2006 Chevy malibu Symptoms and codes

malibu
chevrolet

#1

Hello, My name is Jason. I have a 2006 chevy malibu 2.2 ecotec 4 cyl with ~130,000 miles and i am experiencing the following symptoms:

Car will not rev past 4000 RPMs or go over 70mph. I do have a check engine light with the following two codes: P0068(throttle position) and P0420(cat efficiency)

My question is instead of just replacing the cat where can i take my car (i live in tulsa, ok) to have the cat and the sensors checked before they are written off as bad? Any suggestions are welcome because i know NADA about cars :frowning: thanks!


#2

Oh, If I try to push it past 4000 RPMs i get a, “engine power reduced” message and it feels like my car goes into neutral.


#3

It sounds like the cat is at least partially plugged

That said, cats don’t get plugged for no reasons

Here’s a few things that damage a cat

Engine overheated
excessive oil consumption
ignition misfires
leaking injectors

Are your plugs overdue?

Bottom line . . . the plugged cat is most likely a symptom

diagnose and fix the root cause before installing another cat

And get that tps diagnosed and repaired . . . you might wind up needing a throttle body


#4

Actually, i got a “tune-up” last summer where supposedly they replaced the spark plugs and did some other stuff. Is it possible to root cause the cat problem myself? I dont think my engine has ever overheated, excessive oil consumption i dont know about, i use Mobil one and change my oil about every 3-4000 miles, leaking injectors? Anyway thank you for your comment! In case anyone else has similar issues i’ll post my progress.


#5

The P0068 doesn’t mean that there is a problem with the throttle position sensor (TPS). It means that what the computer sees for throttle position is out of whack with what it is getting from the mass airflow sensor (MAF) and/or manifold absolute pressure sensor (MAP). (I think you might have both MAF and MAP - some GMs do. A lot of cars have only one or the other).

The throttle / gas pedal is really an air pedal. The more you push your foot down the more air comes flowing into the engine. The computer “sees” that air partly via the MAF and/or MAP. All of that along with throttle position (and other stuff) is crucial to how it delivers fuel.

The P0420 actually just means that the readings from your oxygen sensor behind the cat. converter are too much like the readings from the one before the converter. That’s all it means. That WILL happen if the converter is not doing its job, but it can happen for other reasons - like problems, for instance, with fuel metering (!)

For near future reference - drive the car as little as possible until it is sorted out. Your converter might be just fine - FOR NOW. But driving this way might be what kills it. (It’s still possible that it’s already dead). What I would sort out first is the P0068 - because the P0420 may be derivative.

You say you know NADA about cars. If you mostly want to keep it that way start asking anyone you know about who they use for car work. You want to find a locally owned, independent shop that people speak highly of. Name-brand “auto care” chains and many dealer shops will take you for a fun ride when you just want a smart mechanic to figure out your issue.

If you think you’re capable of doing some simple stuff, let me just ask you this - do you know where your air filter is, and would you know how to remove it? If so, I could tell you the first things I would do.


#6

I do know where the air filter is! AND I’ve actually removed it once! Please tell me more lol


#7

Ok. You’ll just need some basic tools (probably a screwdriver, though a small socket set would come in handy), a can of electronics cleaner, and probably some safety glasses.

Attached to the air filter box is that large black accordion-looking ridged tube. It heads to the engine and where it attaches on the engine is the throttle body. That intake tube is probably held on at either end by a big silver hose clamp. Those are probably designed to be loosened by a large flathead screwdriver or small socket (8mm is pretty common).

I keep saying “probably” because I’ve never specifically been under the hood of an '06 Malibu, but the general stuff is pretty generic. It’s possible that the engine side is held on otherwise.

First just look up and down the whole thing carefully and inspect both ends of that tube. Look for anything wrong with it. Any splits or tears or holes? Then check each end for attachment. Is it all tight and held in place well?

If you don’t see anything obvious, just look carefully at either end to see how to loosen it all up and remove it. (It normally is just loosening both hose clamps - no need to remove the clamps). With the hose off, now inspect it even more carefully for anything wrong. Bend those accordion ridges back and forth and look for splits or other damage. These can be razor thin and you should not be able to damage it just by bending and around and stuff so have at it. You can be tough on it.

If you don’t find anything there, go over to the air filter box. I THINK that mounted right there at the corner of the box where the intake hose attaches you should see a little black box mounted on top by a couple of screws with an electrical plug and a bunch of wires going into it. That is your MAF sensor. Inspect. Is it tight? How does the electrical plug look? The wires?

If it all looks good, unplug it and inspect there - at the pins inside the MAF and the wires in the plug. Put on the safety glasses. Wrap a rag around the plug so the you’re looking at the end of it and spray it down with electronics cleaner. Now remove the MAF. Be careful with it - somewhere inside of it are two tiny little wires and you don’t want to damage those. What you want to do is spray it down liberally with electronics cleaner - the target is those two little wires inside. Afterwards shake it out and leave it sit for a few minutes to thoroughly dry. (Electronics cleaner - you’ll see evaporates very quickly).

