Before I replace the pump....

[daves87rs]

Got some parts for the Cobalt to get it ready for pothole season, and have all my fluids checked and ready to change. Car is doing quite well-but it still has the one issue that refuses to go away...though it happens off and on...

Balt can sometimes have horrible pickup (like it doesn't want to go) but once it gets up to speed-fine. It also can run rough, but again-does it once in a while. One thing I have noticed though-the less gas in the tank-the more likely it will have these issues. Most of the time though-it runs and drives fine...and pickup is good for this four banger. Gas mileage has not changed-still gets good MPGs. Throws no CELS. Tested the Fuel pump a while back- came back okay....

Trying to nail this down....still thinking the fuel pump could be dying a very slow death, or something else. Was trying to run through my mind that could cause this, like a bad cat or s sensor issue. Have been considering buying a new pump-but before I replace it-I want to do what I can if there are some things I can do first...though I hate replacing things before the go....but I also don't want the car dying on the way to the new job either....

PS (Yes, I have posted this before-but then I thought it fixed itself-so I didn't want folks to yell at me for that)

Thoughts on parts : Very strong fuel cleaning, o2 sensor, bad cat-just some random thoughts here....

 

[chemman]

I would first check your fuel pressure regulator and then the ground lead to your fuel pump (it might be loose/dirty/corroded where it connects to the frame).

Good luck!

 

[GMBoy]

Colbalts have the fuel filter external and easy to change. Try that.

 

[daves87rs]

Originally Posted By: GMBoy
Colbalts have the fuel filter external and easy to change. Try that.


Been thinking about that too. Made the mistake of letting a shop do that last time (maybe 5-6 years ago), and they didn't connect it right, so it ran out of gas....

) Another guy came out and reconnected it back on.

Been wondering since it is external, whether it might be rusting or not...

 

[Lubener]

Do some testing before throwing parts at it. Fuel pumps usually do not act that way. Check fuel pressure, engine codes, ignition system. . Fuel filter is cheap maintenance and that's what I would replace before digging into it. Vacuum checks can pinpoint a clogged cat. Don't just start going into this guessing.

 

[PolarisX]

Didn't some of those 2.2s also have secondary air injection that can go crazy too?

 

[bluestream]

Hard to believe any reputable shop would change a fuel filter and not check it for leaks .... that could be a huge fire hazard

 

[The_Eric]

You could find a shop with a lab scope and they could take a current draw reading. The waveform will tell you RPM, current draw and if there are bad spots on the commutator. To save money, you could make all the preparations so all he has to do is hook up the probe and look at the waveform. Search the web for good fuel pump waveforms so you know what you're looking at beforehand.

If you have a way of reading OBD II info, look at fuel trims and O2 readings.

 

[daves87rs]

Originally Posted By: Lubener
Do some testing before throwing parts at it. Fuel pumps usually do not act that way. Check fuel pressure, engine codes, ignition system. . Fuel filter is cheap maintenance and that's what I would replace before digging into it. Vacuum checks can pinpoint a clogged cat. Don't just start going into this guessing.


Some testing has happened:

-short time back-fuel pressure tested good
-no engine codes at all
-Starter and battery are good

Agree with the filter change-was thinking about doing that anyways since it's been about 3 years and about 30k...

I have done some looking....but this has stumped me good....

 

[daves87rs]

Originally Posted By: Bluestream
Hard to believe any reputable shop would change a fuel filter and not check it for leaks .... that could be a huge fire hazard



Or make sure it was on....was a brand new guy- he got in quite a bit of trouble too...

 

[daves87rs]

Originally Posted By: The_Eric
You could find a shop with a lab scope and they could take a current draw reading. The waveform will tell you RPM, current draw and if there are bad spots on the commutator. To save money, you could make all the preparations so all he has to do is hook up the probe and look at the waveform. Search the web for good fuel pump waveforms so you know what you're looking at beforehand.

If you have a way of reading OBD II info, look at fuel trims and O2 readings.



Might give that s shot! Thanks!


It was also suggested to me to take a good look at the throttle body too, since it seems to get clogged up on these cars...something else for me to look at as well.....

 

[deanm11]

You can check 'static' sensor data but if it were me, I would data-log using an OBD2 scanner. I don't have a specific recommendation but there are ones available that can datalog for around $30. You would connect it to a laptop to record while driving. Some of them will put markers in the log file when you do something like hit the space bar (eg so you've notated when the car is acting up)

 

[daves87rs]

Originally Posted By: deanm11
You can check 'static' sensor data but if it were me, I would data-log using an OBD2 scanner. I don't have a specific recommendation but there are ones available that can datalog for around $30. You would connect it to a laptop to record while driving. Some of them will put markers in the log file when you do something like hit the space bar (eg so you've notated when the car is acting up)


Like this idea too..never would think that it would work for a regular car like mine, might be able to find out some really cool stuff...

 

[Josh88]

These cars have problems with the throttle body, seen several come through the shop

 

[daves87rs]

Originally Posted By: Josh88
These cars have problems with the throttle body, seen several come through the shop


Also what I am starting to notice on Youtube as well. What had me fooled as something fuel related might simply be a really good cleaning (and soaking) of the throttle body. A couple places that I have checked-stuff that is happening (lagging exceleration,rough idle) seem to be quite common with this issue. So, it looks like another route to explore.

How common is this with the 05-09 models is this that you see?