Technical Cambelt replacement-issue(cyl2,3,multiple misfire)

[500c2k16]

Hello,
new owner of 1.2 8v fiat500c 2016.
Did a preventative cambelt,waterpump and tensioner reppavement. Locked crank, locked camshaft(i have a cheap autodoc kit and camlocking tool couldnt fit because it was too thick so I locked it half way), replaced everything aligned forks, 2 full cam rotations, checked and retensioned tensioner and did 4 more cam rotations. Tools fit in same way as.girst time and tensioner was accurately(forks overlapiing) set. Closed everythhing started the engine. Nice idle but then on the motoway BOOM. Dtc for cyl2,3 misfire and multiple miafires. What on earth is happening. From what I understood it could mean ecu needs to relearn crank/cam position. I just need a bit more insight on what I did wrong and what I can do to fix this... car run very nicely before replacement.

 

[steveras57]

classic signs of cam timing being 1 tooth out!- if you do not use fiat specific tools its easy to get it wrong which is why a lot of owners get a fiat dealership to do this job!- you need to do it again using the correct rather than generic tools if you cant get it right then pay a professional to do it for you!.

 

[500c2k16]

classic signs of cam timing being 1 tooth out!- if you do not use fiat specific tools its easy to get it wrong which is why a lot of owners get a fiat dealership to do this job!- you need to do it again using the correct rather than generic tools if you cant get it right then pay a professional to do it for you!.

Wouldnt cam/cranm sync DTC show up of that were the case?

 

[Pugglt Auld Jock]

Wouldnt cam/cranm sync DTC show up of that were the case?

Not necessarily. I have a "cheap" Neilsen locking kit for these engines and the tools all fit perfectly. I'd not be very confident of the quality of a kit where even one of the tools didn't fit precisely.

You mention an ECU relearn perhaps being needed? I presume you are talking about what is called a "phonic wheel relearn". This is indeed sometimes needed after a cambelt change but the symptoms are not those you mention here. Symptoms are that the engine runs normally but that the Check engine light illuminates and, when scanned, fault codes for miss fires are stored. The "give away clue" though is that, despite the codes being posted, the engine is NOT miss firing and is running normally. These are not your symptoms so I think what steveras57 suggests above is very likely to be your problem. It's a frequent problem encountered if doing the belt change without slackening the camshaft pulley retaining bolt. It's very possible to do the belt change without doing this but great care has to be taken to avoid this problem - there's many posts on here about folk who have fallen foul of this.

Oh, and you'll need a Fiat/Alfa specific scanner, like MES for instance, to do a phonic wheel relearn properly if you find you need to once the belt is correctly timed.

 

[500c2k16]

Not necessarily. I have a "cheap" Neilsen locking kit for these engines and the tools all fit perfectly. I'd not be very confident of the quality of a kit where even one of the tools didn't fit precisely.

You mention an ECU relearn perhaps being needed? I presume you are talking about what is called a "phonic wheel relearn". This is indeed sometimes needed after a cambelt change but the symptoms are not those you mention here. Symptoms are that the engine runs normally but that the Check engine light illuminates and, when scanned, fault codes for miss fires are stored. The "give away clue" though is that, despite the codes being posted, the engine is NOT miss firing and is running normally. These are not your symptoms so I think what steveras57 suggests above is very likely to be your problem. It's a frequent problem encountered if doing the belt change without slackening the camshaft pulley retaining bolt. It's very possible to do the belt change without doing this but great care has to be taken to avoid this problem - there's many posts on here about folk who have fallen foul of this.

Oh, and you'll need a Fiat/Alfa specific scanner, like MES for instance, to do a phonic wheel relearn properly if you find you need to once the belt is correctly timed.

I very much appreciate the time you took to answer and clarify this for me. Thank you!
I will attempt to do the job properly again.
In your experience is it possible that timing lock tools from kit are badly made(tolerances not met) or could it be my inexperience, I am asking since the cam is in proper position and tool goes in only halfway when checking the tool itself it appears too thick..

 

[Pugglt Auld Jock]

I very much appreciate the time you took to answer and clarify this for me. Thank you!
I will attempt to do the job properly again.
In your experience is it possible that timing lock tools from kit are badly made(tolerances not met) or could it be my inexperience, I am asking since the cam is in proper position and tool goes in only halfway when checking the tool itself it appears too thick..

So, can I just check with you? This is the common 1.2 FIRE engine with a VVT cam pulley?

