HELP ! Red lightning bolt woes

[Sportony]

Hello. Newbie to forum here. Hoping for some input from those with greater experience on a mystery that is really vexing me. I am truly stumped with this one. Have a 2003 5.7 hemi automatic, quad cab. 115 K miles on remanufactured engine that was replaced in 2012 due to infamous hemi tick. (230 K on body total). The truck has been meticulously maintained, and was running great - completely normal, without any indication of any problems or issues whatsoever a month ago.

I was driving truck and pulled into the driveway (again without issues). Couple hours later, had to get back in to drive elsewhere. Suddenly after initial startup, it started to idle very wildly. Check engine light and infamous red lightning bolt came on the dashboard. It would start off idling at 3500 RPM for about 2-3 seconds, then would calm down and idle would fluctuate rhythmically between 700 and 1500 RPM. No ticking or pinging, but strong smell of gasoline. Would limp forward if put in drive and would idle erratically, but without shutting off. Now it only runs for about 5-8 seconds with same symptoms, then spits / sputters / cough and then shut off. If you try to put it in drive it cuts out. I have hooked up OBD scanner multiple times with No Error Codes !! (it works with my other vechicles, so doubtful it's a bad scanner).

I have studied youtube videos without much luck on the problem. I'm mechanically inclined with several engine rebuilds under my belt, but all have been older 50s / 60s mopars.

Have replaced or checked the following on the truck (all new or recent replacement)

1. Throttle body
2. PVC valve
3. MAP Sensor
4. Crank sensor
5. Cam sensor
6. new Coil packs
7. New spark plugs
8. Rebuilt alternator 18K miles ago (that still works fine - tested and normal)
9. new battery.
10. Tested fuel pump - working well (tested, works fine, delivers consistent 40 psi with fuel gauge attached)
11. Timing chain and tensioners normal
12. Fuses checked; all appear normal
13. TB sensor in the airbox is routinely cleaned
14. Checked for shorts or cracks / breaks in wiring harness - I could not identify any


Have not tested the APPS (not sure how) nor can I get a new one since it's now a non-production item.

Have not changed O2 sensor as I figured this would produce a code if they were faulty. I do have to replace the harmonic balancer due to the seal cracking and breaking. After removal, I took down the front cover and inspected the timing chain. I thought it may have jumped time, but timing chain and tensioners appear normal after takedown and inspection.

Do I need to do a leakdown or compression test ? I thought red lightning bolt meant some error in electrical or spark. Seems so odd that one drive cycle it runs completely normal, and then the following cycle, without any indication, it runs like crap.

Any help or guidance would be SINCERELY APPRECIATED ...........

 

[Daw14]

Give your o2 sensors and wires a look over , sounds like it could be dumping fuel , maybe like a stuck injector.
May also inspect harnesses for corrosion , any and all accessible. I would start at pcm and work away from there.

 

[Sportony]

I've done that, but I guess a second look over couldn't hurt.

 

[eds0c1]

Any progress on your lightning bolt problems? The several times in 20 years i have owned my truck when that light came on it was either the throttle body or an electrical short somewhere.
Did you install an aftermarket TB on the truck? I did that several times and they always went bad.... i have had my current factory TB on the truck for 10 years..... clean it out every 6 months or so.

 

[UncleGunns]

(parts cannon}

Stop the parts cannon crap and figure out what's actually wrong with the truck. You can get a bidirectional scanner for $100. The APPS1 & APPS2 sensors likely are not bad; they rarely fail. There are articles about replacing with a Mercedes unit if it comes to that.

Parts in the system for throttle control:

APPS sensor pack, throttle body, PCM, and wiring harness in between. Also critical are ground cables and the battery/ battery cables.

APPS sensors - Apps1 should read ~0.4-4.8V on sweep from 0% to 100% throttle, with a smooth gradual curve. Apps2 should read roughly half that, ~0.2-2.5V. Apps2 will also drop to 0.0V on live data graphing; THI IS A NORMAL CONDITION. This is a built-in integrity check between the APPS sensors and the PCM.

FIRST place to start any time you're tryin to diag performance faults is the battery. Make sure voltage is ~12.5+ at off state. Check and ensure the terminals are clean and tight at the battery. Check the "other ends" of the battery cables. There are ground straps on the valve covers that push over the valve cover studs. Make sure they're clean, not corroded, seated properly. They're each about 3" long, and are there to ensure that the valve covers (and COPs) get adequate ground to the block. There's a ground strap at the BACK of the cylinder heads connecting them together too. All these need do be confirmed 100% solid and unmolested. Alternator should also be pumping out ~14.5V at idle.

Electrical gremlins are terrible for any vehicle and will kill your brain.

If the light's on, the truck is in limp mode. There will be trouble codes set. Again, get a decent scanner and figure out what the codes are. Again, AFTER you confirm all the power connections are good.

Look in the manual, or search GooXXX on a "ETC relearn". You can do this with just your foot and the truck's key.

Also, did this start right after it rained/ snowed/ you went off road/ hit a pothole hard? Did you fill the gas tank right before it started?

There are a ton of conditional impacts that can happen where no CEL will be set, but the truck will run like crap. You need to eliminate all causes.

Triangle of combustion: FUEL --> AIR --> SPARK

Figure out whether any of those three is suffering.

AIR - is the truck under water? NO - you probably don't have issues with air. That leaves FUEL and SPARK. Which of those two, or what combination, is impacted? Failing/ failed part? Loose connector? Squirrel-damaged wiring?

Also, don't be surprised if you have a broken valve spring. This is very common on these HEMIs. This is usually an "all of a sudden" condition and the truck will run like hammered sour crap. Scan tools won't show you this failure, but you can see tell tail feedback on a good scanner and with a good brain. A ton of work to diag this failure, but it's not a hard repair as long as it's just a valve spring.

Again, throwing parts without a scan and some real diagnostics is mostly useless...

 

[rjbar46]

A quick look through here & I don't see a fuel filter has ever been changed. Likely not the issue with some of the descriptions, but still.