# Rough start/stumble on startup



## EcoBlue (Nov 23, 2012)

I just picked up my new 2012 Cruze Eco 6MT a week ago. I'm experiencing a stumble when I initially start the car. It doesn't happen every time but usually once every 2-3 times I start the car. It sounds like the car is misfiring when I crank it over, but always fires and idles normally. Temperature doesn't seem to matter; it happens when the motor is warm or cold. Initially I thought the dealer may have had bad gas, but I filled up with 88 octane a couple days ago (I'm in Colorado, so 85 is regular and 88 is midgrade) and I'm still having the same problem.

The dealer has been unable to duplicate the problem. They said there are no codes, but the second time I had it back there they reflashed the computer thinking it might help. The reflash has not helped and I'm still having the same problem. Anybody had this issue with the 1.4t motor? I read a couple posts describing rough starts with an aftermarket flash, but my car is all stock. Any help would be much appreciated!


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## unitednations161 (Mar 13, 2011)

This is completely normal due to emissions retarding the timing on some startups. All our new cars do it. The cruze and the the toyotas!


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## sciphi (Aug 26, 2011)

Can't say I've noticed this. I do get a bad stumble when letting out the clutch right when the idle RPM's drop from 1500 to 1000 after a cold start. That's more me than the car, though.


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## tecollins1 (Nov 6, 2011)

Myself and one other budget tune "BETA" tester noticed this while we were doing the testing. 

It happened every time the engine was started cold.

We both notified them of the issue and it was solved when the final tune came out. This has NOT happened a single time since the update came out.

Not sure how your having issues on a stock "no tune".


Sent from my iPhone using AutoGuide.com App


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## obermd (Mar 3, 2012)

Welcome to Cruzetalk. I haven't noticed this with my Cruze but I did notice it with my Pontiacs on occasion, especially when it was really cold outside. The easiest way to avoid this is turn the key to run and wait for a few seconds. Then start the car. What's happening is the fuel pump isn't starting as quickly as the starter motor can turn the engine over, so you're not getting fuel to all the cylinders. By waiting for a few seconds you'll get fuel to all the cylinders and the problem should go away.


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## The_Madcat (Oct 6, 2012)

Does the fuel system release pressure when the engine is shut off? I haven't seen that behavior before. Every other car I have had FI on, the pressure in the line remains. I could go up to my car hours after it was off and hit the fuel pres release valve and it would have pressure still. If it does not release it, the engine should still have plenty of fuel when it is cranked.


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## obermd (Mar 3, 2012)

The_Madcat said:


> Does the fuel system release pressure when the engine is shut off? I haven't seen that behavior before. Every other car I have had FI on, the pressure in the line remains. I could go up to my car hours after it was off and hit the fuel pres release valve and it would have pressure still. If it does not release it, the engine should still have plenty of fuel when it is cranked.


It's not supposed to. When starting a car, you need a surge of fuel to get going and if the main fuel pump doesn't start quite as fast as the injectors you can get a momentary lack of fuel into the cylinders. The Cruze starts very quickly so I wouldn't be surprised to find a small number of them with fuel pumps that are just a hair slower than the starter motor.


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## EcoBlue (Nov 23, 2012)

Thanks for the input everyone. Interestingly my car seems to do the start stumble mostly when the motor is already warm. It was ~20 degrees this morning and the car started up smoothly, but later when I parked and ran into the store for 15 minutes, I came back and started the car and it stumbled. It does it when cold once in a while but it seems to be less frequent. I'll try turning the key on for a couple seconds to see if that makes a difference (not that you should have to do that on a brand new vehicle).


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## obermd (Mar 3, 2012)

EcoBlue said:


> Thanks for the input everyone. Interestingly my car seems to do the start stumble mostly when the motor is already warm. It was ~20 degrees this morning and the car started up smoothly, but later when I parked and ran into the store for 15 minutes, I came back and started the car and it stumbled. It does it when cold once in a while but it seems to be less frequent. I'll try turning the key on for a couple seconds to see if that makes a difference (not that you should have to do that on a brand new vehicle).


