I've swapped my camshaft on my Sei 1.1 sporting SPI for a 4x4 one from a Punto with less lift and overlap for more bottom end and it works beautifully, i.e. more torque and better fuel economy. However my idle has increased to 950-1050 rpm hot and 1100-1300 cold. This makes a lot of sense, because the Punto has 10 degrees advance, whereas the Sei has 12 degrees. So I was wondering how do you retard the spark advance? The flywheel cover has timing marks and I got a timing strobe and the Fiat ECU scan software, but there is nothing like a distributor to twist? Is advance exclusively managed in the ECU? Second option is to mess with the crank sensor, but that will retard the injection timing an equal number of degrees, 1-2 degrees ballpark). That might not be a problem though, as apparently the SPI squirts 8 times per revolution so the injector is not synchronised with valve opening. People swapping their cams for more agressive ones have the oposite problem and need to advance their spark, how do they do that? I can't find any threads about spark timing, only cam and valve timing!

you can't change it with the stock ecu. maybe a 1.2 ecu will work. you could try to play with the cam timing

From what Punto did you get that 4x4 camshaft? Im looking for one myself for my turbo build haha...

Also, ha Leon

Are all the vacuum pipes connected the correct way round?

D

A 2000 Punto 8V 1.2 It is the one with lower lift and overlap, so more torque and less reving, kind of looses puff after 4500 rpm, should also be stock fitted in MPI Seicentos.

I'll check the hoses, but this happend as soon as I changed the cam, doing nothing else. About hoses. The ECU pressure sensor (matchbox sized box next to the ECU with a hose to the manifold vacuum) has a black and white plastic canister on the hose. I presume it is a filter or a damper to even out pressure oscillations? When blowing through it, it seems completely blocked, is that normal?

Cam timing is less invasive than swapping ECU for a 1.2 one, which will have other differences in mapping than the advance. A little more info: After disconnecting the battery to do an ECU reset and the let it idle until warm, it actually manages to idle at 820-850 as it is supposed to, but in a few days driving around it gets increasingly difficult for the ECU to throttle the idle back. It seems like it tries, but the next lower step on the idle control valve is too little and the ECU throttles back up to prevent the engine from stalling? I cleaned the idle control valve 3 years ago, so I don't presume it should be fouled yet. Are there any other channels in the throttle body that need to be checked relating to idling control? From the top of my head: could this also be an idle up because of low battery voltage? It idles at 14.4V but my battery is old so the generator might be making a greater effort than I imagine. I'm going to Germany in two weeks, where I can drive with my lights off, if it idles better, it is possibly either the battery or the alternator?

Luno said:

A 2000 Punto 8V 1.2 It is the one with lower lift and overlap, so more torque and less reving, kind of looses puff after 4500 rpm, should also be stock fitted in MPI Seicentos.

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Alright, that's actually good news for me then since I took out a 1.1 mpi out of a 2001 sei which will be replaced with a p75 turbo engine. Ill just swap the 866 cam into the mpi sei engine and pass it on, and use the 4x4 cam in my turbo build since ill need the less overlap for my turbo.

Thank you guys. The majority of answers were about a possible vacuum leak.. and it turned out to be right. A tiny oily smudge on the backside of the valve cover was was the result of a hardened valve cover gasket with a crack (only 4 years old!!). Nevertheless a clean up and repair with gasket silicone fixed it. The car still idles higher, albeit for a shorter period than before the fix, but eventually settles where it is supposed to once warm.

I was not completely home on this, as my idle still wanted to jump up in the 1100 rpm occasionally. The luckily yesterday my battery gave completely in after six years service, so I replaced it and presto. Now it idles exactly where is supposed to be. Actually it undershoots now until it settles, but that is really not a problem as the idle is not that low to make the engine cough when pressing down the pedal. But my idle consumption has now gone down with the lower idle RPM to 0.6-0-7 from 0.8-0.9L/h, which is nice and should save me around half a litre per fill-up and also make the engine less hot in city driving. So as also mentioned, besides the small vacuum leak, it had to do with a worn out battery that sagged in voltage in idle and made the alternator kick in as soon as lifted my right foot. In retrospect, I had noticed that when coming off the highway the idle would behave at my first red light and then creep up after a while. So a bad battery, even if it starts a car, taxes the alternator more and wastes fuel, and makes the idle high on a Seicento!!

Interesting to know!

Another twist to this story: On the SPI Seicento and other 90' SPI Fiats, the throttle body has a factory inbuilt vacuumleak: The breather hose from valve cover to filter housing has a small hose branching out midway that goes to a vacuum stud with a pin hole on the throttle body. On some SPI Fiats this leak has further been restricted by a insert in the hose, according to other posts here! I Tried to block it completely with a screw and it further decreased my idle rpm by 30 or so, and made it settle even faster. This is useful from a fuel saving perspective and doesn't slow down throttle response noticeable. I won't know for sure if this is a valid mod before this has been emission tested and there is a risk that this increases HC and CO, but it takes longer for the fan to come on now in summer city driving, so it puts less strain on the engine, and is surely a benefit with the 4X4 cam I'm running. My brakes also have slightly better bite with the higher vacuum.

You can buy the "ignition advance processor" which is normally used for bivalent (Petrol+LPG or CNG ) cars. Some of these devices can shift the ignition in both directions.