Bosch Platinums suck?

Last time I buy Bosch platinums, I guess.

At 115k I did a bunch of stuff on my LT1. It needed an Optispark and water pump, so I took the opportunity to do a roller timing chain set and plugs and wires.

I gapped them all to .052" and used Taylor spiro-core wires. At 140k it started getting a misfire. My first thought was a plugged vent line for the Opti, but it was fine. Then I though maybe I had rubbed through a wire (the factory plastic wire retainers broke and I just routed them logically). By 146k, the misfire was very noticable and I started getting a flashing CEL.

Started pulling plugs. #8 was at .068". One plug was missing the electrode completely, and all of them showed significant gap inconsitencies. Very even and consistent brown/black color, no aluminum flecks, just wasted plugs.

It could be something wrong with fuel or computer causing it, but reading the plugs suggest that its all kosher. LTFT, STFT, and O2 readings all look normal and the knock sensor isn't pulling heaps of timing out. Everything I checked makes me think they were crap plugs.

Anyone else have this issue with Bosch Platinums?

I replaced them with Delcos figuring the OEMs lasted 115k so they couldn't be that bad.

All platinums suck. Use copper and change plugs more often. Another bs move by the industry.

They seemed to work well in old nerve and BMW. But sucked in everything else. Throw a set of acdelco coppers in there and move on.

I had the same experiences with them in my impala ss. Switched back to regular AC delcos in less than 5K miles.

I was once told by a plug manufacturer not to gap platinum plugs, just install them out of the box.

I never had luck with bosch platinum plugs in gm's. My old 3.4 dohc lumina ate a set in 1500 miles, swapped in delco plugs and put 20k on it before getting bored

Don't ever put Bosch Platinums in a Ford Zetec motor. Won't even get 5K miles before you start having problems. Copper plugs at all times.

The 3.7 in the Liberty we had hated them. Copper or nothing for it.

Other than that, I've never really had a issue with platinums, and I run them in just about everything.

I never had a problem with them in my old vehicles, but when I bought my first miata 3 cars ago and everyone preached copper or nothing, I've gone back to the cheapy coppers and haven't had a problem with any vehicle.

I'm a firm believer in running OE (or equivalent) plugs all the time. When I was younger I frequently made the mistake of letting parts counter guys upsell me on platinums and they never ran as well. If you really want a longer-life plug these days, it sounds like iridium is the way to go.

pointofdeparture wrote: I'm a firm believer in running OE (or equivalent) plugs all the time. When I was younger I frequently made the mistake of letting parts counter guys upsell me on platinums and they never ran as well. If you really want a longer-life plug these days, it sounds like iridium is the way to go.

Back when I was a parts counter guy, I was taught to always recommend the exact OE plug if it was available, or at least the OE brand. So NGK/Denso for Japanese cars, Motorcraft for Ford, AC Delco for GM, etc. As a service writer/manager I had the same mentality because it helped eliminate a potential source of comebacks.

My mom's 4.0 Jeep did something like that with Bosch platinum plugs, ran like crap, half of them had the point completely burned off and all were generally awful looking for only being in there a couple years.

I've found that you get best results on a stock application by using the exact plug called out in the owner's manual or on the hood sticker. Cross refs aren't perfect. If that's a short interval copper plug then so be it.

I don't know, my old man's focus got 110k miles before I changed them, 10 bucks a plug is expensive but they last. I think they aren't bosch plugs though maybe motocraft platinums. I use ngk exclusively when available since bosch quit making plugs for the mercedes.

+1 on using OEM-specified plugs whenever possible, barring that, NGK and Denso have been my go to plugs, even in Domestic iron. I stay away from the Iridium plugs though, tried a set in my truck and the Bonneville and they just weren't worth the cost. Stay away from the gimmick plugs too, like the Bosch platinum +4 or the E3 whatever they call it, they aren't any better than a good quality standard electrode plug.

When i was in the industry, i installed them in tons of different cars, domestics, euros and japanese cars. Never had a problem once a good set was in.

I did see a high number missing electrodes or ground straps out of the box, could be bad qc or rough handlong, who knows. Never gapped them, was told thdy are pregapped. I just checked gap.

