Weak startup - spark plugs?

[rh71]

Edit >> sorry move to garage.

08 X5 with inline 6 engine at 50k miles. In the last month the car has struggled to turn over which I attributed to the cold - it does start the first try each time though. But the other day after it turned over it was a very rough idle. This vibration also happened 4 months ago out of the blue and the code pointed to a bad ignition coil - mechanic changed coil 6. It didn't struggle to turn over back then as far as I recall.

The code this time says P0302 which I believe is ignition coil in cylinder 2. My question is does the difficulty turning over point to a bad spark plug which in turn causes a bad ignition coil? Or is it just the coil's issue? I can do the coil but if the plug is causing it then I should do that too. It's supposed to be easy but I'll need additional tools. These OEM plugs are rated for 100k miles however.

 

[BoomerD]

BMW = Bring More Wrenches
BMW = Break My Wallet.

I drove Bimmers for many, many years. Nice cars when they're running right...real PITA when they're not.

 

[jlee]

What do you mean by "difficult turning over"? Is the engine cranking slowly or is it not firing?

 

[rh71]

What do you mean by "difficult turning over"? Is the engine cranking slowly or is it not firing?

Yes cranking slowly almost like the battery is too weak. Never actually got a misfire code unless the above code is it.

One other thing to mention is that over a year ago I had a leaking valve cover gasket replaced and a little bit of oil got to the plugs but the mechanic examined, cleaned, and said they were still OK.

Bottom line I want to know if plugs would cause such an issue and lead to bad coils again down the line.

 

[lxskllr]

I'm just a dummy, but all the coil packs do is apply extreme voltage to the plugs, no? I can't think of anything a plug would do to burn out a coil.

 

[jlee]

Yes cranking slowly almost like the battery is too weak. Never actually got a misfire code unless the above code is it.

One other thing to mention is that over a year ago I had a leaking valve cover gasket replaced and a little bit of oil got to the plugs but the mechanic examined, cleaned, and said they were still OK.

Bottom line I want to know if plugs would cause such an issue and lead to bad coils again down the line.

You could disconnect the spark plugs entirely and that wouldn't change how quickly the engine turns over -- if it's cranking slowly, it's likely the battery or a poor connection between the battery and the starter.

 

[rh71]

Well I swapped out the #2 ignition coil and the rough idle was gone. Started it again an hour later and it's back. Guess I'll have to go after the plugs.

 

[Pacfanweb]

Plugs aren't causing the starter to turn the engine over slowly.

 

[Raizinman]

Try jumping the car with a good battery and see if that helps things. Have you taken a voltage test of the battery? Old batteries can play havoc with the electrical system. How old is your battery? If you don't know specifically, check the battery date code on the top or side of the battery. A1=Jan 20011, B2=Feb 2012, C3=March 2013, D4=April 2014, E5=May 2015 and so on and so on which will give you the date of manufacture of the battery.

 

[Fenixgoon]

it's worth checking your battery to see if it's good anymore. mine crapped out after 6 years.

 

[rh71]

I replaced the battery at year 5. This is year 3 with this one. It could explain the slow turn over especially with the cold and I only drive it a few times a week.

Still getting the rough idle so I suppose that could be a separate issue and not related to the slow start.

What exactly would a bad plug cause? It would still start normally but throw a misfire? What about rough idle or is that strictly the coil?

 

[rh71]

Well I threw a new plug in #2 and no more rough idle.

I guess this is what they call dry fouling - maybe from when I had a gasket leak a year ago. I am sure my other plugs are not too far behind.

 

[dave_the_nerd]

Well I threw a new plug in #2 and no more rough idle.

I guess this is what they call dry fouling - maybe from when I had a gasket leak a year ago. I am sure my other plugs are not too far behind.

Probably should replace all six at the same time. Simple enough to do in most engines. Gives you a chance to clean out the spark plug wells, if you had a leaky gasket. Also, really easy to do, so gives you a chance to spend a couple hours in the garage with a beer and nobody bothering you.

With 50k on the odometer, it might have been time anyway. (Depending on the plug. Some are good for 10-20k, some ~50k, and some 100k+. Depends on the material used.)

 

[rh71]

^ will do after I get back from a trip this weekend. I just want to be sure it's stable for that first.

Cyl 6 is extremely hard to reach too so will take more time.