2008 Tahoe Fuel Delivery Issue?

[NarcolepticNugget]

You didn't by chance use any downstream sensors to replace an upstream sensor? They are different part numbers.

No I didn't re-use any of the old downstream sensors. I actually just put new upstream O2's on a couple weeks ago.

 

[kbuskill]

Any chance you have a leak somewhere allowing unmetered air to enter the engine... intake manifold gaskets, broken vacuum lines... etc.?

MAP sensor issue???

 

[NarcolepticNugget]

Any chance you have a leak somewhere allowing unmetered air to enter the engine... intake manifold gaskets, broken vacuum lines... etc.?

MAP sensor issue???

I've been pondering the thought that it could be an intake issue. It has a new intake gasket on but as for the rest I'd have to check. I've been debating on just replacing the manifold. Think it'd be worth it to change the intake manifold out + MAP sensor just to rule them out?

 

[kbuskill]

I've been pondering the thought that it could be an intake issue. It has a new intake gasket on but as for the rest I'd have to check. I've been debating on just replacing the manifold. Think it'd be worth it to change the intake manifold out + MAP sensor just to rule them out?

I am not a fan of throwing parts at something in hopes that it fixes it but I would certainly be scanning it and looking at the map sensor and also checking ALL the gaskets on the intake manifold by spraying some carb cleaner or starting fluid or something around all the gaskets while the engine is running and listen for a change in the idle speed. Spray pretty much anything AFTER the MAF sensor including intake tube and boots, throttle body gasket, manifold to head mating area, vacuum lines including PCV line... etc.

 

[SLE2013]

Sound like what I was going through but not as harsh... on cold start, the engine would bog, like it's chocking. Changed out the MAF Sensor, had computer update, and Air induction service, $400 later, same thing.

I spent $11.00 on a good fuel injector cleaner for high mileage engine, and filled up using Tier1 gas stations, and the issue is gone!!! Should had done this first. -- moral of the story, I haven't filled up in low tier gas stations, and I will be putting the additive every 5K miles.

 

[NarcolepticNugget]

Sound like what I was going through but not as harsh... on cold start, the engine would bog, like it's chocking. Changed out the MAF Sensor, had computer update, and Air induction service, $400 later, same thing.

I spent $11.00 on a good fuel injector cleaner for high mileage engine, and filled up using Tier1 gas stations, and the issue is gone!!! Should had done this first. -- moral of the story, I haven't filled up in low tier gas stations, and I will be putting the additive every 5K miles.

I wish my issue would have been resolved by some injector cleaner lol. I've tried that & I run 93oct gas since that is what my tune is set for. When I'm driving and try to go WOT that's when my engine bogs down and spits & sputters, very intermittent too.

 

[SLE2013]

I wish my issue would have been resolved by some injector cleaner lol. I've tried that & I run 93oct gas since that is what my tune is set for. When I'm driving and try to go WOT that's when my engine bogs down and spits & sputters, very intermittent too.

Deng. Sorry, lol...

last thing I would do is get a computer update if anything. I did experience the WOT engine bog as well, and yes, it was intermittent.

 

[NarcolepticNugget]

Deng. Sorry, lol...

last thing I would do is get a computer update if anything. I did experience the WOT engine bog as well, and yes, it was intermittent.

No worries lol, I need all the input I can get. So far this issue has eluded several mechanics. If you're just casually cruising around it drives just fine like there's no issue. It's only if you accelerate hard or go WOT that it occurs. I swear this vehicle is a mystery box of unfortunate wonders.

 

[techbiker]

Ben,

I recommend purchasing a Tech2 or MDI. Keep the Tech2 connected and see what happens in the data log when the bog happens. Capture a few bogging events and save them.

You could then send the data log to the dealer or to a knowledgeable tuner to get their opinion. I am 95% sure you will get helpful data from a good data logging session. Your problem sounds like an intermittent issue, possibly originating from one of your vehicle sensors. Could just be a bad electrical connection that is jogged when the motor moves in its mounts.

P.S. How are your motor mounts?

 

[Nashoba]

It almost sounds like a fuel supply issue to me. Having grown up with all carburetor engines, this sounds like a fuel issue to me. If you have not changed your fuel filter, do so. If you have not dumped some fuel treatment into your tank, do so. Bad fuel with water in it was around a lot back in the sixties. When fuel in the tanks got low, water and other contaminants were picked up with the fuel and the exact symptoms you described manifested themselves. Filling the tank often mitigated them for a while but often one just had to dump a lot of STP gas treatment or alcohol in the fuel to get rid of the water. And we often had to put three or four new fuel filters on in relatively short intervals. Sometimes we had to remove the fuel tank and steam it out to get rid of the trash in it. It had to be fuel or fire issues when I was growing up. But it was simple back then. And, having watched the debacle in Oregon where no one knows how to pump gas, there could have been some diesel put into the tank that is still effecting fuel delivery. Who knows with a used vehicle?