Stumped the dealerships today need help

[shoplizard]

***lengthy post just forewarned!! Lol***

Hey all! So we're discussing my 99 obs gmc k1500 burban with the 5.7 4wd sle. Had the cat issue "taken care of"ie removed till i can afford a full exhaust with high flow cats, because i was told that they were the cause of my catalyst efficiency below threshold bank 1 and 2 codes and the reason why its boging down backfiring and acting crazy for the first 30 seconds when I go to drive after work in the morning or anytime it sits for a while. After i feather the gas a bit it goes away and runs fine. We Changed the o2 sensors about 6000 miles ago when i first bought it along with intake gaskets, t stat, belt, transmission issues fixed u joints,shocks and other things. This was all done at the chevy dealership I worked at.

So i took it to the chevy dealership in my new town to get it diagnosed and they found 5 codes. 4 of the catalyst efficiency codes and one dealing with the fuel system running lean. Vac leaks is the first thing that came to mind said the tech So they hooked up things to check fuel pressures, checked plugs wires vac lines etc. everything came back normal. They used 1/4 tank of gas driving it today lol. So they called and said they couldn't figure it out so they took it to the gmc dealership and had their tech check it out and nothing different. They reproduced the issue but no new codes show up when it happens or anything to alert them of whats going on.

So They want to just throw a bunch of parts at it and see what happens. The parts include a upgraded fuel spider conversion, fuel pump and fuel filter(the fuel filter was done 6k ago) plugs wires and cap or what ever i have and checking and removing every vac line and replacing as needed and all new sensors ie tpms iac mass air flow etc. and thats along with a brake booster and master cylinder for the brakes because of the hissing noise it has and that separate issue. They said if they replace all of this and and it still does it then ill be looking at a engine tear down to check for cracked heads and other engine related things. Even though i don't think i have any symptoms that would justify that.

The cost is in the thousands and i cant afford that even at non dealership mechanic rates nor can i do a lot the work my self due to lack of tools work schedules etc. Does anyone have any idea or experience with this issue? Its getting bothersome and want to get this thing mechanical good but its one thing after another. My pocket book might not be able to afford this thing if things keep going wrong. And of course i cant get it to act up to post a video either. Go figure. Sorry if this is all over the board tried to give as much info as possible.


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Good morning, I know this may sound a little off the wall, but I had a 1997 Suburban with 275,000 miles on it. I started getting the low efficiency codes setting. I first checked the HO2S's, I added extensions on the post sensors, I was still getting codes. One day I was doing some work and inspections under the vehicle, I had to pull the exhaust out. So while I had it out I figured there could be no loss if it failed. I took the garden hose and very thoroughly flushed and back flushed both converters. Mixed a bucket of hot water and dish detergent and dumped in into the exhaust and swished around as well as possible and repeated flushes with the hose. I reinstalled the exhaust and we drove it for another 10,000 miles with no codes set and ran better too. This may not work for you and it is a lot of work, but a new set of cats was $900.00 at the time. So as I mentioned earlier there was no loss if it didn't work, but it did. P.S. the cats didn't rattle so they weren't broken.

 

[shoplizard]

More info lol. So its going back to the dealership Saturday but im adding this to the list of symptoms. Pulled the middle spark plug on the passenger side this am and it smelled like raw fuel but wasn't wet. Possible leaking injector?


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Good morning, It sounds like you are having a problem with a leaking fuel pressure regulator. Normally with this problem, the engine will start easily when cold because rich mixture is needed for starting, but when it is warm the excess fuel makes it difficult to start. The regulator is mounted to the fuel spider under the upper plenum. if the throttle body is removed it won't be visible but an inspection, possibly with a flixible camera will reveal a washed area on the lower manifold just below the regulator. If you see this then the regulator is leaking and causing hard starting when warm.

 

[Gmc lovin75]

***lengthy post just forewarned!! Lol***

Hey all! So we're discussing my 99 obs gmc k1500 burban with the 5.7 4wd sle. Had the cat issue "taken care of"ie removed till i can afford a full exhaust with high flow cats, because i was told that they were the cause of my catalyst efficiency below threshold bank 1 and 2 codes and the reason why its boging down backfiring and acting crazy for the first 30 seconds when I go to drive after work in the morning or anytime it sits for a while. After i feather the gas a bit it goes away and runs fine. We Changed the o2 sensors about 6000 miles ago when i first bought it along with intake gaskets, t stat, belt, transmission issues fixed u joints,shocks and other things. This was all done at the chevy dealership I worked at.

So i took it to the chevy dealership in my new town to get it diagnosed and they found 5 codes. 4 of the catalyst efficiency codes and one dealing with the fuel system running lean. Vac leaks is the first thing that came to mind said the tech So they hooked up things to check fuel pressures, checked plugs wires vac lines etc. everything came back normal. They used 1/4 tank of gas driving it today lol. So they called and said they couldn't figure it out so they took it to the gmc dealership and had their tech check it out and nothing different. They reproduced the issue but no new codes show up when it happens or anything to alert them of whats going on.

So They want to just throw a bunch of parts at it and see what happens. The parts include a upgraded fuel spider conversion, fuel pump and fuel filter(the fuel filter was done 6k ago) plugs wires and cap or what ever i have and checking and removing every vac line and replacing as needed and all new sensors ie tpms iac mass air flow etc. and thats along with a brake booster and master cylinder for the brakes because of the hissing noise it has and that separate issue. They said if they replace all of this and and it still does it then ill be looking at a engine tear down to check for cracked heads and other engine related things. Even though i don't think i have any symptoms that would justify that.

