Car stumbles under load < 1500 RPM

[eRiCdWoNg]

I have a 98 Coupe MN6 and its been acting funny lately. If the motor is under load (up hill or high gear) and it is under 1500 RPM, and I press the gas more then 50% of the way the car stumbles.

I first noticed this when I did the "zip tie airbox" mod. At first, I forgot to plug the little vaccuum line thingy into the accordian coupler in the intake track. Now- I did drive around for about 20 miles with this error in place. I figure oops, no big deal I'll just plug it back into place. I plugged it back into place, but it still does it. Then I replaced the entire airbox assembly and even reset the battery. Its still there. Oh yeah, I did try to pull codes, there was nothing. Zero.

Yes I've checked over it to make sure theres no air leaks. I even pulled off the MAF and filled the intake plenum with water to make sure of no leaks. I'm 98% sure that theres no airleaks but I'm a little skeptical of area between the duct that goes over the radiator with the flag on it and the flexible accordian coupler. It sorta just pops on. I'm probbly gonna seal it with sealer.

I wonder if I got a tank of bad gas by coincidence? I'll find out when I filler up again sometime soon.

Any other suggestions???

 

[LMN8R]

My car is bone stock, but occasionally does the same thing. It is invariably remedied by putting Chevron's Techron additive in it. I usually put 2 big bottles (about 40 gallons worth) into a full tank, and the problem goes away fast. I've heard that the Redline and Lucas stuff is good, too, but I'll stay with the Chevron stuff.

 

[cruzer99]

Bad plugs??? How many miles on the plugs?
If a plug is bad or weak it will fail or miss-fire under load.
Good luck

 

[eRiCdWoNg]

Maybe it is the plugs hmmm. They are the originals I believe and if so they're 65,000 miles old. My 1st car I had to buy 4 plugs. The next 6. Now I have to buy 8.... haha.