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5.3 Cold Start

stvdalton

By stvdalton
in Ask A GM Technician

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stvdalton Enthusiast

stvdalton

Posted
Posted

Hi,

Okay, I have a 2002 Chevy Avalanche with 5.3L. Love the truck and engine.

This is the first winter I have ever had the truck and we live in Kentucky. It's been under 20 degrees for the past month or more and that is when the problem started.

I start the truck with no problem, but soon as it starts, it revs to about 2100 rpm, then falls back to normal rpm after 5 seconds or so. Then for about 3-5 minutes it shakes and shutters until it warms up. Almost even dies for the first 1-2 mins. But like I said, once it warms up it's fine. Can let it set at idle 10mins and idles fine. I can drive it all day, no problems. Even let it sit for 2-3 hours and it starts fine. But once it gets completely cold like over night. It will do the shaking and shuttering every time. I'm assuming it has something to do with the bitterly cold weather. So then the "service engine light" has been coming on. But after driving it may go off or may take a couple days, then it goes off. I took it to Autozone today and told them what was up. They said proably "throttle sensor". They checked the codes, had random misfire code, and to lean on bank 1 and bank 2. But they said those codes could be just because it is misfiring when it is doing the horrible start ups.

Help? What do you guys think? I pulled a couple plugs, they seemed a little white but seem to be normal far as I can tell. Also, started truck and sprayed starting fluid on all vaccum hoses I could find. They said it could be a leak. All of that and nothing I could find. What's next to try or do? Thanks!

 

Kyle

AlenWoods Enthusiast

AlenWoods

Posted
Posted

Get a winter tune up. Spark plugs Oil filter *--->Fuel Filter<---* spark plug wires. get some fuel injector cleaner.. and use lighter oil or use thicker oil.. one or the other i cant remember

stvdalton Enthusiast

stvdalton

Posted
  • Author
Posted

I did the fuel injector cleaner twice and also I added some fuel treatment tonight in the tank. I may have to do the tune-up, but only thing that don't make sense is it just happpening with cold weather and only on start-up after setting many hours.

thearborbarber Enthusiast

thearborbarber

Posted
Posted

Since this only happens when it is cold that means the computer will be in Open Loop mode. That will eliminate alot of sensors (maf and O2s). Fueling will be determined by engine load and calculated airflow. Engine load is mainly determined by the TPS. I would check it's voltage through out its sweep range with a scanner (best method) or DMV (ok method). Second if there is more air than is predicted by the computers calculations then you will have a lean condition. That would explain the engine flair up at start up. Check and recheck the vacuum lines. Especially around the PCV system. They get hot and can crack in weird places causing headaches.

 

GM's efi systems are real robust and when they go to closed loop mode (after engine is warmed up) they can hide pretty good size problems by the amount of correction the system can make. My LS1 camaro hid a nice vacuum leak in the PCV line for quite a while till I replaced all the lines. It would only rear its ugly head when cold and once the computer went to closed loop they was enough maf range to correct for it.

stvdalton Enthusiast

stvdalton

Posted
  • Author
Posted

Okay, so tomorrow I will check and recheck all vaccum lines. IS there a good way to check them really? Also the throttle sensor you said, where is that located on this truck? If it happened to be the TPS, then in my way of thinking, my misfire codes and lean condition code is very possible due to that because of the rough idle and actually almost dying out at cold startup. Correct? They came up when the cold start problem came up. Thanks a bunch for the help!!!

thearborbarber Enthusiast

thearborbarber

Posted
Posted
Okay, so tomorrow I will check and recheck all vacuum lines. IS there a good way to check them really? Also the throttle sensor you said, where is that located on this truck? If it happened to be the TPS, then in my way of thinking, my misfire codes and lean condition code is very possible due to that because of the rough idle and actually almost dying out at cold start-up. Correct? They came up when the cold start problem came up. Thanks a bunch for the help!!!

 

Using starter fluid like you were or brake cleaner is good. But move the lines around so you can get the spray in hard to reach places. The TPS is on the throttle body and is on the opposite side of the throttle cable. It would also help if you could get the actual code that was read.

 

Don't let the codes through you either. Just because you get three codes doesn't mean you have three problems. A faulty TPS could cause a the engine to go lean, causing the O2's to read lean and trigger a code and go lean enough to cause a misfire. Hense all three codes for one problem. This is where having a scanner that will show data in real time becomes invaluable!

 

Also get a can of MAF cleaner from the parts store and clean you MAF with it. I forgot it is used in open and closed loop modes.

 

How many miles on your truck anyway?

stvdalton Enthusiast

stvdalton

Posted
  • Author
Posted

Okay I'll give all this a try. I haven't started it yet this morning to see how it does after messing around with stuff last night on it. But will let you know what happens.

The truck has 119K on it. My wife has a 2001 GMC Yukon with same engine. Just an idea, if the TPS is easy to change, would it be a good idea to take her's off her 5.3L and put in place of mine temp? Not sure if they are the same, but might save me money.

I am going to go ahead and do the plugs and possibly wires this week. I'll get a can of MAF cleaner after church today and try that. The MAF is located in line from the air filter correct? I spray it on that piece of wire that goes across inside the intake correct?

