New Spark Plugs Causing Problems?
 

Today, I switched out the old HKS M45RE & M50RE spark plugs (heat ranges 9 & 10) for brand new NGK BUR9EQP (using 9s for both trailing and leading).

The car started up with no issues, but after a short drive, the headlights turned off (not fully off, but it's running on the daytime lights only), stereo shut off, cluster became dim, and the engine ran like crap. The volt meter was giving me a reading of 7.9v, which is way down from the usual 13-14v with the engine running. Felt like it was on life support with just enough juice.

After about 10 minutes, everything came back on and the engine ran smooth again, voltmeter giving a 13.5v reading.

Has anybody experienced this problem before? How could new spark plugs cause this? Could the different heat range throw off the tune? I'm thinking perhaps I accidentally loosened a connector during installation of the spark plugs (due to the very tight space to work with).

Appreciate any feedback!

No, spark plugs will not do this. You probably knocked something loose. Probably a ground.

Rebuild time Ken

Yeah, I'm hoping it's just a loose ground or something.
Another thing worth mentioning is that if I rev it to 2000 rpm, it will take 3-4 seconds to drop back down to the ~1000rpm idle.

Check the big fat one on the engine block next to the spark plugs.

Would you have an image of where you're referring to? Don't have the car with me for the week to check. Really appreciate the help!

Looking from under the car, you'll find the main engine ground (a thick black wire) is bolted into the intermediate housing.

I'll have a look at that next time. Thank you.

Another thought that came to mind - if I accidentally switched the front and rear wires for the leading plugs, could that cause any issues? I read that for FC's it wouldn't matter because they fire at the same time. I assume the same could be said for the FD?

Leading doesn't matter. But don:t switch the trailings!

Well I finally had a look at it today and everything seemed in order. Only thing that was loose was a connection to the positive terminal (not the main cable). I checked the grounding point on the engine block between the spark plugs and it turned out there was nothing bolted on. Thankfully I bought a grounding kit, and added a connection to that location.

Still running the new spark plugs, and everything seems to be running smooth! Hopefully that resolved the issue and I appreciate the help.

I thought I had resolved the issues but it happened again today.. Bad alternator perhaps?

check alternator voltage output to confirm, but yes it can cause rough idle

I'll do a check with a multimeter next time. Not sure why it ran with no problems these past few weeks and suddenly went back to low voltage.

Did a voltage test with the multimeter and everything checked out fine. 14.2ish volts with all accessories on.. I ended up removing the alternator anyway to have to checked at a shop.

In the process, this vacuum line came off. Any idea where it goes?

Someone correct me if I am wrong. But it should go just below the throttle cable bracket on the UIM.

Is this what you're referring to? Really wish I had the car with me to check. What's odd is that I'm running a single turbo - not sure why it has a pressure chamber still.

Sorry, I was wrong. Able to post the diagram for you now, but it is for full sequential. Really not sure why you have the pressure chamber if you are single turbo.

http://www.turborx7.com/images/Techn...e_diagram2.jpg

Appreciate the help! I had a look at that and there is no more connection to that since I have a single - very odd. Might just remove it, but first thing's first - gotta resolve the intermittent voltage drops!

What issues are you having now, exactly?

Exact same thing as last time - a sudden voltage drop while driving that caused the headlights, stereo, ac, etc.. to shut off. This time, the voltage didn't return to normal (although I wasn't going to wait for the car to potentially die on me).

I pulled my alternator out and had it tested - apparently it failed. In a way, that's a relief because at least I know what the cause is. I'll either have it rebuilt, or replaced and hopefully I don't experience this issue anymore.

Had my alternator and battery tested at 3 different places - they all passed now.. Leads me to believe the connection isn't good. I'm going to do the big 3 upgrade (mainly to supplement the charging cable), and hopefully that does the trick.