96 Monte LS Missing or Cutting out?????

My 96 Monte LS 3.1 (132K) started this a few weeks ago. I noticed it when sitting at a stop light with the A/C running, in drive, foot on the brake. Idles good, but the engine intermittantly jerks like it's missing. I can feel it through the chassis and the tach will drop ever so slightly. I hadn't driven it on the highway for quite some time, but did this past weekend. Took it on a 150mi trip. Started off doing it every so often at highway speed. By the time I was almost at the destination, it was jerking so badly and almost consistantly, that it felt like I was hitting potholes on a brand new asphalt road. It was worse when going up hill and with the A/C on. Didn't do it as much on level ground or with the A/C off. I originally thought before this trip that it might be the Idle Air Control valve. My buddy had one off of his 3.1 that turned out wasn't his problem. I swapped mine out and that didn't help. I put a different fuel filter on this weekend when I got home and that did not help. It doesn't seem like it would be the fuel pump, however i'm not discounting it yet. It almost seems to me like one of the coil packs is going. Has anyone experienced the same type of situation? Or Does anyone have any ideas?
Someone said bad gas, but I don't think that is it, as it's had several tanks full ran through it with the same issue. Any help would be appreciated. Thanks!

Sounds like a bad plug or wire.

my 96 monte carlo is having the same problem, it will start some times and feel like its bogging down and stall out. we changed the plugs and wires, fuel filter and the coil packs. it still runs ruff and will bogg down then eventually stall out. i was woundering if you figured out the problem if you could maybe help me out???

Welcome to AF. Start by checking the fuel pressure.

okay, well while changing the fuel filter the fuel line broke because it was rusted, we cut out a section and replaced it and unioned it together it hasnt been leaking. but after we changed the coil packs and the plugs and wires it ran alot better, but after a day it hasnt been starting right. any ideas?

I haven't figured out my problem yet. I've been busy lately and haven't had a chance to do anything about it yet. It does seem to be doing it more often and cutting out worse each time, however it has never completely killed on me yet. I was going to check my plugs and wires, but I opted for some gas dryer in the tank first just to discount any water in the gas (didn't seem to help). I started with the cheap options and then I'll work up the expense ladder. Max Wedge, what is all involved in checking the fuel pressure? I am assuming I'll need a special pressure gage?

Yes you will need a fuel gauge to check fuel. It sounds like you problem is more ignition related rather than fuel. This would be really easy to figure out with a scan tool and monitoring missfire data. You could then focus specifically on the particular cylinder(s) affected. I would start with wetting down the wires to see if they are arcing!

I have had a few MAF sensors cause a boggy symptom especially trying to excellerate onto a freeway. When in doubt unplug it and see if the car runs better. Sounds like you have yours figured out thought.

Either one of you guys losing coolant?

The old 3.1 liter intake gasket. If you losing coolant under the throttle body you will need to get this replaced. I would advise before the oil becomes milky and it will if you wait long enough. If its milky its too late and within a couple of months the engine will develop a rod knock even after you have spent the $800+ dollars to have this repaired.

Lately we have been using Felpro gaskets wich are a rubber impregnated steel gasket that seems to be holding up much better than the O.E. rubber impregnated plastic gasket (even the ones with the metal anti crush sleeves).

If your lucky you can get away with one every 60 to 80k but I have replaced them at the 40k interval as well!

Coolant is fine. My LIM gasket was replaced 24k miles ago. The wires are not arcing as far as I know. I washed the engine last weekend and they were fine. If it was a coil pack, those things pretty much just go dead don't they? I've haven't seen one really give any warning, kinda like the Ignition module. I've had two of them go out on me. One on a 3.1L and one on a 2.8L. Alive one minute, dead the next.
I was talking to my buddy that I got the IAC valve from and he said his car sort of sputtered and acted like mine is doing before his fuel pump went out a few months back. He also has the 3.1, only in a 97 Grand Am GT. His pump was almost $300 at Autozone. The one for this Monte is only $75 thank God....if that is indeed what the problem turns out to be.
The symptoms are very strange. It doesn't seem to be boggy, it just seems to cut out. But it is in really quick bursts. Like when you hit the limit on the top end going 100+....only it does it less dramatically, and really quick. it isn't enough to make you pull your foot from the pedal.
I'm probably gonna check the fuel pressure next like Max Wedge suggested, and then go from there. If I have to, I can drive my truck, so i'm trying to take my time and not spend a ton on this.

Okay, After losing my job and being unemployed for a couple of months due to my former employer going out of business, I've got a new job and am resuming the task of getting this Monte running right again so I don't have to drive my truck as much.

I had the fuel pressure checked, it was fine. I opted for the new plug wires and it did not help the issue. I've had a couple of people mention to me that it could possibly be the crank position sensor. I had to replace one of those on both a 3.1L and a 2.8L engine in the past, but both times, when it failed, it completely killed the car. Do these things sometimes fail slowly? Because my Monte has never killed. I was reading in my Hayne's manual that "later model 3.1 and 3.4 engines have 2 crank sensors. One on the Firewall side of the engine (like my engines in the past had) and one down behind the crank pulley. How do I know if mine has both of these? The book is for '95 thru '03 vehicles. Is there some way of knowing without putting it up on a hoist and looking under there? One of the parts is $18 and the other is $34. I'm also guessing one is very easy to change, and the other is not. If anyone has any advice on this topic, please reply. Thanks!

Any misfire error codes?

