Technical Check engine light at speed after cam belt change

[ZaphodB]

Surely by its very nature an older belt will have stretched ever so slightly. Where as a new belt will be tight. And that slight difference might be sufficient at higher revs to make the sensor see that difference?

They don't stretch per-se (they have stuff built in longitudinally to stop that), they 'fatigue' and start to crack, then risk total failure.
It'll be out by a tooth as others have suggested.

 

[Pugglt Auld Jock]

I do not think phonic wheel has anything to do with your problem and here's what our colleague thinks of it, you might be interested, posted in this other topic


As for what's causing your problem, my money is on the faulty thermostat. The thermostat is broke, it doesn't close when it should. When you hit high speed, the wind hitting the radiator cools down the cooling liquid, that beeing a moment thermostat should close to keep the coolant within working temperature. But it doesn't and the coolant temperature overall drops too much. You won't find any related errors stored but you do get the intermittent check engine light because ECU feels something is not quite right.
So nevermind pausing the music but watch the temperature gauge. Normal needle position is bang on the middle, I say you'll see yours lower than that, possibly just a quarter on the clock.

Mike, Thanks for your posts. Our brains seem to come at things from a different direction and you always make me stop and think.

I completely agree that, where the timing of the engine and how it runs is not controlled by the Phonic wheel relearn procedure. If the belt is correctly fitted that's the important bit. Almost as an afterthought, if the CEL lights subsequently do you then need to do the relearn - which doesn't alter the timing in any way, just turns the light out and keeps the ECU "happy"

I'm not so sure about the faulty thermostat making the CEL flicker though? A failing/failed thermostat is such a common thing on these that I've experienced it several times on Pandas I've owned and also on the Punto - My boy's 2012 had the problem. It often manifests itself with the gauge needle only getting about a quarter of the way up the scale -instead of half way as you show in your picture above. I've never seen the CEL flickering or lighting up due to this. I think the problem you experienced above was more likely to be a high resistance in a connector or, less likely, a problem in a loom somewhere, which was disturbed during your corrective work and this disturbance remade the connection?

So thanks for causing me to exercise my brain - I look forward to your next post.

 

[Pugglt Auld Jock]

Surely by its very nature an older belt will have stretched ever so slightly. Where as a new belt will be tight. And that slight difference might be sufficient at higher revs to make the sensor see that difference?

They don't stretch per-se (they have stuff built in longitudinally to stop that), they 'fatigue' and start to crack, then risk total failure.
It'll be out by a tooth as others have suggested.

I'm in the second "camp" here. As folk may be aware I've done quite a number of these belts both back in the days when I was a working mechanic and latterly working on the several Pandas and my boy's Punto here at home. When we bought our latest Panda - 2010 1.2 60hp (so no VVT but does have the keyless cam pulley) - was that 8 years ago? - it had a slight noise which I thought was a water pump or tensioner bearing so I renewed the belt, water pump and tensioner expecting the noise to go away. Greatly to my surprise, it didn't! I've written quite a lot about what I did to establish the cause, which I've detailed elsewhere so won't go into here. However, part of it involved some quite lengthy contact with the belt manufacturers where I learnt a lot I didn't know about these belts. One thing to emerge is that they really don't stretch at all. They have multi stranded circumferential "strings" of very strong cords (some are carbon fibre - all are materials which don't stretch) These cords are just under the smooth outer surface of the belt under them are the materials which make up the teeth and these materials, I think, can compress very slightly in use, and it's this effect which gives the slight slackness you see in a used belt. This is obvious on the older engines where the tensioner is not spring loaded but less observable on the newer engines which use a spring loaded "automatic" tensioner.

 

[Pugglt Auld Jock]

We've seen this same story many, many times on the forum. Car running perfectly before a belt change done by an independent garage without specific Fiat knowledge or timing tools, timing belt changed, then check engine light comes on if car taken over 3000rpm. Garage denies they've done anything wrong. and starts looking for some other non-existent fault.

Aye jrk, for what looks, at first glance, to be mechanically a simple belt to do, there are an awful lot of folk who end up in trouble. For those not familiar with them, including "seasoned" mechanics, it's the "misfire" code it throws up that causes a lot of the problems and leads folk off down rabbit holes which lead nowhere except to replace lots of components, coils, crankshaft sensors, HT leads, etc, etc which are not needed and don't solve the problem.

