1999 Tahoe Misfire Problems

1999 tahoe 2wd, 4dr with 150,000 miles on it. Runs great around town. It doesn't like the interstate. Misfires, pull p300 code, on the interstate. As long as I don't push it at all it runs fine. Push it in the slightest, it misfires on me all the time. It does run much better through winter months for some reason and is worse in the heat. Afraid to take it on any trips.

Replaced: full tune up, fuel filter. I have run multiple cleaners through it without significant change. Only things haven't tried is the coil. I have been doing research and two big things come to the surface (replace injectors with spider and/or the gears the drive the distributer). I don't want to take it to mechanic and guess at the problem, I'd rather try to fix myself.

Any ideas or known fixes. This seems like a common problem for my research and I haven't seen a solid/consistent answer yet. I would TRULY APPRECIATE THE HELP!!!!!!

1999 tahoe 2wd, 4dr with 150,000 miles on it. Runs great around town. It doesn't like the interstate. Misfires, pull p300 code, on the interstate. As long as I don't push it at all it runs fine. Push it in the slightest, it misfires on me all the time. It does run much better through winter months for some reason and is worse in the heat. Afraid to take it on any trips.

Replaced: full tune up, fuel filter. I have run multiple cleaners through it without significant change. Only things haven't tried is the coil. I have been doing research and two big things come to the surface (replace injectors with spider and/or the gears the drive the distributer). I don't want to take it to mechanic and guess at the problem, I'd rather try to fix myself.

Any ideas or known fixes. This seems like a common problem for my research and I haven't seen a solid/consistent answer yet. I would TRULY APPRECIATE THE HELP!!!!!!

missfires at the higher RPM may be the distributor bearing ...check for rotor excessive movement.. then check for proper fuel pressures. follow the testing proceedure...

use only ac delco plugs.. resistance check plug wires.

then you have the cat converters checked for blockage/restrictions ...

THERE IS NO ONE FIX ANSWER !

jbare, did you ever get this thing up and running,
I am having the same problem...
I have replaced Plug wires, plugs, spider fuel injector, dist cap, rotor, oxyen sensor, crankshaft sensor, and still miss fires. If I come across anything I will let you know. I am doing the work myself, so this is going to get interesting.

jbare, did you ever get this thing up and running,
I am having the same problem...
I have replaced Plug wires, plugs, spider fuel injector, dist cap, rotor, oxyen sensor, crankshaft sensor, and still miss fires. If I come across anything I will let you know. I am doing the work myself, so this is going to get interesting.
i found mine had a bad ignition module on side of coil no more misfires and i timed cam sensor and crank sensoe all set so far 80 dollar fix

1999 tahoe 2wd, 4dr with 150,000 miles on it. Runs great around town. It doesn't like the interstate. Misfires, pull p300 code, on the interstate. As long as I don't push it at all it runs fine. Push it in the slightest, it misfires on me all the time. It does run much better through winter months for some reason and is worse in the heat. Afraid to take it on any trips.

Replaced: full tune up, fuel filter. I have run multiple cleaners through it without significant change. Only things haven't tried is the coil. I have been doing research and two big things come to the surface (replace injectors with spider and/or the gears the drive the distributer). I don't want to take it to mechanic and guess at the problem, I'd rather try to fix myself.

Any ideas or known fixes. This seems like a common problem for my research and I haven't seen a solid/consistent answer yet. I would TRULY APPRECIATE THE HELP!!!!!!
try ignition module did upgrade mpfi distributor crank n cam senser it was the ignition module causing the misfire hope it helps 80 buck fix:naughty:

missfires at the higher RPM may be the distributor bearing ...check for rotor excessive movement.. then check for proper fuel pressures. follow the testing proceedure...

use only ac delco plugs.. resistance check plug wires.

then you have the cat converters checked for blockage/restrictions ...

THERE IS NO ONE FIX ANSWER !

My 99 Yukon did the exact same thing. I drove it like that for about 2 years and it got worse and worse. Finally stopped running all together and it was in fact the distributor bearings. Seems to be a fairly common problem at about that mileage. Mine started at about 175K.

My 99 Yukon did the exact same thing. I drove it like that for about 2 years and it got worse and worse. Finally stopped running all together and it was in fact the distributor bearings. Seems to be a fairly common problem at about that mileage. Mine started at about 175K.

your 175k on this failure is just about all that had this occur with these 350 cu engines.

I have a 97 Tahoe, and it continued to misfire due to the Cat Converters. Replaced the CC with heavy duty CC, because I pull heavy loads, and haven't had a problem since.