Running rich after replacing all injectors

[RocketcCutlass]

Ok so all sensors have been replaced a while ago except crank sensor. Plugs and wires done as well. All GM/AC Delco parts. I replaced all injectors last week and it’s running super rich. So much so it through the P0172, P0175, and P0420 low catalyst efficiency codes this morning. What’s weird is I put the range afm disabler on right after running it monitoring the fuel trims the day I changed the injectors and it didn’t throw any codes at all after a couple hundred miles of driving. This morning on the way to work, just a 10 mile drive, is when it threw the codes. It was only after taking off the range module to monitor the fuel trims to see if it learned new ones. I had been driving all week with the range module on with no issues. I’m wondering if the range module is adjusting the fuel trims enough to stop it from throwing codes. Also it run’s absolutely fine and smooth as butter. Oh and I also did a crank sensor relearn, fuel trim relearn and all the other relearns I could do with my innova tool. Any ideas?

 

[swathdiver]

Both banks rich and it threw a dead cat code for one side. It may need some time to adjust. Did you pull a plug from each side?

What year and engine are you driving and what is the part number of the injectors?

Have you run any Long Term Fuel Trim graphs while idling and driving? I'd be looking for vacuum leaks too.

 

[RocketcCutlass]

It’s a 2011 Tahoe LMG 5.3. The injectors were the factory GM ones that I bought new from rock auto and matched the numbers of the ones I pulled off. I didn’t graph the fuel trims but they stayed at -30.5 driving on both banks and went down to -25.2 when idling. I did not pull a plug. The exhaust doesn’t smell rich and like I said it runs extremely smooth.

 

[swathdiver]

It’s a 2011 Tahoe LMG 5.3. The injectors were the factory GM ones that I bought new from rock auto and matched the numbers of the ones I pulled off. I didn’t graph the fuel trims but they stayed at -30.5 driving on both banks and went down to -25.2 when idling. I did not pull a plug. The exhaust doesn’t smell rich and like I said it runs extremely smooth.

Ok, so the injectors are 12613411 or 217-3411? That's the current number anyway.

Having said that, those trims are the sign of a massive vacuum leak. Can you see the color portion of your intake gaskets? Did you check all the connections between the air cleaner and the throttle body? No connectors on the top of the intake were forgotten? Brake booster line?

 

[RocketcCutlass]

It’s not running like it has a vacuum leak. Also I put the range module back on and the fuel trim codes went away on their own after just 15-20 miles of driving.

 

[RocketcCutlass]

I guess I can spray some brake clean to check for one. It seriously is smooth

 

[GranPrix]

Call Range and see what they say, maybe they've seen this before..

 

[RocketcCutlass]

You were right. Big intake leak. Crazy cause it runs so smooth lol.

 

[Geotrash]

You were right. Big intake leak. Crazy cause it runs so smooth lol.

Yup. Happens on these that they run smooth with a vacuum leak because they can do so much to compensate. Where did you find the leak?

 

[RocketcCutlass]

It’s either an injector seal or the intake manifold. I’m going to pull it and seat the injectors on the manifold properly off the car and just replace the gasket while I’m at it. How common is it to replace the upper intake gasket?

 

[Geotrash]

It’s either an injector seal or the intake manifold. I’m going to pull it and seat the injectors on the manifold properly off the car and just replace the gasket while I’m at it. How common is it to replace the upper intake gasket?

Not common but it's relatively easy.

The thing that seems to trip people up with getting the manifold off is forgetting to release the fuel pressure in the fuel rail (key off, obviously) before trying to get the fuel rail separated from the fuel line. Removing the manifold is a 20 minute job once you've done it a few times. The gaskets themselves clip onto the bottom of the manifold and should be reusable, so unless the manifold were removed to do the injectors, I would suspect a torn or improperly seated injector o-ring.

 

[Fless]

Probably not this, but think about checking it to rule it out: read the alcohol content of the fuel. If you have a flex fuel engine and are not running E85, and the alcohol content reads more than 10%, reset it. That will also reset the LTFTs (which I see you've already done).

 

[RocketcCutlass]

So it’s a seal. When I was spraying the intake what I couldn’t see is the brake clean was pooling up over the intake and getting sucked through the injector seal in the intake. It’s annoying cause I lubed the seals before putting them in. Oh well lol.

 

[Geotrash]

So it’s a seal. When I was spraying the intake what I couldn’t see is the brake clean was pooling up over the intake and getting sucked through the injector seal in the intake. It’s annoying cause I lubed the seals before putting them in. Oh well lol.

Thanks for following up and I'm glad you have your smoking gun!

 

[RocketcCutlass]

Alright… it’s still doing the same thing. I doused the intake and injectors in brake clean and there’s definitely no vacuum leak in that area now. I checked around for other leaks and I don’t see anything. When I put the range module in thought all is well. I don’t get it.

 

[Geotrash]

Alright… it’s still doing the same thing. I doused the intake and injectors in brake clean and there’s definitely no vacuum leak in that area now. I checked around for other leaks and I don’t see anything. When I put the range module in thought all is well. I don’t get it.

It's probably worth a call or email to Range to see what they say. My guess is that the Range device only masks the problem by suppressing the code that would throw the CEL while it's plugged in. They've made a number of firmware updates to the devices to prevent the CEL in certain scenarios.

Did you investigate @Fless 's suggestion above? Another possibility for a vacuum leak is the vacuum brake booster hose - are the connections tight on both ends? It could also be as James suggested that with the new injectors you have better fuel flow and it will take a while for the mapping tables to update themselves and 'settle down'. Should be no harm in driving it a week to see.

 

[RocketcCutlass]

I’ll give it a try with the settling down. All of the connections are good. I can’t think of anything else it could be.

 

[lgrw2288]

Just curious, how much did you spend on the injectors? I only say this because I went through an issue where I had constant lean codes that should have pointed to an intake leak, but in the end it was counterfeit ACDelco injectors. Pissed me off to no end with how much testing I did (the “OEM” injectors that I bought even passed the resistance test too). I put my old ones back in and no more lean codes.

 

[RocketcCutlass]

I ordered the GM ones from Rock auto. The have the GM part numbers on them. The numbers matched the originals. I reseated the intake and retorqued it. Emptied a can of brake clean on it again. Nothing. And now there’s a hesitation off the line. It’s getting aggravating.

 

[RocketcCutlass]

Alright… after driving forever it’s running rich on both banks. There are zero vacuum leaks. Is it really just the injectors flowing way more than it’s used to? I don’t know what I could be missing.