Car: 99 Buick Regal Gs

engine 3800 S/C

Mileage: 115xxx

What I've replaced:
VSS
fuel filter
plugs/wires Ngk tr55s/duralast wire set
transmission fluid/ filter
transmission lines
the cracked vacuum lines
air filter
injectors cleaned
sea foamed


Symptoms(warning its going to be long and boring)
So what happens is the car would just before shifting into forth(40-45mph) start to surge for like 5-10 seconds then stop, ride smoothly, and shift into overdrive. It rarely does it also when shifting into 3rd at 30mph. The surge is only about 200-300 rpms. Its kinda hard to explain by here's a shot at it. Its like a miss fire but without the shudder and CEL/SES. The car is running fine in overdrive one minute, and then I give it a bit of gas to go up a hill and it does the surge, or if I am accelerating into forth the same thing. I give it a bit more gas and accelerate to 50mph and it stops. Sometimes It would do it at 55mph-65mph-70mph, but that is once in a blue moon. I notice it seems to be more frequent when it gets hot outside(like the recent heat wave we just had), or after a drive on the freeway, I have not thrown a single code nor do I have any codes pending. I know for a fact it isn't the torque converter because I can drive for a period of time without a problem then I randomly get the surge out of no where, it does it for a day or two, and then it doesn't happen again for a little while. After a week or two, and the process repeats itself. It was a lot worse before. It used to be a very common thing(everytime going to forth common), but after I did all those repairs/routine tune ups the surge is random. The car shifts very smoothly, quietly and quickly, nor does it slip. My gas mileage is normal 21ish/29ish and the car overall runs smoothly when it doesn't surge. At WOT its very quick and snappy. I have no shudders or surges. This seem to only happens under normal drive conditions.

Needless to say I'm Stumped I am going to try replacing all my vacuum lines tomorrow and see if that does me any good. Feel free to ask any questions to further clarify any symptoms, and any and all advise will be welcomed thank you!

 

Ever get the cat back pressure tested?

 

No I have not, how do you do this? Where?
All that I know is up with my cat is when the car is running and you tap it, the cat it rattles. So it is fair to say it is going bad. I haven't thrown a code yet though, and the cat doesn't glow red after driving for 10 miles.

 

Sometimes the cat being clogged can give symptoms of a transmission problem. Any exhaust shop should be able to test it for you.

 

It wasn't the cat nor the vacuum lines. While driving home, I got it to do it again. This time it would make a little chirping squeak/shriek noise, and would feel like it wanted to die out out upon lighter gas. It started getting fairly consistent, so I disconnected the MAF sensor, low and behold it stopped doing it. I drove it for about 10 miles in overdrive and shifting into 4th couldn't get it to happen again. Would that mean its fair to say its the MAF sensor going bad or overheating?

oh and still didnt throw any code -_-

 

The MAF could also just be dirty, you can try buying MAF cleaner spray and attempting to clean it before you spent the money on a new one.

Security T-20 Torx Bit to remove it.

 

ok ill give that a shot

 

It's usually recommended to clean the MAF every time you do an oil change, but I know that can be a little much for people.

 

Great Advise Mike!

You da man...

I too was going to suggest checkn the MAF...
But once again you beat me to it...LOL

 

so far it seems like its worked. Time will tell though thanks guy!

It was kinda funny though. I took it out looked at it was like, hmmm that doesn't look too dirty..... then i sprayed it. Then looked at it again I was like ooohhh.... that was filthy lol.