Changed intake manifold gaskets - now cyl 1 misfires

[JL232]

Hello,

I've got a problem w/ my 1999 Tahoe (gasoline, 2WD, 105K miles).

I just changed the intake manifold gaskets and now I have 2 problems:

1. Engine idles fast, ~1300 RPM. Code P0507 - Idle Air Control system RPM higher than expected

2. Misfire cylinder 1 - Code 0301


I have change-out the IAC valve, but no change in idle RPM.

I have spark @ cylinder 1.

I have pressure tested the cooling system, no leaks & it holds 17 psi.

Is it likely that both symptoms are caused by an air leak in the intake manifold (even though the cooling system shows no leakage)?

What else should I look for?

Any suggestions welcome, thanks in advance.

 

[haks310]

First, Wlecome to the forum.

Sounds like a vacuum leak around cylinder 1. Get some carb cleaner and spray it around the intake gasket, sure you will find it.