After nine years and roughly $2.4 million in auto parts purchasing, I can say the conclusion is simple: the cheapest part is almost always the most expensive one. I used to pick the lowest quote. Now I pick the part with the lowest total cost of operation (i.e., purchase price plus labor, redo risk, and customer goodwill). That's why I'd rather spec an Aisin A465 transmission than a cheaper reman, ask about the strut health phone number before I order a coil over spring, and check alternator output before I let anyone chase a misfire.
Here's the direct answer to the question everyone asks: can a bad alternator cause a misfire? Yes. Low voltage weakens spark and confuses sensors. But it's rarely only the alternator, just like the perceived price of a transmission is rarely the real price.
Why I can talk about this
I'm a procurement manager at a 40-person automotive component distributor. We supply transmission units, suspension parts, and engine electrical components to independent repair shops and small OEM assembly operations. I've managed the annual buy budget for nine years, negotiated with 40-plus vendors, and documented every order in our cost tracking system. I'm not a transmission engineer or an electrical engineer. What I am is the person who sees the invoices after the promises go wrong.
The cheapest part is almost always the most expensive one—not because the unit price is higher, but because the failure is shared.
What the Aisin A465 transmission taught me
In 2023, we compared the Aisin A465 transmission against two remanufactured alternatives. The Aisin quote was higher by $320. I almost approved the cheaper unit—until I built out the total cost. The reman vendor charged a core return fee that wasn't on the first page of the quote, separate freight for the shipping container, and a 'warranty registration' charge if the old core didn't leave within 30 days. That's a 19% difference hidden in fine print.
Look, the Aisin A465 transmission isn't magic. It's a six-speed automatic, and Aisin has been building the Aisin 6 speed transmission family long enough that the engineering is well proven. I'm not going to explain gear ratios. What I can tell you from a purchasing perspective is this: after we switched to the Aisin 6 speed transmission line for high-mileage commercial vans, our internal quality notes stopped mentioning premature shifts and our labor cost per unit dropped because redo work disappeared.
Even after I approved the Aisin units, I kept second-guessing. What if the cheaper reman was just as good? The two weeks between order and delivery were stressful. Didn't relax until the first unit installed cleanly and shifted exactly as the shop's diagnostic notes predicted.
That's the part that doesn't show up on a purchase order. Every transmission we sell carries our name on the invoice. If it shifts rough or fails in a month, the customer assumes the shop doesn't know what it's doing. That's a brand impact, not just a mechanical one.
Coil over spring: the suspension trap
The same logic applies when sourcing a coil over spring. I once ordered a no-name coil over spring assembly because it was $55 less per side. It fit. It also started squeaking in the third week, and the shop had to pay labor twice, rent an alignment rack, and apologize to the customer.
Here's the thing: a coil over spring changes ride height, damping, and suspension geometry. You aren't just buying a spring—you're buying the engineering that says the top mount, spring seat, and damper work together. That's why I look up the strut health phone number when a new suspension vendor cold-emails us. If I call and nobody can explain whether the strut is gas-charged or walk me through the warranty process, that tells me more than any brochure.
I know 'strut health phone number' sounds like an odd thing to ask for. But a manufacturer that can actually answer suspension questions is usually confident their parts will survive real-world installation mistakes. That confidence is worth a premium.
Can a bad alternator cause a misfire?
Let's deal with the question directly: can a bad alternator cause a misfire? Yes. Low output from an alternator can drop system voltage below 13.5 volts in many OBD-II vehicles. Weak voltage means weak spark, slower injector response, and a PCM that doesn't trust its sensors. I've seen misfire codes P0300 through P0304 traced back to a charging system that was sitting around 12.8 volts.
I'm not an electrical engineer, so I can't speak to every waveform detail. What I can tell you from a buyer's perspective is that the misfire often gets the coil blamed instead of the alternator. A shop calls us with a cylinder 3 misfire and orders coils before anyone checks charging output. The alternator caused the problem, but the coil gets replaced. You solve one misfire and create another when the cheap alternator fails.
In my opinion, a known-brand charging system is the right call here. A bad alternator can cause a misfire, and a 'value priced' alternator can cause a misfire, a dead battery, a fried sensor, and a customer complaint about the shop's professionalism.
The three questions I ask before any big PO
Before I write a purchase order for anything that affects the feel of the vehicle, I use a simple checklist. Our procurement policy now requires quotes from three vendors minimum because of what I almost missed with that first reman transmission:
- What is the total cost if this part fails in the first month? Include the extra labor, the rental diagnostic equipment, and the phone call from an unhappy shop owner.
- Who answers the phone when I have a question? A dedicated strut health phone number or technical support line is a good sign.
- Does the price make sense across the life of the vehicle, not just the life of the part? For example, the Aisin 6 speed transmission costs more upfront, but the reduced comeback rate makes it cheaper by the end of the year.
This checklist isn't fancy. It's just a way to force myself to think about the second-order costs before I commit.
Where I still buy cheap
To be fair, I'm not saying every order should go to the premium brand. Some parts are commodity parts. A standard rubber grommet, a wheel stud, a washer—those are fine to buy by the box from the low-cost source. But the parts that determine the first feel of the vehicle—the shift, the ride, the idle—are the ones to pay for.
Granted, there are exceptions. If you're building a weekend off-road toy and plan to replace the coil over spring every season, a budget unit might make sense. If you're doing a farm truck repair with a three-week window, maybe a reman transmission is logical. I'd still call the strut health phone number first and check the alternator before I spend money on coils. The cheapest part is usually the most expensive one in hindsight—not because the price is high, but because the consequence of failure is.
