Hi all,

I have a 2001 1.2 16v Fiat Punto HLX, and I am having a few problems. Firstly, the car struggles to hold an idle (in the sense that it is *very* rough). For the last few months the car had been cutting out as I approached a traffic light in neutral, and sometimes cut out as the revs often dropped to around 600rpm. I am unsure if the problems I am having now are symptoms to the problem cutting out I faced previously.

Also, when I drive - there is a tapping from the engine (this is only when the car is under load, or if I run through the rev counter quickly). The tapping is not too bad when revving, however it is very noticeable when driving (which I am not doing, just saying to help the diagnosis).

I have a cheap OBDII tool, and there was a P0105, referring to the MAP sensor. I replaced this, and it has made no difference. Due to this, I would assume that there is a problem either elsewhere in the circuit, or the fuel:air mapping is having problems elsewhere. There is also reports of misfires on cylinders 1 and 2, however when checking the spark plug ends they're dry (however, blackened). The car is running rich.

I have tried to check the timing belt, and it seems to be in excellent condition, and seems very tight - is it still possible for it to slip while tight?

I also removed the pre-cat (upstream) oxygen sensor, and tested it by placing a propane torch onto the end of the sensor while reading the output with a voltimeter - it seemed to react quickly. Could it still be a lambda issue?

I am struggling to find the issue, however I am no mechanic and I hope that somebody can help point me in the right direction.

Many thanks in advance,

Chris

By default the engine runs rich. On cold start the lambda is out of circuit. When the engine warms up the lambda signal is used to reduce fuel flow to give a correct fuel/air mixture. If the lambda is not switching (or not properly) the engine will run rich.

You need to get the switching trace from the upstream lambda sensor as this controls the fuel mixture.

The timing belt should be tight so it cannot slip. However old belts can lose teeth until the cams open late and pistons hit valves.

16V engines are not safe when the belt fails. Regardless of how the engine is running, if the cam belt is of unknown age and/or miles it should be changed.

krslynx said:

Hi all,

I have a 2001 1.2 16v Fiat Punto HLX, and I am having a few problems. Firstly, the car struggles to hold an idle (in the sense that it is *very* rough). For the last few months the car had been cutting out as I approached a traffic light in neutral, and sometimes cut out as the revs often dropped to around 600rpm. I am unsure if the problems I am having now are symptoms to the problem cutting out I faced previously.

I have a cheap OBDII tool, and there was a P0105, referring to the MAP sensor. I replaced this, and it has made no difference. Due to this, I would assume that there is a problem either elsewhere in the circuit, or the fuel:air mapping is having problems elsewhere. There is also reports of misfires on cylinders 1 and 2, however when checking the spark plug ends they're dry (however, blackened). The car is running rich.

Click to expand...

I had exactly the same issue. Changed my MAP sensor which mad the EML go away but car still stalled. There is a guide in the punto section for cleaning the throttle body. I did this and my problem was solved not stalled since.

As for the car running rich try lambdas as suggested. I found wrong voltage on pre cat was worse than no voltage(unplugged) pre cat. left mine a couple of months tryign to diagnose (not realising it was lambdas and my mpg was around 28 with wrong voltage 35 with none)

Tony

Thank you for your prompt reply; I have checked the teeth on the Timing belt, and they are all fine. I am hesitant to change the timing belt until I rectify this issue, unless of course the timing can still be off (even if a jump seems impossible).

I have a basic OBDII tool, that I am using with Scantool.net. I understand that to view the switching trace it's best to use an oscillation graph. Is there any software I can use with the dongle to produce an oscillation graph, or should I use some other method?

-- Edit: @Tony: Thanks for your reply; I shall do a throttle body clean tomorrow. Seeing the prices of pre-cat lambda sensors, I am tempted to buy one as it seems like a likely issue.

Also, I have checked the coils, and all plugs seem to be firing fine (and removed plugs one by one, the car still runs (although, like a bag of sh@t)). I will check the ECU part number tomorrow, although they seem expensive and would like that to be a last resort.

Again, many thanks,

Chris

If the cam belt has all its teeth and no signs of cracks at the teeth roots it fine - dont worry about it. It CANNOT jump.

If you dont know its age or if its old, then when you have the car running again change the cam belt.

Thank you for the reply again; yes I intend on doing a full cambelt and water pump replacement after I get the car running again (if I do, otherwise it's getting scrapped) - the car has 74K miles, and as far as I know has not had a new cambelt, so it's due.

