Have you replaced the coil,plug wires??
Have you replaced the coil,plug wires??
The attached screen shots show a normal SA and very odd SA. I wonder if over time, your SA starts looking odd?
dave w
That odd one looks like a limp mode, I thought the module only controls advance in limp mode, and under normal conditions it only signals cylinder static advance and the emc/pcm timing table does the rest. ??Originally Posted by dave w
Dean
it seems most don't last long but every once in a while, one finds a good ICM that lasts a lifetime. dang even the acdelco ICM failed?
are you running a modded computer?
i just had one fail a few days ago(it was two weeks old) the one i replaced was fine. i shoulda left it alone. back to the point. i had just patched my 7747 with the spark advance hack and it failed that evening...coincidence?
sorry been out all weekend. The ICM's have been in the stock computer when it was a 5.0 and failed, in a very light modded 350 with a new distributer and failed and now in my modded 357 and failed. The timing/SA does not look wierd. This time it died and the truck was not even warmed up, I was ideling for about 15 minutes but it was 50 degrees out, shut the truck off and 2 minutes later tried to start and no fuel as the ICM does control allowing fuel. I have had 3 different tbi trucks and this is the only one that has ever given me issues, all were modded and all had headers full exhaust, electric fans, ignition systems or msd coils and moroso 8.65 ultra 40 wires. The coil and wires are about 1yr old as I replaced them right after the ICM died a year ago, for some reason it is about every year which makes no sense. I am gonna try the Artic Silver 5 thermal paste I use on my overclocked gaming computers and see if that helps. I was just throwing this out there to see if anyone else has had this same issue where it dies once a year, I usually put about 10,000 a year on the truck. Anyway thanks for the responses.
i had two icms go out in 3 weeks now. but my connectors where a little loose.(maybe they loose connection enough with engine vibrations to shorten the icm life?) maybe check your pigtails? also my GM icm never fails. but every aftermarket one failed so far. really leaning towards--maybe they are all junk? just some ideas..
One thing I think I have noticed over all 6 of these icm's failing is that it dosen't crank as fast when I start the truck for about a month before it dies. I just think it is very weird it is every year, not a few months or at random times but almost exactly a year apart these things die and dosent matter if gm or aftermarket or performance ones they all fail same time about 1yr. So I am keeping a space in the truck, I have the tools to change it out quickly so if it happens I can change it. I will also see if next time it starts cranking slower when starting and see if that is a side effect before it dies. But we will have to wait for a year because that is the pattern so far.
I have never seen a SA like that in any datalogs and I was datalogging the day before the icm went out. The only thing I notice is it gets harder for the motor to crank over or should say it's like the battery being low and cranking slowly but the battery is fine. Once I replaced the icm it cranked over normally. The icm is very weird piece, I have had it just take out the timing advance and the truck would still run 2x, I have also had it just die where there is no fuel or spark 3x and I have also had it take out the entire distributor.
would you say my icm is bad Dave? when my engine gets up to operating temp, it acts like the timing is way advanced and is hard to start.
attached is a screenshot of the wbo2 spreadsheet with the log pasted into it...
sa 2021-03-12.JPG
important to note, the battery voltage was around 13.5 most of the log, but at the end it was down to around 12.5v i originally suspected the erratic readings due to the voltage going south... the engine was also around 219 degrees at its peak....
Last edited by grumbolt; 03-13-2021 at 10:33 AM. Reason: added voltage and temp data
I don't know if the ICM is faulty or not. Usually an engine won't start with a faulty ICM.
The odd SA might be due to the data stream definition or .adx file.
I would reprogram the chip with the Altitude Spark Bias set to ZERO degrees, leave the other parameters unchanged.
dave w
Leave the altitude bias alone. Not sure why people just program this out with no knowledge of what it is actually there for or what they are doing by removing it. The weird datalog SA is because the logging aoftware is not recognizing a negative number. Zero'ing the bias is adding that much timing to the whole timing map. If it was a bias of 9.81 and you set it to zero, you have added nearly 10° across the entire spark map.
I had not messed with the altitude spark bias in the past, but it was set at 0.
the specs for the engine in its stock form calls for 0 timing and it is set at that...
i have changed out the module and had the alternator tested..
it seems that when i installed the engine in the buggy, i ran the "L" terminal from the alternator to a light bulb then to ignition power... this is how it is represented in the schematics.. in poking around i have seen where a resistor is wired in series with or instead of the lamp on the cs130d alternators and suspect that the bulb in the tracker dash doesnt pull the same amperage as the bulb in the sonoma dash.. i will be ensuring the charging system is operating properly before the next logging session..
do you know how to make the ecu retard the timing when trying to start the engine when it is hot?
thanks, in advance!
From what I remember the ECM does not control the timing during cranking. EST bypass circuit is enabled it cranks off the distributor base timing until about 250 rpm is reached.
How can you accurately say "with no knowledge"?
I can accurately state, you don't know everything!
dave w
I never claimed to know everything, but I do have a fair working knowledge of what the bias values do in the code and also what happens when someone just zeros them out. I have been through the actual code in the motorola assembler and dissasembler as well as worked in the $0D Hac enough to make my own XDF and write my own lines of code in $OD. I also have a fair knowledge of the workings of the MAF OD and MAF OD MPFI code. The datalog is doing those weird numbers because the timing advance is negative in those areas. As soon as the timing value is positive the weird mess goes away. That is why whacking the altitude bias appears to fix it. It is doing the same thing as offsetting the whole timing map the same number of degrees advanced. The bias is simply there so that the table can have a negative number. Guys used to ignore the bias value and several $42 ecu and xdf files were written without the bias value being subtracted out.
Long story short, leave the bias alone, make the timing map positive, make sure the coolant xompensation is not retarding a ton of timing at the coolant temp the engine is running and that there is no knock retard and those weird values will go away. If the engine actually needs negative timing there, simply know that those weird numbers are negative timing values.
Last edited by Fast355; 03-15-2021 at 04:00 AM.
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