 80, instead of what was there. In the hack it said Stay Alive Memory, 118-150, and 128-150, for each of the 2 cells. I changed them all to read 128 (80 in hex). Is that all I needed to do to have all cells reset to 128 at key off?

Still can't find locations for BLM cells besides what I said about the 3 boundaries based on rpm/airflow. Any info is appreciated!

 

They are the ones. Was wondering which mask you are using, $6E it is.

There are six BLM boundry values: 3 for rpm & 3 for airflow. They form a 4 x 4 matrix, such as a tic-tac-toe board (but with another row & column).

RBob.