Hello all.

It's been a while since I posted something but on the positive side I feel more Cento Fanatic than ever. I now own 2 Cento Sportings

I've been a Cento Sporting owner for 4 years now, it has 170.000km on the clock and apart from head gasket gone, no other serious issues so far... it just drives and goes like hell.

Now I've purchased another Cento Sporting... it's a clone from my first one. It's black, 1996, also an airbag version and pretty much the same apart from the aircon my first one has. 120.00km on the clock and MOTed on the day I purchased it. Clean MOT apart from a re-inspection after CO failure (new lambda did the trick, previous owner payed for it)

Now the issue:
-When stepping on the clutch for a roundabout (from 4th to 3rd or 3rd to 2nd), revs drop a lot if I'm not fast enough to pick up the pace. It has cut-out some times so far and seems to get worse if the petrol is getting near the reserve.
-Idles at good revs, runs smooth, fuel mileage is good, so apparently nothing wrong with it.
-After replacing the lambda, the revs went too high on idle so apparently the previous owner messed around with some sort of nut near the throttle body that uses a 3 or 4 hexagonal key and lowered the idle speed (very odd to do that).
-I'm also missing the two tubes/lines that attach to the air filter box. One tube I know that comes from the air intake tubbing, the other one I need to wait for the rain to stop to ckeck from where it comes comparing with my other Cento. Could this be the fault? I mean, people with direct air filters remove them and most cars still run well.

I also checked for master brake cylinder leaks/failure that could induce this problem. Apparently it happens when I downshift and use the brake at the same time. Got the car to idle, pressed the brake pedal a few times and all is smooth, idle wise.

Car is all original... even paper air filter. It has new plugs, oil, filter, etc, etc... I mean, it got a clear MOT 6 days ago.

Car will go to my mechanic next week for a tranquillizing inspection, so I'm just searching for something more specific for him to look at.

Have a great weekend.

You need to check that the pipes on the TB aren't open to air, and that the throttle adjustment on the TB is back to where it should be.

At least you have the other car for reference

Cheers

D

Yes, it's a big advantage to have another Cento to compare with, even if it's slightly different due to aircon configuration.

I've checked and one of the missing tubes that goes ot the airbox comes from the TB... apparently.

Another question: previous owner told me he turned the supposed nut about 3 or 4 times. Is there any way to find out exactly what he did or is it trial and error? Also, any way to find out if he messed around turning the black valve/sensor (we have a different name for it) located on the TB?

Many thanks.

Meanwhile, I've compared both cars on some items. The 2 tubes coming out from air box are defo missing in action.

Another thing is the car idling to high around 1100rmps and when lower seems to rattle/shake a bit. My other one idles at 900rpms and smooth as a kitten.

I'm keeping my fingers crossed it's as simple to fix as placing back the two missing tubes.

In worst scenario I'm thinking about some sort of injector failure or rpms sensor malfunction.

Cento ownership is never easy for a non-mechanic like me

Sort out those pipes and then see what you've got to deal with. They're lack of presence will not help.

Cheers

D

Hello again.

Yesterday I got my hands on another Black Cento on a scrap yard. Took some parts from it, like some temperature sensors, the tubes I needed and so on.

Got home to refit the tubes and surprise... the TB on my car does not have the connection to the airbox (to the temperature thing in the airbox that switches from heated to cold air). By the looks of it, the TB is defo from a Punto 55 because that exit is blocked, but it should be the same as the Cento and Punto share the same engine and injection system.

Mechanic will only be able to check the car from A to Z on thursday so I'm still searching for some answers to what can be causing the cut-out on downshift.

Idle is stable at 1050rmps or about (I think it's a bit high).

My back box is completely broken inside as I ear a lot of rattle. Can this cause lack/excess of backpressure and result in rpms problems?

Thursday will take plugs out, check what ever I can and try to sort it. It's way too dangerous to go around with a cut dying in traffic.

Apart from that, car pulls nicelly, good fuel economy, cooling liquid isn't dropping amd oil level seems to be ok too.

Forgot to mention it needs a new timming belt and tensor. Already have it as previous owner got me a new kit (premium brand). Can this also cause the revs problem?

I'd do the timing belt anyway and make sure the timing is spot on. The revs problem could be the timing a tooth out.

There is one less inlet on some centos because they take the map from the manifold. With the engine running put the end of a finger over each inlet and make sure you identify which has vacuum and which doesn't.

Cheers

D

I placed the finger (dipped in some water to get more feel for air movement) and placed over blocked/missing inlet. No vacuum or activity is showing on that one.

As to the other inlets will leave it to my mechanic to test when we take everything apart.

Been reading all the threads I could find about this subject and similar ones and this surelly is a common problem. Haven't read a simple explanation for it apart for some common possible faults.

I'm happy enought I tracked a Cento for parts in a scrapyard 10 minutes away from work. Should be able to get all the parts I need in case any need switching.

Btw... is it worth getting my butt of to Fiat and have it properly checked on the machine?

RuiG said:

Btw... is it worth getting my butt of to Fiat and have it properly checked on the machine?

Click to expand...

Nope, its unlikley the Fiat dealer will still have the machine for a Cinq.

Cheers

D

At the shop where my mechanic works I know they can check his seat Marbella, so I might have a go there and give his boss some of my hard earned euros.

i had similar problems like that! It was the crank sensor! You got another one, so try it!

Ming

Hello again and thanks for the help.

Can someone point me out to where it is located? In Portugal we use different names for stuff so I'm a bit lost to what it is and where to be found.

Is this the one on the attached image?

yup , number 1 is the correct part. You can just remove it from your other cinq to try it!

Ming

I think tomorrow will visit scrapyard during lunch hours and bring some extra sensors and small bits I will slowly transfer that poor abandoned Cento to my garage until only the chassis remains

All the FIRE series engine uses the same crank sensor. (they are just different lengths of wire)

Ming

Hey again. From the scrapped Cento I removed a couple of sensors. Can someone tell me where the crank sensor connects and if it is blue? I removed one that I think is the temp sensor on the gearbox side of the engine and a blue one that is on the timing belt side. Both sit on top of the engine/intake manifolds.

crank sensor will be right down by the crankshaft pulley. it reads the teeth off the pulley.. pics ??

Hummm... so I guess I have to pick that one also. Those two don't match the description and since I'm doing the timing belt I should test that one too.

crankshaft sensor looks like this. ignore the plug bit though