Jump to content

5.3l After Start Up

ac0905

Recommended Posts

ac0905 New Member

ac0905

Posted
Posted

On my 99 NBS, it acts like it's not going to make it. Quick, easy start everytime, fires right up. Then after a second or two it acts like its going to die, but it doesn't. Just chokes, bogs down a bit and then runs fine.

 

I have to let it warm for about 15-20 seconds every morning or anytime it sits for a while. If I don't let it warm up and try to go, I won't get any throttle response. I can push the gas and it bogs down. I'll push it to the floor, and nothing. It always stays running though.

 

Also, related or not, as I am cruising (45-55 mph) down the road and come up on a hill or something, the rpms go up and down slightly and won't down shift until I really give it some gas. Then it gears down and goes on with no problems.

 

The truck has 185k miles. I bought it with 100k on it 5 yrs ago. I have not had any problems out of it, so there has not been much done to it other than maintenance, tune up, brakes, etc.

 

Does anyone have any ideas?

J-man67 Senior Enthusiast

J-man67

Posted
Posted

Might want to try cleaning the throttle body and MAF. The throttle body can accumulate carbon. It can make the butterfly valve stick. Not sure if it will fix it, but worth a shot. Also, when is the last time you did some maintenance on it? Like plugs, wires, fuel filter, all that jazz?

Spurshot Senior Enthusiast

Spurshot

Posted
Posted

The MAF may be a culprit as Justin said.

 

My 99 6.0L idles a bit rough since I put Bosch plat plugs in it. I've since read about the idle issues associated with the Bosch plugs. Probably go back to AC or Autolites. I had Autolites from about 50k miles until about 200k miles and was perfectly happy with them. I'm due for plug wires on the 99 also.

 

Your downshift scenario may be normal. Hard to diagnose by these posts. But they tend to leave these electronically controlled transmissions in higher gears until you really mash on it. The logic behind that kind of programming probably has to do with fuel economy or emissions. On the otherhand, my 99 6.0L 2500, drops down a gear at the drop of a hat.

 

I'd do the usual tuneup with plugs and add plugwires, fuel and air filters for this old a truck and remove the MAF sensor and check it out, clean as necessary and reinstall.

ac0905 New Member

ac0905

Posted
  • Author
Posted

I cleaned the throttle body about 2 months ago, due to the gas pedal sticking. Took care of that.

 

I installed new plugs around 130k, 185k now. I don't have the traditional plug wires, as you probably know. It has a coil for each plug. I replaced the fuel filter probably 3 yrs ago. Do you think it may be time for these again? New air filter last year, which is a K&N that I clean regularly.

 

What's the best way to clean the MAF? I looked at it when I cleaned the TB, but it didn't "look" dirty. Maybe it doesn't.

 

I have also read, with these motors the intake manifold gasket breaks down and can leak. As the motor heats up, the gasket seals properly, and it doesn't leak. Any possible truth to this?

J-man67 Senior Enthusiast

J-man67

Posted
Posted
I cleaned the throttle body about 2 months ago, due to the gas pedal sticking. Took care of that.

 

I installed new plugs around 130k, 185k now. I don't have the traditional plug wires, as you probably know. It has a coil for each plug. I replaced the fuel filter probably 3 yrs ago. Do you think it may be time for these again? New air filter last year, which is a K&N that I clean regularly.

 

What's the best way to clean the MAF? I looked at it when I cleaned the TB, but it didn't "look" dirty. Maybe it doesn't.

 

Hmm. I got nothing. I would try to clean the MAF and see what that does, then go from there. Just buy some MAF cleaner from your local auto store. Take it out, and use the cleaner. Its a spray can with a straw. Just aim and squirt. Its fast drying, but leave it out for about 10 mins, then re-install. I'd wear some disposable gloves or something. The cleaner is nasty crap.

ac0905 New Member

ac0905

Posted
  • Author
Posted
You should never start a cold engine and then drive off immediatly. :lol::puke::D

 

At minimum give it 30 seconds for the oil to circulate. Unless you don't plan on keeping your truck a long time.

 

Yeaaaah. That's not how I roll.

 

185,000 miles without a problem....

ac0905 New Member

ac0905

Posted
  • Author
Posted
I cleaned the throttle body about 2 months ago, due to the gas pedal sticking. Took care of that.

 

I installed new plugs around 130k, 185k now. I don't have the traditional plug wires, as you probably know. It has a coil for each plug. I replaced the fuel filter probably 3 yrs ago. Do you think it may be time for these again? New air filter last year, which is a K&N that I clean regularly.

 

What's the best way to clean the MAF? I looked at it when I cleaned the TB, but it didn't "look" dirty. Maybe it doesn't.

 

Hmm. I got nothing. I would try to clean the MAF and see what that does, then go from there. Just buy some MAF cleaner from your local auto store. Take it out, and use the cleaner. Its a spray can with a straw. Just aim and squirt. Its fast drying, but leave it out for about 10 mins, then re-install. I'd wear some disposable gloves or something. The cleaner is nasty crap.

