[Modphase]

Hey everyone, new member here. I have an '02 Firebird with a 3800 Series II. As of late, I've been getting a trouble code for a misfire in cylinder 2. I've already replaced plugs/wires/coils but it's still misfiring, so I want to check the cylinder's compression next. I borrowed a compression gauge from O'Reilly, but the thread size on it was too big to screw into the spark plug hole. Is anyone aware of a compression gauge that'll fit that I could buy without breaking the bank?

 

[dezldave961]

Typically, they should come with the extension to get into tighter spots that most engines have. Our plugs are a very common size, so the loaner gauges should have a proper end available (or that specific store lost theirs).

Also, I'd check to see if your coolant system is holding pressure or leaking past the intake gaskets in that area. I'm doing a replacement for a coworker's 3800 Camaro right now due to old stock ones, putting updated aluminum gaskets in to seal the passages again. Water doesn't like to let fire happen as easily, too.

Compression in these engines tends to only goes bad in rare occasions that you did some significant damage. These iron block, iron head setups are pretty stable unless you overheat them or overboost them in stress conditions.

 

[digitalgpbandit]

I would be leaning more towards a fouled injector than a compression issue on the L36, unless as dezl said you somehow did some significant damage.

 

[Modphase]

Typically, they should come with the extension to get into tighter spots that most engines have. Our plugs are a very common size, so the loaner gauges should have a proper end available (or that specific store lost theirs).

Also, I'd check to see if your coolant system is holding pressure or leaking past the intake gaskets in that area. I'm doing a replacement for a coworker's 3800 Camaro right now due to old stock ones, putting updated aluminum gaskets in to seal the passages again. Water doesn't like to let fire happen as easily, too.

Compression in these engines tends to only goes bad in rare occasions that you did some significant damage. These iron block, iron head setups are pretty stable unless you overheat them or overboost them in stress conditions.

Thanks for the advice. I was able to borrow a compression gauge that fits and I tested all 6 cylinders. Compression seems fine. It's interesting that you mentioned the intake gaskets, because yesterday when I was doing some research I discovered that that's a common problem with these engines. That's probably the last thing I'd want to have to fix, so I'll continue doing some tests.

Since we're on the subject now, I might as well go into more detail about how the engine is performing, and maybe you can give me some pointers. Basically, when I accelerate at WOT, the engine will only rev to 4-4.5k before the car starts to bog down. The revs will drop, and if I let it go long enough I'll hear this awful ticking sound, and usually the check engine light will flash.

 

[dezldave961]

Ya, don't beat on a hurt engine. That's essentially Rule#1 of taking care of them. If you already know it's not right, troubleshooting doesn't involve more abuse (moving or parked).

Intake gaskets are pretty straight forward, especially on F-body 3800's. I never dismantled that configuration before this week and had it apart in ~2-3hrs while letting the young owner help. There's YouTube videos for FWD and maybe RWD versions of this task, and the only difference it where some bolts are for things.

 

[schlimthecarguy]

that sounds an awefyull lot like a cat partially clogged

when power starts to drop off youll see the intake MAP on the scanner will read atmospheric pressure even at 50% throttle from the exhaust restriction.

you can remove the upstream O2 and install a backpressure gauge or leave it out and do a quick 4500rpm run, be carefull though