LaserRed

This is my first post on the forum. I'm hoping my recent maintenance experience will be helpful to others...

I am the only owner of a stock (my choice) 1998 V6 Mustang with 56,500 miles. I took it upon myself going into Fall to do some maintenance on the vehicle. Changed oil, filters, plugs, wires, replaced a cracked vacuum hose, fuel filter, EGR valve, and topped fluid levels. The fuel filter and EGR valve were original so I thought it would be a good maintenance item.

I quickly noticed the following symptoms after the maintenance was completed.

* A slight and occasional rough/waivering idle (720 RPM range).
* A consistent engine miss/stumble/rumble between 1000-1200 RPMs. Ran nice and smooth above this RPM range.
* Very random hesitation/studder/slight engine miss while driving in the low RPM ranges (any gear).
* No codes were thrown over a 5 day period of trying to figure this out.

It almost seemd like I bumped a vacuum hose or my fumbling around caused a problem somewhere. Note: All spark plug boots were firmly gripped onto the plugs/coil and positioned correctly. I even thought at one point the PCM needed to adjust to all of the new maintenance additions. Overall, I spent about a week pulling my hair out on this one. So, what was the problem?

Well, turns out my car did not like the Bosch Platinum +2 spark plugs (p/n 4304) recommended by the auto parts store. My quest to find a solution turned up very bad Bosch plug reviews on forums and google searches. So, I simply replaced the Bosch plugs with Autolite double platinum p/n APP605 and all the problems/symptoms above went away. This is just a forum post to hopefully help others diagnose similar symptoms above relating to spark plug brand or possibly failure. Good luck...

BabyGT

Sometimes it pays to be cheap! Good look out lol keep active on the site! Forums aren't just about modified stangs, good maintenance posts and troubleshooting go a long way as well

LaserRed

Thanks for the comment. I really found piecing together symptoms, troubleshooting, and solutions from various forums and google searches was very helpful for my situation. I felt like I needed to give back and report on my specific problem to hopefully help someone else. The spark plug solution mentioned above will most likely not work in every case but just something to consider. I'm still perflexed why those Bosch plugs created such an array of problems in my mustang. It's been about 2 weeks and none of the symptoms mentioned above have returned.