If so then, when you had the belt off did the cam pulley feel "solid". By this I mean, could you "wiggle" it back and forwards relative to the cam. It should be "spring loaded" in the retarded position and feel "solid" when trying to wiggle it by hand. They don't seem to fail much - I've not come across a failed one yet - but, in theory, it's possible. If the pulley isn't solid feeling then you'll never get this right.

But let's assume the pulley is ok. now turn the crankshaft, clockwise please, until the cam locking bar can be inserted into the end of the slot on the cam. This is the slot on the other end of the cam to the pulley (just to be sure we're on the same page here) you should now find the "dumbell" crankshaft locking tool can be fitted to the crank pulley with it's 3 bolts and the one in the end of the arm inserted into the threaded hole in the front of the block. Leave these all slightly loose until they are all started in their threads. If they very nearly fit but are just fractionally out - I'm talking about them being "so very nearly there" you can try wiggling the crankshaft back or forwards just a smidgeon until they drop in. If they are further out than this then either the belt is fitted wrongly - i.e maybe a tooth out - or the cam pulley is incorrectly positioned on the end of the cam. You do know that the cam pulley is not keyed to the camshaft? If the securing bolt on the cam pulley is slackened then the pulley spins free on the end of the camshaft. You then need the locking tools to set it up correctly again. However, if your engine was running well before you fitted the new belt then the positioning of this pulley was probably correct and, if you haven't slackened that bolt (which "lives" under the cap bolt you can see on the front of the pulley - so, if you ever remove it be prepared for oil to leak out - nice big rag recommended) then all's likely to be well in this respect. I'm guessing you didn't slacken that bolt?

Ok, so if you haven't slackened that bolt and tried to fit the new belt with cam and crank locked by the tools, then it pretty much a 100% certainty that your timing is one tooth retarded as it's not possible to correctly engage the belt teeth, with both tools inserted, unless the cam pulley is unlocked. If however you've done it using the tools but without unlocking that, very very tight, bolt - which I have to say is my preferred way to do it, then, having set everything up using the locking tools and positioned the belt round the crank pulley and water pump, you'll find the cam pulley teeth are just slightly "out" and you will only be able to get the teeth to engage by introducing a very small amount of slack into the right hand run of the belt. This is how folk end up with the timing one tooth retarded. Instead, when you are at that last stage of engaging the belt with the cam pulley, remove the cam locking tool and just very slightly advance the cam (and thus it's pulley) until the teeth mesh. Now set the tensioner and you'll see the cam rotate very slightly anticlockwise as the slack is taken out of the right hand run of the belt and now you should find the cam locking tool should drop into it's slot on the back end of the cam.

OOPs, need to get going to be out at youngest boy's house to collect grandchildren from school and take them swimming. I'll come back to this when we're home later in the day. Good luck, hope the above was a help and not to confusing.

 

[500c2k16]

So, can I just check with you? This is the common 1.2 FIRE engine with a VVT cam pulley?

If so then, when you had the belt off did the cam pulley feel "solid". By this I mean, could you "wiggle" it back and forwards relative to the cam. It should be "spring loaded" in the retarded position and feel "solid" when trying to wiggle it by hand. They don't seem to fail much - I've not come across a failed one yet - but, in theory, it's possible. If the pulley isn't solid feeling then you'll never get this right.

But let's assume the pulley is ok. now turn the crankshaft, clockwise please, until the cam locking bar can be inserted into the end of the slot on the cam. This is the slot on the other end of the cam to the pulley (just to be sure we're on the same page here) you should now find the "dumbell" crankshaft locking tool can be fitted to the crank pulley with it's 3 bolts and the one in the end of the arm inserted into the threaded hole in the front of the block. Leave these all slightly loose until they are all started in their threads. If they very nearly fit but are just fractionally out - I'm talking about them being "so very nearly there" you can try wiggling the crankshaft back or forwards just a smidgeon until they drop in. If they are further out than this then either the belt is fitted wrongly - i.e maybe a tooth out - or the cam pulley is incorrectly positioned on the end of the cam. You do know that the cam pulley is not keyed to the camshaft? If the securing bolt on the cam pulley is slackened then the pulley spins free on the end of the camshaft. You then need the locking tools to set it up correctly again. However, if your engine was running well before you fitted the new belt then the positioning of this pulley was probably correct and, if you haven't slackened that bolt (which "lives" under the cap bolt you can see on the front of the pulley - so, if you ever remove it be prepared for oil to leak out - nice big rag recommended) then all's likely to be well in this respect. I'm guessing you didn't slacken that bolt?

