Sucessful replacement of intake gaskets w/knock sensors

[Nicholas McKay]

Here's a brief summary of the issues I was having with my 04 Suburban 1500 Z71 with L59 5.3L Vortec.  I have owned the vehicle for a couple years and always thought there was something "off" about how it idles and performs, especially during the winter.  Due to my limited mechanical knowledge up to this point, I didn't think it was a big deal.  A couple weeks ago, I decided to buy $30 code reader from Amazon.  Within 24 hours, I had many codes pop up, and eventually I found a single issue to fix all of them.  Codes included, knock sensor low voltage bank 2, too lean on both both banks (most consistent code, bank 1 and 2 always showed up together). heated O2 sensor resistance 1 bank 1, random misfire (only once or twice), MAF low voltage, and something about the transfer case I think only once.  I found a video on youtube after searching "lean on both sides 2004 Suburban" and got basically an exact match for my vehicle and it also had the same problem, which is very common on the Vortec engines...it was a bad intake manifold gasket, and by the looks of it, it was the original (I have 288,000 miles).  I'll try to put the pictures in order from the start of the project to the finish.  I cleaned up the heads, and valley pan, changed both knock sensors and the harness, bench tested my MAP sensor and all fuel injectors (hooked up to 12v power supply and shot carb cleaner through them), and power washed the intake manifold.  I left the factory foam on the intake manifold, but I also used sealant to create open (horse shoe shaped) dams around the knock sensors and a line directly underneath each piece of foam to help complete the seal that should have been there to begin with.  Very important: USE FEL-PRO BRAND GASKETS!!!  Many people say they don't fit right, but you just have to make sure that the area around the bolts that they hook around is clean so that they can snap all the way on.  The alignment may look slighly off, but I think it has something to do with how the cylinders are angled.

 

It took me about 3 days, 4 hours a day from start to finish.  When I finished tonight, I primed the fuel lines a few times and checked for leaks, since I removed the rails and injectors because the plastic quick disconnect tools suck.  Well, the smaller size worked on the small line, but the bigger one was not thick enough to get the clips to release.  I was not prepared for the amount of fuel that would come out and I had a propane heater within 3 feet of the vehicle so BE CAREFUL!!  I almost killed myself jumping off the engine and getting my pants caught on the hood latch in order to quickly turn off the heater.  Anyway, I only had to turn the key once for 2 seconds and it started right up, then sputtered for about 10 seconds (no accelerator needed), then seemed to flatten out.  I could no longer hear a hiss coming from the engine bay and it just sounded "healthier".  I took it for a drive and noticed a HUGE performance gain.  I have never felt this much power come from this vehicle.  I would say before the repair, I was only getting 230hp.  Now my guess would be around 285hp.  From the factory, the L59 should produce 295hp.  After starting the engine and before the drive, I got one misfire cylinder 5 code, but I'm assuming it was probably just an air bubble from the fuel lines since the code did not show up again, nor did any other codes for that matter.  I am very happy with how this repair turned out, since the only part I replaced before the intake gasket was the throttle body/IAC assembly, which had a part inside of it rattling around that shouldn't have been, but it hardly made a difference.  About six months ago, my mechanical knowledge was limited so an average grasp of vehicle wiring and electronics a and beginner level grasp of engine mechanics.  Since then, I've just been Googling and YouTubing like no other.  This was by far the most advanced repair I've done to date.  Before this, the biggest repair was a battery, alternator, idler pulley, and belt replacement.

 

I finished up by degreasing the most visible parts of the engine to increase the satisfaction I had already gained from this incredibly fun learning experience.  Also, thank you to all who have been following my posts and for the helpful responses.  I'm sure I will be back soon enough!  The other forums are terrible and I found no help on any of them.

 

I have no idea why it won't let me add photos (something about a 4.88mb limit, but my photos are all around 2mb), so I'll attempt to add them in a reply.  I hope it's not against the forum rules.

 

 

 

[Nicholas McKay]

[Nicholas McKay]

Well I decided to only use 5 photos instead of 8 since I'm sure the site admins don't appreciate what I'm doing, but that post took forever to write, so I decided to make an exception for myself 

[Tahoe02]

You did a great job and thanks for posting the pics. Wow what a difference. Congrats on having a limited amount of mechanical knowledge and tackling that repair by yourself and for being quite successful. Glad you didn't burn your house down and the part about getting your pants caught on the hood release was quite amusing. May have made a great video for " Americas funniest video".

[diyer2]

I quote my dad,

"Can't never could do until you try"

Good job.