 

 

 

Ha. Just aim and squirt, huh? Maybe I'll give that a try.

txab Senior Enthusiast

txab

Posted
Posted
You should never start a cold engine and then drive off immediatly. :lol::puke::D

 

At minimum give it 30 seconds for the oil to circulate. Unless you don't plan on keeping your truck a long time.

 

Yeaaaah. That's not how I roll.

 

185,000 miles without a problem....

 

 

Oh, maybe I misread your post I thought you had a problem. You posted here for a reason...... a problem! :lol:

 

Check:

Fuel filter

Fuel pump

Fuel pressure regulator

Intake manifold leaks

Maf

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • asilverblazer
      Slate Electric Truck

      By asilverblazer · Posted

      I like the idea.  I would pick diesel if I had a choice. I need pictures though.
    • newdude
      Help purchasing a touch screen digitizer

      By newdude · Posted

      I've installed cheap eBay new aftermarket digitizers before.  They work.  Did a bunch of Cadillac CUE (aka Cadillac's MyLink) for someone years ago.  They all worked fine after the repair.    That number 22740886, that is a component part # for GM.  You can use it to search, but its not something that's obtainable at the dealer level.     So pretty much any of these will work - 2015 Colorado Digitizer for sale | eBay
    • asilverblazer
      give me some tips to make my truck look better

      By asilverblazer · Posted

      Black bumper and the later years Z-71 style color matched grille.
    • fondupot
      Exhaust heat while towing!

      By fondupot · Posted

      You can install tailpipes that direct the exhaust sideways vs the OEM one that goes straight back. There are several on the market, do you own research. HOWEVER, you need to make sure the Venturi vents are still intact, otherwise it will throw a engine code. There is a sensor somewhere that detects back pressure on the exhaust. And if it doesn't collect the correct metrics, it will throw the truck into limp mode. 
    • Atlas
      Wow I'm in a pickle. (Broke down truck) and a story.

      By Atlas · Posted

      "Teardown" is complete. Head surfaces are clean and ready, new intake is prepped and ready. Coolant drained and water pump is removed, radiator is removed, new hoses and pump are ready.   The replacement intake is also from a '95 (with I think 260k, the odometer said). Noticeably less pitting where it covers the rear coolant passages. I'm not sure if that's a tribute to more frequent use, more frequent coolant changes/upkeep, or if the intake was machined at some point. But it appears I found a good one.   My coolant hoses were original, and the lower hose still retained the factory spring inside. It's not really rusty, but it's got deposits all over it. Unsure if I should re-install it (will thoroughly clean it first). Someone said hose technology has gotten better since 1995 (has it?) and I don't need the spring. I think modern EPDM is what made those hoses last from 1995-2026, so it's a question of how much suction can the water pump really pull, and will it collapse the hose without a spring?   I'm stopped and waiting for parts, however.   When I first brought the truck home, the fan was intermittently hitting the radiator shroud. I could see someone had monkeyed with the shroud (put a bunch of cardboard as a spacer between the upper/lower shroud halves. Someone said the motor mounts have likely failed and the engine has sagged. I wasn't sure I believed that. The engine is really solid in its mounts: To remove the old intake I *just* nearly permanently welded to the heads with freshly cured RTV and gasket snot two weeks ago, I literally had to use the arms on my lift and a chain with a bolt attached to the intake to pull it loose. It almost picked the front of the truck off the ground before ....scuuuuuuuuuuup.... I could actually hear the gaskets tearing and it broke loose and the whole truck settled back down. Motor barely moved.   SO, those parts I'm waiting on... The lower radiator mounts/bushings had completely failed. The radiator needs to be insulated from the rad support, and the bushings help the rad stand at the correct height. The plastic "baffle" was also destroyed at some point. Someone had attached the shroud to it incorrectly, overlapping a joint that should have been underlapped, creating another suspect issue potentially causing things to hit the fan. Broken tabs, side is busted off, and it's perma-formed/bent where it was jimmied incorrectly.   The baffle? Unobtainum. Long since discontinued from GM, of course. Aftermarket/capa/chinese? Also unobtanium. In GM's infinite wisdom, it appears there are at least two different variations whether the Blazer is 2 or 4 door, and I can't yet tell if they shared the same part with the S-pickups. Plan B, if I can't find a viable used one, will be to create a bracket to re-assemble the critical joint I need to seal a gap with the shroud. But that will bug me, it won't be...perfect.   The water pump bolts appear to have been installed with...plumber's putty. I guess, sure, if it works...? I've found a few "backyard fixes" like that. Someone's been here before....   If I can't find someone to jam bamboo under my fingernails to fill my free time this week I think I'll install the driver's power window motor and replace the rear door speaker that's inop. I've got a genuine GM "9.5" ohm working replacement. Why GM used a non-standard resistance....nevermind. Of course they did, you can get more sound from a cheap factory amp that way.   And the saga goes on...

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...