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Author Topic: '08 5.3 hard starting, especially in cold weather  (Read 1939 times)

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matt_b

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'08 5.3 hard starting, especially in cold weather
« on: December 10, 2016, 06:58:55 AM »

2008 Z71 with 5.3L, around 140K miles.

I've been dealing with this issue for over a year now.  Frequently, when starting my truck, the only way I can get it to start is by cranking for a long time and pumping the gas pedal to get it to fire up.  I've tried turning the key on and waiting, trying to start multiple times, etc. and the only way I can get it to start is pumping the gas.  It seems to get much worse in the cold weather, but I don't have to do it when the engine is warm.  When I do get it started, sometimes there's a massive smoke cloud like it was flooded, other times, nothing at all, like it's starving for fuel.  Once it has been started and running for 30 seconds or so, it runs just fine.  I was getting occasional check engine lights, but I haven't since replacing O2 sensor and MAF sensor.  My engine has the all-too-common AFM lifter noise on startup, but it really hasn't become any worse since I bought it ~2.5 years and 40K miles ago.  I have the AFM disabled with the Range Products device.  I've tried running it without the Range for a while, and no difference.  I've done a lot of troubleshooting/part replacing trying to solve this issue, but no luck so far.  Here are the things I can remember doing trying to address this, in no particular order:

Replaced fuel pump (had some pressure loss before replacing.  It's holding strong after replacing)
Replaced MAF sensor (after numerous cleanings that weren't effective)
Replaced leaking intake manifold gasket
Reset fuel trim
Reset fuel composition (It's a flex fuel model)
Tune up (plugs/wires)
Countless fuel system treatments (additives only)

I'm sure there's a few other things I've tried as well, but can't think of at the moment.

Anyone else have similar issues?  I'm just waiting for that super cold Michigan day when I drain my battery (also rather new) trying to get this ol' girl started.

Thoughts and insights greatly appreciated!
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EXT4ME

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #1 on: December 10, 2016, 07:58:33 AM »

When both my 2004 EXT and my wife's 2006 CTS went through a period of difficult starting, I thoroughly cleaned the throttle body on each vehicle.

The engine side of each throttle body was extremely dirty with carbon build up.

The problem went away after the cleaning and never returned.

Worth a try, I suppose.
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2004 Cadillac Escalade EXT, White Diamond, New Shale front seat leather from The Seat Shop. WeatherTech FloorLiner DigitalFit. Powerflow Pro-Fit Splash Guards. Arnott/Bilstein front shocks and rear air shocks with Arnott air compressor kit. Refinish Restorer. SeaFoam. Goodyear (Now Continental) Gatorback belts.  BFGoodrich Advantage T/A Sport LT.

matt_b

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #2 on: December 10, 2016, 09:53:25 AM »

I knew I was forgetting some of the other things I tried!  I gave the TB a full clean out when I replaced the intake gasket.  It was really nasty when I cleaned it, so I was really hoping it was the fix, but unfortunately it didn't do the trick.  Thanks for the idea though!!!
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CarMech1969

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #3 on: December 10, 2016, 13:24:15 PM »

2008 Z71 with 5.3L, around 140K miles.

I've been dealing with this issue for over a year now.  Frequently, when starting my truck, the only way I can get it to start is by cranking for a long time and pumping the gas pedal to get it to fire up. 

As you likely already know, the only effect pumping the gas has on a fuel injected vehicle is allowing more air to enter the intake.
Which could possibly point to an overfueling condition.
You stated that once it has started and ran for a bit, it's fine after.
Sounds to me that you might have a faulty ECT sensor.
My '92 Sierra ran like total crap one day out of the blue. It idled really high and was puffing black smoke.
Threw in an ECT sensor that I had laying around (gotta love how many GM parts interchange) and the problem was fixed.
They are not expensive to buy and apparently have a high failure rate (on the GMT400 vintage anyway), so I suppose you could give it a try.
Hope this helps!

CarMech1969
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matt_b

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #4 on: December 10, 2016, 17:12:59 PM »

Thanks CarMech!  I'll be honest and admit I had to google ECT sensor.  I had always called it a coolant temp sensor.  I recall replacing the sensor for the gage shortly after I bought the truck.  Talk about a scare! I was only 5 miles away from my house and I look down and the temp gage was pegged.  Lucky for me, it was just the sender.  Is the same sensor used for the fuel injection system, or does it have a separate one?

