diego4

Hello all, I just upgraded my '09 Z06 to a new '13 ZR1 3 days ago. I have a question that I hope someone here will be able to help me with.

Yesterday I noticed for the first time the following: sometimes when I accelerate in gear (to, say, 3000 or 4000 RPM) and then go to neutral and let go of the gas, the engine RPM comes down to a really low RPM (sometimes as low as 300) and then bounces back up to 1700+ RPM (I've seen it go up to 2000 once), then it slowly goes back down to 600 and may go back up again to 900 and down again until it stabilizes at 600.

If I accelerate a little less, let's say to 2000 - 2500 RPM (once again in gear), the variation of RPM is less pronounced but it's still there: it may go down to 600 and then up to 900 and then back down to 600 and stabilize.

All of this bouncing up and down of the tachometer is happening while the car is in neutral (but still moving). All the times I noticed this, the A/C was on - I meant to try it with the A/C off but haven't gotten around to it yet.

Here's the thing: my Z06 never did that. I drove it the same way as I drive the ZR1, frequently going to neutral when there's traffic ahead or I know I'm gonna stop at the light ahead. There was never this bouncing up and down of the tachometer while in neutral.

This behavior only seems to happen if I accelerate while in gear. If the car is already in neutral and I give it some gas and let go, the engine RPM goes steadily back to 600 and stays there.

Does anybody else notice this in your ZR1?

I'm wondering if this could be due to bad gasoline, since the car was sitting at the dealer for months before I bought it. I know they filled the tank for me on the day I bought it, but I didn't check to see how much "old" gas was in the tank before they filled it. However somehow I have a feeling that this strange behavior is not going to go away that easy...

kozmic

I haven't noticed this behavior, but I also have not specifically looked for it.

When you say, 'going to neutral', do you mean simply taking the car out of whatever gear you were in, keeping the clutch pedal depressed as you decelerate, or do you mean taking out of gear and with the clutch pedal released/not depressed? I do the former (out of gear with clutch depressed) all the time, but again have not noticed the behavior you describe. [and I always have the a/c running in Houston...lol].

diego4

I depress the clutch and immediately disengage the gear I'm in (moving the shifter to the neutral position) and release the clutch.

If you have a chance to test it, I'd appreciate it. I'm likely to take my ZR1 back to the dealer to have it looked at this weekend. It would be useful if I had some feedback from other ZR1 owners to confirm they don't have this issue.

Steps to reproduce:

1. turn on A/C (simply push the AUTO button for climate control)
2. accelerate to ~4000 RPM in gear; you don't have to burn rubber, but it should be a somewhat quick acceleration
3. disengage the gear and go to neutral and let go of the gas
4. watch the tachometer to see if it will just go to 600 and stay there, or bounce around.

Sometimes the behavior happens to me and sometimes not. But if I try 4 or 5 times it will usually happen at least once.

Thank you,

--Diego.

C5kid

Sounds like it just needs an idle relearn. That swing in the rpm is the computer over compensating the air needs and then under compensating, then finally catching itself.

I would drive it some more before taking it to the dealer, generally after a good long ride of varying RPM's the PCM can relearn the target idle air.

orange crush zr1

Diego, my 2011 ZR1 does the same thing yours does sometimes. I don't think much of it. If I had to guess why it does it I would say its the blower causing it....but I'm no expert..

Rob

911/Q45

I'm curious why you drive like that? If you leave it in gear as you slow you need the brakes less due to compression braking.

diego4

I think everybody shifts to neutral at some point, but most people do it after revving down, not after revving up as I usually do. I was surprised with this behavior because I never saw my Z06 do the same. The Z06's engine RPM stabilized and idled very nicely on its own - even if it was coming down from a hard acceleration.

The thing is, replacing the brakes is cheaper/simpler than overhauling the engine. Sure, the carbon-ceramic brakes are expensive, but then again, so is the LS9.

kozmic

I tend to agree with C5kid, but I will also try what you're doing, either tonight or tomorrow, to see what happens.

diego4 - You're not running an oil-coated air filter (ala K&N or the like), are you? I only ask, because in my previous life as a mustang guy, the MAF sensors would sometimes get coated with oil from these types of air filters (that had too much oil on them) and would cause a very similar down rev and/or idle behavior as air sucked into the MAF would seemingly move the oils around that had coated the MAF sensor and cause oddness.

Joe C5

Mine does the same thing. Completely stock. In fact, I can stall it by driving it briskly just after it warms up and pushing in the clutch and doing a max G stop. Does not happen often, but in the year I have had the car it's done it twice. I have also seen it sit at 2000 RPM for 5 or 10 seconds if a turn is involved (push in clutch, slow quickly, turn). My 2 C5's and Z06 never did this. Love the car though.

diego4

Thanks for everyone's feedback so far!

kozmic - the car is completely stock.

I'm taking my ZR1 to the dealer tomorrow to be looked at. I used up all the first tank of gas and filled up (with 93 octane) and this weird behavior continues, so it's not due to old gas. It really feels wrong to see the engine come so close to stalling (˜300 RPM, maybe 250), specially considering that it always happens when I'm planning to slow down or stop ahead. As Joe C5 put it, in the event that you need to brake hard when the engine is at 300 RPM, it could stall - and you don't wanna stall in the middle of a panic stop. Now we're talking about a safety issue.

With this behavior, I'd rather have my Z06 back. The engine idle worked flawlessly.