None. No Check engine light, no codes on the OBDII scanner. I drove it tonight and it didn't act up. It does it really bad some days, not as bad other days, and won't do it sometimes. I've ran 'SeaFoam' through it to make sure the gas didn't have water in it. The fact that it does it intermittantly puzzles me. Makes me think it is a sensor or something.

I'm having some sort of the same problem with my girlfriends 97 ls. it will idle at about 900 to 1000 rpm, then dramatically fluctuate up and down between 3-400 and 1200. the idle will eventually stabilize, and if you hit the gas, the idle will immediatly stabilize. On top of that, sometimes it will cut out as soon as you put it in gear. it also throws a p0404 emissions code, but all the vacuum lines in the engine bay are tight. I did have a problem with a random misfire, but i found the number 4 spark plug with excessive gap. tightened the gap, no more misfire.

I'm having some sort of the same problem with my girlfriends 97 ls. it will idle at about 900 to 1000 rpm, then dramatically fluctuate up and down between 3-400 and 1200. the idle will eventually stabilize, and if you hit the gas, the idle will immediatly stabilize. On top of that, sometimes it will cut out as soon as you put it in gear. it also throws a p0404 emissions code, but all the vacuum lines in the engine bay are tight. I did have a problem with a random misfire, but i found the number 4 spark plug with excessive gap. tightened the gap, no more misfire.

Have you looked at the idle air sensor? Just my suggestion.

My 96 Monte LS 3.1 (132K) started this a few weeks ago. I noticed it when sitting at a stop light with the A/C running, in drive, foot on the brake. Idles good, but the engine intermittantly jerks like it's missing. I can feel it through the chassis and the tach will drop ever so slightly. I hadn't driven it on the highway for quite some time, but did this past weekend. Took it on a 150mi trip. Started off doing it every so often at highway speed. By the time I was almost at the destination, it was jerking so badly and almost consistantly, that it felt like I was hitting potholes on a brand new asphalt road. It was worse when going up hill and with the A/C on. Didn't do it as much on level ground or with the A/C off. I originally thought before this trip that it might be the Idle Air Control valve. My buddy had one off of his 3.1 that turned out wasn't his problem. I swapped mine out and that didn't help. I put a different fuel filter on this weekend when I got home and that did not help. It doesn't seem like it would be the fuel pump, however i'm not discounting it yet. It almost seems to me like one of the coil packs is going. Has anyone experienced the same type of situation? Or Does anyone have any ideas?
Someone said bad gas, but I don't think that is it, as it's had several tanks full ran through it with the same issue. Any help would be appreciated. Thanks!

Mass Air Flow Sensor??

Loss of a MAF signal for as little as 600mS will set a DTC. The PCM watches that one pretty closely.

Im having the same, or similar, problem. I have a 97 monte carlo ls and it keeps dying on me at random times, or seems so. It usually cuts out and dies with no prior indications, typically at a stop sign, stop light, and lately when going down the road and begining to let off the gas to slow down for a turn or another vechicle is braking. Oh and of course it has to happen at the busiest intersection. When it does die, the volts and check engine light comes on (and maybe another light but uncertain right now). After dying it takes 1-5mins of sitting there and it will start right back up and run fine but i try to avoid all stops as possible until i get to where im going but thats usually not possible and it dies again. I put it in the shop week after week with the mechanics guessing, which just costed me money. They replaced the computer, still died; replaced ignition module, still died; replaced crank sensors, still died; redid some wiring between crank sensors and ignition module, still died. I ate money on that and the mechanic(s) ate money on it too cause they didnt fix problem. Thats the problem im having. Only suggestions that ive been told was possible TCC solenoid or Mass airflow, but the ppl suggested didnt sound so sure at all and i didnt want to eat more $$ without other opinions. Thanks.

Z74,
My Monte never got as bad as yours is. It never died, just kinda chugged slightly. It ended up just being a bad plug. I actually traded it last March for a '07 Camry, but it was running great when I did. While reading your thread, I was first thinking Crank sensor cause i had another car with a 3.1L that did what you were describing and that was the culprit on that car, but as a read on it looked like you already ruled that out. For what it's worth, my parents used to have a '87 Pontiac 6000 SE with a 2.8L in it that did exactly what yours is doing now. Tried to die when slowing down or when the car was turning, and sometimes would sit there for a little while before it would start up again. I remember my dad saying the guy at the shop said it was the MAP (manifold air pressure) sensor. Might be worth checking into. I didn't see it on your list of stuff already replaced.

Here is another idea that is just a shot in the dark: If you slow down to a stop and it starts to chug, if you slip it into Neutral, does the car keep running? I used to have a '92 Cavalier Z24 with a 3.1L that showed somewhat similar signs, and it would chug or die when I slowed for a turn or slowed for a stop. If I shifted into Neutral, then slammed it back into drive when I needed to go (as long as I had the RPMs) it would be fine. It ended up being a Vehicle speed sensor in the Tranny that was basically not allowing it to downshift and it was like trying to drive a 5-speed in high gear all the time.

Good Luck to you!

Thanks for the advice sierra. Ill be sure to look into that this week.

Im haveing pretty much the same problem with my 97 monte carlo 3.1l v6 mine is having problems starting once it starts it runs good. clean idle as soon as i put it in gear its ruff and gutless. if i give it more than 1/4 gas pedal it wants to die like it was hitting a rev. limiter. I can barely get up to 30 mph and thats only by feathering the gas pedal. I did get a code for a #6 cyl misfire and also a code for fuel system bank 1 was lean. Not quite sure what thats all about anyone have any good ideas?:runaround: i feel like im chasing my tail!