chrispy33033

Trying to find quality coils and plugs. Searching online hasn't resulted in any confidence for one brand over another.

Any recommendations of where to buy a good set of ignition coils and spark plugs?

How critical is the spark plug gap? I notice there are many options. If the gap has particular affect on performance vs efficency I'd like to find anything that will improve fuel economy.

Harleyguy

AutohausAZ.com or Blauparts.com Both of these companies sell quality parts and often have OEM available. They are priced affordably and Autohaus often is quite a bit cheaper. One of the plugs available for the 4.2 motor has triple ground contacts and they come pre-gapped. When I changed mine a couple of years ago I wasn't having any issues but when I pulled a couple of plugs and checked them they looked like they had been used for quite a while. After I changed them I got another 2 mpg on the highway and the motor showed seat of the pants improved performance. That particular motor probably won't give you much over 25 mpg highway. On short stints of an extended road trip you might see 27-28 but overall 25 is normal.

chrispy33033

I'm getting closer to 17 mpg on average. I'd love to hit 25. Even on road trips, I haven't seen that. Blauparts.com doesn't seem to have any coils for sale. AutohausAZ does have them. I'm assuming the $10 more per unit is worth paying over what I find on Rockauto.com? I'd rather spend the extra for a good part but I'm also okay keeping my money for ice cream or treats if there isn't a lot of difference in the quality. What's your opinion?

I'm fairly handy but not crazy knowledgable about the 4.2. I have no doubt I can change the coils and plugs without breaking anything but are there other components that ought to be tested or looked at as part of changing coils and plugs?

Harleyguy

I don't have a whole lot of experience with Rock Auto. What brand are the coils? AutoHaus has OEM coils for about $35 each or for a few dollars more other brands such as TPI or Mehle. How bad are the plugs? Really good plugs aren't too pricey. Depending on who you ask some techs will advise you to change the coils every time you change the plugs as the newer plugs go many thousands of miles. If you think there are other things going on, get a scan done using a VAG specific machine. Personally, based on the mpg and no other apparent problems I would change the plugs and coils as it couldn't hurt anything except your bank account. I am guessing you don't have access to maintenance records.

chrispy33033

Rock Auto has several options ranging from $20 up to $28 per coil. The brands are Airtex/Wells, Delphi, Standard Motor Products, United Motor Products and NGK. This is what spurred the original question as I'm not familiar with these brands. I guess I recognize NGK from their spark plugs. When buying 8 coils the savings of $10 to $15 per coil is significant but I don't want to put low-quality parts on my motor. I don't know a lot about coils and their construction to know if it's super basic and one can't be that much better than another. If there isn't much to a coil then I'll just buy the $20 model but if it makes a significant difference in performance then I will go with more expensive guys. Just hoping to bump into someone with more experience than I have with this motor.

4Driver4

Why are you replacing the coils? They are pretty reliable on the 4.2. Misfires?

chrispy33033

Yes... misfiring. Hoping a full change will improve mpg as well.

caltch

On the plugs for my 4.2 a8 it's a 2000 I've read that in inches .042 is good for fuel efficiency while .032 is better for performance. As for the coil packs I recently bough 4 from amazon for 50 bucks and they seem to be as sturdy feeling as the oem ones my car is having problems atm which is why I've been looking into these things or I'd tell you my luck I set my plugs at .035. Here's a link for the coil packs.

4Driver4

Change the plugs first, then the coil or coils that are misfiring. New Chinese coils aren't going to improve anything. Unless you need to change the coils, don't.

caltch

is it a random misfire or always the same cylinder? If it's the same cylinder aside from plugs and coil packs check the injector an injector not snapped in correctly will give you a misfire on that cylinder.