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Discussion Starter · #1 ·
Okay so I have a 2011 Chevy Cruze ltz 1.4 98xxx miles recently the valve cover/pcv went bad causing misfire and idle surging. I repleaced it and the code p1101 came up so I replaced the mass air flow sensor and it didn't go away. After reading around on here I saw there was a problem with a check valve in the intake on these cars. Mine indeed was missing so I replaced the intake manifold 315 dollar part. Still the code came right back. Found out here is a second check valve on the pcv tube (Air charge bypass tube). Mine was missing cause I could blow both ways in the tube. So I bought a new one and it solved my CEL code but now the car idle jumps up in down from 600 to 800 every time the car is idling. Put the old one back on and the idle is fine at 800 with no jumping around but the check engine light comes back immediately. Anyone had this problem before? Any imput would be great. Thanks
 

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Tried yanking the battery cables to reset fuel trims/adaptives?

Mine ran a little strangely after having the intake manifold, valve cover, and that hose replaced. A day after yanking the cable, it was 100% back to itself.
 

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Discussion Starter · #4 ·
Well I left the battery unplugged for 12 hours. Took it for a 40 mile drive and the idle still fluctuates. Only does it when I'm stopped at a stop sign or in traffic or when it's in park. Idle just jumps up and down continuously from 600 to 800. If I give it a little gas and hold it at 900 it doesn't do it. Doesn't do it when the Cruze control is set either just at idle. To me it has to be that pcv tube. With the old one on the idle stays at 800 with no surging and drives fine but the code comes back. New one it drives fine no code but the idle thing just worrys me. Feels like it's going to stall but it doesn't. Just shakes when it hits 600. Any other ideas. There's no vacuum leaks either.
 

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A few thoughts: (guesses)

How is your A/C doing? The reason I ask is that I wonder if there's a "engine load" problem. If the computer thinks the A/C compressor is on and "learned" the idle for that, then when it turns it off it's going to expect to see the engine load drop and compensate for that. If the compressor is in fact dead, the engine won't respond the way the computer expects.

Another thought is that you might have a updated part without a matching "mate". With all the problems GM has has with the check valves, it wouldn't surprise me but what they did a change. For starters, I'd carefully compare the two pcv tubes to make sure the original was supposed to have a check valve.
 

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Discussion Starter · #6 ·
The a/c works fine. Turns on and off with no problems. Still idles the same with it on or off. I compared hoses, they are identical the only difference is that the old one you can blow either way in the tube and in the new one you can only blow toward the turbo and not toward the intake manifold. I started messing around with the car some more and I noticed it only idles like that in park and neutral. It only does it in drive or reverse if I have the break pedal pressed in. I guess the car automatically goes into neutral when you have the break pedal pressed down. That's the only time it does the idle fluctuating. When the car is first started it won't do it until it idles down from 1500 to 700-800 then it'll start fluctuating.
 

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Discussion Starter · #7 ·
The part # on my old one is 55568267 and the part # on the new one is 25193343. I guess they stopped making the old one cause when I searched it all the ones I see are discontinued from GM. Maybe this is my problem? But how could I get the old one if they don't make them anymore? Or does my car have to be tuned or reprogrammed for the new one?
 

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I'm not finding any details on either of those parts. I'm wondering if GM didn't redevelop the pipe to avoid having to pay for so many manifold replacements. But by using the new part, you've got two check valves. Not sure why it won't work with your old pipe - perhaps it's leaking?
 

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Discussion Starter · #9 ·
Yeah idk what's wrong. There is no leaks coming from the the pipe or where it connects to the turbo or the intake. It runs and drives normal until i stop or put it in park and it does that idle fluctuating. It's so frustrating. Just put 700 dollars worth of parts in it in the past two weeks and it's just one thing after another. I'm going to keep tinkering and doing research before I take it to the dealership. If I don't have anything figured out by next week it'll be going to a dealership.
 

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Discussion Starter · #10 ·
With the old pcv tube air can go both directions and the new tube air can only go towards the turbo. So my question did my old tube have a check valve like the new one and it just up and walk away or jam itself somewhere in that tube or never have one? When the engine is under vacuum it's sucking air through the old pcv tube witch is causing the Code P1101. Now with the new tube and the engine under vacuum it can't suck any air through the tube cause of the check valve in that tube. No code gets thrown with the new tube just fluctuating idle. So if my old tube had a check valve at one time why didn't the idle fluctuate with it? I'm guessing they changed something in that tube that's causing my problem. I don't know if the old tube had a check valve or what it had. Does anyone know anything about the first gen pcv tube (air charge bypass tube) in these cars. Anything would be appreciated I'm stumped.
 

