My 02 Monte SS, 3.8, is having some issues. To make a long story short once the car is warmed up and has been driven for a little while it starts to cut out/misfire, the RPMs go crazy, and then it dies; but only during acceleration as far as I can tell because it doesn't do it at idle. I just replaced the MAF sensor and checked fuel pressure (it was fine). From the research I have done there are many possibilities as to what is going on and before I throw a bunch of time and parts (aka money) into it I would like to try and narrow down the possibilities. Does anyone have any suggestions as to what I should check first? The only codes it is giving me is a 480 which is for the cooling fan I believe.


Side note and not sure if it could be related: my low coolant light always seems to be on recently whether the reservoir is full or not and sitting at idle the car runs hot. I also have an exhaust leak after the cat converter.

 

I was going to say fuel pressure regulator, but if your fuel pressure is up, guess not. Are you testing the pressure after the symptoms manifest themselves.

I had a similar issue before and it was my engines PCV had come apart. Does your 02 still have it's original PCV in it? But again, this could be the start of throwing unnecessary money at this issue.

I guess you don't have a dependable garage to take it in to when it is acting up, they can usually get a good feel for an issue if it's doing it while they are test driving it with you.

Keep us posted, I'm sure others will chime in with potential faulty components.

When was the last time your cooling system was flushed and serviced? What does the underside of your radiator cap look like, clean or a slimy build up. Are you loosing any coolant, ie: from the weep hole at the bottom of the water pump. Pump failure, thermostat, plugged / partially plugged radiator, bad hoses can cause you to overheat at idle. If you low coolant light is always on, pull the sensor out and clean it off, that may save you a couple bucks from buying a new one.

 

With the coolant being low, and high heat temps, and the misfire, I would be tempted to investigate if the head gasket is blown.
Check your oil to see if there is any antifreeze in there.

Being that you are saying the symptoms only happen during acceleration I would still be tempted to lean more towards fueling at first, but the head gasket could also be the cause.

 

Sounds like it could be multiple things..
But lets see if we can narrow it down...

Does the Coolant look like or have particles in it that are milk shake colored?

Can you smell a "sweet" smell from the exhaust. Is there any white smoke from the tail pipe? (Could be a sign of burning coolant)
Since its a 3.8 a common problem is the upper and lower intake gaskets tend to fail... and will need to be replaced. also check around the alternator(Below/around the belt tensioner) theres 2 plastic elbows that will probably also need to be replaced at the same time as they to are plastic and get brittle and begin to leak.. Are you losing coolant?

If so that could also explain the overheating along with theres possibly air in the cooling system.. The low coolant light could be on because its low... and or if its corroted from dirty corroted coolant thus not getting the proper signal due to it being dirty/corroted... also the coolant sensor could be bad.. And need to be replaced.

Since you said you have an exhaust leak at the catalytic converter..
Its quite possible the cat could be clogged.. If you can.. drive it for a few miles and look at the cat..If its glowing RED.. Its a sign that its bad and may need to be replaced.

You could pull the plugs and see if there discolored/corroted a sure sign of theres something burning other than gasoline.

Hope this helps...
Keep us posted of your progress and repairs!
Were here to help!

 

The backfire is caused by the leak in the exhaust. When you decelerate the exhaust draws air into the pipe. It mixes with the unburned fuel in the pipe and creates an explosion.


If you have a P0480 code the engine can run hot when the car is not in motion because the fan is not operational. Find the problem as to why the fan is not working and resolve it. As suggested, pull the sensor and make sure it is clean. The sensors on these cars are also known to malfunction on a regular basis. If it is clean reinstall then check it with a continuity tester prior to purchasing a new one.

 

Thanks guys, I will take all of your comments into consideration.


Both the coolant and oil look fine and I'm not loosing any fluids. I've checked the cat to see if it glows red and it doesn't. Also, she doesn't do this every time we drive her.


It needs a tune up as well as some general maintenance anyway so I'm going to try and accomplish that this weekend. Maybe try to do a ton of troubleshooting while I'm at it.

 

My car flipped out a couple of months ago like you are describing. My spark plug wires went bad. So maybe that helps!

 

@ Da_Man_Wit_A_Plan - how many miles were on your car and how long since a tune up?


I'm going to do the whole kit and caboodle; plugs, wires, filters, flushes, service, etc. and if it STILL does it after checking all of that and more I may just be on the hunt for a new vehicle

 

The new MAF maybe suspect...

Did you use an AC Delco? Or some other brand?

Try unplugging the MAF and drive it...
If the issues go away.. (with the exception of the exhaust backfire)
Then its a Bad/Incorrect MAF...
For the MAF always use AC Delco.

You didn't mention how many miles are on it...
But I would be suspect of a tune up is long past due...

I tuned mine at around 80,000 miles when it needed the upper/lower intakes and elbows replaced..

 

It doesn't matter if the MAF is plugged in or not, still acts the same.


It has close to 170,000 miles and the last tune up I believe was somewhere around 90,000 so it's due.