Desperate need of help - Punto W reg.

[lukeee]

W reg Fiat Punto, 1.2L

For the past month or two my cars been losing a lot of power, shuddering and struggling to accelerate.

This past month it has also been guzzling fuel, as in half a tank in 80 miles, which is more than it usually consumes. It is also throwing out a lot of black soot from the exhaust.

I've taken the car my mechanic, done a reading however no error codes have come up. He's attempted to change the spark plugs however that's done no good.

I've been told it could be the injectors, but I'm in desperate need as I require the car by Monday and don't want to be forking out replacing everything in sight to try and fix it. Anyone have any ideas what it could be?

Thanks, Luke.

 

[Burnerman]

Two things do spring to mind - not in order particularly....
1) The ignition coil pack, that provides electricity to the sparking plugs on demand; (that would normally produce an error code)
2) The coolant temperature sensor, that provides the engine ECU with information that can adjust the fuelling......just like the choke in fact, in the 'good old days'. (That wouldn't produce an error code necessarily.)
John

 

[lukeee]

Two things do spring to mind - not in order particularly....
1) The ignition coil pack, that provides electricity to the sparking plugs on demand; (that would normally produce an error code)
2) The coolant temperature sensor, that provides the engine ECU with information that can adjust the fuelling......just like the choke in fact, in the 'good old days'. (That wouldn't produce an error code necessarily.)
John

I was told something similar to the choke, air flow meter is it? My car doesn't have one of those but I'll throw the idea at my mechanic tomorrow see what he says.

It's really frustrating as I'm pretty clueless with cars past the basics so I don't have a clue what I'm looking for, and only noticed a major problem when my car was going through petrol so won't know immediately if it's fixed until I've drove it a while

 

[lukeee]

After looking around again, a lot of people talking about MAP or LAMBDA sensors, can anyone confirm whether these would be a cause?

 

[Avocet]

Lambda sensor would have thrown up a fault code. They adjust the mixture to keep the emissions within certain limits. Highly unlikely to be that. MAP sensors are unusual, but I'm not familiar with the Punto. It stands (I think!) for Manifold Absolute Pressure and measure the inlet manifold vacuum. Again, I'd have thought it would have thrown up a fault code if faulty. There are also things called "MAF" sensors (Mass Air Flow) which are more common. They do the same job as an airflow meter. Again, I would have thought it would throw up a fault code.

It's possible that you have a collapsed catalyst partially blocking the exhaust. That would give a loss of power and because it's not an electronic component, no fault code. Also as Burnerman suggests, Coolant Temperature Sensor (failed in such a way as to think the car is running too cold, so it's on "choke" all the time) or one or more coil packs (but I'd have thought you'd feel a misfire). I take it it's nothing daft like the brakes binding?

 

[lukeee]

Lambda sensor would have thrown up a fault code. They adjust the mixture to keep the emissions within certain limits. Highly unlikely to be that. MAP sensors are unusual, but I'm not familiar with the Punto. It stands (I think!) for Manifold Absolute Pressure and measure the inlet manifold vacuum. Again, I'd have thought it would have thrown up a fault code if faulty. There are also things called "MAF" sensors (Mass Air Flow) which are more common. They do the same job as an airflow meter. Again, I would have thought it would throw up a fault code.

It's possible that you have a collapsed catalyst partially blocking the exhaust. That would give a loss of power and because it's not an electronic component, no fault code. Also as Burnerman suggests, Coolant Temperature Sensor (failed in such a way as to think the car is running too cold, so it's on "choke" all the time) or one or more coil packs (but I'd have thought you'd feel a misfire). I take it it's nothing daft like the brakes binding?

It is misfiring, sorry I knew I'd leave something important out. I wouldn't know about the brakes binding, but assume that's something my mechanic would have picked up. I'm taking it back early in the morning, I'll throw these suggestions at him although he doesn't seen the character to take suggestions well.

I appreciate all feedback, this is my first car.

It's been misfiring for a while now, but didn't think much of it, it's only this past month I'd say I've been noticing the loss of power, but the severe loss of petrol is a joke and couldn't go on with it.

 

[Mursal]

If its misfiring you should have a wet spark plug? From there hopefully it is just a faulty coil pack for that cylinder. But if its not lack of spark it could well be that cylinder, therefore internal.
To be honest rushing to solve a problem that you have lived with for some time, is a sure way to over spend on repairs.

 

[lukeee]

If its misfiring you should have a wet spark plug? From there hopefully it is just a faulty coil pack for that cylinder. But if its not lack of spark it could well be that cylinder, therefore internal.
To be honest rushing to solve a problem that you have lived with for some time, is a sure way to over spend on repairs.

I understand, I haven't needed the car as such for the past few months, but starting Monday it'll be putting in some miles.

 

[mfarrow]

MAP is Manifold Absolute Pressure and Lambda is a letter in the greek alphabet, otherwise used in this context to mean a sensor which records the amount of oxygen in the exhaust gasses.

Something is telling your engine that it is either:

- Really cold (coolant sensor)
- There is a lot of air in the exhaust (lambda sensor)
- The amount of air entering the engine is more than it actually is (MAP/MAF sensor(s))

Now, there can be problems with the sensors themselves, or something more obvious/mechanical could be at fault.

For example, excess oxygen in the exhaust could be caused by an air leak in the manifold, or a piston not firing, which means none of it turns into carbon monoxide, and the ECU 'thinks' the mix isn't rich enough, so turns up the wick. This makes the engine pumps in more fuel and, ironically, actually reduces the efficiency of the burn, which means more oxygen from the healthy cylinders as a result. A viscous circle.

I would therefore start with simple things, plugs, leads etc. If it's missing then it is an ignition fault. If it's happening from cold that might push the coolant sensor down the list.

 

[Avocet]

OK, the misfire changes things somewhat. Are you certain you haven't got an engine management light on? (Does it work)? (Yellow one with a picture of an engine usually). A persistent misfire means that the fuel and air mixture from the misfiring cylinder is going into the exhaust without being burned. If this has been happening for a while and is bad enough to noticeably affect fuel economy, I'd have thought it would have put the light on as the lambda sensor goes out of range, trying to adjust the mixture enough to compensate for that. You might have more than one fault (coolant temperature sensor AND coil pack, perhaps). Also have a look for a big air leak between the MAF (if it has one) and the engine. They're usually connected by a big bore rubber hose with some corrugations in it to allow the engine to move about. They sometimes crack on the underside of the corrugations and let air in.

As an aside, if your mechanic doesn't take suggestions easily, you might wish to start looking for another one. Someone who is genuinely good at his job and is secure in his own abilities won't get grumpy when a customer is trying to make a genuinely helpful suggestion!

 

[Avocet]

When did it last have a decent service, by the way?

Oh, and (long shot this one) ask him to check the fuel pressure. The pressure regulator may have jammed shut so the fuel pressure is way too high.

 

[Belle427]

if its not plugs or coil pack related a faulty maf sensor can cause this, these rarely flag a light or leave codes when playing up.
If it has one you can disconnect it and then take it for a drive, if the maf sensor is faulty the car should run better although it wont be perfect.