I think this pretty much rules out the fuel pump start-up. In this case I'd go with unitednations161's thought of emissions. The exhaust system is also under pressure while operating, but it's supposed to depressurize when you turn off the car. I don't know how long this depressurization takes, but I would expect it to be pretty quick. 

I was working with a cold start assumption of a cold start. By the way, when it's really cold outside I always give the main fuel pump about 5 seconds to get going before starting the car. Long, old habit.


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## Chevy Customer Care (Oct 29, 2011)

EcoBlue said:


> I just picked up my new 2012 Cruze Eco 6MT a week ago. I'm experiencing a stumble when I initially start the car. It doesn't happen every time but usually once every 2-3 times I start the car. It sounds like the car is misfiring when I crank it over, but always fires and idles normally. Temperature doesn't seem to matter; it happens when the motor is warm or cold. Initially I thought the dealer may have had bad gas, but I filled up with 88 octane a couple days ago (I'm in Colorado, so 85 is regular and 88 is midgrade) and I'm still having the same problem.
> 
> The dealer has been unable to duplicate the problem. They said there are no codes, but the second time I had it back there they reflashed the computer thinking it might help. The reflash has not helped and I'm still having the same problem. Anybody had this issue with the 1.4t motor? I read a couple posts describing rough starts with an aftermarket flash, but my car is all stock. Any help would be much appreciated!




EcoBlue,
I would like to apologize for the issues that you are experiencing with your Cruze. I would be happy to look into this for you. Can you please send me a PM with your name, address, phone number, VIN, current mileage and the name of your dealer? I look forward to your response.
Thank you,
Stacy Chevrolet Customer Service


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## Bohdan (Apr 28, 2012)

My Cruze has started up great all the time hot or cold. Just a thought perhaps the Sparkplugs are improperly gapped from the Factory if so here we go again.


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## obermd (Mar 3, 2012)

This doesn't sound like a spark plug gap issue (unless they are way out of spec). It sounds more like a fuel/exhaust pressure issue to me. Too little fuel pressure can cause this as can too much exhaust back pressure.


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## EcoBlue (Nov 23, 2012)

Just thought I would post an update to this thread. After reading about plug gaps on this site, I did properly gap the plugs. It seemed to help a little but I still get the 'stumble start' on 25-30% of my startups. I've owned many cars over the years and have never had anything that started like this, but it looks like it's something I may just have to live with.


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## LS1LOL (Feb 24, 2013)

I have actually experienced this same thing. What the one guy above said about getting the tune updated is something that I would like to do I will have to see if that works.


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## YKNWT (Oct 6, 2012)

I have an 2012 Eco M/T with a trifecta budget tune and have this same problem. Will try the waiting a few seconds thing and report back.


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## jblackburn (Apr 14, 2012)

YKNWT said:


> I have an 2012 Eco M/T with a trifecta budget tune and have this same problem. Will try the waiting a few seconds thing and report back.


This seems to be a common issue with the Trifecta tunes. Check with them to see if there's an updated tune for your car.

OP, is it kinda a knocking noise when warm? The flywheel on these cars is really noisy when hot.


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## EcoBlue (Nov 23, 2012)

jblackburn said:


> OP, is it kinda a knocking noise when warm? The flywheel on these cars is really noisy when hot.


Not really a knocking, it's almost like the car is having a slight stumble or misfire the entire time the starter is cranking. Then when it fires it runs fine. There isn't a defined cranking sound like on every other car.


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## Kris D (Apr 2, 2011)

I have a 2011 eco MT.. with K&N intake.. some starts it chuggs really bad then smooths out. I have sprayed off the mass air flow sensor with the proper cleaner. No luck.


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## YKNWT (Oct 6, 2012)

Turning the key on for a few seconds before actually starting the vehicle seems to have solved the problrm in my case.


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