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That picture of the radiator cap is normal crud build up around cap and radiator neck for any liquid cooled engine. The question is, what is the condition of the antifreeze? If it is 5 years old, drain it and put new fluid in.
Very strange build up. Is your PCV Valve functioning properly????
That would be the very first thing that I would check!! Make sure that all the vacuum lines are in good shape and not cracked or deteriorated.
Use some SEAFOAM in the crankcase and do another oil change after it has had a chance to clean the crankcase and monitor at each fuel fill to see if you have any further issues.
Bill i think you hit the nail. Yesterday i found a previously repaired vaccum hose/soft rubber boot with a hole. Passenger side, approx 3/8" dia X 2" long, on the intake manifold directly behind the throttle body, runs along the top of the passenger valve cover. (what line is this?)
I replaced it and now the car is idling very low. Also, after hard acceleration, while the clutch is depressed and sometimes at a redlight, the rpms drop so low the car shuts off. Sounds like a vaccum leak or PCV valve.. THOUGHTS??
Yea that aint the water cap fellas.. and someone should drink cranberry juice; helps with the cramps..
Does the hose connect to the intake manifold or the throttle body? (not evident by your description)
It could be the PCV return to the intake...if you recently replaced it, it might take a little bit for the PCM to adjust...If it was leaking before, the new hose effectively "changes" the airflow and everything needs time to adjust. I just finished a fairly long battle with PCV hose routing and the LS7 valley cover (integrated PCV orifice AND oil separator)...and after all the wrench-turning was complete, the car stalled out a few times at stop signs, etc. after about 15 miles of driving, that condition cleared and everything is fine now...
HTH
Heres a shot of an LS1 engine with the standard LS1 PCV hoses tubibg and fittings. Theres a funky two into one coupler and that can and will deteriorate as will other rubber fittings in the PCV system:
The LS6 or 2004 engine has an entirely different PCV system and this BOOT frequently gets soft and rips and causes a bad vacuum leak. Look at the U shaped tube that goes from the valve valley cover to the fitting on the intake manifold:
Bill
After you fix your vacuum leaks, do an IDLE RELEARN to get the engine to idle correctly.
The hose was the PCV valve hose, shown in the bottom of bills picture. I replaced the hose, pcv and reset the idle. Idles better but still not smooth like it should be. Some of the other vacuum lines are not as tight as i like her, so that will be the next step. Then the seafoam. Thanks