3100 real bad surge

[mainaa]

newbie here needs your knowledge to steer me in the right direction, my 95 grand am gt is surging bad, there is no check engine light on, and it idles fine, it has the problems when it gets up to cruising speed, when the automatic shifts into overdrive it vibrates bad, apply the gas slightly to kick it down it gets way better but the surge is still there in third, does not seem to having any problems going from a stop, just at cruising speed, with it in park and revving the engine steadily there is a slight surge and when it gets to four grand it cuts out like a rev limiter, do these cut out at 4 grand or am i having a fuel or electrical problem? the car idles fine, and has 170.000 on it. please steer me in the right direction...thanks

[voyager]

they cut out at ~6000rpm at WOT.. so yeah, that's a problem.

how long has it been since you changed the spark plugs/wires? fuel filter?

does the exhaust smell odd?

[mainaa]

the plugs and wires do have about 15.000 miles on them, and have not changed the fuel filter in ages, i live in maine and this winter ran it real low on fuel a couple of times enough so the light came on but never ran it out of gas,
my exhaust does smell odd, there is a hole in my left muffler near the back of it,
and when sitting in my car with it running with the door open it smells pretty strong,
i was figuring it was just the exhaust coming out of the bottom of the car instead of out the tip, also the coil packs had some corrosion on them and cleaned them up didnt help though.

[voyager]

i'd change the fuel filter; i change mine every 2nd or 3rd oil change.. a bad catalytic converter can cause surging & bucking, which is why i asked about the exhaust smell, but it's not the only thing that it could be.

it could be a misfire too, but the plugs are relatively new.. plugs should last 80-100,000mi. you could take the car to an autozone/advance auto type of place where they will hook it up to a scanner for free; they can check for proper operation of the injectors etc.
could also be a vacuum leak, but i'm leaning towards the catalytic converter since i bet it's never been changed either, and 170,000mi is a bit over the life of them. i'd change the fuel filter, use some injector cleaner, and see if it helps. that stuff's cheap and ought to be done anyway.. if not, you might want to look at fixing the exhaust. if you ever wanted to upgrade it for performance, this might be the time.


i misread your first post - with the car in park, there is a rev limitter around 4000rpm, so yeah, that bit's normal.

[mainaa]

i will change the filter this weekend and try some injector cleaner, you are probably right about the converter, the exhaust system on this car is all factory, nothing has ever been replaced, so all of it is over 10 years old.. and it didnt start out this bad it just gradually got worse, thank you for the info.

[voyager]

hope it fixes your problem! thankfully, all the stuff i mentioned is pretty cheap.