Weird issues with the GF's 04 6i

[StealthWyvern]

Warning long winded post ahead....

I've been trying to trouble shoot some weird issues with my girls 6i. First of all no CELs are on the car. The car is a 04 6i atx with that lame ass sport shift crap and has around 100k miles on it.

Here lately she has been telling me that her car acts up from time to time mainly while in the drive through at McDonalds. She says the car feels like its pulses and wants to move. So she has to press the brake harder to keep it still. Also she says she has has issues with the brakes before where she has to press the brakes harder to stop. Edit: She recently informed me that the Tach DOES go up by 300-500 rpms

The thing is I can't get the stupid car to act up when I drive it. We have taken her car everywhere for a week or so and it never acted up for me.

Also another weird thing the car does or well did was felt like you take your foot completely off the gas on the highway and just slows down.(I did not take my foot off the gas)That was the only thing that I was able to get the car to do but I since then taken it out and flogged it around and changed the plugs. That issue hasn't came back yet or at least she hasn't told me.

I have flushed her brakes out 3 times to get all the crap out of the system. The first fluid change on the brakes the fluid was pretty damn foul even with my bad allergies which is why I flushed it so many times.

Now I know this car is a fly by wire step so I do not know if the two issues are related or not with the pulsing. The issues only come up every now and then and you can't reproduce it on demand.


Anyone have any idea where I can look to see what the hell is going on?

Edit: I know it sounds like somethings on its way out but what I have no idea... brake booster, TPS, thorttlebody?

 

[SJP0tato]

Also another weird thing the car does or well did was felt like you take your foot completely off the gas on the highway and just slows down. That was the only thing that I was able to get the car to do but I since then taken it out and flogged it around and changed the plugs.

That's pretty normal, the engine should be compression braking if you're not on the gas pedal at all on the highway.

Maybe try cleaning the throttle body with some spray cleaner? Could be there's some carbon build-up where the throttle plate rests which sometimes makes the plate stick open intermittently, which would cause the engine to stay revved higher and cause the symptoms she describes.
It might also be worthwhile to clean the MAF sensor while you're in there as well (make sure to use MAF specific cleaner). At 100k miles chances are it has some carbon build-up on it as well.

 

[StealthWyvern]

That's pretty normal, the engine should be compression braking if you're not on the gas pedal at all on the highway.

Maybe try cleaning the throttle body with some spray cleaner? Could be there's some carbon build-up where the throttle plate rests which sometimes makes the plate stick open intermittently, which would cause the engine to stay revved higher and cause the symptoms she describes.
It might also be worthwhile to clean the MAF sensor while you're in there as well (make sure to use MAF specific cleaner). At 100k miles chances are it has some carbon build-up on it as well.

Yeah, but its not normal if it acts like you take your foot off the gas when you didn't... which is or well was the issue.

Also the MAF was replaced around 60k-ish. It couldn't hurt to clean it or the throttle body. However if it was either one of those two wouldn't it be more consistent then once in a blue moon?

 

[StealthWyvern]

Wel the issue is back... She did take time and notice that the rpms did in fact jump up by 3-500 when it was acting up! I have no idea what to look to on this now. She said it did this going down the road this time instead of in drive through were it normally happens.

 

[StealthWyvern]

Forgot to mention, I haven't gotten off my lazy ass and cleaned the thorttle body just yet. Beings that it a fly by wire setup is thier anything I need to do differently compared to a normal run of the mill throttle body when cleaning?

 

[StealthWyvern]

Well I cleaned the throttle body and it did make the car feel smoother to her! However it made the pulse-ing in the car movement softer. So I guess I need to hit it again with the carb cleaner another day.

It finally did it to her while I was in the car. It almost felt like someone very lightly tapping the gas but nor really enough to notice. Sort of like a extremely light lugging of a gear in a standard car but hers in a automatic.

 

[FORZDA 1]

Strangely enough, it sounds to me like the PCV valve needs replaced.... When it leaks, the engine will pick up rpms and surge.