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Discussion Starter · #12 ·
That was a good write up. I just wish I could figure my problem out. It has to be that tube. Everything points to the tube. But I have a new one so what else could it be. No vacuum leaks. New cam/valve cover, new intake manifold, new pcv tube and new MAF sensor. The check valve in the tube is in working order and the check valve in the intake is there and I assume in working or cause it's new. All parts have 65 miles on them. No engine lights so there must be no problem with anything. Except the idle but for some reason it's not enough to set off a code. You would think a code would be set off cause it hits 600 rpm and the motor vibrates bad then jumps up to 800 rpm and does this continuously until you start moving. I know this isn't normal. The thing that gets me is that with the old tube it idles just fine but p1101 comes on within 2 miles of driving because the check valve is not there allowing air to be flowed in from the vacuum from the engine. But if it's supposed to have the check valve there like the new one then why does it idle like that with the new tube? Makes no sense to me.
 

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Discussion Starter · #13 ·
So this is the end of the pcv tube. The part the clips on to your turbo housing. As you can see I cut it in half to see if it had a check valve and it did indeed. It had a hole on the rubber grommet/check valve which was allowing air to go back to the intake under vacuum. So in fact you shouldn't be able to to blow air toward you intake through this pcv hose.
 

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That is indeed very strange behavior. It's like what I might expect to see with a vacuum leak somewhere else, but your car is already showing it's pretty sensitive to unmetered air when the other hose is put on.

Do you have an OBD2 scanner where you can monitor airflow values and O2 sensor readings at idle?
 

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Discussion Starter · #16 ·
That's a perfect write up on the pcv system. I do have a cheap Walmart code reader but it doesn't monitor anything. The vlave cover is new and I assume in working order. No strange noises or anything. If it wasn't in good working order you'd think the disk in the cover would fail. The oil dipstick is seated good and there is no vacuum leak there, same as the oil fill hole on the valve cover. Cap is tight and no vacuum there or air escaping. I'm going to make a appointment at the dealership so they can hook it up to there 5000 dollar scan tool and hopefully come up with something. Thanks for the info guys I appreciate it.
 

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Discussion Starter · #17 ·
I did see somewhere in here you can do a ECM reset doing a sequence with the key. I'll try that but I thought unplugging the battery for awhile would do that. You guys know anything about that?
 

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After staring at the diagram, here's what I'm seeing. With the old tube in place, the PCV was actually pulling air from the air intake - not from the engine. With the new tube, it's having to pull some air though the engine. (And the PCV valve cover.) For some reason, that's not quite right.

There is something you might want to consider. It's a trick from the old ODBI days. With a fully warmed up engine, put the transmission into drive, set the hand brake and just let the car idle for 10 minutes or so. Force the computer to learn the engine without any interruption. With any luck, it will either learn how to idle properly, or it will set a code that points the way to the problem.
 
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Discussion Starter · #19 ·
Okay so I let it idle for 30 minutes. First I let it idle in drive for 10 minutes with E-brake on and the idle only fluctuated for like 30 seconds maybe and then it went to normal about 800 rpm for that 10 minutes. Next I let it idle for 10 minutes in park and it was intermittent. It would do it for 30 seconds then start idling fine for 30 seconds then it would do that back and fourth sometimes it was doing it for a minute switch back and fourth. Next I left it in park and just started trying things like turning the a/c on. It wouldn't do it with the ac on. It jumped up to 850-900 rpms and idled fine. Turn it off and idle fine for a minute and go back to fluctuating but not terribly bad. Like 750-800 back and forth. I then put it in drive with no brake on and it wouldn't do it. Touch the break pedal and it'll do it for a little bit then go back to normal. Put it back in park and it'll do it intermittent jumping up and down from 800 to 750 and some times 800-700 or 650 and then it'll stay normal at 800 for a little bit and go back to the fluctuating. Yeah my mind is blown. I don't know what the problem is.
 

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If you had a scan tool, it would be interesting to see what the various engine temperatures were being reported as.

My guess at this point is that you have a slight vacuum leak somewhere. Or perhaps the throttle body needs cleaning. Any additional load like putting it in gear/brake off or turning on the A/C seems to cover it. It's only when totally unloaded will it act up.
 
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