Technical Bad idling after cambelt change

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Technical Bad idling after cambelt change

CeALJo

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May 2, 2010
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Hello,

Need some advice for my brava 1.6 16V.

I have just changed the cambelt, because of a major failure. All valves and valve guides are changed. As well as the other belts.
I got everything back togheter (I used the timing tool, turned the engine by hand for at least 4 turns and the markings were fine) and started it up. backed out from the garage to have it idle and bleed the cooling water.
It started nicely and when cold it ran good but warm, it stalled on me a few times. It runs fine with some rpm's and on the road, it accelerates good and responds.

Now I'm wondering what can have caused this bad idling?:bang:

I've tried to search this and other forum but with no luck. Someone says that ICV or IAT could be the problem. Others says the lambda or spark plugs or the HV leads, one says that one tooth could be off (wierd since I used the timing tool). Also if it a tooth would be off I think that would be noticable when driving.

Any ideas????
 
Try to measure the crank sensor, it should have between 575 to 750 ohm's. I had the same issues you describe + erratic idling and changing the crank sensor helped.
 
Checked crank sensor, it was OK, checked the coil, lambda, air tempsensor. All was OK.

I also had the fiatecuscan connected and saw that the ICV was changing, atleast the values changed, however there where a difference when I disconnected the ICV. I ran more smoothly. The rpms where at approx 835rpm, and the engine sounded better. BUT, when I started to check this some more I noticed that the ECU wanted the engine to run at 700rpm, this value was what the ECU was trying to adjust the idling too.
According to the manual the idling should be 850rpm.

The question is now, how come the ECU wants to adjust the engine to 700 rpm????
WHY???? What to do???
 
Ok so the thing goes like this: if you say that it was trying to adjust at 700 rpm it might be that it's taking more air that it should be. Check the air intake system to see if there are no holes in it.
About the ICV this works like this:
-when starting: the position of the ICV it's controled according to engine coolant temperature and battery voltage.
-when warming up: the position is corrected according to coolant temp.
-when warm: the position is dependant on signal from rpm sensor (TDC)
-when in over-run: the position is dependant on the status of the throttle potentiometer position.
So this being said, you should also check the coolant temp sensor (between 0 and 20 degrees Celsius it should have between 10 and 20 Kohm) and throttle position sensor (0-1200 ohm at 23 degrees Celsius).
As a last resort, if you don't find any faults with this, try to see if the timing is right, althought if is wrong you should have either rough running or loss of power do to bad timing.
You could also try a remap of the ECU (at you're own risk).
 
The very first thing i would be doing is this

Get the engine timed up to TDC, do this as precisely as you can
Try to re-fit the timing tools i bet they don't fit.
The front cam will be out by a fraction causing the poor running.
 
check compression.
i had this problem after mi cam belt change.
one piston had a bent valve resulting in rough running at idle and reduced power while running
 
Thanks for the help.
Now it works as it should, the idling is good and it doesn't stall. I did the timing again and apperantly the timing was a little off.
I do have to say that this engine type is extremly sensitive with the timing.
Also Fiat could have made this a little easier, made good markings to show when the timing is correct.

I noticed that there is a simple way of getting the timing correct.
Maybe there are other ways but this did the trick for me.

Lock the cams and engine to TDC. Get the cam belt tight and slide it over the inlet cam wheel, then do the same with the exhaust, tighten the adjuster and turn the engine a couple of turns (clockwise).
Check the the tension of the belt. If ok then continue otherwise correct tension of the cam belt.
When again at TDC check the timing position (most probalby the exhaust is not correct), turn the engine one more turn and when the exhaust timing is correct lock the exhaust cam & loosen the bolt for the exhaust cam wheel and turn the engine into TDC and inlet to correct timing.
When doing it this way you have the cams timing & TDC correct also the tension of the belt is correct. Remember to tighten all bolts again.
 
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