My 99 SL1 has a jerk when applying gas pedal

[nuwt]

My 99 SL1 has a jerk when applying gas pedal. If I let off gas pedal and coast the acclerate again it jerks then runs smooth. It does it if I push in the clutch or if I leave it engaged. I am thinking motor mount. Anyone else had this problem?
Its got new plugs and isnt missing.

[saturnspeed_12]

i dont fully grasp the problem, but check the upper mount.

[nuwt]

I'll try to explain fully. When it idles and runs itruns smooth, but if I let off the gas and "coast", as if someone is turning in front of me and I don't use the brakes just slow down, and then reapply the gas it acts as if missing. It jumps and jerks the runs fine. Thats the only time it does it and it will do it in any gear, all I have to do is take my foot of the pedal and coast for a few secs then give it the gas again. It does it under moderate acceleration the worst, but does it at any acceleration. It just started on last tank of gas, I added mavels mystery oil to the gas tank, maybe that will clean out any gunk in injectors or water in gas if that is it. nit is almost like the carbs on older cars that would spit when cold if you give it to much gas. But it does it all the time.

[saturnspeed_12]

ok so its like jerking, not just a single jerk upon getting back on throttle?

im thinking its not the mount. but to check anyways, with the car running, get under the hood and open throtle quickly several times. the motor should barely rock. if it rocks quiet a bit, the mount is bad.

now i cant say for sure what your problem is. its another one of those things were it can be several items.

[AkinaSpeedStar]

i have had this happen to me before, also check the fuel fillter, fuel pumps i find usealy go out on saturns at like 130,000 i dont know how many miles you have but there is that maybe too? so do a fuel presure test.

[nuwt]

Well this started after I filled up at walmart. First time using walmart gas and may be my last. I will go back to buying the cheaper gas. I got the S10 doing a MMO soak at the moment. As soosn as I get it back running I will do a thorough check on the Saturn. If my wifes Neon doesnt act up.

[saturnspeed_12]

well you could simple have bad gas from the sounds of it.

i guess if you can, try and hold off doing anything till you get different gas in there.

[nuwt]

ok so its like jerking, not just a single jerk upon getting back on throttle?

It is like that except sometimes it does it more than once.

[nuwt]

ok, I have replaced plugs and checked fuel pressure. it is at 47 pounds. I sprayed carb cleaner and checked for vacumn leaks all around including intake. I have a fresh tank of gas with seaform additive and it still missing/jerking. It is gettting worse tho, idles fine, runs fine, just acts up on acceleration and worse under 2000 rpm's. the only time it doesnt jerk or miss is when it is floored. I pulled each wire off and there was a noticeable difference in the rpms each time.
any other ideas?

[saturnspeed_12]

do you have an automatic? but it also sounds like your wires could be bad. it sounds very similar to a load misfire, which happens at low rpms under a load or can happen under acceleration except if it is punched pretty good. if you have an auto and it misses until you make it upshift, its likely it could be wires but then it could also be the trans.

although pulling each wire showed a difference in the engine running while sitting still, just shows you dont have a constant misfire. when the load is added while driving, then the misfire comes out.

[nuwt]

Well I found the problem! After pulling the plugs out (The new plugs) for the 3rd time! I was going to put an old set back in. and low and behold! the porcelain on 2 of the ac delco plugs had brown streaks. Almost as if it hair line cracks all over.I pulled them out before to double check and they were not brown, but today they were. I put a set of old plugs in and drove it and no jerking, missing or anything. I got 2 bad plugs when I purchased new ones.
I will try to take a couple pics tomorrow.