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Hoping someone can point me in the right direction here, I have been chasing this intermittent start/die. The engine catches then dies, the only constant is it only happens on a warm engine. But it’s so intermittent that the only way I can catch it is to keep my data scanner on at all times when I start the car up.
My gut is telling me it could be the used OE Bosch MAF just because of age and that it may be getting a heat soak? I swapped both the MAF relays as I had spares with no change. It’s odd because the car runs great with no CEL.
I am thinking of just trying a reman MAF but hate throwing parts at it.
I have a data scan of it happening that I will try to load up.
When looking at the L98 start sequence this also leads me to a MAF issue as it happens when the engine “catches”. Which is when the ECM pulls data from the MAF which uses that info for the injector pulse width.
One thing I just noticed on the data log is the injector pulse width goes up to 6.15 when I have my issue which is much higher than the nominal 2.2 as referenced in the start up sequence. On my other data logs when the car starts/runs normal it never goes much higher than 3 and then quickly goes to 2.2 ish at start up.
If I do replace the MAF I will likely go with the blue streak Bosch reman, the local O’reilly’s can order it and with a lifetime warranty, I think buying local is the way here in case the reman has issues, rockauto is a pain to deal with on exchanges or warranty in my experience.
When looking at the L98 start sequence this also leads me to a MAF issue as it happens when the engine “catches”. Which is when the ECM pulls data from the MAF which uses that info for the injector pulse width.
One thing I just noticed on the data log is the injector pulse width goes up to 6.15 when I have my issue which is much higher than the nominal 2.2 as referenced in the start up sequence. On my other data logs when the car starts/runs normal it never goes much higher than 3 and then quickly goes to 2.2 ish at start up.
If I do replace the MAF I will likely go with the blue streak Bosch reman, the local O’reilly’s can order it and with a lifetime warranty, I think buying local is the way here in case the reman has issues, rockauto is a pain to deal with on exchanges or warranty in my experience.
Where I am at is I don’t know if a bad MAF can cause the higher injector pulse width? The ECM is only a few years old and is a NOS AC Delco.
Battery voltage is pretty bad when you first crank. What's the condition of the cables? If it's doing the thing, does it still do it with a jumper pack attached?
Battery voltage is pretty bad when you first crank. What's the condition of the cables? If it's doing the thing, does it still do it with a jumper pack attached?
The cables look to be in excellent shape along with the terminals as I was just inspecting those the other day, the connections are clean and tight at the starter too. I do not have a jumper pack, I can swing by the parts store to have them test it or see if my buddy has one. It’s a 5yr old Interstate so it’s not new.
These TPI cars get weird with a weak battery as well. I will review my other data logs when the car starts normal and see what the battery is doing
Here is another data log of when the car starts normally that I took a day or so before the one with the issue. Battery voltage looked lower on cranking there too.
It does drop briefly on the 2nd log, but look at the much more normal charging voltage after (13.1v). 11.9v is like, alternator not charging voltage.
I am going to go back through my battery cables and grounds but I am leaning towards the just over 5 year old battery is the problem. As you pointed out the voltage dips too low when cranking the engine.
IMO, your first posted log is not really saying anything. You cranked for less than 1 sec. During that time, the ecm saw Reference Period while cranking, the engine reached 300rpm while cranking, thus ecm declared it running. Immediately after, all data flat lines and are, IMO, inaccurate. Worth, mentioning, there was no battery voltage at beginning of log. IMO, the voltage drop during cranking is normal based on many logs I have reviewed.
The 6.15msec is normal in my IMO. Here's why:
Looking at first frame when engine is declared running (both logs)
In your second log, you get 3.45msec with MAF at 13.47g/sec, AFR at 12.7, INT 128, BLM 118, RPM 750. I don't have your injector flow rate, but I suspect it's 22# or 24#. Irrelevant in my comparison calculation though. I can estimate it.
In your first log, you get 6.15msec with MAF at 9.8g/sec, AFR 12.51, INT 128, BLM 118, RPM 300. Based on same calculation, the INJ BPW is where it should be.
Your MAF appears normal to me based on your second log. It fluctuates immediately after start-up. It's an indication that ecm does no rely on default settings to established air flow as if the MAF would be defective. If you want to experiment, data log with MAF unplugged. You'll see the difference.
