WARNING: Bosch Platinum Plugs & GM DIS
Shawn R. Lin
Anyone with a GM car which uses a Distributorless Ignition System (DIS)
may want to consider avoiding the use of Bosch Platinum spark plugs
(assuming they have not undergone a design change in the past 2-3
years).
I put Bosch Platinum plugs about three years ago, a 1989 Oldsmobile
Cutlass Supreme 2.8L V6 MPFI. The plugs never gave me any trouble, but
I had a bad injector and pulled the plugs while diagnosing the car's
problem. I was rather disappointed to see that on 4 out of 6 plugs, the
tiny platinum center electrode, which is normally flush with the top of
the center insulator, had eroded. There was nothing left in the center
insulator but a tiny hole where the platinum electrode used to be. By
bending back the side electrode and sticking a small pin in the hole, I
discovered the platinum center electrode had eroded 1 to 2mm below the
top surface of the center insulator. This was after 25k miles and 1
year later! The OEM AC Delco plugs that were in there previously, had
lasted much longer. Needless to say, I replaced all the Bosch Platinum
plugs with conventional plugs (in this case, Champion Gold).
For several weeks, my girlfriend's '88 Olds Cutlass Supreme with the
same 2.8L MPFI V6 has been occasionally running poorly and stalling.
About 2-1/2 years ago, I put Bosch Platinum plugs in her car too (BEFORE
I discovered my car ate them up). My girlfriend drives very little, and
nearly 100% city miles. Suspecting the Bosch plugs, I decided to
replace them today. The plugs only had about 10k miles on them. They
were not fouled, but like my car, it had eaten the center electrodes on
3 out of 6 plugs. The center electrode on one plug was eroded nearly
3mm! The gap had become over twice what it should be! I put some cheap
AC Delco OEM plugs in her car, and now it runs fine and hasn't stalled
yet.
Either the Bosch plugs are poorly designed, or GM's DIS system is too
"hot" for them. I believe it's very likely that anyone with a GM car
that uses DIS may also have a problem with the Bosch Platinum plugs
being eaten up rather quickly and possibly causing reliability problems,
unless Bosch has changed their design recently.
--
Shawn Lin SMSU student from Springfield, MO USA
http://science.smsu.edu/~lin
Scottibod
I have seen many times where platinum spark plugs (not just Bosch) have
actually degraded the performance of the vehicle. I had an electrical engineer
bring his 1991 toyota pickup with a 22-RE engine for an extremely rough run
condition. After scoping the ignition system I found that there might be a
problem with the plugs so I pulled one and found that it was platinum. I
replaced the plugs with Nippondenso u-groove copper's and the engine ran great.
I called the customer and told him what I had found and he did not believe me
(He is an engineer therefore he is better than me) even when I showed him how
well the engine ran with regular plugs. He told me to put the old plugs back
in and something to the effect that I didn't know what I was talking about. He
drove away with a very bad running engine and was disgruntled because I charged
him an hour of labor for my time. Some people just can not see the forest
through the trees.
-S. Russell Tucker
Da Kamaro
some people are just @#$#@#$ morons! I've heard besides that, the platinum
plugs(which by the way, only have platinum tips wow! ) wear away after awhile
anyway, leaving you with a regular plug.
Mark Kolber
The distributorless ignition system applies reverse voltage to 1/2 of
the plugs. Perhaps plat. plugs cannot tolerate this.
Mark
SPACES ADDED TO MAYKE SERVER HAPPY
X
Thomas R. Serrano
It seems that all of the respondents to this thread had found problems with
the plugs after using them over a period of years. I submit that poor
engine tuning or engine trouble could have caused the demise of the plugs,
not vice versa.
I have had no problems with any platinum (or other) plugs that I have
used in excess of 50,000. However, I have seen a GM 3.0L V-6 crack spark
plugs because of problems with the ignition problem. The plugs were not
platinum.
I am not saying that the respondents are not correct, only that they
seem to be considering the plugs the source of the problem because they are
the affected component.
Tom Serrano
cont...@epix.net
Thomas R. Serrano wrote:
> It seems that all of the respondents to this thread had found problems with
> the plugs after using them over a period of years. I submit that poor
> engine tuning or engine trouble could have caused the demise of the plugs,
> not vice versa.
> I have had no problems with any platinum (or other) plugs that I have
> used in excess of 50,000. However, I have seen a GM 3.0L V-6 crack spark
> plugs because of problems with the ignition problem. The plugs were not
> platinum.
> I am not saying that the respondents are not correct, only that they
> seem to be considering the plugs the source of the problem because they are
> the affected component.
>
> Tom Serrano
You can say what you want and I will say that you are lucky. I put Bosch
Platinum plugs in my 89 Topaz, while performing other maintenance (new engine,
A/C work, etc.) The engine ran rough the moment I started it and would surge
when under load. It would also stall at idle. The hotter it was outside, the
worst the problems. Since the plugs were new and from a reputable manufacturer
I didn't suspect them. I also didn't have anything to check the secondary
ignition pattern, although I did test the spark output using Fords high energy
ignition tester (the one that looks like a spark plug with no center
electrode.) Nice spark, unfortunately the Bosches weren't letting that nice
spark get to the fuel-air mixture in the cylinder. What followed was a two
month ordeal of troubleshooting and parts substitution, i.e., new fuel pump,
new TFI module, tried a couple used MAP sensors, a different ECM,
point-to-point checks of wiring, testing all ground wires, etc. I then noticed
a posting on the net concerning derivability problems with Bosch Platinum
plugs, so I went out and purchased a set of Autolite Platinum plugs (which I
always used) and installed them. It was like a miracle! Problem positively
gone. I still have the old Bosch Platinum plugs and would be happy to give them
away (< 500 miles on them). I will never use them again. Sure, they may work OK
in some cars, but I want a plug that always works.