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

sierra77 · 08-25-2008, 10:26 AM

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!

maxwedge · 08-25-2008, 10:50 AM

Sounds like a bad plug or wire.

shelly963.1 · 09-02-2008, 05:02 PM

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???

maxwedge · 09-02-2008, 07:07 PM

Welcome to AF. Start by checking the fuel pressure.

shelly963.1 · 09-02-2008, 07:21 PM

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?

sierra77 · 09-03-2008, 09:26 AM

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?

Airjer_ · 09-03-2008, 01:24 PM

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.

Mickey#1 · 09-03-2008, 01:41 PM

Either one of you guys losing coolant?

Airjer_ · 09-03-2008, 01:54 PM

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!

sierra77 · 09-03-2008, 04:23 PM

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.

sierra77 · 11-29-2008, 04:56 PM

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!

Blue Bowtie · 12-01-2008, 10:15 PM

Any misfire error codes?

sierra77 · 12-02-2008, 05:14 PM

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.

cusz28 · 12-07-2008, 06:23 PM

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.

96MonteCarlo34 · 12-13-2008, 12:14 AM

Quote:

Originally Posted by cusz28

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.

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