5.3 Cold Start

[stvdalton]

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

[stvdalton]

GM dealership confirmed intake gasket leak. Total fix including scanner fee, $315.00. Hated to spend it, but much easier to let them do it, I had to do nothing except work some overtime! HA! Thanks, hope this helps someone.

[stvdalton]

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]

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]

Yeah I'm afraid of that. Thinking about trying a couple more things tonight. Maybe swap the MAP sensor. Where is that thing though?

Also, I started it this morning after setting last night, it started and only revved again to 1400 rpm and then back to 1000rpm. Then for about 10 seconds it ran fine. I thought, it's fixed. Then it start shuttering/shaking. So I just shut it off and went to work. Disgusting. But it's weird, it has been revving a lot higher until I cleaned the MAF and swapped the TPS. But it still isn't right though. So I'm thinking tonight of swapping the MAF from my wife's and trying it. Then if still same problem, swap the MAP sensor. If I can find it. HA!

WOW...if any of those sensors were gone they would have thrown a code long ago....Bring it to a shop with a diagnostic tool...stop wasting your time and patients. You could have a sensor going bad...but there are a lot of sensors on your engine that cause this same symptom...and your not going to be able to change all of them. the diagnostic tool will show what those sensors are performing like and can tell you if one is on its way out. The cost of a diagnostic with a tech 2 is whatever 1/2 an hour labor is...they'll tell you what sensor is gone...you take the truck home and get one of those sensors and change it. Job done...and it takes you an hour....not 3 freekin days.

[88m53453]

duh...way back on p1....i suggested the gaskets....;) just do it and there are only 2 to worry about, also, as stated, a good time to check the knock sensors

[Sjaimeeyenm]

It's your manifold gasket. When cold the gasket shrinks causing a vacuum leak. After engine warms up gasket expands, fixing vacuum leak and engine idles smooth. Change you manifold gasket if you want to fix your problem

[Nytemare]

I think your right. I may try to swap the MAF sensors tonight just for the fun of it. I called my local GM dealer, man they want $84 to hook it up and tell what it needs. So I called a GM dealer my buddy lives by, it's only 25 miles away from me and they want $45 to hook it up and tell me what I need. So that's better. I talked to them though and they said it could be the upper or the lower intake gasket. i had no idea there were 2. We'll see though.

Sure are 2.

technically 3...two, one for each head to intake mating surface...and another one that goes under the manifold...has the two holes for the knock sensors.

[Nytemare]

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.

[stvdalton]

I think your right. I may try to swap the MAF sensors tonight just for the fun of it. I called my local GM dealer, man they want $84 to hook it up and tell what it needs. So I called a GM dealer my buddy lives by, it's only 25 miles away from me and they want $45 to hook it up and tell me what I need. So that's better. I talked to them though and they said it could be the upper or the lower intake gasket. i had no idea there were 2. We'll see though.

[88m53453]

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

[Dnt]

Most shop worth their salt have a smoke test machine Have a smoke test done on the intake it only takes a minute and the leak can be pinponted. You might find something unexpected like a split in a hose that is not easily accessible would cost you maybe 4 bucks instead of 400.

[stvdalton]

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!

[thearborbarber]

Just about everything will swap between the two engines. You are starting to get to the part where you are going to need a scanner to view sensor data in real time.

[jgaff]

So did the intake gaskets fix the problem? I have a 02 Tahoe that does the same thing, has a lean condition on bank 2, and the fuel economy has gone down the drain. I have been dragging my feet about changing it out, but probably need to get it done. Just making sure that fixed your problem!

[AlenWoods]

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