i have been trying to solve my cold start issue.... the car wont go into open loop when i first start it, it makes popping sounds like its flooding out but if i hold the gas (for like one minute) and "pretend" to make it run into open loop then shut the engine off. it will run in open loop with i normal high idle after i start it the second time. its been cold lately (50s-60s) but could it be something else

s5? the s5's use the coolant temp sensor to figure out if its warmed up enough to go into closed loop (about 65c), if its not working it might turn the check engine light on.



s4's use a switch in the bottom of the radiator, the wires like to get pinched under the battery box

but then why does it go into open loop after i start it again after running it for a minute. my co-workers tell me that the 255lph fuel pump is forcing more fuel through injectors since the pressure has increased.

if it doesnt have a check engine light it could be the fuel pump



it could be a bad 02 sensor too

how do i test the O2 sensor??

the test is how old is it? Replace it anyway.

damn i replaced the O2 sensor and i swapped back to the old fuel pump and i still cant start the car when its hot. i am running out of parts to replace.

Make sure ur injector seats and orings aren't leaking they tend to dry out and cause a vacume leak gave me hot start problems for the longest