It just did the same thing yesterday. It happens for the first 100 metres or less on first and second gear, then goes away. It's like as if it was misfiring bouncing a bit, running rich.

Hopefully it's nothing too serious.

As I remeber from Renault forum, when engine is cold, ECU is maintaining rpms mainly by coolant temp sensor. But these values can be visible via on-line diag. Of course there is a lot of other parameters to calculaye final rpm management...I tink the best way is online giag and person who understand all readings (not a guy like "there are no errors so its ok")

Now that weather's warmer it also does jerk on 1st and 2nd gear also with warm engine but it doesn't happen all the time. It may be two issues and sometimes it's the driver releasing the clutch too fast. :worship: I don't believe it to be worn clutch either.

Sure MES can tell injector and other calibration values and can probably tell which sensor values are off. Sometimes it's cheaper to change a sensor for 25€ than going to a specialist. Ckp- sensor is one sensor to replace on my list. I had to peek under the timing belt cover, and had to touch the ckp- wiring once. That made the car behave itself for several months. It may be worth checking. What do you believe to be the correct resistance value for that sensor?

Ckp..?

Crank position..??

eeeno said:

What do you believe to be the correct resistance value for that sensor?

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I think that sensor is an Hall effect one, so you won't read any significant value since it delivers something like a square wave reflecting the teeth pattern on the pulley ...

BRs, Bernie

I have done some repairs like changing the thermostat housing along with the coolant and also valve cover gasket.

After removing the heatshield of the exhaust manifold I was surprised to see three studs missing! First cylinder doesn't have any bolts and second lacks the top bolt. Ran the engine and sprayed some water with washing up liquid and confirmed leaky first cylinder.

This is a relief because it may not be costly repair at all and engine may not have an internal fault and all symptoms are due to the leaking exhaust manifold. The knocking an ticking have become more audible so the leak is gradually getting worse.


Is it a known fault of Fire engines to have snapped exhaust manifold studs? I don't think anyone would be just so dumb to keep on snapping the studs if the first attempt was unsuccesful. :bang: There's no stud left, they've snapped right before the manifold.

I'm definetily leaving the extraction of the studs to a professional. :worship:

eeeno said:

Is it a known fault of Fire engines to have snapped exhaust manifold studs?

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Yes and no (it's 50/50% design and user/mechanic incompetence fault). Plus a little bit of bad-luck, time, corrosion.
Simple (cheapest possible style) studs are not helping.
Similar topic (look at the picture): https://www.fiatforum.com/grande-punto/477363-cooked-engine.html?p=4508286

eeeno said:

I don't think anyone would be just so dumb to keep on snapping the studs if the first attempt was unsuccesful.

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Unfortunately yes, many people are dumb like that. Including "professional" mechanics (grease-monkeys).
But sometimes you have no choice, it will break, no matter what.
Worst thing is fixing someone else's failed repair attempt, like drilling off-center.

eeeno said:

I'm definitely leaving the extraction of the studs to a professional.

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It depends how experienced DIY-mechanic/hobbyist you are. But yes, it is a tough job (one of the ugliest ever). And time consuming (so warning: mechanics will "cut the corners" and make inferior repair possibly - you will end-up fixing it yourself later).

It sounds like a job best left to a professional who has done these for more than a decade. I've never successfully drilled any bolts so, this is not a good subject to practice on !

These may snap due to thermal expansion over time and stress. I've no idea if these problems should arise much later than now though. Bad quality studs or just ingenious engineering.

Broken exhaust manifold studs were replaced except for one and it doesn't jerk any more. The mechanic said that broken exhaust manifold studs are very common on Fiat engines.


The one which was broken inside the engine cover had been given treatment by some enthusiastic but clueless diy - guy. I'll tell you. It's not worth it to try to cut corners. It's only a couple of hours of labor and more if someone has done an improper job. :bang: Experts routinely replace these easily if they have not been given diy treatment.

The car works fine for now but it will start leaking again. Surely it can be fixed properly but it's going to have to wait for a total head gasket failure. Not doing any engine repairs until necessary.


I wonder if majority of driveability complaints are due to leaking exhaust gasket and broken studs.

This reminds me something... I changed one broken stud (during mounting nut back it broke like butter). I drilled hole into it, then tried extractor, but extractor also broke inside broken stud!!! So I drilled it all, made new thread and used bigger stud. Hell! Another stud broke also like butter but I could catch it with pliers, unscrew out and add new one. So yes, I can confirm that used studs (6+ years in my case) are weak

the fuel trims look wrong short term should wave between - 2.5 to +2.5

The lack of power was due to a minimal leak from the exhaust manifold gasket but the jerking reoccured.

I replaced the smaller breather hose behind the airfilter box and later did the throttle body relearn procedure (Stilo instructions) and so far the problem has not reappeared.

The car had been without the battery and lost the throttle body setup at some point. :idea:

The clutch plate appeared to be dirty and doing some cleaning to it appears to fix it for several months. Surely there's some wear to it but it doesn't need to be changed yet. Also gentle use of the clutch doesn't clean it so it's due to driving style.