mark my 2000 ss down as another faulty lower intake manifold gasket thats shot.

 

Not uncommon. GM and other manufacturers used nylon intake gaskets. When you replace them, make sure to get the updated Fel-Pro aluminum intake gaskets. They cost just a little extra, but well worth it.

Intake gaskets on a 3800 are a piece of cake to do.

 

I've been trying to diagnose lean bank 1 on my 2000 SS. The long term trim is always above 16% at idle. I have checked and re-checked vacuum lines and cannot find an issue. At idle I am reading -68 to -70 kPa intake pressure. Did your intake gasket have these symptoms? I'm at the point of replacing it just to try to resolve the issue.

 

@Bryan_p88 - It's normally best to start your own thread about your problem, but here's what I can tell you.
My experience with LIM gaskets failing result mostly in lose of coolant (either going out of the engine or in the oil).

In trying to diagnose the Lean Bank 1 code have you:
- Changed the O2 sensor? These sensors do fail once in a while and should be changed I believe around 70,000-100,000 miles. If you have changed it, try to stay with an AC Delco sensor. People have been known to have issue with BOSCH sensors (I am running a Delphi myself, I accidentally ruined mine when I installed a PLOG that had junk in it). The reason the O2 sensor is important is the PCM is "tuned" to the specs of the OEM one, others may vary a little.
- In checking for vacuum leaks, how did you do it? Visual inspection? My recommendation, take a can of starting fluid, with the engine running at idle, mist the starting fluid around all vac lines. If there is a leak, the fluid with get sucked in and change the idle. Focus on that region until you pin point the problem.
- Clean the MAF sensor (with the cleaner from the parts stores). These can get dirty and cause all types of errors/problems.

 

Thanks very much for the reply. I replaced both oxygen sensors last week because they were original with 262000 kms on them, and a recent exhaust gasket failure melted the wires off one. A few months ago I bought a can of ether and sprayed anywhere I could think of with the engine running but I could detect anything. I have not lost any coolant but while checking the brake booster vacuum I noticed that the plastic tube that goes in the back of the plastic plenum had oil on it. I thought that was a strange place for oil to be!

 

Sorry I forgot to mention that I have not cleaned the MAF since replacing it last year. At idle it reads 4-5 g/s. I'll try giving it a clean though. I'm familiar with cleaning them.

 

my monte had a engine comartment fire recall, i took it to my local chevy dealer where work was completed, they found oil leak which i knew about. i asked for estimate on repair which they said was a leaking lower intake manifold gasket. $1500...yeah right. now i find out today when my wife was using my car her brother topped off fluids and put prestone in instead of dexcool, i thought oil was in my coolant but now i think its sludge from mixing coolants. i hope nothing is damaged. later today i'm going to flush coolins system. can that oil leak be coming from lim gasket or is the dealer trying to make a few bcks off me?

 

I only have 985 miles on my Monte but I already bought a new updated manifold and FelPro gasket set to have on standby. I will probably just replace at around 30-40k miles...

 

I think they are known to leak oil around the valve covers. I know mine does and I can smell it once in a while but I won't be worried about changing them unless I do the intake gaskets. Since everything will be apart anyway. Gaskets are not expensive and it's not a hard job. I'm thinking I will spend roughly $150 at the most and 4 or 5 hours since it is the first time.

 

What are the differences between the old and your updated intake? I looked on Rock Auto and they aren't that expensive so I was thinking about one for mine if I go that route.