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Discussion Starter #1
Sooo... I have another injector question...

I have a 2002 GMC LB7 with 80k miles, and the injectors were replaced at about 30-40k miles by the last owner under the warranty GM had for them (he was also the original owner). The truck smokes a little at idle when in park, and it gets worse when in drive (white smoke). I used my PPE to read the injector balance rates, and they are all within the +/- 4 number... but I have never read a thread of what it means when the reading disappears (I rev it a little, then that reading goes back to a normal 2.5ish before changing to a blank reading for the #7 injector).

I tried adding Lucas additive which didnt help... and I have ordered a bottle of Opti-Lube XPD (on its way and should arrive tomorrow). Is there anything else that I can do to extend the life since these didnt last very long, or should I get it fixed ASAP before it does some serious engine damage?

Thanks in advance, and sorry for another LB7 thread... the blank balance rate reading seemed like something new that I couldnt find in a thread search on the forum.
 

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The balance test is only for idle, the second you touch the throttle all of them will read 0s.

The correct way to test balance rates is to get the truck up to temp, set the parking brake and put it in drive, then check the rates at idle. They should be within +/-6.

If the injectors are bad, or you think they are bad, have an injector return rate test performed. If indeed you havesome bad ones rpelace them immediately.
 

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Discussion Starter #3
The balance test is only for idle, the second you touch the throttle all of them will read 0s.

The correct way to test balance rates is to get the truck up to temp, set the parking brake and put it in drive, then check the rates at idle. They should be within +/-6.

If the injectors are bad, or you think they are bad, have an injector return rate test performed. If indeed you havesome bad ones rpelace them immediately.
Thanks. I will try that this evening for sure!

The zero reading was at idle for that injector #7 which is what confused me...
 

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the TSB that was done on mine from the dealership, said it had to be within +-4%. All of mine were good and the thing still smokes like a freight train.
 

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Discussion Starter #5
the TSB that was done on mine from the dealership, said it had to be within +-4%. All of mine were good and the thing still smokes like a freight train.
How did they know what ones to replace then? Isnt it like a $700 diagnostic test?
 

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the dealership here said it was $89 to have the test done...you could buy 2 injectors from them for $700
 

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Discussion Starter #9
I just dropped the truck off last night, and the guy said "drop it off and we will take care of it for you, no problem"

I thought it was out of the injector warranty timeframe because it was a 2002, but I confirmed that he meant "take care of it" UNDER WARRANTY. We will see when he calls me back today... supposedly he said it will not cost me a penny. I have read many horror stories about this injector issue, so hopefully this will be an exception to the norm...
 

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Discussion Starter #10
Just got the call back from the service department. They said that it is not my injectors... this dealership has had GM engineers out there before to check out the issue on other LB7s, and it is considered "normal".

He also said that he mis-read my warranty, and mine was already up because it was over the 7 years.

I guess that I will just be ignoring it unless it gets worse or the truck actually starts running rough or develops any other symptoms.
 

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does the truck hard start at all? like it takes awhile to turn over and fire up?
 
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