Thanks Again,
Matt
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CarMech1969

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #5 on: December 10, 2016, 17:18:19 PM »

Thanks CarMech!  I'll be honest and admit I had to google ECT sensor.  I had always called it a coolant temp sensor.  I recall replacing the sensor for the gage shortly after I bought the truck.  Talk about a scare! I was only 5 miles away from my house and I look down and the temp gage was pegged.  Lucky for me, it was just the sender.  Is the same sensor used for the fuel injection system, or does it have a separate one?

Thanks Again,
Matt

The sensor for the temp gauge is a separate sensor.
The ECT sensor is a 2 wire sensor which sends engine temperature information to the PCM.
The PCM then will adjust fuel delivery based on that. (Cold engines need a richer mixture)

CarMech1969
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Owner of a 2002 Avalanche 2500 series, 4X4

MS03 2500

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #6 on: December 10, 2016, 21:26:01 PM »

We need more info what color was the smoke, also when the check engine light came on did you scan for engine codes.
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matt_b

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #7 on: December 11, 2016, 07:19:34 AM »

Smoke was dark gray/black indicating rich condition.  Codes were P0172 and P0175 (also indicating rich), but I haven't seen the CEL since I replaced the MAF sensor a little over a month ago.
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matt_b

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #8 on: December 12, 2016, 19:52:53 PM »

CarMech,

First off, I was mistaken when I said I replaced the coolant temp sender.  It was actually the oil pressure sensor.  I just remembered seeing a gage in the total wrong position unexpectedly.  In some quick online searches, I'm only finding one engine coolant temp sensor and it's near the #1 plug.  Is that the right one?  I can't seem to find another PN or location for the other sensor.

Thanks,
Matt
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matt_b

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #9 on: January 14, 2017, 06:09:37 AM »

SOLVED!!!  I finally remembered to post an update.  CarMech had it right!  I replaced the $10 ECT sensor and the problem immediately went away.  Gotta love it when you spend a bunch of time and money trying to fix something, then its a $10 sensor that takes 2 minutes to replace that fixes it!

Thanks everyone for your help.  Hopefully this will save someone else some time and money in the future!
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EXT4ME

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #10 on: January 14, 2017, 09:07:04 AM »

Outstanding!

 :thumbsup:
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2004 Cadillac Escalade EXT, White Diamond, New Shale front seat leather from The Seat Shop. WeatherTech FloorLiner DigitalFit. Powerflow Pro-Fit Splash Guards. Arnott/Bilstein front shocks and rear air shocks with Arnott air compressor kit. Refinish Restorer. SeaFoam. Goodyear (Now Continental) Gatorback belts.  BFGoodrich Advantage T/A Sport LT.

CarMech1969

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #11 on: July 8, 2017, 06:06:21 AM »

SOLVED!!!  I finally remembered to post an update.  CarMech had it right!  I replaced the $10 ECT sensor and the problem immediately went away.  Gotta love it when you spend a bunch of time and money trying to fix something, then its a $10 sensor that takes 2 minutes to replace that fixes it!

Thanks everyone for your help.  Hopefully this will save someone else some time and money in the future!

Cool beans!  :cool:

CarMech1969
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Sam H.

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Re: '08 5.3 hard starting, especially in cold weather
« Reply #12 on: January 12, 2020, 11:14:06 AM »

Hello! I had the same problem. Very rough starts in the morning when my truck had sat out in the cold over night. It wouldn’t happen in the summer but as the cold Illinois weather set in here we go again! So after tightening the intake bolts. And cleaning the mass air flow sensor. Nothing changed. I would get a check engine light and the remote start wouldn’t work.

So what fixed the issue was I ran a tank of E85 through it.  The check engine light went off after the tank and I went back to regular gas. Well the light came back on. So I ran 3 tanks of E85 through it and I haven had a problem for over a month now. It has to have something to do with a sensor that detects how much ethanol is in the gas. If anyone knows what and where that would be located that would be awesome. But at least it’s working fine now.
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