96 burb 7.4 misfire after 5.0 injectors

[BeXtreme]

Also, the plugs, wires and distributor were not changed. only FPR and injectors.




Regarding the test. Do i test this around the plenum where gasket meets lower intake or lower intake? (This question may sound dumb after what I just explained the missing hoses lol).

Fix all of your vacuum leaks first before you do anything else. Once you have NO MORE VACUUM LEAKS, then reset the computer and try again. If it is still having misfire and fuel trim issues, then you need to spray along every parting surface. Throttle body to manifold, upper manifold to lower manifold, lower manifold to cylinder heads, etc....

If the engine RPM changes while you are spraying a specific spot, you found a leak.

 

[RichLo]

I'm not replying to these correctly. sorry...

I had the negative terminal off yesterday and back on before starting and pulling recent data. I read somewhere that you pull the positive off and touch the two cables together to reset?? Or is negative off sufficient?

I dont want to condone touching the positive cable to the negative but it seems logical to discharge all capacitors. I just let the battery sit unhooked for an extended period to reset the computer... Overnight should have been enough. Maybe if you dont want to do the cable touch thing you can try unplugging the ECU overnight also in case there was something residual feeding the system like a larger radio capacitor or something.

 

[Tan1998K2500]

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This is the intake side of the PCV system on the right side of the engine, you definitely need that elbow there otherwise your engine and intake manifold will just suck in all sorts of air that it shouldn't be

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This is the outlet side of the PCV system with that plastic hose with two rubber ends on it. On the engine side, you have the PCV valve and then on the intake manifold side, it'll just be pulling air from there if it isn't connected as well. The other thing I would double check is the little vacuum line for the FPR. Verify you reconnected it and verify the line is in good condition because I know mine was literally falling apart when I bought the truck

 

[mehcs]

Has it set any codes or did i miss that?

not getting

Fix all of your vacuum leaks first before you do anything else. Once you have NO MORE VACUUM LEAKS, then reset the computer and try again. If it is still having misfire and fuel trim issues, then you need to spray along every parting surface. Throttle body to manifold, upper manifold to lower manifold, lower manifold to cylinder heads, etc....

If the engine RPM changes while you are spraying a specific spot, you found a leak.

Do you have an idea what this is?
And the one below? Missing both when purchased truck and ran fine prior.

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[mehcs]

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This is the intake side of the PCV system on the right side of the engine, you definitely need that elbow there otherwise your engine and intake manifold will just suck in all sorts of air that it shouldn't be

You must be registered for see images attach

This is the outlet side of the PCV system with that plastic hose with two rubber ends on it. On the engine side, you have the PCV valve and then on the intake manifold side, it'll just be pulling air from there if it isn't connected as well. The other thing I would double check is the little vacuum line for the FPR. Verify you reconnected it and verify the line is in good condition because I know mine was literally falling apart when I bought the truck

Hi There, confirmed those are both connected. Just reposted pic of the dang green check valve that i'm missing. starts in the charcoal canister. the other one is on top of the manifold, has small right angle boot with small 1/8" ish plastic line.. Have another dangling from passenger side firewall. not sure what that is or if they go together. i try to take better pics. pulled those off internet.

 

[Tan1998K2500]

Hi There, confirmed those are both connected. Just reposted pic of the dang green check valve that i'm missing. starts in the charcoal canister. the other one is on top of the manifold, has small right angle boot with small 1/8" ish plastic line.. Have another dangling from passenger side firewall. not sure what that is or if they go together. i try to take better pics. pulled those off internet.

The green check valve is a pressure testing location for the evap system, nothing connects to it unless you're pressure testing.

Do you have a vacuum brake booster on your truck by any chance because that might be it. I don't have a connection point there or on the firewall but I have hydroboost brakes

 

[mehcs]

The green check valve is a pressure testing location for the evap system, nothing connects to it unless you're pressure testing.

Do you have a vacuum brake booster on your truck by any chance because that might be it. I don't have a connection point there or on the firewall but I have hydroboost brakes

OK, the green is missing for me. the two lines are not connected. Just dangling.

not sure about vacuum brake booster.

 

[mehcs]

the second pic is the line going into the firewall. There's two there, one looks like a rubber hose that drops down. the other that's broken is plastic.

 

[Tan1998K2500]

I do believe those should be connected. After some researching, the suburbans have a heater control valve for the rear a/c and heat and it's vacuum operated off the manifold. Which would explain why my truck doesn't have that connection or that line. So if you can, connect the line

 

[mehcs]

I do believe those should be connected. After some researching, the suburbans have a heater control valve for the rear a/c and heat and it's vacuum operated off the manifold. Which would explain why my truck doesn't have that connection or that line. So if you can, connect the line

I can connect for sure.... would this be contributing to my potential/likely vacuum leak?? Same question for the missing check valve for evap..
Thanks for your help.