I have a 2002 Buick PA (not ultra) that is giving me fits. It sputters and hesitates during acceleration but only when going forward. I can back up as fast as I want and it never sputters or hesitates. The SES light is not on and there are no codes in the computer.
My mechanic noticed the car runs right when the MAF and AIT sensors are unplugged even though the SES light come on. So he changed those along with the TPS but no luck. Since the problem was still there he reinstalled my original parts, charged me nothing and suggested I take the car to the dealer.
The dealer charged me $1500 to change the MAF, TPS, IAT, AIT and MAP sensors but no difference in how it runs. I was surprised that they asked for $1500 without telling me the car wasn’t fixed. I took it back to the dealer and they now want to change the PCM but they won’t give a guarantee changing the computer will fix the car. I sense their plan is to change parts at my expense until the car works or I run out of money.
I bought a cable and some software thinking I could compare the readings from my 1999 Alero 3.5 with those of the Buick and perhaps get a clue to a sensor or something that isn’t functioning normally.
What I noticed is that my spark advance is all over the place during acceleration (see below). I then compared to the spark advance with the MAF and IAT sensors disconnected and believe my problem definitely has to do with the spark advance.
My questions to you fine people are what do you see in these graphs? What sensors effect or impact the spark advance?
This is the chart with the sensors connected IE.. car messing up.
Here is the chart with the sensors unplugged which means the SES light is on but the ICM is controlling the spark.