Had my coolant tank swapped the other day, mechanic did a road test and says the car is misfiring at high RPMs and needs new spark plugs. I did my own road test last night and it felt and sounded smooth as butter.. What should I be listening for? Nothing sounded or felt like it was missing a beat. Should I have someone check out the ECU for misfires?

I'm a little surprised because I did them about 20,000 miles ago. Shouldn't they last 30-50k?

How many hours of labor do most shops quote? This is one of the pricier jobs, no? I'm seeing the DIY on Renntech, sounds like a bit of a pain, but it's still an engine-in job as far as I can tell... Sounds like the worst of both worlds: expensive, but I can't use the engine coming out as an excuse to do other mods

Thanks for any info
Justin

 

I'm not sure if this is a "real" answer but it seems logical to me that if you're driving the car at high RPMs and don't feel any misfires and the car is operating smooth, then why would you want to swap them out? I'm pretty sure misfires would be noticeable as the car would be breaking up.

 

You don't provide any information about your car other than 2001. Any mods? What plugs are you using? Depending on how you drive, where you drive and mods, plugs can go rather quickly or last...

 

It's stock - K16s. 48k miles, plugs last changed at 28k. Only mods are unrelated (997 shifter, wheels, DVs). Receipt shows plugs listed as "FR6LDC".

Only one track day on them. Street driving, I go fast sometimes, but not all the time.

 

it depends what plugs were used? On any modded car 20K is pretty good. Not sure if you used Bosch FR6s? Those will last longer than Berus.

 

Ask the "mechanic" if he logged it somehow, or is he just guessing. If he logs it and you, in fact, have high RPM misfires, do the plugs, if not, find a new "mechanic".

 

I assume that's what FR6LDC specified in the above message means. So hence my surprise that an unmodded car would burn through them in ~20k.

Yes, this sounds like the best idea. I just thought it might be something I could diagnose myself. I'll continue to keep my ear open, and ask them to plug in next time I'm somewhere with a diagnostic reader.

 

my car has had a cyl 2 misfire for months, according to the Durametric, I can't feel it or hear it...car seems to run fine.

 

Well it could have been the Beru's and not Bosch's that got installed? Other thing to check is the coil packs themselves (see what their condition is like).

 

20k miles is about average on a 996TT. If you can get 30k miles out of them, you are doing really good!