Now go to the engine side of where the tube attaches - over at the throttle body. I THINK that right behind there you’ll see you MAP sensor. For the MAP sensor, I would just look to see if it’s loose, inspect the plug and wiring, and probably pull its plug and clean things up with the electronics cleaner as you did with the MAF. Let that all dry, put it all back together - then stop and double check that everything is all back together. Note that it all needs to be where the whole thing from the air box on forward is sealed - if air leaks anywhere it causes problems. Go for a drive.

Don’t get your hopes up. You might have just done all of that for nothing. But sometimes its just the simplest stuff. I’m still haunted by a time when I was young and dumb and had my car towed to a shop because my lug nuts were loose. Duh…weird noise from the wheels - maybe I should check the lug nuts before assuming something really complicated and dumping a ton of money on a two truck and service charge at the shop.


#8

Good comments above. The TPS tells the computer (or at least is supposed to) the amount the gas pedal is pressed down. The problem could be the sensor itself isn’t reporting that accurately, or that it is actually pressed down the amount sensed, but something else being measured is not consistent with it being pressed that much; e.g. not enough air flow. (Which could in fact be the case if the cat were severely clogged.) If you can find a factory service manual it will give you instructions what to do with that code. A chiltons, Haynes manual might have this info also. AllData computer database probably has it too. Many manufacturers give you access to the vehicles factory service manual via the internet for a small fee, likewise with AllData.

There’s a fairly simple test for a clogged cat called a backpressure test. Probably worth it to have that done by your shop.


#9

In addition to all the above, I think in your car, the TPS is attached to the gas pedal and not the throttle body. The throttle body is opened by a little motor.

But your problem could be as simple as a vacuum leak. There are a couple of vacuum lines at the top of the throttle body, or very near it, possibly one has become disconnected or the block they go to had come loose. Any air that gets into the manifold that doesn’t go by the MAF will cause a fuel metering problem and will cause the problems you see.

If you don’t have a MAF, just a MAP, then the extra air confuses the computer because the manifold vacuum will be lower than it should be based on RPM and throttle position, again throwing off the fuel metering.

A loose air duct from the air filter to the throttle body can also cause issues, the clamps need to be snug.


#10

Holy smoke, thats alot of good information. This weekend i’ll follow those steps lined out by cigroller, and keith (checking for a disconnected/damaged vacuum line) and if that doesnt help, i’ll find a shop that will do a backpressure test. I’ll report back with any findings, thanks alot!


#11

Well, after you do all of that, if it makes no difference, then you’re not looking for a back pressure test.

What you need next is the good locally owned shop with a good diagnostician to put it on a scantool. With that they will be able to get real time data on what the various sensors are up to, including the O2 sensors. At some point in the middle of it they may decide that a backpressure test is warranted.


#12

Ok, I’ll start looking for one now just in case. Thanks again!


#13

Well, if u go to shop and tell tech your car runs bad, has code for tps and cat, he might get a little huffy. Some techs hate customers trying to tell them how to fix car. Usually ends up in a you/me fight. I am curious to see what route the tech will take with you.


#14

So…crazy thing happened! It snowed this weekend! So, i didnt do anything LOL…next weekend


#15

So, i’ve cleaned the MAF sensor, and…it got WAY worse! Now it will barely go 40mph :frowning: and occasionally completely stops accelerating. Although the engine will still be running…


#16

Checking for a throttle position sensor on the fritz is usually a pretty easy thing for a good inde shop with experience in your make/model to do. I’ve done it myself on my Corolla, took about 1/2 hour. I expect for a Malibu it shouldn’t be that expensive.


#17

@Jasonthedudley, you may want to provide some more details on everything that you did, including double-checking and verifying that everything got buttoned up properly after the MAF cleanings and other inspections. (Tight hose clamps, electrical plugs, mounting screws/bolts etc) @George is right that you do need to check the TPS. That’s actually not too difficult if you have and know how to use a voltmeter. And even easier for a shop with even a basic scantool.


#18

Sure, i took the MAF sensor out. Sprayed it down with MAF sensor cleaner from Oreillys. Waited about 15 minutes and put it back in. Drove around from about 10-15 minutes and it was good until i hit about 40-50 mph and i got the same reduction in power, it actually reduced to basically 700 rpms and i had to drive about 10 mph all the way home…so now i am only getting the P0102 code. I also bought a new MAF sensor and installed it but there was no change. Still got the same symptoms and code.


#19

A friend had a torque converter replaced, after cat and o2 were replaced with no effect.


#20

You never mentioned a P0102 before. Was that there all along? Is it now the only code? That code isn’t for the MAF sensor , it is for the MAF sensor circuit. The sensor itself is only part of the circuit. So you need to inspect the wiring for damage, and make sure that the plug was clean and plugged in correctly.