Chevy Cust Svc

Hey diego,

Keep me posted on the dealer visit. If there is anything I can do please let me know. I am also curious on the diagnosis,

Kelly J.
Chevrolet Customer Care

mrhead

I have this issue on mine also. Granted, I only 2k miles on it, but it should not act this way. Mine is also sluggish reacting off idle when releasing the clutch pedal. I'm wondering if GM has an updated calibration to address this. Should be a simple fix as my 08 is steady as a rock @ idle & I drive it the same way.

OnPoint

Mine has never done anything like that.

diego4

I took the car to the dealer this morning and left it there. They just called me back. Since I'm keeping a full diary of this issue from day 1, I'm going to just copy/paste the entries from today below. By the way, it's great to see a response from Chevy Cust Svc above in this thread. Right now I'm not satisfied with my new hundred-thousand-dollar car and I'm feeling that I took my Z06 for granted, since the Z06's engine was much more stable.

2013-08-13 (Tuesday) 8:18am (mileage = 254) I arrived at Carl Black (the Chevy dealer) with the car for them to look at it. I was greeted by Tim Brown at the Service department. I showed him one of the iPhone videos I made of the tachometer of my car during previous occurrences of the issue. He asked me to take the technician (Tom) for a drive and show him the issue. Tom said he checked for possible software updates for the car and there were none. He also said he tried to pull any codes from the engine and there were none. I drove the car with Tom in the passenger seat and attempted a few times to accelerate and shift to neutral. Each time, there was a minor surge in RPM of +200 to +300 RPM. When we were about to pull into the Carl Black dealership again, the car had a bigger surge, going down to 400 RPM and up to 1400 RPM, and I instantly pointed it out to Tom while it was happening. Tom said he was going to open a case with General Motors about this issue. I told Tom that I was going to e-mail him one of my iPhone videos with a previous occurrence of the issue, which I did as soon as I got home. Tim Brown gave me a loaner car which I drove back home.

2013-08-13 (Tuesday) 4:03pm I received a call from Tim Brown at Carl Black. He told me that they have contacted GM tech support and GM tech support said that they've seen this issue with 2012 models but not 2013. GM tech support provided them with a software update and they applied it but didn't notice any difference. They're going to keep the car overnight and test it again in the morning with the engine cold. He said I should expect a call mid-morning tomorrow (8/14). I asked to be transferred to Chris Gosselin (the salesperson who sold me the ZR1) and they said he is busy with a customer and will call me back. I left my name and number.

diego4

My ZR1 is also "sluggish reacting off idle when releasing the clutch pedal", exactly as you described yours. I know that with a turbo- or super-charged vehicle the torque can be low when starting to roll, but I have had 2 other turbo-charged cars (both completely stock, and one which I still own) and neither had this sluggishness. It kinda feels like the engine is knocking, really, unless I give it a lot of throttle like I'm going to launch the car every time. I can see how the two things (sluggishness and near-stalling) could be related.

Chevy Cust Svc

Hey Diego,

Thank you so much for the update! I will document this and hopefully this afternoon you will have some good news. It sounds like your dealership is on top of this. Please again let me know what the word is when you hear from them. Thanks,

Kelly J.
Chevrolet Customer Care

diego4

Here is my latest update. From a "business" perspective, I have told the salesperson (Chris Gosselin) at the dealer (Carl Black of Orlando) that I'd like to undo the deal if possible and get my Z06 back, since it has a stable engine that always inspired confidence. He said he's not in a position to make that call and that he would put me in contact with the right person, but that was yesterday 5:45pm and I haven't heard from them yet.

Meanwhile, from a technical perspective, the update is as follows.

2013-08-14 (Wednesday) 3:02pm Tim Brown called me back and told me that they've been back and forth with GM Tech Assistance (not tech support as I wrote earlier). Tech Assistance advised them to replace 2 parts: the master flow sensor and the throttle position sensor. After replacing each part, the issue persisted. They are continuing to work with GM Tech Assistance. It sounds like the car is going to stay overnight again. Tim said he will call me with any updates.

kozmic

Apologies deigo, I haven't yet had a chance to test this on mine yet.

If it is not one of MAF, IAT, or TPS sensors, then I would suspect a slight intake leak somewhere after the MAF that is causing a slight lean condition (too much air of the amount of fuel being delivered) causing the idle rpms to dip.

Just another thought I had... but again, based more on my experience with my previous cars rather than this one.

Hope they get is fixed for you...

diego4

Thanks, I passed it along to Tom, the technician who is working on my ZR1. (I previously got his e-mail address in order to send him the iPhone video I made of the issue.)

diego4

Here's an update. The issue persists and my experience with this Chevy dealer is turning sour. They told me that a field engineer from GM was going to come this week on Monday or Tuesday. I asked to meet the engineer and they told me they were going to advise me when he would be here so that I could come and meet him.

Well, yesterday (Monday) I spoke to the service advisor and they told me there was no sign of the GM field engineer. Today I tried reaching the service advisor and left multiple messages and never heard from him. Then a lady called me back to relay the message that there was still no sign of the field engineer today. Then around 8pm I got an e-mail from the technician that works there and he told me that the field engineer was there on Monday, and that he said this issue is considered "normal" for the ZR1.

So we have two problems here. The first one is a Chevy service dealer that passed misinformation to me about a GM field engineer who may or may not have been really onsite to see the car. The second problem is a mechanical issue that won't go away and causes the car to near-stall several times a day. I'm being asked to take the car as it is, in spite of the fact that it's a brand new, very expensive car with a bumper-to-bumper warranty. I'm not a happy customer now. The car has been at the dealer for more than a week now, and the issue has not been fixed. Chevy Cust Svc - I would really like to have a talk, please. How can I reach you?