Really rough Idle

[jonmon6691]

I started my SHO up in a parking lot today and it started idling very
low at around 450 and the throttle kept pulsing itself up to 800ish.
If I pushed the throttle it idled up normally but when it went back
down, it would idle like real low again. So I checked the KOEO codes
right there and the only one was a continuous memory code of 528. The
book says that is a clutch switch relay failure. So I drove it home
and did the KOER codes and everything passed. I also did a cylinder
balance test which showed that cylinder 2 failed but when I ran the
test again I got code 90 (all pass.) the book says that a failure,
then a pass is an indication of a weak cylinder, not a dead one. I
should also note that the car has 189k miles on it and it is 9k miles
overdue for the 3rd 60k (The previous owner said he did the first 2 on
time.)

What do you think the problem is, or do I just desperately need to do
my upper 60k?

PS There has been a faint clicking sound coming from the upper part of
the engine that has gotten quite loud over the past few months, I'm
guessing this is a valve train noise and is another indication of
needing that 60k.

Thanks

 

[jonmon6691]

Anyone?

 

[Eastcoast SHO]

maybe bad injector

 

[itwonder]

Check for water and oil in the plug wells. If that checks out okay, I would swap in known good coil pack.

 

[jonmon6691]

It doesn't happen every time I start the car. It has happened 2 more times since I wrote that, and I am beginning to think it might be the feul pump. I can tell when it will happen because instead of the normal whine from the fuel pump it does a sort of muffled gurgling noise. It also sound like hissing air coming from the engine.