Quote:
Originally Posted by Rundtinden
The car has done 130 000 km.
Stock air filter.
Mods: Plenum is from Pedro with a splitter in it. Throttlebody from an early 996. Stainless steel exhaust and headers. Underdrive pulley. This configuration worked fine until I put it away for two years.
Has changed the plugs, inspected the coils, changed oil, filter and air filter. New waterpump and coolant. Changed a sleeve with a hole in it. Has checked twice with start gas, cannot find any more vaacum leaks.
It was stored with very little fuel in it. Have not changed the fuel filter yet.
Will try clean the MAF and change the filter tomorrow.
The car now idles at around 900 rpm. Up and down maybe 100. When I have driven for a bit the idle seems to rise to about 1200. Then settle down again if I hit the throttle for a second.
At 2500 rpm and above I cannot detect any misfires. With light throttle and below 2500 I can hear and feel less than smooth operation from the engine.
With full throttle it picks up speed fast without any detectable misfires.
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Classic intake air issue symptoms.
I believe you either have a vacuum leak.
An issue with the MAF.
Or an issue with the IACV = intake air control valve.
The IACV bypasses air around the throttle body butterfly so the engine can idle properly. They are fairly simple and can stick and hang up.
They can be disassembled and cleaned.
You can try cleaning the MAF use only cleaner spray made for MAF'S
Don't touch any part except the MAF housing.
If that does not work try unplugging it and see if it idles differently.
If it does the MAF is suspect.
If the issue remains look at the IACV.
Also possible is a vacuum leak via the EVAP sytem or the SAI system.
Let me know how you go.
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