Hello chaps,

I come to you cap-in-hand in desperate need of some advice. My car is a 1999 Punto 60SX.

About 6 months ago it developed this weird stuttering/hesitation problem. Mainly when cold and when accelerating from a low speed.

Tried a few things but no dice, it was annoying but the car was drivable. Since then the fuel economy has been getting worse (from around 43/44 MPG to 38/39). Could be due to winter, but I started noticing it in August.

So last weekend it started doing the 'thing' more frequently. Like every time I accelerated from a stop. Basically it was kangaroo-ing for a few seconds after take off, no matter how much gas I used.

I thought it was time to take a good look. I took off the HT leads and a couple of them were a bit corroded, so I put it down to that and drove to Halfords. On the way it was EVEN WORSE, like it was firing on 3 cylinders? I changed the leads outside the store, but it was exactly the same.

It is now undrivable. There is no power, major stuttering and it sounds like "bom-bom-bom-bom", not the nice purr I'm used to.

Ok, here's what I've tried.

Checked oil and water - all good.
Compression test - all good.
HT leads - new
Spark plugs - 10k miles on them (Bosch Super 4s) but in good condition. No real clues on the plugs. A bit sooty maybe?
Coils - new around 2k miles ago (one of the things I tried recently).
Injector - Tried another one (that was previously OK). Car was exactly the same.
Valve Timing - Spot on.

I should add that it got progressively worse over the weekend; first it was just hesitation (but otherwise OK), then it got really bad (idle still fine, but borderline stalling when applying power to the wheels), then it was bad all the time, even at idle - when cold, hot, whenever.

So. Any ideas? Fuel pump? Bad spark (ECU?)? I'll do any test you recommend and report back. I'd really appreciate your help.


Regards,

ST

Hows your crank sensor? It sounds like the timing has gone off a few degrees or the tensioner isn't secured and is loosening

60SX, so does that will make it a Mk1? When was the fuel filter last changed? Could be fuel starvation.

m20b25 said:

Hows your crank sensor? It sounds like the timing has gone off a few degrees or the tensioner isn't secured and is loosening

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To me, it is like the timing is off and that was my first thought. I checked using the cam sprocket and the flywheel, which is how I set it last time, and it is bang on. Tension is good, belt looks good and was changed 10k miles ago.

Crank sensor is original, from the information I have.

DasArab said:

60SX, so does that will make it a Mk1? When was the fuel filter last changed? Could be fuel starvation.

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It is indeed a mk1. Fuel filter changed 10k miles ago. My spidey-sense is telling me it is fuel related as when it started to get worse it was when accelerating (demanding more pressure?), but flow was good (maintained speeds OK).

Were have you been geting your fuel?

thelad said:

Were have you been geting your fuel?

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Same places as normal, although I haven't filled up in a while. Either Tesco or Esso.

Iv noticed my mk1 1.1 8v runs a lot better on esso, shell or bp, wont go back to supermarket stuff now. Just out of intrest try runing it with the tank cap off.

thelad said:

Just out of intrest try runing it with the tank cap off.

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I am intrigued. What is the thinking here?

No ECU warning light?

what were the Compression Figures for wet and dry?

i'd be suspecting the fuel pump is eitehr blocked or its struggling to pump
Or the pump is going - but the injectors aint working properly

Ziggy

have you changed that crank sensor yet?

If it runs/starts better with the fuel tank cap up it would show if the tank vent was partly blocked. Worth a try.

My money is on the TDC sensor. Fuel pump is a possibility, but TDC an easier job anyway and the fuel pumps are generally very reliable.

Thanks very much for your help guys!

fingers99 said:

No ECU warning light?

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Nope. I have the means to connect a laptop to the car though as I have in the past. Will check all the sensors at the same time (throttle position, MAP and so on). Terrible weather outside at the moment though!

Ziggy122 said:

what were the Compression Figures for wet and dry?

i'd be suspecting the fuel pump is eitehr blocked or its struggling to pump
Or the pump is going - but the injectors aint working properly

Ziggy

Click to expand...

Sorry I didn't write the figures down. I ran the engine for a bit, then removed the fuel pump fuse to get the chambers clear and did a test after that. All the figures were in the upper part of the 'green zone', so around 180 psi? All cylinders very similar so I didn't do a wet test.

dave said:

have you changed that crank sensor yet?

Click to expand...

Should I change it?

thelad said:

If it runs/starts better with the fuel tank cap up it would show if the tank vent was partly blocked. Worth a try.

Click to expand...

I will try this next.

fingers99 said:

My money is on the TDC sensor. Fuel pump is a possibility, but TDC an easier job anyway and the fuel pumps are generally very reliable.

Click to expand...

Is there a way I can check the TDC sensor?

i would

Is there a way I can check the TDC sensor?

Yes, but since the misfire is intermittent, the fault will be, too.

They're cheap enough (and often faulty) so I'd just replace.

Hi All,
I am the new guy here.
ST60SX, I do have the same problem, that got worse over time. For the last 5 days it is terminal . The things I tried and changed- spark plugs, leads, engine pressure's good,coils changed and......crank shaft(brand new)....same thing.
Called the smartest heads overseas, and was told to take and spray clean a sesnsor.....do not know what is called......it is located under the air fillter , right of the big HOLE. Needs to be unplugged and a couple of tiny star screws to be undone. what is to be pulled off is like half a pan with a little electr. part in it.Aparently this is the PROBLEM.Will atempt the procedure on Saturday.I understand my car is all good , but little unknown el. problem is causing the whole havoc. Forget about Cranks and staff ST ...and I understand that it is unlikely a comp will detect this.
Anyway. Share your experience if you attempt before me.
Cheers

Bit of an update.

I connected the car to my laptop. Throttle position and MAP sensor working good (vacuum looks good as well). Temp sensors seem to be working as well.

Nikk I think you are refering to the air intake temperature sensor. A small red thermistor located under the airbox. It seemed pretty accurate yesterday (showing around 13 C) but will test it properly this evening.

Will update with more info later.

The little red thermistor (assuming Mk1, and not a wierd hybrid) only does real work on warm up. Every SPI car with after market induction has them chucked in the bin.

FIXED !!

It was a spark plug. Here's how I found it:

I didn't want to disconnect plugs while it was running (apparently this can damage some EFI ECUs?) so I disconnected one whole coil pack. The car still started. With the other one connected on its own it didn't start. I figured it was a problem with one of these two cylinders.

I took these two plugs out and the resistance of the centre electrode was 5.4 KOhms on one and 12.8 KOhms on the other.

I had a spare one and it was 4.8 KOhms. I have since found out the resistance is supposed to be around 5 KOhms.

I replaced the spark plug with the spare and it now works great.

I'm confused though as these plugs have only done 10k miles? Visually it looks perfect - not sure what happened here. No warning in the ECU error log either and no EML. Very weird.

In any case, thanks for all your suggestions - I made a contribution to the site to say thanks.