can anyone help

[20vturbo1983]

hi all i dont know if im posting this in the right place but i need some help i have an a4 1.8t 2002 the problem is when started from cold all is fine but when it warms up the idle speed rises to about 1100rpm its been to audi and i now think they are just ripping me off its had a new trottle body, coilpacks, temp sensor, dv valve, vacuum lines and still the problem remains the same any help in solving this would be great cheers

[diagnosticator]

Sounds like they are just "throwing parts" at the problem. Need more information. Are/where there any fault codes stored in the engine ECU fault memory associated with the high idle speed? If there is fault codes, what are the code numbers? (Initially and currently.) The high idle speed exists when the engine is at normal operating temp, with the temp gage needle at ~half of full scale, (~12 O'Clock,) right?

[20vturbo1983]

hi yes this happens when the car is at normal temp 90c. I think the fault code says idle speed higher than expected exeeded upper limit but i will check this tommoro and post with code and exactly what it says oh ye when the fault code appears it can be cleared and it sometimes takes a few days to come back on. the problem started with the car not idleing correctly slight missfire only at idle and a fault code of pressure drop between turbo and throttle body this was solved by replacing pcv valve and a vacuum pipe and i dont have this code anymore and idle is smooth appart from it being too high. sorry this is so longwinded but have been trying to cure this for a while now and am clean out of ideas and money lol

[diagnosticator]

Make sure the diverter/bypass valve diaphragm is not leaking. Regardless of the prior parts replacements, the cause of the high idle is false or unmeasured air leaking into the intake manifold at some point on the downstream side of the throttle valve.
From what you described, the cold post start up high idle as normal, then after about 30 seconds, the idle slows to curb idle speed at ~800 rpm, then as the engine temp increases to 90c, the idle speed increases to ~1100 rpm, right? If that is correct, whatever is leaking false air into the manifold, is effected by engine temp, as in a leak getting worse as the parts heat up and expand, etc.