Rough RS4 start upon cold

[Jism]

Hi.

My B5 RS4 Avant gives a rough start upon cold, takes sometimes longer to 'crank' and eventually start. Replaced the Coolant sensor on the back of the engine, is this the Engine speed sensor otherwise that's causing this?

Other then a rough start when cold it works seamless.

[vavJETTAw36]

Check your fuel pressure. If the rs4 uses a 4 bar fpr, pressure will be 61 psi/68 fpr unplugged. Then turn off car and check pressure. Should only bleed 10psi in 10 minutes


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[Jism]

Fuel pump is brand new, installed a 6 to 8 months ago. Shoud'nt be the problem.

I've heard engine speed sensor that might cause this.

[vavJETTAw36]

It's the check valve that goes bad and causes this issue.


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[christianb5s4]

It's the check valve that goes bad and causes this issue.


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You're referencing the check valve on the pump? If so, that wouldn't cause his hard starts just at cold, it would cause longer cranking at any engine temperature after the car has sat off for anything more than 15 minutes (aka the time it takes for fuel pressure to drop with engine off).

[Jism]

I got told Engine speed sensor, or a sensor that's on the front of the engine (HALL) or whatever.

Coolant (green one) is replaced. This did'nt fix it. It's not a real issue, it still starts and runs perfectly fine, just upon cold it takes a little longer to crank. No error messages so far.

[landfill]

Once the CPS is completely dead your
car will no longer start. To rule that out
you need to do some diagnostics. Take
your multimeter to the speed sensor aka
crankshaft position sensor. Check your
reference voltage as well.

[landfill]

Or a scanner with a built in probe can
moniter the CPS for you and tell you if
it's acting up.

[Jism]

CPS was replaced at the time back when the fuel pump was replaced.