What is wrong with Bosch spark plugs for Toyotas?

I recently asked about reducing my HC emissions for my smog test in Texas at this newsgroup. Several of the responses indicated that they suggested changing from the Bosch platinum spark plugs I now use on my 91Camry LE. They suggested using NGK and Denso. How are these plugs better than the Bosch plugs. Are they constructed better? Is there any proof that one brand is better than another?

Reply to
Al Kondo
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Engine designed with NGK and ND plugs. Some have experience poor performance with non-NGK/ND plugs. You may have other problems not related to the plugs, but might start with using the recommended OEM plugs.

Reply to
jjjsan

Several years ago I replaced the plugs in my Sister's Honda Civic. I let the salesman at AutoZone sell me a set of Autolite Platinum Plugs for the engine. I installed them and the engine appeared to run fine. However within a day the check engine light was on and the engine was running in limp home mode. I checked the codes and it was suffering from random misfires. I pulled the plugs, checked the gaps, reinstalled them, and cleared the check engine code. Once again the engine appeared to run fine. However, the next day the check engine light was back on and the engine was running rough. So I pulled the Autolites out and replaced them with the recommended AC plugs (only thing I could fine easily on a Sunday afternoon). Again the car seemed to run perfectly - for one day. The next day the check engine light was on and the engine was running rough. So, I went to Pep boys (horrors) and asked for the NGKs listed in the owner's guide. I installed these and no problem for 50,000 miles.

So what can be different? Heat range, resistance, insulator configuration, reach, gasket configuration, etc.,etc. For whatever reason Japanese engines seem to be very sensitive to minor variations in sparkplug design. For my Fords, I buy Motorcraft. For anything else I try to find the plugs specified by the manufacturer. If the manufacturer's recommended plugs aren't readily available, I buy NGKs if they offer them for the application. Under no circumstances would I use the Bosch plugs in a Japanese vehicle. And I absolutely refuse to even consider using the multiple electrode Bosch plugs in any application unless specified by the vehicle manufacturer.

Ed

"Al Kondo" wrote in message news: snipped-for-privacy@news.hal-pc.org...

Reply to
C. E. White

High HC with low CO can mean a plug problem, and it's safest to use one of the plug brands listed in the owner's manual, or at least use Japanese plugs in Japanese brand cars, American brand in American brand or Chrysler cars, and Bosch in non-Chrysler German brand cars. Also at least some Hondas seem to need NGKs, but Toyotas should do fine with Densos since Toyota owns much of Denso.

Reply to
do_not_spam_me

Another man who puts supreme confidence into a manufacturer's recommendations...great!...the right stuff indeed...who knows his engine better, him, who has spent thousands and thousands of dollars in designing, tweaking and fine tuning that engine to a fare-thee-well or some brash teenager with an overblown sense of confidence and a bee in his bonnet that whispers 'you know best'?

Reply to
Gord Beaman

Have you ever looked at the positive electrode on the Bosch platinum plugs and compared it to the ND? The Bosch platinum electodes are almost microscopic - the amount of platinum is very small and the cross section of the firing tip of the electrode is very, very small. The original equipment ND uses a more conventionally sized electrode with platinum plating that extends from the ceramic tip, whereas the Bosch is flush. At 60,000 miles, the ND still looked fine and the gap was still good, last time I changed mine. If you check the gap on the ND plugs, would recommend go or no go type wire thickness gauge so you avoid scratching the platinum coating. So, yes, they're constructed differently and one is better for your Toyota. The main point is that many people have experienced problems with the Bosch in their Toyotas. High HC (hydrocarbon) readings on an emissions test is simply unburned fuel.

Reply to
nospampls2002

Yeah, I noticed when I put Bosch's in I just passed HC, and then when I changed back to ND's the HCs went *WAY* down!

Reply to
Hachiroku

DON'T USE CHAMPIONS!!! 1978 Corolla w/40K, decided to give it a tune-up. Damn thing wouldn't start if the temp was below 50 degrees!!! A trip to Foreign Autoparts for NGKs fixed it right up. I don't even use Champs in lawnmowers anymore!

Reply to
Hachiroku

gotta agree but used to own big block dodges wouldn`t run on anything but champions NGK or Denso in Toyotas

Reply to
PCK

The almost-microscopic flush platinum electrode is supposed to heat up easier and therefore ionize the air more readily than a conventional tip. Really. Why it never seems to work as well as NGK or ND platinum plugs is puzzling.

Reply to
do_not_spam_me

Have had Bosch 2+ Platinum in my 2000 sienna for about 10K and never had any problems, for 1/3 the cost. Don't know why so many people are complaining about it.

Reply to
ZR

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