I am working on my grandmothers Malibu and the check engine light was on. I pluged the diagnostic computer into the port and it read that the O2 sesnor bank 1 sensor1 was bad and that the trans. had low voltage. The reason i was working on her car was because it was missing under a load , like when she would go up a hill or giving it throttle from a stop the car would miss for lack of a better word. Anyway, i replaced the sensor but i have no idea how to fix the low voltage problem. the check engine light went off but the car still misses. If anyone can please help i would be greatful.

 

That's why I'm here. I have a '99 Malibu w/ 3.1 and it is doing something very similar. The car has been very reliable, and I've done most of the maintenance for all of its 230K miles.

The car starts immediately when I turn the switch and idles just fine. But when I drive and try to accelerate or go up a small grade, the engine begins to misfire and lose power. Once I return to level ground the engine runs smoothly again. When this first began, the check engine light was not on, but came on later. Also, the engine will accelerate just fine in park or nuetral without a load.

I have been told this can be an ignition problem, but I wonder if it is a fuel pump problem. Any ideas?

 

I'm curious... your description of the problem isn't "missing " or "misfire " because thatwould certainly set a problem code. You should first off check to see what if any codes there are.

You could test your theory of thefuel pump only having a problem on an incline buy jacking up the front of the car and see if the problem shows up then.

I'm inclining to think the problem is lack of powerpossiblydue to a torque converter lock solenoid.

 

Well, my first problem is an inability to check the codes...without going to a dealership or something.

Harold started this thread and since it sounds like my problem, I joined in. To clarify, I interpretted "missing" as "misfire".

But the car is running and the check engine light is out, now. I've been following all the troubleshooting steps in my Haynes manual with each sensor step by step. I found no problems with the ignition system, too. I just came back from a short trip to a good test hill, and once I began climbing, it started to misfire. It was uneven. If I eased off the gas, it stopped.

The car is now sitting in the garage and the check engine light is off.

 

gmdinusa... I was replying in general to both your post and harold's since they have similar problems ( as you stated ) which I believe is likely not a " missing " or " misfire ".

You can go to autozone to have the codes read for free apparently. Just because the CEL is not lit doesn't mean there isn't a problem code. The computer stores these.

You should check to see what the problem code is ( if any ) to give an idea what the problem is.

 

I thought that Auto Zone only checked alternators and batteries. That's good info.

 

Hello,
Was justreading this to kill some time and realised that my car had a similar problem which is like loosing power under load and specially when it warms up a bit. The only thing that fixed this was the MAF sensor (Mass air flow sensor). As far as i remember, the quick test is to remove the connections on this sensor which is on the airfilter assembly and test drive the car. When doing this the idling will be bad and the car may stall in idling but should not give you that lack of power symptom.
Gud luck.

 

bank on it not being a fuel pump, thye dont usually gradually go they just quit and thats it....could be mass air flow sensor, if the car is not getting enough air and fuel it will misfire, could be bad plugs, that will cause a bad misfire under load as well, or clogged cat in the exhaust....all hte screwing around your gonna do just take it to a dealer and have it checked, might caost you a hundred bucks but at least you will know which part to change out instead of swapping parts like mad and guessing...

 

There is likely going to be a P0300 code for misfires.

 

Would a bas mass airflow sensor throw any error codes? I have an 05 Malibu that is having hesitation and lack of power issues, similar to what the original poster stated. I've been to the dealer twice and both times they say that there are no error codes being reported and that is drove "within normal" when they test drove it.