98 Lesabre - Stumbles accelerating from turn, or going straight

[schmcole]

Hello, and thank you for reading this.

I bought my Grandma's Old Buick almost 2 years ago. Pretty happy with it; but it has had 2 nagging problems since I bought it. Also, I have the full service history, and this vehicle was well maintained. I got it in 2010 with 66K on the Od.!!! Right now it's at 97K - oil changes every 3000+/- 30 to 100 mi -

1. Weird problem - started shortly after I bought it. It hesitates, or stumbles accelerating from dead stop, usually in a left turn, and usually when it has just started for the day. Lately it has gotten worse and does it going in a straight line, and now it happens about every other time I go to accelerate from a dead stop.

The crazy thing is, I noticed that lately it seems to get better after an oil change. I dont know if it always reacted that way or not... It still happens, but not nearly as much. - I do check my oil, every now and then I have to add a quart after about 1 month of driving (If I have been driving it hard) When I say hard, I mean like taking 1st up to 4K RPM

I have read that there was a PCM Flash; the symptoms relating to this fix are identical to my symptoms - I looked at the PCM and it has "Flash 2006" written on the outside - to my huge disappointment. I have checked a lot of the obvious things - air filter, vacuum leaks, fuel pressure reg, fuel filter... This brings me to my next complaint - the check engine light....

2. Nagging P0446 code - took it to mechanic to fix, first time he said it just needed a tune-up - light was off when I got it back and it came back on after about 2 weeks. I could not bring it right back, because I could not be without my car. Then, it came time to pass emissions...Mechanic replaced fuel tank pressure sensor, and some other BS part. It passed emissions, but the light came back on after 2 weeks of driving. I know what the P0446 code means, but I think it is a false positive or something.

Now, that was the history over the past 2 years. Now lately, I have been getting very fed up with the hesitation - plus I needed to address a few other issues... Just this past weekend, I took the beast in for an oil change, check engine light and all - after oil change, no hesitation. However, I didn't drive it for very long - got home with it, and fixed the horn switch in steering wheel (spring contact retaining thingy broke) I disconnected the battery, it was unplugged for over an hour.

I noticed when I put it back together the check engine light was off (stored codes cleared?) However, it is running better than ever after the full reset. I guess I have narrowed it down a little bit. After spending a lot of time reading this weekend, I checked over those simple things I mentioned in earlier, plus I cleaned the MAF. ( after I fixed the horn)

So, the light is off, car is running great - hasn't hesitated on me yet since the battery was disconnected, and computer reset.

I am 45 mi. into a fresh oil change - I will pay closer attention to when the performance starts to suck...before or after the light comes on (Cause I know it will eventually)

Sorry for the rambling - I don't expect anyone to offer up the exact solution, more like sharing my pain - and hoping someone has an Idea - because all the obvious causes of this behavior have been checked...

lastly, and maybe I should have started my post off with this one...

1. can a P0446 cause the kind of stumbling described above and in the post linked below?

http://buickforums.com/forums/showthread.php?t=25719

 

[dcraig1000]

As far as the 0446 code its probably a clogged vent valve
1) find the location of the vent valve; , locate the charcoal canister and trace the vent line to the vent valve.
2) Take the bracket loose with a 5/8 wrench.
3) Spin the valve around so the side with the hole is facing you.
4) Take an air compressor and blow the vent valve out.
5) reinstall and clear the code and it's fixed.