The cost is in the thousands and i cant afford that even at non dealership mechanic rates nor can i do a lot the work my self due to lack of tools work schedules etc. Does anyone have any idea or experience with this issue? Its getting bothersome and want to get this thing mechanical good but its one thing after another. My pocket book might not be able to afford this thing if things keep going wrong. And of course i cant get it to act up to post a video either. Go figure. Sorry if this is all over the board tried to give as much info as possible.


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Check your distributor and clean your MAF.. I had the same problem and doing that fixed mine

 

[mrb5314]

I know there are a lot of folks smarter and much more familiar with how this stuff works than me. With that said, I will tell you what happened to mine and maybe you can use the info to help your issue.

First, which I am surprised at, is no one has mentioned the throttle body. I have had to replace mine and it had similar symptoms.

Second, this is what I was referring to. I had an issue with the AC. It would work intermittently. It got to where it would work as long as I was accelerating. I had it vacuumed down and recharged a couple of times. I had the pressure switches changed. I dealt with it in and out of shops for a year. it got to where it would only work when I made left turns. Crazy right? I thought so. Me being the crazy one.
I finally took it to a dealer where I knew someone and told them not to give it back until they figured it out and fixed it.
Two days later, they said they fixed it. They said they had their tech work on it all day for two days straight trying to figure it out.
What happened was when the engine was installed originally (had 180,000 on it at this point) the wire loom that leads to the compressor was resting near the engine mount, exhaust area. So, over time, it stretched slightly, the look wore off, then the sheathing on the wire wore off, which in turn allowed the wires to touch the frame. So when I would accelerate or make a left turn, the engine would shift slightly, allowing it to "un-short" itself letting the AC work for a second or two. The engine would shift back, short it out, and bang. No more AC. It wasn't a difficult fix. Some solder and tape and was good as new. No problems since.

Moral of this is it may not be an obvious problem, especially when it seems like you have tried a bunch of stuff. Start checking other things to make sure there isn't something stupid pinched, shorted, or otherwise in the wrong place causing your problems. Hope this helps and I can't believe it if anyone read all the way through!! Lol.

 

[jiggie]

Good morning, It sounds like you are having a problem with a leaking fuel pressure regulator. Normally with this problem, the engine will start easily when cold because rich mixture is needed for starting, but when it is warm the excess fuel makes it difficult to start. The regulator is mounted to the fuel spider under the upper plenum. if the throttle body is removed it won't be visible but an inspection, possibly with a flixible camera will reveal a washed area on the lower manifold just below the regulator. If you see this then the regulator is leaking and causing hard starting when warm.

Thats what the thought is. I dont have any hard starting though. Fires right up every time.


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[RFC]

Its a lean backfire and bucking and no power, looks like it needs a mass airflow sensor, it won't set a code for a mass airflow sensor in the old/ new body styles in those years. The reason I know this is I spent 2 years trying to figure it out my personal one and I worked for GM at the time and Techline did't know how to fix it and I had replaced all the parts you did. If you have a K&N air filter the oil gets on the sensor and it can create the problem also. Hope this helps.

 

[nathanhanover]

***lengthy post just forewarned!! Lol***

Hey all! So we're discussing my 99 obs gmc k1500 burban with the 5.7 4wd sle. Had the cat issue "taken care of"ie removed till i can afford a full exhaust with high flow cats, because i was told that they were the cause of my catalyst efficiency below threshold bank 1 and 2 codes and the reason why its boging down backfiring and acting crazy for the first 30 seconds when I go to drive after work in the morning or anytime it sits for a while. After i feather the gas a bit it goes away and runs fine. We Changed the o2 sensors about 6000 miles ago when i first bought it along with intake gaskets, t stat, belt, transmission issues fixed u joints,shocks and other things. This was all done at the chevy dealership I worked at.

So i took it to the chevy dealership in my new town to get it diagnosed and they found 5 codes. 4 of the catalyst efficiency codes and one dealing with the fuel system running lean. Vac leaks is the first thing that came to mind said the tech So they hooked up things to check fuel pressures, checked plugs wires vac lines etc. everything came back normal. They used 1/4 tank of gas driving it today lol. So they called and said they couldn't figure it out so they took it to the gmc dealership and had their tech check it out and nothing different. They reproduced the issue but no new codes show up when it happens or anything to alert them of whats going on.

So They want to just throw a bunch of parts at it and see what happens. The parts include a upgraded fuel spider conversion, fuel pump and fuel filter(the fuel filter was done 6k ago) plugs wires and cap or what ever i have and checking and removing every vac line and replacing as needed and all new sensors ie tpms iac mass air flow etc. and thats along with a brake booster and master cylinder for the brakes because of the hissing noise it has and that separate issue. They said if they replace all of this and and it still does it then ill be looking at a engine tear down to check for cracked heads and other engine related things. Even though i don't think i have any symptoms that would justify that.

The cost is in the thousands and i cant afford that even at non dealership mechanic rates nor can i do a lot the work my self due to lack of tools work schedules etc. Does anyone have any idea or experience with this issue? Its getting bothersome and want to get this thing mechanical good but its one thing after another. My pocket book might not be able to afford this thing if things keep going wrong. And of course i cant get it to act up to post a video either. Go figure. Sorry if this is all over the board tried to give as much info as possible.


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Sell it and buy one that's good.

 

[nathanhanover]

Sell it and look for a Tahoe that's solid running.

 

[jiggie]

Sell it and look for a Tahoe that's solid running.

If i could afford it i would lol. Id love to have a 05 burb with the ls engine and long wheel base like I have now.


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[jiggie]

Good news yesterday from the dealership. They are confident that I have leaking injectors. The feel that the spfi to mpfi and nee plugs wires coil cap and rotor will fix the issues. So going to do the inexpensive stuff first. Other than that the t case seal front end stuff ie ball joints tie rods etc and fluid flushes is all it needs. Hopefully this is the end of it.


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