I have an '02, recent work includes intake gasket. I keep getting misfire codes from #2 cylinder. After a couple thousand miles, I am getting a loud knocking or tapping sound that sounds like it's coming from the front of the engine. I removed the sepentine belt with no effect on the noise. This happens only when the engine has warmed up, not upon start up. Compression is good on #2. After having it diagnosed as everything from bad valves to bearing noise, the last diagnosis points to the EGR valve. Any suggestion would be appreciated.

 

Are you sure you have an EGR valve?

I'm pretty sure 2001 was the last year for the EGR system.

 

At a certain point during the '02 model year, the engine was altered to not use an EGR valve. Mine does not have one, either.

 

I agree, no EGR valve, besides, they don't make noise, especially if it's not equipped

If the intake gaskets were leaking coolant into the oil, it's very possible the noise you're hearing is a collapsed lifter. When coolant works its way into a lifter, it will bleed down too rapidly, collapse, and rattle like hell. If it's an exhaust lifter, you'll still build compression.

 

After a thorough search, mine definitly doesn't have an EGR valve. Is there a port under the intake in the head from the old EGR system that has a block out plate that could be leaking? My misfire codes keep coming from cylinder #2. Thanks in advance.

 

The intake manifold does not have the EGR passages or fittings for the valve or exhaust tube.

Misfire and noise from front of engine when warm... #2 cylinder is the first cylinder on the passenger side. Remove the rocker arm cover and inspect the exhaust push rod & lifter. You shouldn't be able to move the push rod up or down by hand.... there should be zero play in the push rod between the rocker arm and the lifter.

 

I had some time today, so I pulled #2 plug to inspect. Found it to be an
AC 41-940 instead of a 41-993. I had them replaced by a local mechanic shortly after the intake gasket. Checked all the others (except #3...yea) and they were the correct 41-993. They look physically similar, but the shoulder looks slightly different on the 41-940. So I replaced it with the 41-993, and started it up. Still getting the tapping/clacking noise after warmup (4-5 minutes) but after 15 miles or so, no "flashy light" misfire signal. The noise and the misfire codes may be separate issues. I guess next I have to start pulling it apart. Should I start with the valve covers to check for a collapsed lifter or excess play in the valve train? If it is a lifter, don't I have to pull the intake anyway? Thanks in advance.

 

41-940 has been superceeded to 41-993, either one will work. To check the valve train you need to remove the rocker arm cover. To replace a lifter(s), the rocker arm cover and the lower intake must be removed.

 

I did some checking and it was the 41-932 that was superseded with the 41-993. The 41-940 I pulled out of #2 goes to a 3.4 v6 Olds and Pontiac. It also looks like a hotter plug, which could possibly help cause the misfire codes. Thanks for the responses, guys.

 

You're absolutely correct, 41-932 was superseded by 41-993, I stand corrected. On the 41-940, wrong spark plugs can definitely cause misfires.