I think i have about 60k on the set in my dodge.

My personal projects or Performance cars always get copper ngks. Never really noticed a differenece but its what ive always ran. Never got a bad one out of the box

Ngk all the things.

In reply to 06HHR:

Except in cases where the car actually calls for a funky one. E.G. this is the OE plug for a few 90s-00s Toyotas.

They don't seem to work well in every application. I tried a set in my stock TR6 and suffered misfires and fouling, so swapped back to copper plugs. When we were setting up another TR6 with Megasquirt-based EFI, I used these same plugs just to fill the spark plug holes until I could get new plugs. After three seasons, they're still there and working well. Maybe they needed a stronger coil or more precise mixture. I'd rather pull the plugs occasionally just to read them and keep them from sticking in the head rather than forgetting about them for 100k miles.

Bosch platinums suck unless you get the OE-spec ones that are like $30 a plug or something.

Can't say I've ever had a problem with any set of plugs and I've run both copper and platinum at times in the past. Anymore I just stick to OE, though. I actually had three AZ employees all but refuse to sell me copper plugs for my turbo Volvo one time as they insisted on trying to sell me platinums. It was the most bizarre parts store experience I've had.

A buddy of mine tried those E3 plugs in his 1.8t Passat one time and they made the car nearly undriveable. Bucking, misfiring, threw several codes, ect. Swapped them back after a day or two and the car was fine again.

GM needs AC Delco like I need oxygen. I never had so many problems out of plugs as when I tried something else.

That said, until recently everything I owned got a fresh set of Bosch Platinums and never had any trouble from any of them.

Bosch makes a lot of good products. Spark plugs are not one of them.

KyAllroad wrote: GM needs AC Delco like I need oxygen. I never had so many problems out of plugs as when I tried something else. That said, until recently everything I owned got a fresh set of Bosch Platinums and never had any trouble from any of them.

It is WEIRD how cars can be so brand-specific when it comes to spark plugs.

GM run best with AC Delco. Fords run best with Motorcraft. Chryslers are the only cars in the world that like Champions. And Euro cars prefer Bosch and Japanese cars prefer NGK, if they don't specify weird Denso plugs.

NGK does make some seriously good spark plugs that work well in anything. But don't put Bosch plugs in anything that doesn't speak German. Or Champions in anything that isn't Mopar.

Furious_E wrote: Can't say I've ever had a problem with any set of plugs and I've run both copper and platinum at times in the past. Anymore I just stick to OE, though. I actually had three AZ employees all but refuse to sell me copper plugs for my turbo Volvo one time as they insisted on trying to sell me platinums. It was the most bizarre parts store experience I've had. A buddy of mine tried those E3 plugs in his 1.8t Passat one time and they made the car nearly undriveable. Bucking, misfiring, threw several codes, ect. Swapped them back after a day or two and the car was fine again.

This right here is why I ALWAYS give the parts store counter guys the part number for the spark plugs I want (and a number of other things, too) and flat-out refuse to tell them what car they are going on. It lets me avoid having to say to the guy, "Look putz, I know more than you about cars in general, and more about what I am doing with MY car in particular. Sell me the plugs I am asking for RTFN."

I agree that plugs tend to be brand-specific. No idea why, but its so true. They are an insulated conductor; doesn't seem to be any reason why a brand would work better in a certain vehicle. I can understand why mixing types of plugs could be an issue, like putting copper in where iridium was spec'd, or using a regular plug in a Toyota instead of the dual-electrode like BrokenYugo mentioned, but for cripes sake they're a conductor with ceramic around it that delivers 50,000 volts. Should be a no-brainer.

The reason I went Bosch Platinum was because OE spec was platinum. Copper doesn't cut it behind an Optispark. This time I went back with Delco Platinums. They weren't parts counter, they are Auto Zone, but its likely they are the same plug... or at least close enough.

I have used Bosch Platinums in many engines before and they never gave me any issue, but 30k has me weirded out.

On the gapping part, yes most plugs are pre-gapped and usually close enough to just install right away, but I always check them. IIRC, there were two out of spec when I installed these; I assume a dropped crate during shipping or something.