Spark Plugs & Coil Packs

[AP 997S]

I'm just about to change my spark plugs and was wondering if I should change the coil packs too?

I'm on original plugs and coil packs; my 997S is close to 7 years old (build date Aug. 2004) but I just have 23K miles.

I've seen them cracked from heat and age on other 'P' cars.

No misses or tell tale signs of bad plugs or coils but I think it would be good preventative maintenance to replace them all. I might get a bit better MPG and performance as well.

:thankyou: :thankyou: :thankyou:

[Loren]

Perhaps this will help...

[AP 997S]

Thanks Loren for the 'trouble-shooting' chart.

Like I said I don't have any misfires, hesitations, etc.

I just think it would be 'good practice' to replace them after nearly 7 years of usage.

[PAULSPEED]

Save your money and get Radiators and

hoses for a southern California car.

Paul

[wvicary]

If money isn't a problem I would replace them but only with OEM parts. The coils due fail and as you'll be in there just swap them out.

[AP 997S]

Save your money and get Radiators and

hoses for a southern California car.

Paul

'Global Warming' hasn't reached us yet so I'm good in that department.

[AP 997S]

If money isn't a problem I would replace them but only with OEM parts. The coils due fail and as you'll be in there just swap them out.

That was my sentiments as well. Beru Coil Packs run about $40 per so it's like 5/6 tanks of gas.

I'm going on a 700 mile road trip in October (Porsche Reunion at Laguna Seca) so I'm looking at stuff to make the trip 'uneventful' from that standpoint.

[Rapewta]

The coil-packs have no moving parts. They work or they don't. Nothing to slowly start giving up.

They are just a lot of wire wound inside an a plastic capsel. I think one of the biggest problems causing

a break-down is over tightening the screws when mounting them. Heat also but they crack (plastic) when over tightened.

Save your hard earned cash and spend it at the reunion.

[MichaelL]

Coil packs can deteriorate from road spray, particularly, if salt laden. If any cracking or visible surface defects are present, replace them. Probably a good idea to replace all if one is near failure. Coil failure is more common in cars that are driven in the winter or not garaged.

[AP 997S]

Thanks for all the inputs.

I decided to change both plugs and coil packs.

Ordered them from Sunset Porsche. Went w/ the 'generic' Bosch plug (FGR5KQEO) rather than the Porsche branded version. I figured they were was the same w/ just a marking change.

[Doug_B_928]

In reading the Factory Workshop Manual I noticed that it does not appear to advise one to disconnect the battery before replacing the spark plugs. I also see that there are a lot of things that need to be reset after disconnecting the battery, so I guess one doesn't want to do so any more than one has to. Is it true that spark plugs should be changed with the battery connected?

TIA

[Loren]

In reading the Factory Workshop Manual I noticed that it does not appear to advise one to disconnect the battery before replacing the spark plugs. I also see that there are a lot of things that need to be reset after disconnecting the battery, so I guess one doesn't want to do so any more than one has to. Is it true that spark plugs should be changed with the battery connected?

TIA

As long as the key is off and removed you should be fine.

[Doug_B_928]

In reading the Factory Workshop Manual I noticed that it does not appear to advise one to disconnect the battery before replacing the spark plugs. I also see that there are a lot of things that need to be reset after disconnecting the battery, so I guess one doesn't want to do so any more than one has to. Is it true that spark plugs should be changed with the battery connected?

TIA

As long as the key is off and removed you should be fine.

Excellent, thank you Loren.

[PAULSPEED]

Rennsport 4 is this October 14, 15 and 16.

Hope to see you there.

http://zone77.org/

Paul

Zone 7 Webmaster

GGR - Vice President

Edited September 14, 2011 by PAULSPEED

[Doug_B_928]

I've ordered Bosch spark plugs from Pelican. The salesman said that he thinks they are pre-gapped for the 997. FWSM says the gap should be 1.6 +/- .05mm. On the bosch website it says that they come gapped to 1.4mm. Do most people just install them as they come, or do you ensure that they are at 1.6?

[PAULSPEED]

Always check. New plugs should not need adjusting.

Paul

[Doug_B_928]

Always check. New plugs should not need adjusting.

Paul

Thanks, Paul. So, in your experience the Bosch plugs come with a 1.6mm gap?

Doug

[PAULSPEED]

I do not remember what the gap is. I always ask for the

gap when I buy them.

All plugs are fine but I perfer NGK 1st overall. I have to look to see

what plugs I last bought for the Porsche.

Paul

[logray]

If you bought the Beru, Bosch, or "Porsche" 4 prong plugs, they come pre-gapped to the right specs. I'm also not sure how one would gap a 4 prong plug anyways... at least I've never heard of anyone doing that before.

I had a set of single prong NGK's, didn't really notice a difference with the 4 prongers.

[Doug_B_928]

If you bought the Beru, Bosch, or "Porsche" 4 prong plugs, they come pre-gapped to the right specs. I'm also not sure how one would gap a 4 prong plug anyways... at least I've never heard of anyone doing that before.

I had a set of single prong NGK's, didn't really notice a difference with the 4 prongers.

I've never had 4 prong plugs before, but salesman at Pelican said to check the gap and, according to him, one can gap each prong the same as if there were only one.

Doug

[PAULSPEED]

Just checked and the last Porsche plugs I bought were Bosch.

Paul

[mxt_77]

Has anyone actually tested the resistance on a set of new coils?  I just got a set of new Beru coils, and the resistance between pins 1 & 15 on all 6 of them is right at 1.0ohm.  The chart above indicates that it should be 0.3-0.7ohms.

 

Should I be concerned?

[Mijostyn]

Absolutely not. Most inexpensive meters have a lot of error getting close to Zero. If you use 10 different meters you will get 10 different readings. When the coils fail the resistance goes very high all the way to completely open. 

 

Has anyone actually tested the resistance on a set of new coils?  I just got a set of new Beru coils, and the resistance between pins 1 & 15 on all 6 of them is right at 1.0ohm.  The chart above indicates that it should be 0.3-0.7ohms.

 

Should I be concerned?

[jl-c]

just connect the meter leads together and lets say for arguments sake they read 0.3 Ohms, deduct that from your reading and you've got the actual reading. (or at least as accurate as you are getting with that meter) In reality accurate readings are done with 4 leads to sense inputs on the meter too (usually an accurate bench meter, not hand held) that removes the resistance of the actual leads. 

[mxt_77]

Thanks for the replies.

After removing the old coil packs, I saw that they are, indeed, different part numbers.  The original (factory) coils for my 2008 Carrera S were Beru 0040100021 (Porsche 997.602.102.00).  The new ones were Beru 0040100036.  The old ones were a little less consistent.  They were 0.7-1.0 ohms, so still about the same resistance.

 

The new ones are installed, and so far things are looking good.  I was previously having some intermittent misfires (when the car was very hot from long drives or track days) and low MPG under normal driving.  It's hard to reproduce the misfire symptom, but I should be able to tell pretty quickly if my MPGs have improved.