Rough cold startup - TerrainForum.net: GMC Terrain Forum
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post #1 of 16 (permalink) Old 06-05-2017, 07:20 PM Thread Starter
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Rough cold startup

I hope this is going into the right forum....

I'm trying to get ideas as to what's going on with my 2010 GMC Terrain SLT i4. When I start the car up after it's been sitting for several hours- like 8 hours or so... in other words, a COLD start- I get a very rough startup. The entire car shakes. RPMs start at around 1500 RPMs and slowly work their way down to about 510 RPMs and then stay. If you try to backup or drive while the car is stuttering, the engine will sound like it may stall out. After about 10-15 seconds after initially starting up, the car is fine and drives normally.
EDIT: No current error codes

I've tried several things to fix the issue:
1) Reassembled the intake several times
2) replaced the MAF
3) replaced the MAF gasket
4) cleaned the throttle body
5) REPLACED the throttle body
6) Replaced the throttle body gasket
7) replaced the MAP sensor
8 ) replaced the spark plugs
9) had the engine mounts inspected and they were fine
EDIT: 10) I had the High pressure fuel pump replaced under recall.
EDIT: 11) Both input and exhaust camshaft position actuators have been replaced because I had codes P0010 and P0014 (did this myself).

I was doing everything myself because I brought the car to the closest (still 45 minutes away) dealership and they turned me away saying that 1) everything sounds fine (but they would only listen to the car after being warmed up!), and 2) to do a diagnostic, they'd need to keep the car over night and wouldn't provide a loaner car. This is my only car and I work unusual hours, so I NEED a loaner. I'm fine with leaving the car there over night, but I also need to be able to get home and to get to work.

Anyone have any idea of what's going on!? I can provide any answers to any additional questions. Just ask!
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post #2 of 16 (permalink) Old 06-05-2017, 08:02 PM
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Re: Rough cold startup

I would still guess the actuators. I think you have to reprogram the ECU after the procedure.

2018 Equinox LT1 1.5 L 4 cyl, AWD, S/R Cajun Red Tintcoat/Black

2010 Equinox LTZ 2.4 L 4 cyl, FWD, S/R Cardinal Red/Black
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post #3 of 16 (permalink) Old 06-05-2017, 08:05 PM
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Re: Rough cold startup

You could rent a car. They are not that expensive.
I know, I would hate to have to spend even more money on the diagnosis only to have them say nothing is wrong.

You already covered most of the items I would have thought about.

Jeff from Iowa, Purchased 2011 Nox in Nov. 2016, Manufacture date 10-10, 2.4l, AWD
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post #4 of 16 (permalink) Old 06-05-2017, 08:52 PM
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Re: Rough cold startup

The oil level is okay? It's not consuming oil?

Does it sound like a cement truck once warmed up? Might be the timing chain starting to go. There is recall for premature timing chain wear. I think it applies to the 2010s.

2012 Equinox 2.4L 1LT AWD, black, 80,000 miles
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post #5 of 16 (permalink) Old 06-05-2017, 10:43 PM
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Re: Rough cold startup

I suspect you have one or more fuel injectors that are defective and/or sticking.

When the vehicle is shut off for an extended period of time, it permits fuel to leak past the clogged or defective injector(s) - which floods the engine with raw fuel. When you start the vehicle, it is flooded and running extremely rich - thus the rough running engine.

If you restart the engine while warm - there has not been enough time for the injectors to leak raw fuel into the engine. It should restart easily when warm / hot.

If you are old enough to remember vehicles with carburators, the condition is similar to a stuck choke.

You may want to try one or two treatments of Techron Fuel System Cleaner Plus (the name has changed recently with a "new look" bottle"). This may clean the injectors and dislodge any pieces of grit that are keeping the injectors open. Follow the instructions on the bottle label.

Good luck.


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post #6 of 16 (permalink) Old 06-06-2017, 06:31 AM
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Re: Rough cold startup

C5

I like your explanation, and best of all, it comes with a potentially cheap and easy solution.


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2010 Equinox LTZ 2.4 L 4 cyl, FWD, S/R Cardinal Red/Black
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post #7 of 16 (permalink) Old 06-06-2017, 09:13 AM
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Re: Rough cold startup

I like free solutions best. . . . .

"Anything "Free" is worth saving up for !

