I have a 99 Tahoe with 168K miles on it. It has developed a low speed hard misfire after the vehicle warms up. It happens when the go pedal is lightly pressed off idle, and at low rpm cruising such as 40 mph and 1500 rpm. The misfire is a hard miss like the ignition is momentarily turned off and then back on. My son and I have replaced the plugs and the dist. cap and rotor. Next thought is either the plug wires or......?

Under heavier acceleration or higher rpm cruising it does not have the misfire.

EGR is activated at part throttle conditions so that is an area to look at. EGR solenoid needs to hold a vaccum. EGR valve could be sticking.

//2000CAYukon

Good AC delco plugs?

Good hot blue spark at spark plugs?

Camshaft retard setting?

Low fuel pressure and bad or dirty MAF sensor will give misfire.

What is fuel pressure readings?

Problem solved. It was the plug wires. Specifically, it had two boots that were cracked and allowing current to bleed through to the head. These were Accel 9000 wires that I put on not quite 4 years and 80K miles ago. I replaced them with good old Duralast wires from Autozone. I would have thought the Accel wires would have outlasted the truck, but they did not.

Buy the way, this was the final step in what amounted to a cheap tune up. Autolite plugs, Duralast cap and rotor, and now Duralast wires. Still using the Accel coil I put in 4 years back along with the Accel coil wire.....just in case. With 168K miles and no other problems, what else would have been worth the money.

Glad you found problem.
Thanks for posting back the fix.

Boots can crack from heat or get damaged changing plugs.
Also use good AC delco plugs plug wires