I replaced the Crankcase Vent Valve last weekend and about a day after completing the job, I developed a pretty bad rough idle. I had a local parts store scan with an OBD II reader and they pulled codes 0306, 0300, 1347, and 0174. The rough idle worsened to the point that the car became sluggish while driving and was missing quite badly at idle. I removed the DISA actuator unit, cleaned it with carb spray, and carefully reinstalling ensuring the rubber gasket seated correctly. The SES code cleared right away and the car ran perfectly for about 24 hours. This morning, the rough idle returned and after a 15 minute drive to work, the car was running quite poorly with the SES light back on. What are the chances the intake actuator is shot? I have 68k miles on the car and no idle issues before replacing the CCV. I removed the actuator unit for the CCV replacement so it's quite coincidental that I now have an idle issue. I did notice while cleaning the actuator that the flap occasionally hung up after manually twisting it closed. It would stick in the 45 deg vs. full 90 degree position but I thought this may be due to some carb cleaner interfering with the bellow while wet. Any ideas on what else to check would be appreciated before I drop $200 on a new unit. Thanks.
I have seen faulty DISA valves cause vacuum leaks, which will cause idle problems. Sometimes it is just the O ring that seals them to the intake, and sometimes the bodies are cracked. Check yours for cracks, or run the car and spray the suspected intake leak area with carb cleaner to see if the idle changes. If so, you have a vacuum leak. If you have a little hand held vacuum pump you can see if the valve itself works (IIRC they are vacuum actuated) and holds vacuum. PS, if you catch stuff on fire with the carb cleaner, I take no responsibility.
I used carb cleaner to check for vaccum leaks as a first step when the rough idle appeared and didn't notice any change in RPM. The gasket appears to be fine. While driving home tonight, the SES light stayed on but the idle was noticeably better. I'm wondering if the gate in the DISA is not fully opening and closing. It didn't fully spring open a few times after manually closing it during cleaning. What is cold idle position for the valve? The static position is fully open but if I knew the gate position for cold idle vs. warm throttle, I might be able to pinpoint if it's not opening based on the engine response.
Update: I replaced the DISA which resolved the rough idle. However, the SES light is still on and throttle response is sluggish. I pulled lean codes which continue point to a vaccum leak so I removed the entire intake boot and inspected for cracks - checked out ok. The TBI was tight and I used a new gasket when reinstalling during the CVV replacment. All four CVV hoses are new and connected firmly to the valve. since this started 24 hours after the CVV replacement, it has to be somewhere on the intake and related to the parts removed but everything checks ok. The only two options I can think of are 1) the oil dipstick tub o-ring which I didn't replace. The tube was loosened and swiveled out of the way but not fully removed during the CVV swap or 2) the oil filler cap which I cleaned to remove yellow condensation build-up. Any ideas where to look next? Lean codes won't definitely point to the failed component and i'm out of ideas.
Closing the loop for the benefit of others. I gave up and took the car to the dealer this week. It took them two days, 3 smoke tests and over 4 hours to determine there are no vacuum leaks. After flashing the DME, the throttle reponse was fixed and the SES light went out. Why the DME needed reflashed in the first place is a mystery. To complicate everything, the tstat threw a code (stuck open) sometime over the past couple of weeks which also trips the SES light. That had no affect on the throttle response but obviously complicates trouble shooting why the SES light is on. The car is now running fine and I have a tstat replacement ahead of me this weekend ($70 part vs. $300 for the dealer to install.) Best of all, the dealer only charged me for one hour of labor. For once, I felt like I got a deal.
Sweet! Anyhow, beware when changing the T stat that these cars are hard to bleed. THere are 2 bleed screws I believe, and you should have full heat on defrost if it is bled properly. Keep checking that on the test drive because if the heat goes away at any time, you have an air bubble.
