Need help with high octane gas problems.

I bought a 98 GTP a couple months ago. For some reason, when I drove it off the lot, I put about half a tank of 87 octane in the engine (I know that it needs 91 or better), which caused the "Service Engine Soon" light to come on and caused the engine to jerk or shudder repeatedly when accelerating from a stop. Ever since then, I've used 93 octane. Well, just last night, the engine light came on again, and the same problems happened even though it had been filled with 93 a couple days ago. I know that we put Sunoco Super 93 octane in the engine last time, but just for the heck of it, before calling the mechanic, this morning I added about 5 gallons of BP/Amoco 93 octane, and immediately after starting the car, the engine light went off and the car ran fine.

Is this jerkiness a common problem, caused by something like a bed sensor and not having anything to do with the gas? Or is it possible that we got a bad batch of gasoline (or worse, did we get ripped off)? I'd really appreciate anyone's opinions.

Maybe u have some bad gas.

Ive been running 89 octane in my GP for atleast 2 months now and have not had any problems.

try replacing the fuel filter and putting some water remover in your gas..i doubt it has to do with the octane if its not modded. if that doesnt solve it check your plugs

gtgp97 - Well, I haven't modified anything yet. How difficult is it to change the fuel filter? And why would I need to put water remover in the gas? How could water get in the fuel system, and how can I keep that from happening again?

a few months after i bought my 98 gtp I put the 83 octane and my car would shudder and jerk. it had a brand new fuel filter on it, but when checked the plugs the electrodes were burned almost completely off. and it hasnt done it since I changed the plugs and wires.

the fuel filter is real easy to change. iv done it twice on mine. it's in front of the rear drivers side tire near the brake lines. you'll have to pull the fuel pump fuse and start the car and let it run(until it dies) to get the fuel system depressurized. then it sould be safe to change it. it doesn't require any kind of special tools.. just two wrenches(from what i remember)

gtgp97 - Well, I haven't modified anything yet. How difficult is it to change the fuel filter? And why would I need to put water remover in the gas? How could water get in the fuel system, and how can I keep that from happening again?


there is always some water in the tanks at the gas station. You especially dont want to get gas while there is a tanker trucker filling the underground tanks. You ll have the dirt and water all mixed up with the gas

Rubberman's right...I work at a Chevron, and usually there's no problem with the water in the gas tanks, because the water and gas will separate. But if you got gas shortly after the tanker had been there to fill up the underground tanks, it was all mixed up. I agree that you should try replacing the fuel filter...you DON'T want to have to replace the fuel pump...$258 and change...and that was what it cost the dealership for the pump. And that's not counting labor, which was $100. I could have done it myself, but I didn't have the time.

where is the pump located? If its inthe tank itself then i would be happy to have a mechanic replace it. My 94 S10 SS fuel pump went out and had to drop the tank and way too hard to replace it.

yea all u need for the fuel filter change is 2 wrenches...if its like mine, its cylinder-shaped..and if i remember right, all u need the wrenches for is to take it apart...it more or less slides right out after its all apart (both metal lines are taken off of it)...installation is the reverse of disassembly...its fairly easy.

a few months after i bought my 98 gtp I put the 83 octane and my car would shudder and jerk. it had a brand new fuel filter on it, but when checked the plugs the electrodes were burned almost completely off. and it hasnt done it since I changed the plugs and wires.


is there 83 octane?? if there is then i can see why it would shudder...f/i and low octance dont mix well

The pump is in the fuel tank. That's why I went ahead and let the dealership do it. I COULD have done it, but like I said, didn't have the time.

Well, first of all if the car tell U to use 91 octane or better do that. Secondly GTPGirl is correct, when you get watter in your system even tought using the correct octane rating the SES will come on and the car will Jerk. Never hurts to change the air and fuel filter and adding stuff to stabilize (a.k.a Stabil) and get the water out the gas.