Lost 200 rpm off the top end

[03mike]

Hi, felt like I fouled a plug on my 98 gtx limited, so I changed them and it runs better, but I've lost 200 rpm off the top end and it feels a little sluggish. Anyone have any ideas?
Thanks

 

[mikidymac]

Check your water regulator on the muffler, that is typically the source of the 200 rpm loss. It should not be leaking or have any holes in the diaphragm.

 

[03mike]

Thanks, I have a follow on question. Where's the water regulator and will it leak after it's been run or do you need to be running the engine to see it leak?

 

[mikidymac]

It's on the water box with the red cap and you should see dried water spots if it is leaking. Do not adjust the red button on the cap.

 

[03mike]

That looks very similar to the power valve cover. I'm guessing it comes apart the same way? And the diaphragm is inside it for easy verification?
Thanks again for your advice!

 

[etemplet]

Check your compression it shouldn't be sluggish.

 

[mikidymac]

Check your compression it shouldn't be sluggish.

Good catch, I didn't notice the sluggish part until you said that.

 

[etemplet]

Good catch, I didn't notice the sluggish part until you said that.

Ha ha, you know the more you are around these things.....

 

[03mike]

I checked the compression and it was 90 in the front cylinder and 85 in the rear. That seems really low. I'm going to check it again tomorrow with a different gage.

 

[mikidymac]

Check with another gauge. Probably wouldn’t run if it was that low.

 

[03mike]

Check with another gauge. Probably wouldn’t run if it was that low.

Finally got another another gauge and got 120 on both cylinders. Does seem correct?
Thanks