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C4 1.4 hard to start and keep going
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Author Post
Inna   
Thu Apr 02 2026, 07:49pm
Member No: #51409
Joined: Jun 12 2018
Location: Ireland
 Hi there,
my trusty C4 Coupe has developed an issue over the last few weeks.

It’s hard to start when cold but will eventually start after 3 of 4 goes of the key. Runs fine then until I rev it and then stalls or revs go low then recovers back to normal. Weirdy no lights or codes on Diagbox. Can hear the fuel pump.

I’ve changed the fuel pump, camshaft sensor, coil pack and spark plugs but no different. Have the noticed the engine does shake a bit sometimes. No mayonnaise under the oil cap but small about of white smoke when revving. Have checked and changed the engine fuse box BSM but no different.

She’s a 1.4 16v petrol. Any help or suggestions would be massively appreciated.
Ap0qalypto   
Fri Apr 03 2026, 07:52am
Member No: #52161
Joined: Sep 21 2018
Location: Republic of Serbia
 Check for air in the fuel system, also if you are loosing coolant
Nickbrown123   
Thu Apr 09 2026, 11:12pm
Member No: #61140
Joined: Sep 03 2023
Location: Zagreb, Croatia
wrote ...
It’s hard to start when cold but will eventually start after 3 of 4 goes of the key. Runs fine then until https://atelierrebul.hr/shop/category/mirisi-za-dom-difuzori-23 I rev it and then stalls or revs go low then recovers back to normal. https://fmctel.com/sl/opticni-kabli Weirdy no lights or codes on Diagbox.

That's a frustrating set of symptoms, especially with no codes showing up. Since you've covered a lot of the common culprits, have you checked the engine coolant temperature (ECT) sensor? A faulty one can often cause issues with cold starting and fuel mixture, leading to stalling or rough idle, without necessarily triggering a fault code right away. It's relatively inexpensive to replace and worth considering.
Nickbrown123   
Fri Apr 10 2026, 12:09pm
Member No: #61140
Joined: Sep 03 2023
Location: Zagreb, Croatia
That's a very solid suggestion, Nickbrown123. Inna, if the ECT sensor doesn't prove to be the culprit, it might also be worth inspecting the throttle body for carbon buildup or diligently checking for any vacuum leaks. These can often lead to similar symptoms without triggering fault codes.
Nickbrown123   
Fri Apr 10 2026, 12:20pm
Member No: #61140
Joined: Sep 03 2023
Location: Zagreb, Croatia
That's a truly puzzling issue, especially with no fault codes appearing. Considering all the components you've already addressed and the excellent suggestions regarding the ECT sensor and potential vacuum leaks, it might also be worth investigating the crankshaft position sensor. An intermittent fault with this sensor can often lead to difficult cold starts and stalling under load, even without immediately triggering a diagnostic trouble code.
Nickbrown123   
Fri Apr 10 2026, 12:26pm
Member No: #61140
Joined: Sep 03 2023
Location: Zagreb, Croatia
This is indeed a tough one without codes, especially after replacing so many components. Building on the excellent suggestions already made, it might be worth diving deeper into the fuel delivery system. Sometimes, an intermittent issue with the fuel pressure regulator or even partially clogged injectors can manifest as these exact symptoms when the engine demands more fuel, causing it to struggle or stall without necessarily throwing a code. A comprehensive check of the fuel system's integrity could reveal something subtle.
Nickbrown123   
Fri Apr 10 2026, 12:37pm
Member No: #61140
Joined: Sep 03 2023
Location: Zagreb, Croatia
That's a truly baffling problem, especially with no diagnostic codes. Since you've already covered so many key components and checked for various leaks, it might be worth taking a look at the Mass Air Flow (MAF) sensor. A dirty or intermittently failing MAF can sometimes cause these exact symptoms—difficult cold starts and stalling under load due to incorrect air-fuel mixture—without always triggering a fault code.
Ap0qalypto   
Fri Apr 10 2026, 03:32pm
Member No: #52161
Joined: Sep 21 2018
Location: Republic of Serbia
 @Nickbrown123 are you a bot?
 

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