Thread: Hesitates on acceleration sometimes, gas pedal not very senitive

About three months ago I had my 2001 GT stall at idle and rev high and low on its own so I too it to the dealer and they told me I have a bad Mass Airflow Sensor, ok, replaced it $500 bucks right there. About 2 months ago the car just suddenly feel apart, not getting proper reading from the gas pedal and just jerking back and forth and eventually stalling in the middle of a left turn downtown at 11pm. Ok so I tow the POS to the dealer again, they tell me it was a bad MAF...again...replace it under warranty and send me on my way. I stopped to ask "Are you sure the MAF is the only thing wrong in there, maybe something is damaging it?" and the tech told me that since it was only 2 months since the last replacement the best bet is that is was just a defective part.

Now a couple weeks after getting it fixed the second time, my car just doesn't feel the same. It hesitates on the lower gears and the pressure I exert on the gas pedal just doesn't match up to the RPM going up, unless i take my foot off and try again, and then it will rev higher. I have never driven another GP so I do not what what is typical gas pedal resistance and sensitivity but this doesn't feel right.

Also at idle I can sometimes see the RPM needle waver up and down ever so slightly(like it did before it stalled months ago) and if you sit in the car at idle for long enough, you begin to notice a series or pattern of "shudders" that vibrate the car, and again this used to happen right before stall.

What the hell is going on guys?

i am having a similar issue.. never stalled but when im at a stoplight, and the car is warm, if i give 3/4 throttle, it boggs/misfire til it reaches about 2500-3000 rpms then it takes off. also when im on the freeway, it seems to bogg down when i hit the gas, inless i punch it hard enough for it to downshift. when accelerating it seems to shudder in slight jolts. i have replaced plugs and wires, air filter, fuel filter, egr valve and not sure what else. i have no CEL or codes and the car runs the best in the morning when engine is still cool..--im starting to lean towards a coil pack starting to fail when its hot or torque converter( having already had a little tranny problems and replaced pressure solenoid and changes fluid). car has 145K.. *sorry for the novel* (also sometimes has sorta sloppy shifts...fluid looks ok) any suggestions would be great!

ctracer,
i thought so as well but i just replaced the cat with a magnaflow cat and the rear O2 sensor as well, about 3 months ago.. sorry forgot to put that in my post!

ive also read online that the shifting-type issue could also be caused by the tps failing. im going to try and clean my thottle body and maf and see if that does anything.. what else might i clean/inspect that could be an easy fix that i may have not noticed.. thanks for the help.. what about the coils starting to fail when the engine warms up(could this be the problem)?

My symptoms very similar to baker01gt's. car "vibrates" at idle, can feel it thru the floorboards and steering wheel, and it kind of "grumbles at the same time. Used to be smooth as silk. At 3/4 throttle, accel thru ~ 2500-3000 rpm range can watch tach flutter its way up and accel is a series of mild surges until reach highway speed or let of gas and get back on again without kicking down. A GM mechanic told me I needed to have him clean the throttle body and fuel injection system. Could that be it? I was worried maybe a tranny problem, but it acts fine except possibly for this.

Also, I replaced the radiator a year ago and put new coolant in at that time. I took the cap off the other day and it is covered with dark, rusty red/black colored sludge that has an almost rubbery consistancy. I thought oil was leaking into cooling system but took it to GM dealer for a pressure test to con firm a leak and they said no leak and it is not oil in the coolant. However, they had no idea what the substance is or where it came from. They just told me it was "gunk" from the system and to flush the cooling system out. ???? What do you guys think about all this?

PS. My car is a 1999 Grand Prix GT. Sorry!

It looks like this mystery issue could be the result of anything from expensive engine sensors, transmission systems, the Cat-convert, TB and pedal problems.

I am definately not going to pick and poke at the problem a thousands bucks at a time so should we start saving up for a new car? I mean it sounds like no expert can pin-point this until some extensive trial and error.

Originally Posted by LePrix

About three months ago I had my 2001 GT stall at idle and rev high and low on its own so I too it to the dealer and they told me I have a bad Mass Airflow Sensor, ok, replaced it $500 bucks right there. About 2 months ago the car just suddenly feel apart, not getting proper reading from the gas pedal and just jerking back and forth and eventually stalling in the middle of a left turn downtown at 11pm. Ok so I tow the POS to the dealer again, they tell me it was a bad MAF...again...replace it under warranty and send me on my way. I stopped to ask "Are you sure the MAF is the only thing wrong in there, maybe something is damaging it?" and the tech told me that since it was only 2 months since the last replacement the best bet is that is was just a defective part.

Now a couple weeks after getting it fixed the second time, my car just doesn't feel the same. It hesitates on the lower gears and the pressure I exert on the gas pedal just doesn't match up to the RPM going up, unless i take my foot off and try again, and then it will rev higher. I have never driven another GP so I do not what what is typical gas pedal resistance and sensitivity but this doesn't feel right.

Also at idle I can sometimes see the RPM needle waver up and down ever so slightly(like it did before it stalled months ago) and if you sit in the car at idle for long enough, you begin to notice a series or pattern of "shudders" that vibrate the car, and again this used to happen right before stall.

What the hell is going on guys?

It definitely sounds like something is causing that maf to go bad like you said, check to make sure your intake tubing is all tight and snug, also make sure your filter is clean, are you running a k&n filter? I've heard these filters come with too much oil and can damage mafs. The maf is very easy to remove and replace yourself for like 150 bucks. try spraying the maf with a can of maf cleaner and see if it helps at all. Is it throwing a code? When I had maf problems it would tjhrow an intermittent code. Maf problems suck. I wish you luck.

Originally Posted by Fivefingerdeathpunch

go clean the TPS and IAC sensor and see if that does anything.


and why on earth are you going to a dealer, they raped you on price for that MAF sensor, thay are like 160 new from napa or autozone and take maybe 2 min to swap if that.

I heard aftermarket MAFs are even worse that OEM. I guess I did get raped, didn't I?

I know for a fact that my cat isn't in the greatest shape, could that be a drivability/acceleration issue? What is the relationship between the MAF and the cat? Could an old cat contaminate a MAF?

No, but a bad MAF may mess up the cat.

Originally Posted by LePrix

I heard aftermarket MAFs are even worse that OEM. I guess I did get raped, didn't I?

I know for a fact that my cat isn't in the greatest shape, could that be a drivability/acceleration issue? What is the relationship between the MAF and the cat? Could an old cat contaminate a MAF?

well for future reference if you have to replace the maf get a t20 torx security bit "one with a little hole drilled in the tip" and it literally takes no time to replace it.

i bought a maf from autozone and have no problems.

but before you do anything the real question here is are you getting a ses light???? either way you need to have it checked for any current or history codes.

i just replaced my alternator the other day but when i had it tested at AZ they said i had a bad alternator and battery..
after replacing the alternator i had it tested again and still says bad battery. i thought that the new alternator would kinda recharge my "bad" battery but didnt..
would this cause the problem and how?
Thanks!!
(still fighting this problem)