Ok, so if you haven't slackened that bolt and tried to fit the new belt with cam and crank locked by the tools, then it pretty much a 100% certainty that your timing is one tooth retarded as it's not possible to correctly engage the belt teeth, with both tools inserted, unless the cam pulley is unlocked. If however you've done it using the tools but without unlocking that, very very tight, bolt - which I have to say is my preferred way to do it, then, having set everything up using the locking tools and positioned the belt round the crank pulley and water pump, you'll find the cam pulley teeth are just slightly "out" and you will only be able to get the teeth to engage by introducing a very small amount of slack into the right hand run of the belt. This is how folk end up with the timing one tooth retarded. Instead, when you are at that last stage of engaging the belt with the cam pulley, remove the cam locking tool and just very slightly advance the cam (and thus it's pulley) until the teeth mesh. Now set the tensioner and you'll see the cam rotate very slightly anticlockwise as the slack is taken out of the right hand run of the belt and now you should find the cam locking tool should drop into it's slot on the back end of the cam.

OOPs, need to get going to be out at youngest boy's house to collect grandchildren from school and take them swimming. I'll come back to this when we're home later in the day. Good luck, hope the above was a help and not to confusing.

I was certain this was not a VVT but yurns out the phase transformer is incorporated into the camshaft pulley... so yes it is a VVT. I haven slacken the camshaft pulley bolt at all. I have read a guide on here that specifically tells that VVT need this done in certain cases. So Your explanation and reasoning was very informative and helpful! I very much appreciate it!
Will get on the job once kids are asleep tonight. Just so you can understand my situation I will write down my coirse of action and maybe you will see what went wrong. I have a clue but I really dont trust myself anymore..
1st attempt.
Removed everything to access belt and camshaft.
Turned crank pulley(CRP) until I reached TDC and could fit my dumbell locking tool. locked everything on CRP and went to camshaft pulley(CAP).
Went to put in camshaft locking tool but wouldnt fit. It was well aligned but just the plate(10° plate on the tool) couldnt be fully seated into the grove(cam was in correct position, rrctangular grove was up top) so I put it in halfway. Removed the tensioner replaced the belt and !! put the new belt in with too much slack(1 tooth worth of slack) on the cam/crank side. Stupid me, this was my first belt job if that explains my dumb mistake. Tensioned the pulley one time(NOT TO MAX-mistake?) and tensioned the bolt to 25Nm. Removed locking tools. Did 4 crank revolutions , inserted locking tools and noticed the tensioner fork moved so I slackened the bolt again, retensioned so forks align(I didnt think it mattered so I tightened it a bit more so the forks werent perfectly flush). Tightened the nut 25Nm and put everytjing back together. Started the car and immediatly got cam/crank synch bank 1 sensor a DTC. Turned it off and next day...did my 2nd attempt.
Removed everything neccessary.
Locked the CRP, now first I slackened the tensioner lifted the belt a bit and moved the camshaftpulley 1 tooth forward(clockwise), now the tool still engaged only halfway deep, after this I tensioned the belt from crank-->waterpump-->cam and made sure no slack! than tensioned the tensioner again not max but so forks align and unlocked CAP and CRP and did 4 crank revolutions. Lovked the CAP and CRP, retensioned the tensioner so forks aligned (now being careful that forks perfectly align) and torqued the tensioner nut. Unlocked CRP and CAP and did 8 crank revolutions just to be sure the tensioner was good and it was good and aligned. Put everything back together. Started the car, no issues. Got it up to temp and went home via highway. On highway engine light starts flashing I immediatly stop check my cheap.obd reader and it says cyl2,3 misfire and multiple misfires detected. So here I am baffled. Well not so much anymore seems, like I advanced it now and first time the belt slack was giving issues. Dont know. will attempt to do it today properly via the forum guide.
Enjoy you facepalms and laughs. And thank yoi for your help!

 

[jackwhoo]

You problem happens very very often.

Cure is phonic wheel relearn.

The crank pulley (phonic wheel) has a lot of play in the holes the bolts go through to clamp it to crank sprocket . If phonic wheel removed then refitted the learn procedure is required.

it can be done without a scan tool.

 

[jackwhoo]

You don't need the laptop.
Drive until car warm and engine light flashing, do the rev procedure shown from 1.22 onwards