Thanks a million.

thearborbarber Enthusiast

thearborbarber

Posted
Posted

The TPS should be the same. Make one change at a time so you know what fixed or made it better or worse. The maf is the after the airbox. To clean it, just spray the entire area thoroughly.

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
Hi,

Okay, I have a 2002 Chevy Avalanche with 5.3L. Love the truck and engine.

This is the first winter I have ever had the truck and we live in Kentucky. It's been under 20 degrees for the past month or more and that is when the problem started.

I start the truck with no problem, but soon as it starts, it revs to about 2100 rpm, then falls back to normal rpm after 5 seconds or so. Then for about 3-5 minutes it shakes and shutters until it warms up. Almost even dies for the first 1-2 mins. But like I said, once it warms up it's fine. Can let it set at idle 10mins and idles fine. I can drive it all day, no problems. Even let it sit for 2-3 hours and it starts fine. But once it gets completely cold like over night. It will do the shaking and shuttering every time. I'm assuming it has something to do with the bitterly cold weather. So then the "service engine light" has been coming on. But after driving it may go off or may take a couple days, then it goes off. I took it to Autozone today and told them what was up. They said proably "throttle sensor". They checked the codes, had random misfire code, and to lean on bank 1 and bank 2. But they said those codes could be just because it is misfiring when it is doing the horrible start ups.

Help? What do you guys think? I pulled a couple plugs, they seemed a little white but seem to be normal far as I can tell. Also, started truck and sprayed starting fluid on all vaccum hoses I could find. They said it could be a leak. All of that and nothing I could find. What's next to try or do? Thanks!

 

Kyle

 

Sounds to me like you need a better shop.

If the TPS(throttle position sensor) were gone you would have a code saying it was gone.

 

if you have a random misfire code and nothing saying its misfiring on a specific cylinder, you don't have issues with plugs and wires.

 

If its lean on both banks...you probably have a dirty MAF. Or a plugged fuel filter. Bring it to a dealership that actually knows what the codes mean and is not guessing on what it could be. I mean, probably and maybe don't fix your truck...and probably and maybe cost mega bucks.

 

I mean you may have all your ignition coils gone...you probably have as issue with all 4 O2 sensors..I just cost you 1600 bucks...oh actually it was your $9 fuel filter that was the problem....sorry.

 

Get it to a dealership or a better shop that has a tech II scan tool.

 

 

Edit...For the love of God...don't change out those TPS. they have to be set up...its not a matter of pulling them and bolting them in. They have to be set up with a multi-meter...and there's a procedure for that.

88m53453 Enthusiast

88m53453

Posted
Posted

just had this exact problem on my wife's 03 tahoe, 130k, after searching, i decided to replace the intake gaskets, problem solved. Repair took me about 2-2.5 hours

 

codes were 171 and 174 fwiw

stvdalton Enthusiast

stvdalton

Posted
  • Author
Posted

Thanks for the input so far.

 

Okay, I swapped TPS with my wife's GMC yukon 5.3L. Also I cleaned the MAF with this $$$ cleaner I got today. My wife's yukon was cold. hasn't been started in 2 days. Got the TPS from my 5.3 put on and started her truck. Started fine, no shutter or almost dying. So I put her TPS on mine, started mine though it was still warm and it seemed okay, but I won't know if it helped until I let it sit for a while to be completely cold. Should know sometime tonight, but kinda doubt it helped because my wife's was cold and it started like normally.

 

The codes autozone pulled yesterday were the following:

P0174-BELIEVE BOTH OF THESE ARE AIR/FUEL IN BANK 1 AND 2 RICH/LEAN

PO171

P0300-RANDOM MISFIRE

P0106

 

 

A buddy of mine said it could possibly be the MAP sensor? BNot sure what that is or where it is and if I could swap my wife's and mine and see. I know a dealer could proably figure it out, but man I'm needing to try to save money. So as of now I haven't spent and money other than the MAF cleaner. Still am going to do spark plugs anyways on mine and my wife's 5.3L.

 

What's next to try guys?????

stvdalton Enthusiast

stvdalton

Posted
  • Author
Posted

Just got home, truck has been sitting about 6 hrs. 17 degrees outside. I started it, at first I thought it was good, it didn't rev quite as high but still kinda high, the it started the shuttering and shaking. This time I put it in gear and the rpms of course dropped even a little more and the minute later, the SES light came on, but started blinking. So I put back in gear and rev up to 2000 rpm and it went away completly. Of course 3-5 mins. later engine warmed up and running fine. So not sure where to go from here. Thinking of swapping the MAF from my wife's yukon and seeing if that helps. Also going to get new plugs. Pretty sure that won't help though. Are there any other things I could swap from my wife's yukon like sensors temp. for testing?

Really hoping it isn't the intake gaskets. Quite a few people think it could be. But why only when it is really cold?

I read the link you sent me, it talk about the MAP sensor a lot. Where is that and would it be a good thing to swap from my wife's yukon? Atleast swapping stuff is free so far. HA!

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