Bottom line is that the belt hasn't been replaced correctly and/or a poor quality aftermarket belt was used. The timing is now a bit out, not enough to cause any immediate damage, but enough to put the check engine light on. When changing the belt on this engine, there are countless ways to go wrong and get into difficulties. Garages without specific brand knowledge are some of the most common offenders in this respect; often they start by removing the old belt and then look for timing marks which aren't there, by then they're already in a bad place.

Agree with all of that, Although I'm not quite sure how many belt manufacturers there actually are. I suspect less than we maybe think with a relatively small number of manufacturer's supplying their belts to sellers rebranded appropriately? I do worry about the proliferation of inferior quality counterfeit parts though so would always buy a brand I know to be of good quality - Gates, Continental, Dayco, etc. - and from a trusted source.

The solution is to take the car to either a Fiat specialist or a franchised dealer and have the belt replaced again. Unfortunately a new belt will be required, since the tensioning procedure doesn't quite work correctly with a belt that's been in service, even if only for a very short while.

Whatever your "take" on the efficacy of reusing belts, the workshop will be warrantying their work so you can't reasonably expect them to reuse parts or fail to follow the recommended tensioning procedure. I couldn't see any main dealer deviating from this, but an "indy" might especially if you're known to them and can vouch for the parts being new. But, in that case, why didn't you go to them in the first place?

If doing this fixes the problem, and I think there is a very good chance that it will, then I'd be pursuing the first garage for full reimbursement of what they have charged you in parts and labour for changing the belt. There's no way I'd let the first garage do any further work on the car; they've already demonstrated their incompetence.

Good luck with that? but worth a try. I always say to folk who come to me for help that it's time well spent seeking out a reliable small, often family owned, make specific if possible, garage/workshop, before you need them - unfortunately easier said than done though.

 

[Pugglt Auld Jock]

Thinking further on the subject - Although, so far, I've not knowingly come across this problem, the crankshaft pulley on these engines has a "built in" key which engages with the slot in the crankshaft. It's not very substantial and can shear allowing the pulley to move in relation to the crankshaft. Because the "dumbbell" crank locking tool is fixed to this pulley, and NOT the crankshaft itself, if the pulley has moved you're not going to know about it and you'll never get the cam timing "right". To check, remove spark plugs 1&2 or 3&4 (you've probably removed them all already anyway to make the engine easier to turn over?) Fit the "dumbbell" tool and then, using a probe, (wooden dowling is good enough) check the adjacent two pistons are at the same height in the bores. With the Dumbbell in place all pistons should be exactly at "half mast" as far as I know? If they're not then you may have a sheared key and you need to remove the crank pulley - that's the pulley which drives the cambelt, not the outer pulley which drives the aux (fan) belt, its held in place by the big bolt in the middle and is pretty tight. A genuine manufacturer replacement is, so I'm told, recommended as there are some rather "iffy" pattern parts out there.

Edit. the camshaft doesn't "suffer" from this problem as the timing tool engauges directly with the shaft itself, not the pulley.

 

[jrkitching]

for what looks, at first glance, to be mechanically a simple belt to do, there are an awful lot of folk who end up in trouble

One way to increase your chances of ending up in trouble is to phone round the local backstreet garages, and give the job to a place you've never used before that's given you the cheapest quote.

If in doubt, it's worth paying a bit extra and taking it to a franchised dealer; it may not cost as much as you might think.

 

[Pugglt Auld Jock]

One way to increase your chances of ending up in trouble is to phone round the local backstreet garages, and give the job to a place you've never used before that's given you the cheapest quote.

AAAAARGH. and yet so many fall foul of this.

If in doubt, it's worth paying a bit extra and taking it to a franchised dealer; it may not cost as much as you might think.

I agree, but, if they seem to be giving you a "silly expensive" price just ask how they've costed it. When I decided Becky needed her's done, although I fully intended to do it myself, I asked around several of the garages around me, including the main dealer, and was very surprised to find the main dealer quoting nearly double the price. I'd actually called in in person for the quote as I was passing their door and, while recovering from the "shock" noticed they had a price menu for a number of jobs on the wall behind the receptionist. They listed fitting a timing belt and fitting a water pump as two separate jobs! As we know, the labour task for doing either of these is almost identical - same parts need to be removed - stripped - to complete the job. So there is a great deal of duplication if either job is done separately but very little if both belt and pump are done at the same time. Their receptionist had simply added the two listed tasks together when pricing them up - thus virtually doubling the actual labour involved and not needed. Might be worth querying a main dealer price with this in mind?

