B5 s4 only starts when engine is cold

[Glennb]

My b5 will only start when engine is cold and turns off when driving sometimes. When it does turn off I need to wait until the engine is completely cold to turn back on. Also, my rpm has a lot of lag, it will shoot up and have no engagement with the engine for about 1 second and then it will engage.

I haven't used a scammer or vag com because I can't get one until later this week

I hope I don't need to take it to the dealer

[Trb1]

Sounds like a coolant temp sensor. Has no idea what the engine temp is so it defaults to really rich mixture no matter what.

[Glennb]

Yeah I've been told that thank you

[das4]

crank sensor maybe. scan will ultimately be your best bet here

[2.8L]

I also vote for crank sensor

[2.8L]

Sounds like a coolant temp sensor. Has no idea what the engine temp is so it defaults to really rich mixture no matter what.

Car would still run

[Trb1]

Car would still run

Not necessarily. Warm starts can sometimes be really hard. Depending on conditions it won't always start.

[Peter1.8t]

CPS. Search.

[MyXbfS4]

i vote crank sensor also, the exact same thing you're describing happened to my b5 and then my bf's and thats what it was.

[jpulll]

my buddies Benz back in the day had the same issue. turned out to be crank sensor.

[auditrackspeed]

Car would still run

not true my old s4 would not start on due to coolant sensor

[dubzackvr6]

Crank position sensor.


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[geeky]

They're both cheap and easy to replace. Do both.

[Jesse_Boyer]

crank sensor maybe. scan will ultimately be your best bet here

I also vote for crank sensor

i vote crank sensor also, the exact same thing you're describing happened to my b5 and then my bf's and thats what it was.

my buddies Benz back in the day had the same issue. turned out to be crank sensor.

Crank position sensor.

Same problem, same result (CPS.) Mine gave a code for CPS failure as well.

If you can't scan it, apparently cranking the engine over and watching the tach fail to move would indicate a lack of signal from the CPS.

[christianb5s4]

not true my old s4 would not start on due to coolant sensor

Ditto. When mine failed, the car would only barely run if I gave it gas. Would die or not start if I didn't, I agree though sounds like a crank position sensor. Do both though, coolant temp sensors are a known failing point on these cars and is super cheap/easy to replace.