I'll also look about getting a lambda sensor off an 8v Punto, will it be compatible with a 16v Punto?

Regards, and thanks,

Chris

The car will get sorted its very unlikely to be terminal damage. Just be methodical.

If the Lambda is faulty a used one might be no better. They are fragile devices easily upset. Even coolant from a failed head gasket can kill them. But if you can get one free then give it a try and then check its voltage trace.

A fault codes scan and lambda trace will help sort it out.

Hi, thanks; I've done a part search and the Lambda sensor I have installed currently has part no. 0258006206. When searching for this part number, it seems to only direct to Bosche parts, which on average sell for ~75 pounds. Is it possible to use a 4-wire generic Zirconia sensor with an 18mm fitment or is this inadvisable?

Here are examples of what I'm looking at:

Bosch Sensor, on eBay [sorry, I can't post links with <5 posts, copy&paste is required =( ]
bit.ly/hJw0ND

Aftermarket Sensor, on eBay
bit.ly/fYg70m

I understand that you get what you pay for and whatnot, but surely there must be cheaper alternatives (for a cheap car) that are satisfactory?

Regards, and many thanks for the help!

Chris

Edit: Also, I cleaned the throttle body earlier, and the idle has become a lot smoother. I believe this will fix any intermittent cut-outs I had previously. I am betting a lot that the current tapping is due to the over-fuelling of the chambers, causing misfires, making the pistons knock under load. Thanks!

2nd Edit: Purchased Lambda from SHOP4PARTs, hopefully will arrive soon. Will post if it fixes, or if I have more issues. Many thanks!

The cheap lambdas are best avoided. Shop 4 parts stuff should be ok.

Presumably, you've extracted the existing sensor's voltage trace and its substandard.

Correct. =)

Regards,

Chris

anyway, in your place I would like first to measure compression.
My recomendations:
Check the compression. If ok, then work with your obd2 tool, check lamba sensors graph, then temperature sensor.
p.s just dissasembled two of these engines and unfortunately - there are many weak points....

Hi, thanks for your reply; I've had the compression measured by a mechanic yesterday and he told me it was fine as I do not have the compression gauge to do it myself.

The current Lambda sensor seems like it's providing substandard output, so I've ordered a new one from SHOP4PARTs and hopefully that will arrive on Monday, or Tuesday (not sure what the delivery speed is). What should I be checking for on the temperature sensor?

Many thanks in your replies, they have been extremely useful!

Regards,

Chris

On temperature sensors you should check temperature. It can show -20C, while there's +20C realy. And according to your temperature sensor data ECU can make faulty calculations for injection and timing.
Conserning oxigen sensor, what do you call substandart output? Is it stright line? If it's not and it reacts to rpm's, then it's alive. Maybe something else causes it to make substandart output?

Using Scantool.net the Lambda Sensor responds with a voltage output, however any software that supports some kind of oscillation graph just flat lines. The intake air sensor showed ~23 degrees c (about right), engine coolant was ~53 degrees c.

Regards, and thanks,

Chris

Edit: The flashing EML (which I believe is a sign of generic misfire) is now a lot more common. I guess I will wait until I put a new Lambda sensor in to see if it removes the misfiring.

OKay, so I have the new Lambda sensor - I've fitted it to the car, yet the car responds no differently. I have now unplugged the negative terminal of the battery, and I am going to leave it for 2 hours to in the hopes that if the ECU is adaptive, any stored mappings will be removed.

If that does not fix the fault, I am going to attempt re-checking the injectors however after that I am quite stumped as to what the problem is.

Advice?

Many thanks,

Chris

Edit: I'll provide a video to help with the diagnosis once the ECU has been reset (if that does anything).

Okay, so I now have a video of the engine noise. Please note that this is with a new Lambda sensor.



Sorry for the rotation, no idea why YouTube has done that. =/

That sounds mechanical like a broken piston or dry cam shaft.

WhiteSei said:

That sounds mechanical like a broken piston or dry cam shaft.

Click to expand...

Aiye, my dad is saying the same. We're going to take off the rocker head tomorrow (when my brother gives me the Fiat book) and have a look to see for any signs of ware.

Regards,

Chris

Have you just had the head gasket changed?

Nope, and there's no signs of head gasket failure.