Last week I suddenly noticed a loss of power from my 2000 mk2 punto. I experience poor acceleration particularly at higher speeds, sometimes it struggles to get over 50-60 mph. When driving it sometimes loses power and then suddenly regains it, as if you took your foot off the accelerator and immediately put it back on. My mpg is also poorer that usual. The engine idles perfect and their is no obvious problem. I don't have any error codes. It was serviced 8 months ago and only done 3000 miles since. Since the service I noticed the oil level get slightly lower , its half way up the mark now. This wasn't the case the previous time I serviced it. Since I bought the car a few years ago I always had to top up the coolant every few months. I'm thinking the oil and the coolant could be due to the head gasket going but would that suddenly cause the symptoms that I am getting? I remember I drove it in the morning and it was perfect and drove it again that night and noticed performance issues. Thanks

i would say coil packs
but can also be ht leads, spark plugs, head gasket, fuel pump...

How could I troubleshoot to try and find out exactly what's wrong, or is it a case of replace and see if its fixed

Coil packs would probably be a good start since they are an easy fix

for ht leads you could start car and check at night if you see some lightning bolts jumping around

Those symptoms are also what you get with a timing belt out or jumping a tooth.
Second thought on reading your post properly.............scratch the tooth jump notion.
Power won't come back on it's own unless it's a magic belt that is jumping back and forth .
Leads, coil packs, plugs it is and maybe even an injector.

Power coming and going - when under load
Back at idle - its fine again

Thats a classic sign of a coil pack or both failing under load - getting ready for replacing

Me?
I'd do the whole lot
Spark plugs - HT leads and Coils

ziggy

Thanks, I'll replace the coil pack next week

I didn't replace the coil packs. Sometimes when I stop at the traffic lights the engine vibrates quite a lot when at idle. Almost like its miss firing but not quite. I was speaking to a mechanic who used to work in a fiat garage. He said its definitely not the coil packs because if it was there would be an error code which there isn't. He said its either the cat is breaking up or the fuel pump is not supplying enough pressure.

is this 1.2 8v?

It is flisko

measure compression and fuel pressure

did car fail on gases?

"When driving it sometimes loses power and then suddenly regains it, as if you took your foot off the accelerator and immediately put it back on."

i still say bad coil packs, did you try another pair off a working car?

I agree the coil packs would be an easy cheap fix that would at least rule them out as being the problem. When I went to get them I was told it could not be the coil packs because if it was I would be getting a fault code.
Unfortunately I don't have the equipment to measure fuel pressure or compression myself. Car never failed on gases. Tomorrow, I'm going to cut the cat off and see if its clogged, hopefully it is.

conors891 said:

I agree the coil packs would be an easy cheap fix that would at least rule them out as being the problem. When I went to get them I was told it could not be the coil packs because if it was I would be getting a fault code.
Unfortunately I don't have the equipment to measure fuel pressure or compression myself. Car never failed on gases. Tomorrow, I'm going to cut the cat off and see if its clogged, hopefully it is.

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waste of time cutting cat off, drive to a test to check for gases, they usually do it for free if you say if they can only check gases, used coil packs arent that much, or if you can find someone with same car in your area and try to swap them, you dont need to unbolt yours, just connect cables to new ones and see if car is acting different, 4 allen bolts per coil

"If the coil pack was gone there would be a fault code" do you agree with this flisko? I don't believe everything a mechanic tells me but he said its either low fuel pressure or high exhaust pressure. I want to have checked those two things first before I go back to him and tell him he's wrong.

Remember if it is running badly you will be harming your Cat and potentially making things worse.

You need to do a compression test to check the headgasket... a common failing on these engines and straightforward to repair on these engines if you catch it early enough.

If it starts running badly try to identify which cylinders are bad by taking off plug leads one at a time (avoid shocks!) - a dodgy cylinder will make no difference to the engine running.

A failing HG should affect 2 adjacent cylinders.

The coolant loss should be investigated if it's not the HG.. the engine had temp sensors in the coolant feeding back to the ECU to control fuelling, so if these aren't in the water then it could give erratic results. A full flush and service of the cooling system might help if the HG is OK.

The oil loss might be due to using a lighter oil at the service?

Problem is that most of the time it runs fine. If the engine didn't run at all it would be much easier to diagnose. I'm not loosing much coolent or oil. Coolent I have to top up once or twice between services and oil level is halfway down the mark since last service(April) so again not much.

I stopped at traffic lights last night and the engine started vibrating badly as it does sometimes when I stop. But this time the rpm suddenly dropped to the point of cutting out but then perked up again just in time. This is starting to seem more and more like a fuel problem. Could someone explain how exactly the power to the pump is controlled when the engine is running? I know it supply's 12v to the pump at the start for priming. I know the car doesn't have a fuel pressure sensor so I'm curious to how it works. Thanks

conors891 said:

I stopped at traffic lights last night and the engine started vibrating badly as it does sometimes when I stop. But this time the rpm suddenly dropped to the point of cutting out but then perked up again just in time. This is starting to seem more and more like a fuel problem. Could someone explain how exactly the power to the pump is controlled when the engine is running? I know it supply's 12v to the pump at the start for priming. I know the car doesn't have a fuel pressure sensor so I'm curious to how it works. Thanks

Click to expand...

The Car prime up by applying 12v to motor as said
When engine is running, the 12v feed is restored

The Punto uses IIRC a return-less system
I believe the pump has a regulator in it - so it dumps excess fuel Pressure back into the tank

Coming upto a Set of lights - the car suddenly struggles to run and suddenly picks up
That the sign of a potentially clogged throttle body butterfly valve
The goo that forms around the flap and body causes an air restriction causing it to stall on return to idle as the vital gap is much smaller then it should be

The car see's its struggling and the Idle valve kicks in fast and hard to recover

This is fine the idle valve now has control, but when you drive off the idle valve closes again

Ziggy