anybody have ideas about this? car idles fine on start up once warm (about 800 rpm). when i depress the clutch the rpms jump up to about 1500, will stay there for about 5-10 seconds, then comes down to normal (again 800-1000 rpm). same when i'm driving. if i come to a light, as i'm braking and depress the clutch, rpms will drop smoothly down to about 1500, get stuck there for 5-10 seconds, then drop down to normal. all i did was clean the throttle body, throw new oil and filter in, along with a bottle of techron. no luck. the car does miss when warmed up. i'm pretty sure that's just cylinder deposits b/c car has high mileage and was abused somewhat (timings fine, plugs, wires and distrib cap are new). it also has a cylinder knock for 1st couple seconds when started in the morning till the oil gets circulating (its a beater, but its my beater)
i'd appreciate any advice...

 

It might be your IACV-AAC valve, or your O2 sensor. Describe the "knock" a little more.

 

its a "tack tack tack" sound. only happens when 1st starting the car and only lasts a couple seconds; the sound you get when the piston rings are getting worn out, leaving a little too much clearance between the piston and cylinder. i know the o2 senor is good but what's an iacv-acc valve?

 

Dont' worry, it's not Piston Slap, I get that noise too, it's lifter tick caused by oil drainback. The lifters make a loud ticking sound at startup because at night the oil drains out of the cylinder heads and they're like the last thing to get oil. Using an oil filter with a good anti-drainback valve (Purolator Pure-One, OEM) with maintain some oil pressure overnight and using thicker oil will help too (5W-30 to 10W-30). Just make sure you let the car warm up. Don't use FRAM oil filters, they are crap (to quote a NAPA store owner). IACV-AAC is the Idle Air Control Valve with an Auxiliary Air Control valve attached to it. It controls idle stability and adds a little power when you do things that create a slight power drain, like use the power steering, brakes or AC while driving. Do a search on "AAC valve", "IACV" and "idle control valve" and you'll get plenty of symptoms to check for. I'd say it's this since you've cleaned your throttle body and such. Check for a vacuum leak too, they'll have similar effects.

 

thanks much for the advice. preciate it much.

 

BTW, when I said 5W-30 to 10W-30, I meant switching from one to the other, I am currently doing this same thing since summer is on the way.