When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
While trying to figure out why my car had idle issues, I scoured the internet to find about 100 other threads where people had a variation of the same thing: lean idle. Some had it intermittently and some on a regular basis. It also seems everyone has a different reason for it happening, and NOBODY ever posted a fix. So here's mine, in case it happens to work for someone:
History of what the car was doing:
1. Intermittent lean idle on WARM starts. Would last approx 10-15sec then return to normal. It did this for almost a year. AFR was in the 18-19:1
2. Progressed to intermittent lean idle at random times. Stop lights, parking lots, warm starts. 18:1 AFRs
3. Progressed to intermittent lean idle at random times, including driving. 19:1 AFRs
What finally caused a light bulb to go off is when I was driving home from work. It's a 25min drive each way and I got there fine.. on the way home, i got to my off ramp when the gauges started to dim, my battery and oil lights started to flicker, and the engine was losing power. The car died when I put into neutral to coast down the onramp. Ah ha! I'm losing power! The battery was new, so I figured, "alternator!".
But then, I popped the clutch and the car drove fine home, then to the shop the next day. WTF?
A multimeter test showed the battery was fine and an amp meter clamp showed alternator was fine. Stumped.
I kept driving the car, hoping something would fail and reveal itself as the weak link. No such luck.
Things I tried to no avail:
1. Swapping three IACVs.
2. Different battery
3. Jumping a new wire from alternator to battery
3. Keeping battery on a tender
4. Checking all grounds
5. Looking for shorts.
6. Check all vacuum lines
7. Adjust BISS
8. Swap O2 sensors
My gut still said alternator, so ... I bought a new, OEM one. Quite the $275 leap of faith, but I had no other alternator to swap for testing purposes and I REALLY didn't want to do that job more than once (which turned out to only take about 1.5hrs. Awesome).
In the days that passed, before the alt arrived, I found this:
I didn't even realize I had it LOL. What luck, as it changed everything. I immediately hooked it up and saw my car was at "3" while running and the car idling rough as crap because it was at 18:1. I revved the engine and managed to get "6" to flicker, but then back down to "3" as idle came back down. I was still a bit baffled because my battery/e brake lights weren't staying one.
I then hypothesized that since I'm seeing approx 12.5v, that may not be enough to trigger the CELs on the dash. Maybe it WAS the alternator.
So, alternator came in, I swapped it in about 1.5hrs, maybe less, and boom. Fixed. Also, battery tenders don't max out batteries like an alternator does, so.. when my alternator wasn't working well, the battery wasn't charging completely. The tender wasn't able to to do it either, so that would explain why it was lean, even after being on the tender all night.
TL/DR:
Car idled lean. Turned out to be the alternator. Fixed. Harbor Freight alternator tester was the key to everything.
After it's warmed up, and getting to a stoplight in neutral, RPMs drop to like 3-400 and bounce up, vacuum drops to -10 from -19, and it's trying to recover on it's own. If I free rev it while standing still, and when taking foot of the gas pedal, when the RPMs drop back down, they go too low, and car almost dies, but catches itself.
I will go buy one of those alternator testers to check it out.
Thanks for posting your solution.
After it's warmed up, and getting to a stoplight in neutral, RPMs drop to like 3-400 and bounce up, vacuum drops to -10 from -19, and it's trying to recover on it's own. If I free rev it while standing still, and when taking foot of the gas pedal, when the RPMs drop back down, they go too low, and car almost dies, but catches itself.
I will go buy one of those alternator testers to check it out.
Thanks for posting your solution.
It looked like your AFRs were good, though? If so, I wouldn't suspect the same problem. y car was idling at about 18:1 when it acted up. Have you checked the BISS and IACV and all the lines? I assume so, as I'm sure we've all read through these threads and tried everything by now LOL
I did see my AFR go lean sometimes when the idle has issues.
I checked the voltage on the battery and while the car is running and it is showing 14.2V. When the idle has issues and the RPM goes down to like 300, the voltage drops to 13.0V and then climbs back to 14.2V.
No boost leaks, iacv seems fine but who really knows, since the idle issue is only happening sometimes, and it corrects itself
I did see my AFR go lean sometimes when the idle has issues.
I checked the voltage on the battery and while the car is running and it is showing 14.2V. When the idle has issues and the RPM goes down to like 300, the voltage drops to 13.0V and then climbs back to 14.2V.
So may possibilities... but it's worth a try! So, the idle drops, it goes lean, and vacuum decreases as well?
The tester I used was under $20 and i grabbed it "just for the hell of it". haha. Good thing. It's a cheap test, so why not? Especially if you have exhausted all of your free options.
Jan 26, 2017, 09:54 PM
