2002 Grand AM Chug on incline low MPG

[Vicki7]

I have a 2002 V6 3.4 L and it chugs on incline when you are going down the highway. It occassionally will chug when you first start to go as well. The MPG on it are also really low. I think somewhere around 15-18mpg. We have changed the spark plugs and the wires, still having the problems. Anyone have an idea of what else it might be?

Oh yes, there are no lights but haven't checked the codes yet.

[xeroinfinity]

Welcome to AF.

Is thier any thing else you notice the car does?

I would say change the fuel filter and or check the fuel pressure.The test port is on the pass side of engine.
Should be 41-47psi. These filters do need changed pretty frequently.

[Vicki7]

We just changed the fuel filter in November, and it's maybe been driven 1000 miles since then, we went on a trip and that's when we reallly noticed the chug.

As for anything else it does, it does shift quite often, especially when on an incline, which is leading me to think it's a transmission problem.

[xeroinfinity]

I would try and find out what your fuel pressure is as this might be your trouble.

How about when you turn left, does it rev or slip ?

If you have over 60K miles I'd change your transmssion fluid & filter.
Right now its probly low, so when you go up hill it looses pump pressure.

Btw-Their is no dip stick to check the fluid either.
Needs to be on a lift to remove the check plug located on the pass. side of the trans.

Let me know what you find out & Good Luck

[grfnkl]

Here's another thought. It could be your catalytic Converter. When they clog up, you'll have low MPG hard time driving the car like it has no power, transmission slipping and no lights come on on the dash. I can say this from experience. this is just a nother idea for you too look into. Good luck

[Vicki7]

Do any of you think it could be the fuel pump? I think so, hubby does not. I don't want to replace it if I don't have to but I wonder if it might be worth looking in to.

Hubby is a mechanic on leave with no tools, so this is driving him nuts not being able to figure out what the issue is. He is going to take it in to Checker today to see if they can pull any codes. I'll let you know what comes of that.

[grfnkl]

I don't think it would be the fuel pump. If it was you would be having more problems, such as stalling or not starting at all. Strange things do happen though.

[Vicki7]

Hello there, me again Since we posted this, so much has gone wrong with the car.

It now has a P303 code? it was set because when you are accelerating uphill, or rather trying to "punch it", the tranny won't shift, it stops at 5 1/2 grand on the tach and the check engine soon light flashes. After you stop accelerating, the light turns off and the car chugs like it's not getting fuel. We've cleaned the master air flow sensors, checked for vacuum leaks, changed the spark plugs and wires, and still it's doing it. ANY advice please??

[xeroinfinity]

P303 is cylinder 3 misfire.

For some reason that cylinder likes to misfire.

Things to check would be wire harness for the injectors, could be a short.
Probly a good idea to test the injectors with a noid light,
or test thier resistance with an ohm meter to see if that is what's causing the misfire.

Also most of these models will red line at 5500 rpms. Unless its running great you wont get to 6000 rpms.

Though usually when the light flashes that means something is wrong and a dealer should look it over
At least thats what the booklet that came in the cars glovebox says.

And about poor MPG check/test the O2 sensors

[Vicki7]

The thing about the 5500 rpms is that it won't shift to another gear, it will stay in the same gear and just rev high and not go any faster...

[snupytcb]

it sounds to me like an injector problem they can be tested seperatly with a modis scanner. as for the mil light flashing that usually means it's a misfire problem.

[xeroinfinity]

The thing about the 5500 rpms is that it won't shift to another gear, it will stay in the same gear and just rev high and not go any faster...

Probly should have said that soooner !

It is going to probly need to goto a Trans or other qualified shop to diagnose the problem.

If you havent changed the trans filter & fliud that migth be something to try before you take it in.

Hope that helps.

[Vicki7]

What is the reason for the p303 misfire code if it's in the tranny? Or is that a whole nother story?

[Love Cars]

Hi Viki. I'm new to this site and was looking for info on the same type problem. I own a 95 Grand Am and I think the Lock-up torque converter switch is not working. It acts like a manual trans. and not pushing in the clutch. Transmission keeps pulling when you try to slow down! Chug Chug

Mine misfires when it tries to kill the engine and will not shift correctly. Stays in lower gears (higher RPM less MPG)???

Sounds like the same problem. What do you think Xeroinfinity????

Love Cars

[xeroinfinity]

What is the reason for the p303 misfire code if it's in the tranny? Or is that a whole nother story?

p0303 is a cylinder #3 misfire very typical on GA's.
Could be ingintion system, plugs & wires, could be a bad coil, ignition module.
It can also be cuased by a bad fuel injector, a short in the injector wiring harness for #3 cyl, dirty or contaminated fuel.
Has nothing to do with the transmission

Originally Posted by Love Cars

Hi Viki. I'm new to this site and was looking for info on the same type problem. I own a 95 Grand Am and I think the Lock-up torque converter switch is not working. It acts like a manual trans. and not pushing in the clutch. Transmission keeps pulling when you try to slow down! Chug Chug

Mine misfires when it tries to kill the engine and will not shift correctly. Stays in lower gears (higher RPM less MPG)???

Sounds like the same problem. What do you think Xeroinfinity????

Love Cars

Your troubles could be a TCC solenoid which if bad usually makes the car die when slowing at stops because it doesnt disengage the torq converter.
This was a problem on early models not the 96 and up.

So NO these are not related problems in my opinion.

and Welcome to AF Love Cars.

ps I believe we have went over all of this on page 1