hesitation when engine cold.

ray_r400 · Unread post by **ray_r400** » 23 Dec 2025, 22:14

hi all
I have a hesatation when my engine is cold.
the short term fuel trim is -100. all the time.
I have changed the plugs leads and coil pack and pre 02 sensor.
the b1-s2 voltage is up and down 0.100v to 0.400v.
so could this be post cat 02 sensor or injectors that is coursing the issue.
I have no fault codes.
2011 1.2 16v clio. 99000 miles
thanks Ray

Unread post by **mickthemaverick** » 23 Dec 2025, 22:43

I know nothing about Renault engines, however my initial reaction to your post is to wonder if the ecu is getting correct engine temperature info from the sensor?

Unread post by **Paul-R** » 23 Dec 2025, 23:43

You say you have no fault codes. What are you using to check for these?

ray_r400 · Unread post by **ray_r400** » 24 Dec 2025, 05:41

thank you for your reply
obd 11 scanner.
vd700. also running live data through it.

ray_r400 · Unread post by **ray_r400** » 24 Dec 2025, 05:43

the temp goes up on the car the same as my scanner reading.
so it seems OK.

Unread post by **Paul-R** » 24 Dec 2025, 06:14

The VD700 is only about £50 so may not be up to the job. You need to get the car read by a more high end scanner to be sure of codes.

ray_r400 · Unread post by **ray_r400** » 24 Dec 2025, 10:34

my friend has a snap on zues+ scanner and the
only fault found was oil level sensor.
nothing else.
thanks

Unread post by **Paul-R** » 24 Dec 2025, 11:24

Yes, that should be good enough!

Have you checked the spark plugs? Some engines are extremely fussy and require not just the right heat range but from a specific manufacturer. Equivalents just don't work properly. I don't know this engine to be more specific.

ray_r400 · Unread post by **ray_r400** » 24 Dec 2025, 19:59

thank you
yes plugs have been changed 12 months ago.
it was ok then ordered from euro car parts using the reg.
all plugs are in the same condition:, not wet or burnt.

ray_r400 · Unread post by **ray_r400** » 27 Dec 2025, 22:23

hi does any one know if pre and post 02 sensors are the same.
when I goolgle it it just gives me one sensor.
I might try and change the post as well.
I think my battle is my "short term fuel trim" b1-s2 is -100. so its over fueling .
thanks Ray
should be 0.

ray_r400 · Unread post by **ray_r400** » 28 Dec 2025, 13:17

I disconnected my post 02 sensor plug
and my reading is still -100 stft. and I still have a voltage.
so does this point to sensor being bad.

thanks Ray

ray_r400 · Unread post by **ray_r400** » 28 Dec 2025, 13:33

I ran live data with just ignition on and my stft b1-s1is still showing -100 even if car not running.

ray_r400 · Unread post by **ray_r400** » 01 Jan 2026, 15:24

just realised that the -100 stft is a default.
so this is what I have tried today.
I removed the knock sensor plug to check for voltage and there is no voltage.
0v even with the car at idle.
should I get a reading.

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hesitation when engine cold.

hesitation when engine cold.

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