OK, now I finally converted to the other side. I put a ignition control module in my HEI dist and took out the howell fuel only chip. Now the stupd thing is....I still have same problem I had before I converted!! I have a stumble at 1000-1300 RPM and cant GET IT OUT and after going table by table and constant by constant still no chnages , in stumble that is, I finally hit the mother load.....it is in my main spark table. I went to the 800 and 1000 range and bumped it up and down, and could move stumble around...YIPPPEEEE!!!!! Now keep in mind I did this as a whole, I put in 2 accross the board at 800 and 1000, the same goes for when I went down. Because when the map/rpm hit wrong settngs it did get a bit rough but still I think I found it.

Now, can someone please explain to me how to do the calculations in "spark tables for idiots" ??? I went back and found a mechanical advance table / vacuum advance table for my engine but do not get the concept or formula for calculating them for this table. Here is a link to the tables....if the main page comes up , scroll down to bottom of page and hit "vac table"

http://www.geocities.com/jeeperaz/hei.htm

Plus I'm not sure on how to read the tables to get the numbers needed to put into equations .....need that explained too , PLEASE. Every thing I have on motor is stock with the exception of the Hei, which is now ICM / ecm controlled.

As always thanks in advance for any info.

 

Dude, your question is way out there....

You need to tell us what ECM you are using as well as what bin.

You also need a scanner or data logger of some type to determine what engine load the stumble occurs at to try to adjust your spark table.

Without more info, that is about the best answer you are going to get.....

 

Fare enough, I am using a 4288 ecm and the same AO bin file that came with it. I do have the scanner and datalogger (winaldl) but at same time am not sure what to look for when scanning or logging.

Its hard to see the stumble for me on both as well...the main stumble is when just barely giving it the gas to get going from 900 to 1200rpm's and the same goes when just cruise idling say in second/third gear . Its hard to log where you cant keep the throttle at too. I have to rev it up to get it over the stumble and to get moving. I tried logging several times but when the truck is in that rpm range it goes into convulsions and starts serging back and forth. logger always says its lean also, shows around 140 or so.......move everything up BPW and VE1 and 2 according to log and then it floods out.....rev it up and get going again , start logger and still says I'm lean......HMM????

Sorry about not enough info, if I need more again just say something again. Still would like to know how to take basic advance curves off charts to calculate to put onto table? I did get the post where grumpy re-posted the spark table calculations. I'm about half way into it now. So far , really good stuff and good gouge.

As always thanks in advance for any info.

 

I am unsure if this link will help you....

Rectifying a Surging Idle , Stumble upon rev.....

 

Definitely be careful if you're trying to duplicate a mechanical advance curve. I know that at least in my ECM, the SA in the main table probably is not as much as the engine is getting at the dist. If it was, then I'm looking at 20° total SA at high rpm and that can't be right. There must be an adder (or table) somewhere that Tunercat can't (or won't) find.

 

I agree with ya' Kev. I'm not sure what is where in the SA's. Just because I used the same bin wth same settings with both mechanical and ICM's and have same outcome. Granted I am a newbie but I still can do trial and error. I did how ever go back a have a bud come over an set my timing back to stock settings. It is 10 btdc at 1600 rpm and will not touch that again or at least till some thing points me that way. I will also set this setting in my tunerpro bin for initial setting. See I dont get that either is "initial settting" at idle or what the stock setting called for? Because at idle it runs at like 5-6 btdc and at 1600 goes to 10.

Now when I look at my tunerpro file it starts off at 400 rpm and 20 kpa at 15.33 and when it gets to 100 goes down to 10.33, from what I read I thougt it was supposed to be 10.33 across the board for 400 and 800 rpm's?? That is what my initial setting was and that was what is supposed to be in there correct??? I still would like to get the calculations from the base line charts too?? Just not sure how to get the numbers off and into the formula???
As always thanks in advance for any info.

P.S. if there is something missing or not enough info please feel free to smack me and point out what is missing!!!!! Gotta know what I'm doing wrong before I can correct it.

 

If you have an erratic idle you can set the SA to be the same in the idle RPMs and load ranges. Otherwise, it makes sense that the SA would decrease as manifold pressure increases. 20kPa, btw, is overrun. Start looking at 30kPa and higher for the idle load range. Or check the scantool.

 

I can work with that kev but for now I need to basically put in a complete SA table for my engine. I using the 4288/A0 ecm from a 4.3L chevy for on my 4.2L jeep engine. The two tables are completely different, close but different. Thats why I would like to be able to take the vac advance/mechanical advance from original stock 4.2 and do all my own calculations to put on this table.

 

Does that ECM's ALDL data stream include SA? If not, you might want to consider one that does, as it will be difficult to accurately dial in an exact spark curve. You could do a rough test with a timing light, the kind that has an advance dial on it. Just time it, then look at the cal and see exactly what you think the ECM is commanding, after including all the variables that effect SA (like initial SA, base @ dist, cool comp, etc). Then maybe you could figure in a constant for how much the ECM is off the real spark and input your curve knowing that.

 

OK, Kev now you REALLY cought my ear now and I'm listening. Yes I can see spark in winaldl but that is in counts. Is there something I should/can look for? I do also have a scanner but do not know what to look for on that either, can you expound on this please? (expound= word for the day, almost seem edu'macated huh?) I read grumpys re-post of the guy who did the spark write up and understand the counts (16 = magic number) but would have to put that in effect and try it, but like I said I'm not sure how to take from original tables and calculate? I also do have a timing light with the advance thingy on the back of it but dont know how to use/adjust for what I am looking for. For example when I set the "static" timing to 10 degree's (mine is at 10 btdc at 1600 rpm) and told buddy that it was set he let off gas and out of curiosity at idle I shot it again. It was at like 5 or 6 btdc when I looked at it........My advance on back of timing light was at "0" so I then started turing it up and when I got to zero on the actual truck/balancer mark it was at 15.......what does this mean??? I never did go back and check to see what it would do at 1600 again but can easily do so. Can you explain this ??? Or with timing light what does this tell me??

Dont leave me hangin' now Kev......LOL.....as always thanks in advance for any info.

 

Do you have a timing chain problem perhaps?

 

Wouldnt think so because when I end up in limp home mode due to my outstanding program tuning ability (or I'll just undo ostrich) it runs great. No stumble no hesitation not nothing just hall's butt. Gas economy sucks...but I'll give that up for power anyday. I even went back and checked part numbers to make sure I had correct ones, o2 mainly, to make sure it was for my ecm. Changed injectors to a konw set of good ones for a 6 cyl. , when I scan I seem to get the right numbers....it always idles great just when trying to idle when I open throttle a bit or when at the same cruise speed.

I guess what I need to do is go back re-read some timing post's , get the intructions on the timng light to see what the numbers on back represent and find some tables where someone actually took the tables from a stock vac / mech advance manuals table for a specific car ,who did the calculations and then used them to come up with basic table for there vehicle. Every thing I seem to see is people using stock files and working with what someone else already figured out for that particular application. Thanks for the info though, I saved it to my docs for further refreneing. I will figure out how to put my base calc's in for my app.