Hi I'm the owner of a 2002 Pontiac Grand Am, 3.4 liter V6, with 240,000 miles on the odometer. Recently, the revs started to rise and fall when its idling out of gear, and it shifts extremely hard in reverse and drive. I had taken it to a mechanic in my area and he said he had fixed a couple of vacuum leaks on the car, and it seemed to run well afterwards. Not long after, however, it started up again, with the revs going so low that it would stall in idle, and when I would engage reverse. So far, I've replaced the camshaft sensor, knock sensor, and O2 sensor, but I haven't been able to trace out any vacuum leaks. It doesnt want to stall anymore, but it still rises and falls in the revs in idle, and still shifts hard. I also made a video on my phone of what it's actually doing, if that would help. I'm really stumped by this and I'd greatly appreciate any info that can point me in the right direction. Thanks so much!
Robert Chirino III
Dragoon, AZ
Well, the obvious questions are these:
When did you last check the transmission fluid level?
When did you last check the transmission fluid level quality?
When was the last time an ATF drain and fill was performed on this transmission?
That is where I would start.
To answer your questions Geriscan, I had actually checked and refilled the transmission fluid a month ago, and from what I could tell, the quality seemed to be good, with no severe discoloration or foreign material. I also rechecked it a week ago, and the level seems fine as well as the quality. I'm not completely sure how it would affect the idling issue, but I've been wrong before.
A few other things come to mind:
The Mass Air Flow sensor is dirty or malfunctioning;
The Throttle Body is dirty or malfunctioning;
The Idle Air Control Valve (which is usually attached to the Throttle Body) is dirty or malfunctioning;
The PCM is going bad.
Good Luck.
Quick recap on my Grand Am: I fixed(temporarily)the vacuum leak that was causing idling issues, so it doesn't have a rise and fall in revs. Unfortunately, the transmission still shifts hard while driving and putting it in reverse and drive as well. I've already checked the fluid level in the car again; no issue there. I had them run the scan again but the only code that came up was for the master flow sensor, and I've already ordered a new one. I thought about it possibly being the pressure solenoid on the transmission, but once again, not for sure.
Given the age of the vehicle and the number of miles, you might want a general inspection of it, in order to assess if you want to put more miles into it. At AgcoAuto.com, they discuss what kinds of things they look for in this general inspection: http://www.agcoauto.com/content/General_Inspection
So a quick update on the Grand Am. I had a mechanic shop run two diagnostics on the car, and they both brought up codes for the purge valve and the master air flow sensor. I replaced both sensors, and fixed a vacuum leak going from the air intake to the valve cover. The idle is steady and even now, but the engine check light is still on, and the transmission was still shifting hard. I also changed the trannie fluid and filter, but it still shifts hard when going into reverse or drive, and when driving. At this point, I haven't had a change to have it diagnosed again, but I've been told it could be the pressure control solenoid. When I changed the fluid out, I didnt see any metal shavings in the pan. Not sure what else to do at the moment.