[durtkillon]

From what I've read on this site and others, Bosch ICV issues are not uncommon:



[color="#225985"][color="#225985"]Car won't idle[/color] [size="2"][color="#a4a4a4"]in[/color] [/size][size="2"][color="#777777"]Engine[/color][/size][size="2"][color="#777777"] - solution was to replace [/color][/size][/color]



[color="#225985"]Idle Control Valve[/color][size="2"][color="#a4a4a4"]in[/color] [/size][size="2"][color="#777777"]Electrical Gremlins[/color][/size][size="2"][color="#777777"] [/color][/size]







[color="#225985"]idle control valve[/color][size="2"][color="#a4a4a4"]in[/color] [/size][size="2"][color="#777777"]What is that noise?[/color][/size][size="2"][color="#777777"] [/color][/size]







[color="#225985"]Idle Control Valve R&R and cleaning[/color][size="2"][color="#a4a4a4"]in[/color] [/size][size="2"][color="#777777"]Engine & Drivetrain[/color][/size][size="2"][color="#777777"] [/color][/size]



They go by many names, idle air control (iac) valve, idle speed regulator, idle speed actuator, idle control valve... The failures are not unique to Bosch, but the price of the replacement part is. I suspect timing, valve health and air filters play a role in thier longevity and cleanliness.







I would benefit from a good vacuum leak test procedure for this car (hint, hint). I'm familiar with the carb cleaner method and gauge test. That would be a great write up since idle and cold start problems on these cars seem common. What are the most common leaks?

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[mdss]

My car is a manual chaps so once i clean it i will let you know i may look for a vacuum leak as flash says as to ignore flash is a silly thing i have learnt even in the short time i have been a user on this great site.

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[rl968]

ICV part isnt cheap. Best bet is to try to find a working used one. Might not be common, but mine failed and obd gave a code.

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[tamathumper]

When the ICV in my 944S went, it would run great except when I let off the gas, the RPMs would "crash" and stumble back down to idle.

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[flash]

tama - that is exactly what an ICV problem is usually like. the ICV lets more air in at idle when needed. the part that steers me away from the ICV is the cold start timing symptom.



if it were the ICV, it should not change unless it were really stuck shut, in which case it would almost certainly stall off throttle.



it's possible, but i tend to think that one of the many vacuum hoses are more likely the culprit, or the throttle body is too closed at idle to allow enough air in during the enriched period of the first 60 seconds.

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[mdss]

throttle body adjusted today with no improvement with the little screw underneath....could they have made it any smaller!



When i get a chance i'll do a vacuum check and after that the icv.

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[John]

Here's a vac. leak tester you may want to try ...



http://www.968forums.com/topic/8374-vacu...msearch__1

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[mdss]

Ok guys so i think it is sorted and this is the sequence of events.



Flash and you guys advised me that i should check the throttle position sensor which after seeing the voltage was too high we adjusted and this yielded nothing BUT i then used the screw on the bottom of the throttle body to lower the rpm slightly as it was high when warm i.e. 950rpm.



After winding the screw and the idle down one full turn the idle was just above the line below the 1000rpm gauge i assume this is about 750-800 rpm and magically this seems to have solved it.

No problems from cold and now when the revs are falling from almost cold when its driven initially the revs fall much slower as they approach a thousand and this was the region where the problem was.



So to conclude all of what flash and the rest of you clever people said was right but it seems that both the throttle position sensor and the idle control screw on the throttle body need to be adjusted so they are in harmony.#



Thanks again for all the help

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[rl968]

Glad you got it sorted. thanks for posting final result.

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[durtkillon]

This thread inspired me to check my vacuum system. Since I have a D1R SC kit installed, the vitamin bottle tester above would not work, so I fashoned one out of a 2" PVC cap and used a presta valve from my local bike shop. Total cost? 98 cents.



Does it work? Yes. Do I have leaks? Oh yeah. I hate to admit it, but the worst one was at the idle control valve. I did not have the clamps tight enough. The next worst one seems to be coming from the trottle body - new o-rings on order (6 bucks). The old ones are as brittle as a saltine. If there are other leaks, I can't tell until I get the throttle body tight.



I have a boost gauge installed, so I didn't need to install a gauge on my tester. Also, my bike pumps all have gauges, but the resolution is not that great.

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