Can you data log MAF voltage? If not, have a voltmeter monitor B12 before and after start-up.
There is a way to data log MAF voltage. I find it extremally helpful in trouble shooting. You need to do a simple mod to your BIN and ADX. Here's a link that explains it:
Now, what would cause your issue? Hard to say without being there. If it does not fire-up when warm with less than 1 sec crank, maybe you could try holding the key just a bit longer. Also, try adding a bit throttle but not too much. If it helps, it's a rich crank condition. If not, it could be lean. The MAF is not involved at cranking. If the engine would fire-up and die immediately after, the MAF could be involved. But in your case, the engine never really fired-up.
When looking at the L98 start sequence this also leads me to a MAF issue as it happens when the engine “catches”. Which is when the ECM pulls data from the MAF which uses that info for the injector pulse width.
Yes, but it needs proper fueling from cranking to transition to Start-Up Enrichment in Open Loop. In your first log, the engine dies immediately. It never really started-up. I suspect cranking fueling is at fault. Having said that, a tune can not untune itself. So if the problem is recent and the tune has not been changed, the tune should not be the problem. Something else has changed that causes the tune to not be efficient.
I am going to go back through my battery cables and grounds but I am leaning towards the just over 5 year old battery is the problem. As you pointed out the voltage dips too low when cranking the engine.
It's not a bad idea to change a 5 year old battery. However, I doubt it is your problem. But, it's smart to cover your bases and make sure everything is in order.
Sb, thanks for the info and tips. When the issue happens the engine doesn’t quite catch…it seems to turn over strong but battery voltage when cranking seems low from what I’ve read. It acts like it just doesn’t have enough juice to finish starting. My daily driver did the same last winter but only when using the remote start, battery was on its way out and after replacement was good to go.
I may put a pin in this seeing as how I have about a month left of driving season up here and I don’t want to replace a battery just for it to sit on a tender all winter in my garage.
Sb, thanks for the info and tips. When the issue happens the engine doesn’t quite catch…it seems to turn over strong but battery voltage when cranking seems low from what I’ve read. It acts like it just doesn’t have enough juice to finish starting. My daily driver did the same last winter but only when using the remote start, battery was on its way out and after replacement was good to go.
I may put a pin in this seeing as how I have about a month left of driving season up here and I don’t want to replace a battery just for it to sit on a tender all winter in my garage.
Great!
Yep, hard to tell when one can not hear, feal, smell or see.. lol
A log can only tell so much.
I did have a problem with a bad battery on a TPI SD. It would crank endlessly and not fire when cold. However, you would not feel it was a weak battery. Engine was just cranking like there was no fuel or spark. No smell of raw fuel though. It would fire only when reaching over 300rpm (confirmed by scanner) and engine declared running. I suspect, the bad battery was creating some gremlins that would prevent fueling or something. New battery and trickle charger solved the problem. Hard to tell with monitoring voltage. On many logs I have reviewed, voltage goes down in 9s, 8s and even 7s during cranking without any issues.
Just wanted to update the thread, I actually picked up a decent-ish battery tester that was on sale (topdon BT200) and tested my battery after giving it a full charge with my trickle charger.
It did not take long to fully charge but once I hooked up the tester it showed the battery is at just over 50% health and needs replacing. The other test I performed was a cranking test and as Komet pointed out the voltage was low and confirmed by the tester. I also checked the charging system just to cover all my bases and that tested out good.
Looks like the first order of business in the Spring is a new battery, I may go with another Interstate or give an Easter penn product a shot, I’ve heard good things about Deka and Napa the legend batteries or maybe Oreillys as they carry them under their house brand.
Although I can’t vouch for dependability I really liked the Topdon BT200, super easy to use and seems to work well for a home shop.
I have installed NOCO Genius onboard chargers on my cars. I now always plug them when they are parked, even off season. No more plug, unplug battery cables. I use Walmart batteries and they seem to last.
I have a battery tender I use in the winter but was late to the game on it as I just started using it last fall. You can’t beat Walmart warranty I hear as well and they are everywhere.
09-17-2023, 12:50 PM
