Unexplained RPM/power loss and dropping revs (posted video of problem)

[johnoski]

So, I just checked the A/T fluid based on a transmission post I read about not enough fluid. Apparently mine is over-filled. Not sure who filled it (I did not), but the fluid covers the entire portion of the dip stick before the twist (well past all the holes). This was check cold (not run for over 24 hours). Also the fluid was not a clear pink color. It was more a dark brownish pink. It appears it needs to be changed, but can it being over filled cause these symptoms? Anyone know?

[avguy]

... Apparently mine is over-filled. Not sure who filled it (I did not) ... Also the fluid was not a clear pink color. It was more a dark brownish pink. ...

Based on what you found, it seems there's a good possibility the tranny fluid has mixed with coolant. You could try calling your local Stealership, tell them you found coolant mixed in with the tranny fluid, and see what their reaction to that is. Based on a prior post from another member, I believe that Chevy is well aware of this fluid mixing problem in the 2009, and probably would like to keep it as quiet as possible. Perhaps they might be willing to repair or replace the tranny for zero or at least a reasonable price.
If they claim to be unaware of this problem, I would send the fluid to a lab for testing - I think Blackstone Labs does a basic test for $25, which includes checking for coolant. But do not change the fluid now, because you will then no longer have the evidence of this problem, should you decide to pursue it further with Mother Chevy.

[johnoski]

***NEW INFO*** (12/26/13)

This car is no longer under warranty. Draining the Tranny fluid, changing the filter, and cleaning out the pan, did not help the issue at all.

While I was with extended family over the past couple weeks, an uncle of mine suggested that it could be the fuel pump starting to go bad. He noted from his experience, that when they start to go bad, they will work fine at first, then after a few minutes they get hot and start acting up and can lose pressure. So I did a little testing of the fuel pump. Here is what I did:

1. Pulled up the back seat and removed the cover exposing the pump connections. I connected leads to the Positive and Negative wires (Brown and Black), and drove the car while monitoring the voltages present. When the car is driving normal or accelerating, the voltage is at a steady 13.78 +/- 0.02 volts. When I am braking or at a stop light, the voltage drops a bit to 13.62 +/- 0.02 volts. This seems normal to me since the higher voltage is when the pump is under stress, and the lower is when the pump is not. If I am not correct in this logic... please correct me When it did act up the voltage was all over the place. Sometimes it dropped between 13.5-10.5 volts, and sometimes it only dropped about 0.0 to 0.3 volts.

2. Second, I did a voltage drop test on both the positive and negative sides of the fuel pump power circuit. On the positive side the voltage was 12.59 volts with the engine off, and 0.46 with the engine on. This was obtained by connecting the positive lead of my multi-meter to the positive terminal on the battery, and the negative lead to an extension connected to the positive wire on the pump (brown wire). On the negative side the voltage was 0.00 with the car off, and 0.40 with the engine on. The negative was obtained by connecting the negative lead to the negative terminal on the battery, and the positive lead to an extension connected to the negative wire on the pump (black wire). Again, I think this is normal, but correct me if I am wrong.

I am beginning to believe this is a fuel pump problem. Since the pump is like $350-$400, I would like some other opinions before I pay for a new one.

Also, the CEL finally came on. I never thought I would be happy to say that. The plan is go an have those checked tomorrow at a local shop.

Thanks!

[petrified.rabbit]

I wouldn't go by voltage to determine a good pump, it will vary based on rpm in the aveo, just as the headlight dim and bright with rpm the signal power to the fuel pump will fluctuate. and based on your attempt to get the voltage as an issue, the fuel pump relay would crap out first.. most likely. I had to replace my fuel pump in my car, i think i had maybe 5000 miles at the time? it just quit all together.

you need to check the fuel pressure at the rail to determine if you have a power loss from the pump.

have you replaced the spark plugs yet? i skimmed back through the post and didnt see it. IF not that then you need to get rolling data of a scan tool to hone in on things like a dirty maf, or bad o2. (just not bad enough to cause a cel).

[johnoski]

I did put the spark plugs in that you and gothstone recommended. No luck with that.

[johnoski]

OK... Took it by the local garage to have the codes read. There were a lot of 02 Sensor Bank 1 codes. A single Map failure was found mixed in. I did not think to get the Pxxxx number until after I left. The tech cleared the failures and reset the CEL. Hopefully it will come back so I can get an actual code number. I just hate driving it. The car has gotten much worse over time.

It not loses the RPMs all the time. It is fine for the first 1-5 minutes, then it fails for the next 15-20, works again for about 5 then fails again for another 15-20. Thankfully, most of the times I need to drive it, it is only 15-20 minutes at a time.

[avguy]

With that type of code it does now seem like an engine-related issue and not the transmission. Depending on which code(s) are actually set, I'm wondering about the new cats that the dealer replaced (or at least said they did). Do you have the paperwork showing which cats they installed? I've read posts from others saying that an aftermarket cat didn't work properly, and eventually had to be replaced with the better one (i.e. more $$$). But perhaps it's just simply that one or both of the O2 sensors are bad.
It's unusual for a cat to go early like your's did, and whatever took them out might have done the same thing to those sensors. That would at least be a relatively inexpensive fix. Get all of the codes as quick as you can, or maybe just take a shot at replacing the O2 sensors, because you want to get that rough running fixed before it causes additional problems.

[johnoski]

I read that the CAT or O2 sensors wont cause issues like this. Was that inaccurate info? Also, I read that a way to check the MAP sensor is to start the car and remove the power cable from the sensor. If it acts the same, then the sensor is bad. Also, when the car is on, but not running, it should read about 4.5 to 5.0 volts. When idling, it should read about 0.5 to 1.5 volts, and when under stress (higher RPMs), the voltage should rise with the RPMs. Is any of this accurate?

[avguy]

Being primary contributors in the closed loop, I would think that bad O2 sensors and/or cat could be the cause what you're seeing. But it could of course be other things as well, which is why it's important to get the exact codes in the order they're read, to help diagnose the problem.

[Pooh Man]

the first O2 could cause crappy driving conditions. As learned by experience the O2 sensors should be pulled when welding the exhaust cus the excessive heat could kill the sensor.