TBI ignition control module

[grumbolt]

The attached screen shots show a normal SA and very odd SA. I wonder if over time, your SA starts looking odd?

dave w

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....

[dave w]

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

[Fast355]

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.

[grumbolt]

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!

[Fast355]

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.

[TeamSlewis3]

But even with the "base" timing map in the icm code it would still be WAY dependent on how many HC's he's actually got floating around in the cylinder. Maybe it's flooding and no amount of spark correction will help. OR the opposite could do the same. we were always trained the switchover controlling was @ 450 rpm. If youv'e ever had to revive a no starting RX* you guys will know what I'm saying about wasting time with timing, how wet is it inside when the event happens?

[Fast355]

But even with the "base" timing map in the icm code it would still be WAY dependent on how many HC's he's actually got floating around in the cylinder. Maybe it's flooding and no amount of spark correction will help. OR the opposite could do the same. we were always trained the switchover controlling was @ 450 rpm. If youv'e ever had to revive a no starting RX* you guys will know what I'm saying about wasting time with timing, how wet is it inside when the event happens?

If its freewheeling on the starter that is one thing, but kickback on the starter is over advanced base timing or a weak starter.

That being said the stock 100K mile Vortec 350 PM mini starter from my 97 Express van has no issues spinning over my 11:1 383 with a Q-Jet sitting on it with 14° initial timing. It cranks at 220 psi. It may be time for him to upgrade the starter, test the battery or replace the cables.

[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.

How can you accurately say "with no knowledge"?

I can accurately state, you don't know everything!

dave w

[Fast355]

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.

[1project2many]

The ecm generally is not involved in controlling timing below 450 rpm. In order to retard spark timing during crank one would set the timing with a base angle of less than zero degrees. The reference angle in the chip should be adjusted to match the actual angle of the distributor so the timing tables continue to be correct. Early TBI engines were set at 6 degrees then GM moved to to zero degrees. I'd love to have the "real" answer for that change.

Fuel delivery is delayed during cranking as well, generally by a number of reference pulses. "Back in the day" a properly adjusted and not leaking Quadrajet would usually allow the engine to start with the shortest application of the key if the engine was warm. By working with IAC Park position or initial IAC position (depends on cal) and the number of reference pulses before fuel is enabled it's possible to get an EFI engine to start as quickly.

Speaking of quick starts, I've switched a number of GM vehicles over to use Ford in-tank pumps. I have replaced more GM pumps than any other make. And I've worked on Ford vehicles with over 300,000 miles on the original pump. Side benefits seem to be a better check valve and less time before the system is at full pressure. I believe a 99 or 2000 Lincoln Navigator w/ V8 is the application to look at.

The most common failure modes I used to see with these ICM's are no spark when hot, no spark ever, and no reference pulses to ECM. Often a "No spark hot" complaint could be traced back to a faulty pickup coil. Sometimes I'd even get a truck that had received two or three modules replaced "elsewhere." It's much easier to get the problem fixed in one try when someone else has already tried all the easy solutions.

I keep hearing that ignition modules are garbage these days. Folks say you can put in two or three in a row just to get one that works. That alone could make diagnosis a nightmare. But the basics still apply! Ensure you have a good 12V supply to the coil, especially during cranking, and to the module. Ensure the module is properly grounded. Clean the mounting surface and use heat transfer paste (not dielectric grease) between the module and distributor. There are two vent holes in the bottom of the distributor. They are protected by tiny screens that get plugged. Clean them! I've actually installed ported vacuum fittings on the bottom of distributors to help keep air moving through and to reduce the buildup of nitric acid in the dictributor. I promise it helps the components last longer.

If the engine is cranking slower before the module dies, I have to ask if there's any chance you're having battery or charging issues? Is it always at the end of winter? When more power is directed to the starter there is less available for the coil. The ICM controls current through the coil so the lower the voltage, the longer the ICM leaves the coil turned on. Although this shouldn't change the total amount of heat generated, I have to wonder if shorter bursts of higher current may do less long term damage than longer on times with less time between for cooling. But ultimately we're talking about microseconds and the difference may be academic.

I agree that the "wierd" timing values posted by grumbolt appear to be normal values misrepresented by the datalog software. It's possible to edit the definition file so the timing displays correctly.

[TeamSlewis3]

You know I was talking to an old trans builder "mentor" whom I watched for a couple weeks with a service writers FORD F-150 ......... GOTTA SWITCH TPOUGHBOOKS APPARENTLY

[TeamSlewis3]

Ok so the freind is a fairly savvy fellow but kinda always gives me greif because I "work too hard" . Ya know when I met em in our 30's he already had race cars and drove one of the vette's to work. Long story short I sat back patiently as I watched our service writers 50 somethin 289 truck just eat him up on what he SWORE was "fuel loading" . He ahad done a tune up already, then modules coils, scopes..... I said looks like a burn line issue. Couple days later he found that cracked plug. My question is this: those screens they put in the bottom of the lower plate I've seen clogged ,green , no srceen, But I believe it is a heat issue that over time a small voltage problem whether groung or power finally deathnails it. High humidity? Not enough time ,short trip condesation?But I'll agree with the previous poster I have NEVER in 30+ years seen an ICM come back from the dead or cause an obvious data issue thats an anomoly that can't be felt in the foot. I have seen ECM's do weird stuff and give false data that if correct can only be captured by scoping nputs, even then, output can be incorect w/out any codes. Seems like these old ones can have tons wrong and no codes..... the early days!! Carb guys going SEE thems junk! I'm kidding. I loved my elecrtronic Q-jet opening up those flaps in that hood, and it SOUNDED way cooler than the Cross-Fire pace car I had that did the same. So I mentioned my knocking or phantom knocking and he just asked "why not just go with the $50 HEI?" and I know it goes against most thinking but I'd like to run the HEI with external VORTECH the ICM driving the timing. Any Ideas?

[1project2many]

My first two EFI systems cost me $200 but had to jump in the dumpster to remove a bunch of parts. One was an '83 Crossfire (the manifold is on my pickup) and the other was TPI. I spent years asking people how to make changes to 'em. Kept getting asked why waste my time? Cause in 10 - 20 years you won't find a carburetor in the junkyard.

Most of my ignition modules last for years. I actually changed one in my '57 two summers ago. It was a used OEM module I put in when I switched the truck to EFI in '93. For a while my '99 Vortec truck was giving me fits with intermittent misfires that appeared to be a few different issues. I found coil burn through twice, a bad module once, and a bad rotor several times. It turns out the power wire to the coil and module was chafed and shorting. I'm guessing the power interruptions were causing misfires that led to the other issues. After the wire was repaired the truck runs very well.

I'm gonna say "possibly" to the external Vortec module on HEI. There's no bypass mode built into the Vortec or LT1 module. And there's nothing to convert the crank signal to a square wave. So I'm thinking that if I only had access to automotive parts I'd investigate using the HEI module to trigger the LT1 / Vortec module. If you can do that you'd move the high current switching out of the HEI module. Research the signal from the ecm / pcm. If it's driven low similar to a coil - signal then you may be able to wire the coil- from the HEI module directly to the pcm input on the Vortec module.

[grumbolt]

I agree that the "wierd" timing values posted by grumbolt appear to be normal values misrepresented by the datalog software. It's possible to edit the definition file so the timing displays correctly.

excuse the noobness, but what would have to be changed? and would it be in the A217 $0D TP5 v250.adx file?

would it be as simple as changing the "range low" in the picture to a negative number?
spark definition.JPG

[tayto]

Acdelco TPI pump (Left) & Bosch Cherokee pump (Right)