Electrical/alt/coils?

[skiller1234]

Hi, hope it’s a great day for all! Having an issue and could really use another brain .
Relevant history. 1999 lx470 220k. Over summer the alternator dies while on road trip, no choice but to have random shop replace. Month ago, misfire, replaced plugs and coils. 3 weeks ago new timing belt etc.

Couple weeks ago driving down from mountains, getting all kinds of weird shifting issues, then truck stalls at light near home. Able to limp to garage. Nothing really found, they torqued the spark plugs down for good measure, and advised that sometimes aftermarket coils can cause strange things. I think it’s a good shop and they are trustworthy.

Everything runs fine till tonight driving home from same location as the first time. Same symptoms as before, but I look closer and notice revs dropping way low while lifting from gas, causing some hard driveline hits getting back on gas. I also notice the headlights dimming while coasting. Truck stalls again when coming to a stop. I was able to limp it home by driving slow in second and taking turns at speed, coast into garage when it stalls pulling in. Jump out to hunt for a voltmeter, but turn on truck, it idles fine and voltage decent at 13.8 idle.

Worried about it dying while driving, does it sound like the alternator could be fritzing out causing the shifting and idle issues? Or has anyone seen aftermarket coils cause anything like this?

any ideas highly welcomed and appreciated!

skiller

 

[Ayune]

Sounds like your replacement alternator is going out. Headlights dimming is the real clue here, that’s a separate path than the ignition. And the coils can’t gang up on you in some twisted spark conspiracy, they’ll fail one at a time and stay that way.

So the core electrical health of your truck is suspect. That points to alternator/battery.

 

[MycoManiac]

Sounds like your replacement alternator is going out. Headlights dimming is the real clue here, that’s a separate path than the ignition. And the coils can’t gang up on you in some twisted spark conspiracy, they’ll fail one at a time and stay that way.

So the core electrical health of your truck is suspect. That points to alternator/battery.

Those two things. Check battery. If hood, alternator. Barring some crazy wiring ecm issue.

 

[skiller1234]

That's where I am leaning - but I never had the alternator affect shifting/idle like that.. Of course crappy alternator put in by first mechanic in yellow pages out of state = not much chance of any financial restitution..

 

[Ayune]

That's where I am leaning - but I never had the alternator affect shifting/idle like that.. Of course crappy alternator put in by first mechanic in yellow pages out of state = not much chance of any financial restitution..

Bad voltage regulation can make any ECU act funny so nothing is off the table. The regulator is on the back of the alternator, depending on brand you could probably replace just that, but most folks here would recommend ponying up for at least a rebuilt OEM alternator that’ll last longer than a few months.

 

[jsloden]

It might not be all of your coils going out but it only takes one to make it shift funny. I had that exact problem in mine. It honestly felt like the torque converter was going out and was shifting funny in all gears. The weirdest part about all of it was that I never got a CEL. It took a while before it started having a misfire at idle. When it did I just started unplugging the coils troubleshooting it the old fashioned way. Turned out the number 8 coil had a cracked boot. It was arching inside the sparkplug tube. I replaced the rubber boot on the coil since it was a denso and still working fine. The truck ran perfect after that. That was six months ago and everything is still fine.

 

[medtro]

Hi, hope it’s a great day for all! Having an issue and could really use another brain .
Relevant history. 1999 lx470 220k. Over summer the alternator dies while on road trip, no choice but to have random shop replace. Month ago, misfire, replaced plugs and coils. 3 weeks ago new timing belt etc.

Couple weeks ago driving down from mountains, getting all kinds of weird shifting issues, then truck stalls at light near home. Able to limp to garage. Nothing really found, they torqued the spark plugs down for good measure, and advised that sometimes aftermarket coils can cause strange things. I think it’s a good shop and they are trustworthy.

Everything runs fine till tonight driving home from same location as the first time. Same symptoms as before, but I look closer and notice revs dropping way low while lifting from gas, causing some hard driveline hits getting back on gas. I also notice the headlights dimming while coasting. Truck stalls again when coming to a stop. I was able to limp it home by driving slow in second and taking turns at speed, coast into garage when it stalls pulling in. Jump out to hunt for a voltmeter, but turn on truck, it idles fine and voltage decent at 13.8 idle.

Worried about it dying while driving, does it sound like the alternator could be fritzing out causing the shifting and idle issues? Or has anyone seen aftermarket coils cause anything like this?

any ideas highly welcomed and appreciated!

skiller

I have similar thing happened recently. 1999 LX470 with 220k miles. Battery and ABS lights on and engine stalled within a mile. No shifting issue. Engine wouldn't crank after that. Put in another good battery, drove it for less than a mile stalled and wouldn't start again. I was not able to limb home. A reman alternator from dealer fixed the problem.

 

[skiller1234]

Want to say thanks for the responses. Still unsolved - its intermittent right so hard to nail down. Its odd that its only really happened badly in that one certain situation - driving home from higher elevation at night - 3 times now spaced out. I am starting to notice the idle fluctuating a bit during the day though - bounces around for a few seconds before it settles down. I did check the ground wire - sanded it down and made sure it wasn't corroded etc. Honestly I was thinking it might be time to move on and wanted to get the timing belt done before selling it. Now I don't wanna pass on a weird problem...

 

[skiller1234]

Well - bumping this back up. After searching around in here I noticed several examples of a bad ground causing odd issues - so I sanded down and cleaned up the ground wire - which seemed to do the trick - until it didn't. Happened again last night - its so odd but thinking through the times its always been at night - when its pretty cold, and driving down from a higher altitude. Maybe its a fuel pressure thing? I'm going to swap out the fuel filter next chance I get as I have no idea when it was last done - but has anyone seen a pump act odd at cold temps?

Again symptoms being off hesitancy when cruising, revs dropping when coasting causing big whiplash when getting back on the throttle, unable to hold idle when pulling up to a stop.

 

[2001LC]

I'd start with a good tune up and coolant service. Which includes new Dense coils, if yours are some China made junk.. Take care of all vacuum leaks also. Make sure fluids as they should be.

If you'd like to stop by some day, for me to look over. Send me a PM.

 

[skiller1234]

I'd start with a good tune up and coolant service. Which includes new Dense coils, if yours are some China made junk.. Take care of all vacuum leaks also. Make sure fluids as they should be.

If you'd like to stop by some day, for me to look over. Send me a PM.

Ugh - Thank you I appreciate that very much. Just popped a new radiator last summer so that should be fine. I have the old coils - gonna order a couple new ones - swap the old ones back in and see if I can track down which one was causing my issue previously. Also fuel filter cuz I already got it. If that's not it - I may take you up on your very kind offer!