WallyP

Just a random data point that may or may not have any bearing on the 928...

The wife's Caddy STS with Northstar engine (quad-cam high-output all-aluminum V-8) suddenly started running very poorly. I did some reading on-line, and discovered that virtually every Caddy or Northstar forum had bad reviews on Bosch platinum plugs.

I pulled out the Bosch platinums I put in about 20,000 miles ago (platinum plugs should be good for 100,000 according to Cadillac) and replaced them with (expensive) AC-Delco Platinum Pro plugs as originally equipped. Did nothing else, but problem solved! The engine runs better than it has in quite a while. No roughness, no misfiring.

The Bosch plugs looked fine. No idea why the Northstar doesn't like them. We have known for some time that the 928 likes the Bosch copper plugs better than the platinum ones. I wonder if AC-Delco make a platinum plug for the 928...

polecat702

AC makes the Professional Platinum plug, as an OE replacement.

I used to use the AC plugs in my 87 & 89. I've since switched to the Pulstar (capacitor) plugs.
www.pulstar.com

Bjbpe

Hey Polecat:

Did you notice any improvement in fuel mileage, power, etc. with the pulse plug?

michael j wright

The ONLY plugs I will sell for any newer GM make is original AC Delco. If I sell any other, the customer will always be back complaing. Like Wally, I have no idea as to why, maybe resistance?

polecat702

Sure did the car is much more responsive, and gets better mileage, about 12% improvement, in the 928.
The Polecat is where they made a hugh difference, with the blower motor. I couldn't keep plugs in it, burned the electrodes out in 5000 miles. The Pulstars don't burn up, plus they're guaranteed for life. They are expensive $13.00 a plug.

I think they're worth every penny. They really work, not some advertising gemmick. The set in the Polecat was given to me at SEMA, last year.

FWIW, I've never run any other brand, but AC Delco.

Earl Gillstrom

Wally,

This is a known fact. Many shops look first for Bosch plugs for any driveability problems.
They are bad in most cars, not just Caddys. Original plugs are best in any car.

Interesting that Bosch Plats are not even good in 928s

Earl

WallyP

OK, what are the original plugs for the 928? I have always assumed the Bosch copper were the OE plugs.

Yep, ACDelco makes a Platinum Pro plug for the 928.
http://shop.advanceautoparts.com/web...erm=spark+plug
The Advance discount at the moment is 15%. Anybody want to be the guinea pig?

Bertrand Daoust

Joe,

Do you use the Pulstar Platinum or Iridium Series plugs?

I want to try something else next spring.
Good thread Wally. Thanks.

NickT

This is what that link tells me:

This part does not fit 1988 Porsche 928 S4

polecat702

Bert, I was given a set of the Iridium plugs for the Polecat. I bought another set for my 89 S4.

928 at last

Apparently it's an "EXACT FT" for a 1990 S4........

longleader

Fits my 83

polecat702

AC Delco part # 41-802 platinum pro plugs, exact fit replacement. These are what I used to run in my 87 & 89 before I switched to the Pulstars.

outbackgeorgia

My 79 came with Beru plugs, don't have the part number. Worked fine. Use plain Bosch copper in the 87. No problems.
Dave

danglerb

Lots of negative reviews on the Pulstar at Amazon, many reporting damage from using the plugs. I would use a LOT of caution before trying them.
http://www.amazon.com/Pulstar-BE-1-P...ews/B000WMHEBE