The receptionist couldn't "see" it until the stores manager, a chap I know in passing, came out with some customer parts and I got to speak to him. He talked to the desk staff and the price then came down considerably. Still slightly more than the "wee guys" but affordable - especially when you take into account that they automatically put it on their diagnostic gear before handing it back to you (I was told they do this on every one)

 

[Ralf S.]

I

Thinking further on the subject - Although, so far, I've not knowingly come across this problem, the crankshaft pulley on these engines has a "built in" key which engages with the slot in the crankshaft. It's not very substantial and can shear allowing the pulley to move in relation to the crankshaft. Because the "dumbbell" crank locking tool is fixed to this pulley, and NOT the crankshaft itself, if the pulley has moved you're not going to know about it and you'll never get the cam timing "right". To check, remove spark plugs 1&2 or 3&4 (you've probably removed them all already anyway to make the engine easier to turn over?) Fit the "dumbbell" tool and then, using a probe, (wooden dowling is good enough) check the adjacent two pistons are at the same height in the bores. With the Dumbbell in place all pistons should be exactly at "half mast" as far as I know? If they're not then you may have a sheared key and you need to remove the crank pulley - that's the pulley which drives the cambelt, not the outer pulley which drives the aux (fan) belt, its held in place by the big bolt in the middle and is pretty tight. A genuine manufacturer replacement is, so I'm told, recommended as there are some rather "iffy" pattern parts out there.

Edit. the camshaft doesn't "suffer" from this problem as the timing tool engauges directly with the shaft itself, not the pulley.

I think this is a good test to do... if the piston heights are different then there's a problem.

My old Stilo had a sheared key on the camshaft pulley (one side was broken off) so it had a few degrees of variation. The mark on the pulley never lined up with the arrow on the pulley shield (which is plastic and is visibly deformed). It looks like someone fitted the pulley to line up with the arrow, and then just tightened it up without the key being engaged, so it eventually cracked the edge off the key before the key could fall into the slot.

Before I figured all this out.. I got quite good at doing the timing by eye .. mainly by fitting the cam deliberately "half a tooth out" (according to the pulley shield) but eventually I bought a new pulley to fix it properly and .. the pulley shield arrow and pulley mark still didn't line up. Then I guessed that the pulley shield arrow is the problem, not the pulley. It's been fine "half a tooth out" ever since.


Ralf S.

 

[KS95]

Got it booked into the fiat specialist for Friday morning. Guy on the phone made it sound like it was more serious than a phonic wheel reset. £70something for diagnostics and they recommend I pursue the original garage for a refund if they end up needing to do work

 

[KS95]

Got it booked into the fiat specialist for Friday morning. Guy on the phone made it sound like it was more serious than a phonic wheel reset. £70something for diagnostics and they recommend I pursue the original garage for a refund if they end up needing to do work

It's Days in Milton Keynes who seem to be reviewed favourably on this forum, although I didn't see any recent posts regarding them. Does anyone know them?

 

[Mike1alike]

Mike, Thanks for your posts. Our brains seem to come at things from a different direction and you always make me stop and think.

I noticed that myself, we coming to things from different angles. And I do too appreciate your posts, thank you for them.
Regarding faulty thermostat making CEL flicker I wonder myself if that is possible, wondered at the time, too. I had that very short time after I got the car and didn't know much about Fiat at the time. I think it was like you said, something else causing CEL to flicker and was just a coincidence seeing it when the thermostat was bad. But I will definitely look into that next time the thermostat goes bad, to be 100% sure.

Got it booked into the fiat specialist for Friday morning.

We are looking forward into report about it and wish you to not be something complicated nor expensive.

 

[KS95]

I noticed that myself, we coming to things from different angles. And I do too appreciate your posts, thank you for them.
Regarding faulty thermostat making CEL flicker I wonder myself if that is possible, wondered at the time, too. I had that very short time after I got the car and didn't know much about Fiat at the time. I think it was like you said, something else causing CEL to flicker and was just a coincidence seeing it when the thermostat was bad. But I will definitely look into that next time the thermostat goes bad, to be 100% sure.

We are looking forward into report about it and wish you to not be something complicated nor expensive.

Thank you! I'm crossing my fingers that it's just something software related or something on the cheaper end of the scale like spark plugs.

They recommended on the phone I pursue the original garage if they're able to give me evidence the work caused the problem