Hi folks,

Oh boy, seems I'm getting random problems now after my cam build and tune that don't even seem related to the build. Anyway, latest issue is that my car would crank healthy today but wouldn't start. It's been driving fine last couple days and even last night, and it fires right up until this morning. I saw this morning that my battery voltage was below 12.5 (it varied between 12.1-12.3) and immediately suspected that this was causing it because I've heard about some of the system electronics are not happy below 12.5V. I ran with this assumption and went on to jump my car, despite that it cranked healthy and strongly, just to raise voltage above 12.5. With it jumped, it took a while but eventually it did start but felt like it needed gas pedal to keep it from stalling for about 6 seconds until it finally "woke up" and did it's normal cold-start idle procedure without assistance of gas pedal. Afterwards, it warmed up normally, idled normally, and drove normally and I was able to make it to work without further issues.

FYI: My WOT power is solid and I have no hiccups while driving or idling. Also, during driving my alternator takes over and raises voltage to between 14.0-14.5V or so.

Could this symptom be attributed to batt voltage below 12.5V? I'm tempted to go straight to get a new battery after work and start there.

 

Well yes I'd have the battery load tested first then proceed. Is the car MAF or "speed density" tuned ???...Without looking at some hard data we would only be guessing here...you have a scan tool ??...if not it could be:
1) cam sensor
2) if it's just difficult starting cold could be an ECT sensor issue but I see your in Miami but it probably does get a little cool in the morning...you get an extra shot of that good stuff until the engine warms up a bit !!
3) MAF sensor...you could try disconnecting it and see what happens...might be under reporting air flow but since it's running food under load maybe not !!
4) Low fuel pressure, clogged fuel filter, or leaking check valve in the fuel feed line

Like I said without a little diagnostic work you'll just be firing the "parts canon" !!....look 6 threads down...kevbot is trying to figure this out too !...maybe get with your tuner also !!
** Did you do a crank variation relearn" after your engine work ??...should be done !!

 

Thanks for quick reply. Let me give you some follow up info:

1) It was MAF tuned. MAF was cleaned with CRC MAF cleaner spray before I buttoned up things on the build and I haven't had an issue with MAF nor before nor after.
2) I don't have scan tool but I know how to pull codes from DIC. If this is not enough, I could borrow or purchase a scan tool. I can pull the codes from DIC during my lunch break and report back.
3) cam sensor - It has not been replaced recently. I will pull codes from DIC and see if it tells me anything.
4) It was pretty cold this morning for Miami at 54F BUT I have a brand new ECT sensor installed.
5) About low fuel pressure, I have no leaks and I have not hard data to back up this claim but if it's clogged fuel filter, wouldn't I have the issue consistently? I was dyno tuned on Tuesday and fuel pressure was solid and motor had no problem pulling all way to 7k and making 397WHP so I doubt I have fuel delivery issues. Like I said, once it fired up after having it jumped and charging for a couple of minutes, it started (kind of rough, but it started, and it cleared up and idled strongly with it's normal "Cold start" RPM raise and decent to idle after a couple of seconds. Also, today's morning drive after was flawless, including WOTs and idle.

 

Super !!...yes, you can see if there are any...OK, it runs fine we'll rule out fuel pressure but it would be interesting to see if the fuel pressure holds after the fuel prime (check valve leaking)...now anytime you change a sensor it's a good idea to check it's wiring...you only accomplished 50% of the job...was it an OEM ECT sensor or aftermarket ??...can easily be checked with an ohm meter. Is the Cam sensor OEM also ??...would be great if you can borrow one but it's nice to have your own !!

 

More additional info:

1) ECT sensor is some random brand from AutoZone but it's equivalent to OEM. Had to get this one because I accidentally broke the old OEM one (the plastic plug portion) during reassembly on the build and was on a time crunch at that point to finish build and it was only brand available. I have an AC Delco OEM one that I had already ordered brand new in the box I can replace if necessary, but I think I can discard the sensor being a problem quickly if I monitor my coolant temp next time I start it. If it looks good on the DIC then I shouldn't have a problem. I'll report back later on this on my next startup.
2) Cam sensor is OEM and original one for all that matter. Has 90k on the clock.
3) This could maybe be related or maybe not but I actually had the 'Service Column Lock' pop up for FIRST TIME EVER yesterday when I started my car after work. Stalled 3 times immediately due to the 2mph cutoff. After that I had no issues and was able to drive back home. I suspected a bad ignition switch as a likely candidate to this and hearing it's a common failure point, I went ahead and ordered an OEM AC DELCO ignition switch yesterday because I want to avoid electrical gremlins at all costs, so we will soon be able to discard the ignition switch, maybe by next week when it arrives and I have time to replace it.

Now I went during lunch break for some other checks:

4) Codes are the following:
PCM - no codes
TCS - C1221H, C1222H, C1255H (I suspect this is all from dyno tuning on Tuesday, I haven't cleared anything in a while)
BCM - no codes
SDM - U1096H
IPC - no codes
BO RFA - no codes.

5) My batt voltage when I got back to car from lunch was 12.4V, ECT = 100F, Oil Temp = 100F. With this I went ahead and tried to crank and start. Started right up immediately and strong with no issues. Definitely an intermittent problem. As it idled my batt voltage went up to 14.4V with the alternator running, and when I turned engine off again, it went down to 12.8-12.9V. I suspect battery drainage is occurring since this morning it was at 12.1V. Not sure if this is root cause but this might as well contribute.

6) My tuner confirmed my cold temperature tables for startup are all dialed in and I shouldn't have any problems coming from temp variations due to the tune. I believe him too.

 

 

 

Mine was. Had P1518 code pointing to TAC. Replaced TAC. Crank but no start. Bit the bullet and replaced electrical portion (the rear end) of the Ignition Switch. Started right up.
May be your tune.OR...

 

If the tune is not the problem, I suspect the ignition switch. Contacts in the switch burn and then a large number of symptoms appear including crank no start, multiple DIC warnings, low voltage, reduced power, rough running after start.

Bad ignition switch contacts can present problems intermittently until the switch becomes so compromised that a total no start condition arises.

A clue to a bad ignition switch is that the engine starts normally after a crank no start, or crank and start but bad running, by cycling the key to off and re trying.

 

Turabo87,
Read your thread, just wanted to mention, I have an almost new ignition switch, from my keyless ignition if you want PM me. My old one had a worn contact problem and I didn't trust the contact points cleaning so installed a new one until the keyless install this winter.. Rather sell it to a CF member than ebay it.