07 5.3 vortec misfire has me stumped

[fitterjohn]

On those you normally have to use your short term fuel trim on the scanner to see if it's the intake gasket, they go lean on one bank when they get the bad intake gasket, changed tons of them. I once had a problem on an 03 5.3 like that and it ended up being that they plugs in it had way too much gap. Though it was a turboed motor, but it's free to check.

[The Extractor]

my 04 5.3 was doing similar stuff. Pull the 02 sensors and shake them, if they rattle, replace them. Fixed all my problems.

[MarkCO]

07 was the first year for the AFM (Active Fuel Management) system. This is the system that would deactivate 4 cylinders for better MPG. I have heard (on message boards) that the 07 and 08 5.3's, in particular, had problems relating to the AFM malfunctioning. Not sure exactly what the symptoms are (my 5.3 is an 04) but it may be something to check.

Based on the common problems and what you have already eliminated...AFM would be my bet. Have had a few friends that this has happened to with the 07 and 08 5.3s and they had similar symptoms.

[Martinjmpr]

The Tahoe/Yukon forum has a lot of good institutional knowledge. I would go there and post the question.

http://www.tahoeyukonforum.com/

Warning: The site is ad-heavy and can be a bit buggy.

[DFBrews]

Figured it out broken valve spring #3 intake going to swap it out and see what happens. I did bore scope the hole and it doesn't appear to have hit the piston

[ray1970]

Figured it out broken valve spring #3 intake going to swap it out and see what happens. I did bore scope the hole and it doesn't appear to have hit the piston

Good catch. I used to replace a lot of broken valve springs on the 3.8 V-6 engines back in the early to mid 1990's. I haven't heard of the 5.3 breaking valve springs. Is this a fairly common problem or did you just happen to have one fail?

[Graves]

Figured it out broken valve spring #3 intake going to swap it out and see what happens. I did bore scope the hole and it doesn't appear to have hit the piston

Soooo, I can have my parking spot back meow?

[DFBrews]

Soooo, I can have my parking spot back meow?

No.

[DFBrews]

Ray I dont know I have not had a chance to do any research on it I found it after work. ( the tahoe is sitting in my working parking I have been working on it as I have had time.

My last 3 vehicles have been 2 Subies and now a tacoma with a 1991 GMC being the last amercian car i owned. so I am out of the loop on the american engine side.

[MarkCO]

Good catch. I used to replace a lot of broken valve springs on the 3.8 V-6 engines back in the early to mid 1990's. I haven't heard of the 5.3 breaking valve springs. Is this a fairly common problem or did you just happen to have one fail?

On AFM engines, yes. Not on the others.