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Join Date: Aug 2003
Location: Louisville, KY
Posts: 98
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Bosch Platinum +4 plugs made my car sick
I was recently given a set of Bosch Platinum +4 spark plugs, which I installed when I had the engine out for a clutch job. When done, the car stumbled like a blackout brigade! It acted like it was very rich and loading up at low revs, and had bad flat spots all the way up to 5,000 rpm.
I had read on posts here (after installing them, of course) that the platinums can cause problems (Thanks "stlrj"!  ). Upon removing the plugs today, they actually looked good. I put standard WR7DCs back in, took it for a test run - she ran like new .Now I'm curious as to why the +4s don't work good. They have the 4 ground points for the electrode - maybe that just doesn't work well with the combustion chamber characteristics in these cars. At any rate, don't waste your time and $. Cheers,
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'85 Carrera Coupe, White Gold Metallic - 8" rear Fuchs, Fittipaldi steering wheel, Weltmeister short shift, Turbo tie rods. "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough horsepower." - Mark Donohue |
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09-12-2003, 07:12 PM
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How did you gap them? I read that the platinums are actually less conductive than copper plugs. Their only advantage is that you can run them longer.
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993 |
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09-12-2003, 07:17 PM
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Location: Louisville, KY
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Didn't gap them. Bosch says they're pre-gapped, and never need re-gapping. Especially in the garbage can... The center electrode is actually flush with the insulator tip.
Regarding the conductivity, I would think the Pl is naturally a better conductor than the Cu, similar to gold. And it is actually a good catalyst, exploding hydrogen and oxygen in its' presence. Strange. I've also read about the platinum lasting longer. But not much good if the thing runs like cr@p! Oh well.
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'85 Carrera Coupe, White Gold Metallic - 8" rear Fuchs, Fittipaldi steering wheel, Weltmeister short shift, Turbo tie rods. "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough horsepower." - Mark Donohue Last edited by Carrera Sled; 09-12-2003 at 08:10 PM.. |
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09-12-2003, 07:50 PM
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Join Date: Dec 1999
Location: Novato, CA
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Probably not a plug problem as much as an ignition cable issue. Seems you cables are not up to delivering a full 15kv of spark without shorting out.
Make sense? Joe |
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09-13-2003, 02:12 PM
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Location: Louisville, KY
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Good point. That crossed my mind, too. They appear to be the original Beru cables, with 89k on the car. But wouldn't it be consistent with both plugs? Seems to run good now. I don't have a megger tester; I'll look at them running at night, looking for shorts. Thanks for the idea, Joe.
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'85 Carrera Coupe, White Gold Metallic - 8" rear Fuchs, Fittipaldi steering wheel, Weltmeister short shift, Turbo tie rods. "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough horsepower." - Mark Donohue |
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09-13-2003, 02:27 PM
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Driving member
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This is a plug problem. I posted on here a year ago about having this after using the same plugs. I know not everyone who uses them has this but a friend of mine that races 911s said that he has heard of guys burning a piston from these plugs.
Do a search and you will bring up some stuff on this. I think there are some things that should be left as stock with these cars. For me the plugs are one of those things.
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Jerry '86 coupe gone but not forgotten Unlike women, a race car is an inanimate object. Therefore it must, eventually, respond to reason. |
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09-13-2003, 03:05 PM
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Join Date: Dec 1999
Location: Novato, CA
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Ben,
Some plugs require a higher voltage to jump the larger gaps that are so common today in order to take full advantage of the larger kernal for more complete combustion. That said, a good test would be to use your engine ignition as the megger by introducing some water on your distributor cap and plug wires at idle and then listen to the snap of sparks jumping to ground as your engine sputters. No point in just watching your engine in the dark since there is no load on your ignition system and the voltage requirements would be minimal which would not be a true test. You might try the H20 test on your standard plugs before trying it on plugs with much higher voltage requirements. If your ignition system cannot pass with your original plugs, you'll need to address that problem by replacing your ignition cabes with ones that will not short out with a little water. Cheers, Joe 86 Carrera w/ plugs gapped at 0.060" and H20 tested |
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09-14-2003, 07:03 AM
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Monkey+Football
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Anyone have an opinion on the Bosch plus 2's?
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<Insert witty comment> 85 Targa Wong Chip Fabspeed M&K Bilsteins and a bunch of other stuff. |
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09-14-2003, 07:16 AM
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Join Date: Dec 1999
Location: Novato, CA
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Now I'm curious as to why the +4s don't work good.
It's not so much that the +4s are at fault as much as the ignition systems on 911s are of such poor quality, particularly the OEM Beru cables, that are not capable of transmitting maximum secondary voltage to the plugs without sorting to ground, cables designed to fail with too many connections at critical areas for potential shorts. What makes it more difficult is the conception that because these seemingly high quality and very expensive wires are the best that money can buy when in fact they are the root of the problem. That's why factory specs for plug gaps is never more than 0.028" because they know their cables cannot handle anything larger that would require a higher voltage that would fail and go to ground before reaching the plugs. As far as I can tell, the engineers are just trying to cover their a$$e$ by recommending smaller plug gaps rather than a very expensive recall to replace poor ignition cables. And so far, they seem to get away with it! Cheers, Joe Last edited by stlrj; 09-14-2003 at 05:15 PM.. |
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09-14-2003, 05:10 PM
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Ive been told not to use any type of platinum
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Jeff 83 SC, Guards Red. |
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09-14-2003, 05:20 PM
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1986 Porsche carrera coupe 3.2
