02 GM has hesitation/vibration when I give it gas

[Spinn12]

Hey GM folks. First off, nice forum. Thanks for the work you guys do to help each other out. Mind if I leech some of that? Got a question for you.

My 2002 Grand Marquis has 104k miles. I got it from my family after my grandpa died a couple of years ago. I took it from 59k miles to its present, changing the oil and not much else other than tires.

Last week, when I was pulling up a decently steep hill at about 35 MPH, I got a stutter. The best way I know how to describe it is as if the car was being driven by a belt and the belt was slipping. It does this at the same interval, no matter what speed and no matter what RPM which leads me to believe that it's probably an electrical/ignition issue. I had to drive a good amount of miles, the next day, but the car wasn't doing anything else so I didn't pay it much thought. I had no problem making a 7 hour trip that next day, and the car was fine until yesterday.

I noticed tonight that it was doing the same thing as I was taking off from a stop sign. Obviously, it affects the power and so my takeoff wasn't as quick as it should have been.

I haven't had the time to do anything to the car yet (I don't drive it daily, as i work from home) but from what I'm seeing, it looks like it could be a few things:

MAF - Plan to get a can of cleaner and spray this off
Plugs/Wires - I've never changed them. I would doubt if they've ever been changed. Doing so this weekend.
Torque Convertor - God I hope not. Now we start talking money.
Transmission clutches - This is the horror story from my dad. Again, I'm hoping not because I don't have the cash for that.

So would you guys care to add to the list? I'd appreciate any help.

[Spinn12]

Also, adding Fuel Filter to the list. The car has more noticable problems at lower amounts of throttle, with the problems becoming far less severe as the amount of throttle is increased. That seems to suggest, to me, that I have a clogged fuel filter. It's letting enough fuel past that it will idle just fine, but when I try to accelerate or put the car under load, it's not getting enough gas through the system. To my knowledge, the fuel filter has never been changed, so the 104k miles would definitely mean that it's time.

Clogged injector/s could also be the issue, given the previous idea.

[Mercracer]

COP (coil on plug) is a common failure. Fuel filter is a normal maintenance item so it will not hurt to change it.

[Spinn12]

Thanks Merc. That's kinda my thought too, about the fuel filter. I'm going to change it, the air filter and clean the MAF first. I figure I can fire it up after that and see if I need to do the plugs immediately. If I do, it's only a couple of blocks down to Auto Zone and then another half hour to get those done.

[79lincolnlover]

Welcome. Has the plastic intake been replaced yet??

[miamibob]

Thought they got rid of the plastic after the 2001 model???

[sly]

just the coolant tube is aluminum... the rest is still plastic I think.

[Spinn12]

Welcome. Has the plastic intake been replaced yet??

Not that I have done, anyway. A quick look around seems to show that it was only a problem through the 2001 models though.

[zoomie]

id replace the COPS and plugs then worry about the MAF , but id check for codes first if its misfiring a code would tell you what cylinder usually

[Spinn12]

id replace the COPS and plugs then worry about the MAF , but id check for codes first if its misfiring a code would tell you what cylinder usually

Good point there, for sure. I'm not getting a CEL, but I think Auto Zone can hook me up to tell me if it's throwing a code.

[Spinn12]

An update to this, as well. Tonight (first time I've driven it since I wrote this, going to start the "fixes" tomorrow) it started having a rough idle. I had this same situation before with a 2002 VW Jetta that had a COP system and what I found was that one of my coil packs was popping up and not seating as it was supposed to. In that case, I replaced the COPs with a newer model that stayed seated and the problem was fixed.

Headed over tomorrow to go pick up the parts and then dig into this thing to get the COPs and plugs changed.

[BigMerc96]

Pretty typical Misfire symptoms, if you've never changed the plugs, do them first before jumping into changing the coils. As the plugs wear, the gap gets larger and it takes more juice for them to fire correctly. Your coils are probably getting alittle weak at this point as well BUT, changing the plugs out for prperly gapped new ones may be enough to fix the misfire.