car wont start when hot.....

final5-0 said:

I found some info from an older thread back in 11-05 that may help so
I just pasted it here for you

Three fixed parameters in the pcm fuel tables come into play when talking about startup.

1) Time
2) Load
3) ECT

We are dealing with two fuel tables.

1) fuel_table_base_OL
2) fuel_table_startup_OL

The base table is where you see the commanded ratio and it is used during warm up conditions.

The startup table is where you see values that are subtracted from the base table to give you a fatter ratio and time comes into play here.

You asked about hot start conditions so lets use that as an example.

btw, we're gonna use an unmodified j4j1 file for our little example.

Say you've been driving around and go in the house for a while and decide to go somewhere else. When you start the car for the second time, the ECT is 180*

Most NA h/c/i combos will idle at a load of say about .20 to .30 so we will use that load factor.

Looking at the base table you see the pcm is commanding a ratio of 14.302 at that load value and ECT.

Looking at the startup table in the 180* temp column at 0 to 6 seconds you see the value of 1.716. Notice as the time increases, the value decreases until finally at 40 seconds, the values in the table are no longer used.

Here are the commanded, startup, and final ratio values

00-06 secs cmd 14.302 startup 1.716 final ratio of 12.586
07-10 secs cmd 14.302 startup 1.487 final ratio of 12.815
11-20 secs cmd 14.302 startup 1.259 final ratio of 13.043
21-40 secs cmd 14.302 startup 0.572 final ratio of 13.73

At this point in time, you most likely go from Open Loop to Closed Loop conditions and the O2's are calling the shots to achieve the pcm's goal of 14.7 CL happiness.

The Fix is to go to the 210 & 240 ECT columns in the startup table and zero out those entire columns. If need be, you could always play with the values in the 180* column as well.

Grady

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final5-0 said:

Gee Roger

Those tables have been around for as long as I can remember

I have seen some say on the Tweecer site the newer software
(which I don't use btw) has had some of the definition names
changed but I could not say if those two tables are in that group

I would also say the method BobCat put up has a focus on the
cranking time period where as the info I gave is for after the
motor has fired

I've seen some say they divided the old and new size inj for a
starting place to tweec with the cranking stuff. You are just
trying to cut down the fuel as the new inj is now much
larger than the old

Grady

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final5-0 said:

Yes Sir

I don't know if I could call it handy as I don't remember where I got
it stashed but ... I got it somewhere and I can dig it up if you wish.

If you wanted to see those tables .......

A easy way for you to see them unmodified and my tweecs to them
would be for you to download the file of my complete j4j1 tune
in screen shots from my site.

Grady

Click to expand...

final5-0 said:

Do you have a wb and if so ... what is it showing currently at idle

What are your K's now doing

Here are a few things ... but ... you may have already done them

Low slope at 42
High slope at 50.4

Load in breakpoints for 42's

Cut your minimum pulse width in half

Grady

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