Another possible cts issue?

[Frunzman]

Recently replaced thermostat and expansion tank on my 02 a4 1.8t. Having a new issue now along with still having shitty heat. If my car sits for approximately 8 hours (overnight or while at work) I try to start the car, it turns over for a while, starts after about 8-10 seconds. rough for the first few seconds and cel and epc light comes on and it idles a little higher at about 1200rpms. I can turn the car off immediatly, and start again with no hesitation and no epc light and 750rpms. Car heats up perfectly with no fluctuation. No overheating no stalling. Car runs great after the restart. Getting a p0420 which I believe is for 02 sensor and p1296 codes... after countless hours of research seems cts may be the culprit but many seem to have other symptoms. If the car sits for any shorter period of time and I start, it starts right up no light no issue. Anyone have any ideas???

[Frunzman]

Anyone? This is driving me nuts

[eljay]

I am no expert, but I would change the CTS. It's cheap and if it hasn't been changed, it could manifest itself with the symptoms you have.

[Frunzman]

Changed both coolant temp sensors. Pulled throttle body and cleaned it. And fixed a small vacuum leak o found. Issue still persists. Intermittent but still harder to start after sitting...

[tHatOne guY]

Had the exact same issue w/ my B5, put in a new CTS at the back of the cyl head it was fixed.

P0420 indicates more than likely a faulty catalytic converter. In the Bentley a P1296 mentions F265- Map Controlled Engine Cooling T-Stat

Have you checked the coolant temp measuring blocks just prior to starting the engine?

[87supraman]

CTS. I have the same issue currently. Fix it quick, the rough idle caused an engine mount to fail on mine.

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[Frunzman]

As I said before I did change both cts's. No change. I pulled spark plugs they look a little iffy so I will be replacing them tomorrow. Can a o2 sensor cause any starting issues? This is truly driving me up the wall...

[Let it snow]

It wouldn't be the O2 sensor in a cold start. Perhaps the fuel system is loosing pressure when it sits. Next time try turning the key to acc to prime the pump but don't start it. Wait a second and prime it again then start it. See if that changes anything.

[Frunzman]

Ok.... so I have replaced a faulty coil pack, new spark plugs, both coolant temp sensors, thermostat, and unrelated valve cover gasket and expansion tank. Still having the multiple cranks to start (intermittenly) only ever after sitting for 8 hours or more. Once started epc light comes on with 1200 rpm idle. Turn car off and on light is gone and smooth sailing until the next morning or later that day. This all started after replacing the thermostat so I did remove the throttle body again and cleaned it but still same issue. I have tried the "priming fuel pump" method but makes no difference. If it wants to start it does otherwise it turns until it's stumbles and starts usually 3rd or 4th try. Please... anyone have any ideas?

[Frunzman]

I keep reading about the crankshaft positioning sensor, but most have issues with stalling. Car never stalls.

[Frunzman]

Also I know this sounds crazy.... but if I don't drive the car,.... as in work on it. Start and let idle to ensure car runs, shut off and try to start in the morning it starts right up everytime. If I drive he car, as in go to work in the morning and try to start I'm the afternoon like clockwork I get the hard Starr and epc.... ?