5.3 Cold Start

[stvdalton]

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!

[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.

[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.

[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.

[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

[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.

[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!

[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

[78Firebird]

Hi,

Sounds like you have a vaccum leak. That would cause the shaking and the miss fire codes along with the lean code. GM intake gaskets are famous for leaking. The gasket contracts when truck is cold. As the engine warms up it expands enough to seal and the truck runs good. The safe and easy way to check this is with a small propane torch. Start the truck( made need some one to keep it running) turn on the torch, just the gas, and move along where intake and the head meet. If the idle smooths out then you found the problem. The best thing would be to take it to a decent shop and have it diagnoised. Cheaper in the long run as opposed to throwing parts at it. We all can guess and share our experiences with you. But without actually looking at the truck, thats all it is. Guessing.

[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.