engine misses until warm

[okk9]

My trusty 91 Explorer has developed a problem over the last few days. Seems that when I pull out of the driveway and head out, the engine has a bad miss/hesitation upon acceleration. It's noticable enough to cause the truck to shutter, however as the temp gauge reaches the "N" it stops missing and runs fine the rest of the day. It only does it when the engine is cold and within approx. 2 miles it stops. I'm still getting 18-20 mpg, about 20k ago I put new Bosch platnium plugs and wires, It has a KN air filter and I've checked for trouble codes and there are none. It has 140k and I've owned it for 4 years and take great care of it. Has anyone else had this problem? Any help with diagnosis would be great.

 

[murrajm5]

Try doing what we used to call "power braking" by placing it in drive and holding down the brake pedal while giving it the gas. Make sure you get the rpms up at least 2000 and see if you have any missing, backfiring or sputtering. If so, it is most likely a bad plug. I had Bosch platinums and one went bad and gave me the same symptoms.