2015 Equinox LTZ 3.6L FWD Champagne Silver Metallic *Build Date 1-08-2015 * *34,465 miles 3-11-2019
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post #8 of 16 (permalink) Old 06-06-2017, 09:16 AM
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Re: Rough cold startup

hi ,

xTooltipElement

Service Information Home Number Search New Bulletins Bulletin Search Feedback TIS2Web Help


Document ID: 4679536
--------------------------------------------------------------------------------

#PIP5180A: Diagnostic Tips For SIDI Hard Start Cold - (Jan 24, 2017)
Subject: Diagnostic Tips For SIDI Hard Start Cold

Models: 2009-2016 Buick Enclave
2010-2016 Buick LaCrosse
2010-2017 Buick Regal
2012-2017 Buick Verano
2013-2015 Cadillac ATS
2008-2015 Cadillac CTS
2008-2010 Cadillac STS
2008-2016 Cadillac SRX
2013-2016 Cadillac XTS
2010-2015 Chevrolet Camaro
2012-2014 Chevrolet Caprice PPV
2012-2014 Chevrolet Captiva Sport
2010-2017 Chevrolet Equinox
2012-2017 Chevrolet Impala
2009-2017 Chevrolet Traverse
2009-2016 GMC Acadia
2010-2017 GMC Terrain
2009-2010 Saturn Outlook
Equipped with SIDI 4 or 6 cylinder engines

--------------------------------------------------------------------------------

This PI was superseded to update Model Years. Please discard PIP5180.


--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Hard start, extended crank, or black smoke from the exhaust when starting.

Recommendation/Instructions
Basic Tests:
Verify Fuel Quality?

Spark Test with ST125, if a coil issue is suspected then follow Ignition System Diagnostics.

Perform a Compression Test.

You should see 150-185 Average Compression, no cylinder should be less than 140 psi on a HFV6.

You should see 170-200 Average Compression, no cylinder should read less than 100 psi on the 4 cylinder engine.

If the condition is a “Hard Start Cold” only, and you suspect that you may have a carbon issue causing a valve to stay open, follow the latest version of PIP5029 and perform a cold compression test.

Also install a vacuum gauge prior to cold start and watch needle for signs of a sticking valve.

Fuel System Check:
*Follow all these steps in order.

The following tests should be done after an overnight cold soak.

Set your vehicle up with the CH 48027 digital pressure gauge and J37287 fuel line with shut-off valve.

Run vehicle to purge all air from fuel system and then shut vehicle off and let sit overnight.

Unplug the injector harness connector.

Next Morning:
Key On and do not start engine – Using a CH 48027 Digital Pressure Gauge, verify “Key On” engine off, prime pulse fuel pressure should be between 55-60 psi. Record reading.

This test will confirm correct operation of the in-tank fuel pump assembly.

Use your Tech2 or GDS set in PSI to also confirm what the Fuel Rail Pressure Sensor is reading as this should always be close to what your Digital Fuel Pressure Gauge reads for low side pressure during this test.

This will also confirm if there is an off-set with the Fuel Rail Pressure Sensor.

Next you will crank the engine to see if it fires.

With the injector harness connectors unplugged, the injectors are now electrically disabled so no fuel should be delivered to the engine.

When cranking over the engine, if engine fires this means that one or more injectors have been leaking and have introduced fuel into one or more cylinders.

Reconnect the injector harness connectors and start the engine, let the vehicle run for ten minutes and then shut vehicle down.

You will now close the shut-off valve in the J37287 Fuel Line, which will now separate the engine side of the fuel system from the rear section of the return- less fuel system.

Using the CH 48027 Digital Pressure Gauge, look for a drop in the high side of the fuel system, by monitoring low side pressure.

With the J37287 valve closed, the system should hold at least 60 psi for a few hours.

If you see a rapid decrease in fuel pressure, this would indicate a leaking High Pressure Fuel Pump or leaking injectors since the fuel pressure cannot bleed off to the tank as your J37287 valve is closed.
[/color]
All this is assuming that your gauge is good with no leaks or any leaks at the Schrader valve.


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post #9 of 16 (permalink) Old 06-06-2017, 03:37 PM
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Re: Rough cold startup

My 2014 is doing the same exact thing.

2014 Equinox LT2 2.4L I4 Leather heated seats, remote start, power lift gate.
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post #10 of 16 (permalink) Old 06-07-2017, 06:12 AM Thread Starter
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Re: Rough cold startup

I finally got the dealership to lend me a car while they diagnose the problem. Thing is, I have to wait until next week because they have nothing available until June 14.
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