Technical Spark Plugs for Seicento

[gp3000000]

I am trying to get rid of this stupid pinking problem which has plagued my Seicento since I've had it, I cured it the first time by reducing the gaps on my NGK plugs to 30 thou, the second time I cured it by changing plugs to Bosch Super plus. Now it's come back, gradually, and it's worse than ever. Before, it only ever pinked on hills and badly when cold. Now, it does both of these but pinks whenever accelerating too.

When I put the Bosch plugs in, I measured the gap, which was 30 thou out of the box. I've just took them out and the gap is still 30 thou. The plugs have done less than 5,000 miles and they smell WIERD. Not like they usually do, these smell of burning plastic!

Anyway, there seem to be many threads with many opinions on what is the best plugs for the centos. Most say NGK, and to stay away from Bosch. Some say use Bosch Super 4s (with the 4 electrodes). Some say use Denso's, I've not heard of them before.

For now, I'm putting the plugs back in gapped to 28 thou. Just to see what it'll do.

Any help greatly appreciated,

 

[rallycinq]

Why do you think the plugs are the cause rather than effect?

Is this MPi?

Cheers

SPD

 

[gp3000000]

Yep MPI.

The reason I thought they are the cause is that I cured it last time before by gapping, then the next time by replacing the plugs.

What other cause could there be?

 

[allanhelen]

Pinking is usually timing or fuelling related, plugs are only usually a factor in forced induction applications so look elsewhere


BTW don't use Denso's they are over priced and cr*p in my experience NGK's Rule!!

 

[gp3000000]

Well with the spark gap at 0.7mm (27.5thou), it's a lot better. Not pinking on hills anymore, was pinking slightly when cold. Have to see tomorrow morning when it's been left overnight. The plugs seem to cure this each time only for it to come back a couple of months??? Maybe pinking is the wrong word, it's what my dad referred to it as when it first happened.

 

[allanhelen]

are you sure you are just not driving the car properly and are in in too high a gear at the wrong time?

 

[rallycinq]

Does the MPi have a knock sensor?

Cheers

SPD

 

[gp3000000]

Can't remember where I read it, but I'm pretty sure it was somewhere on this forum, that the MPI has a knock sensor but the ECU does nothing with the information it provides.

Should have mentioned earlier, I run it exclusively on Shell V-Power 99 now, as the pinking is a lot worse on 95 fuel, as pinking is pre-ignition and a higher octane rating causes slower burning, this makes sense to me.

Allenhelen, I don't think I change up too early, if anything I change up too late, because the acceleration was so bad in the higher gear because of the pinking!

Since I changed the gap, it seems that the car responds better when you change up.

 

[rallycinq]

The car should run perfectly on 95. There is a sensor playing up somewhere.

Possibly temp, either coolant or air.

Cheers

SPD

 

[gp3000000]

Coolant sensor's in the back of the head, isn't it?

Is the air temp sensor in the throttle body?

If I put a meter on them, what should I be seeing? Resistance changing?

 

[rallycinq]

Not sure on MPi, I'm afraid.

I am sure an MPi guru wll be along in a minute or two.

Or

The info might be available in the Punto FAQS/guides.

Cheers

SPD

 

[dendjoker]

the air temp is in the throtle bodie, you've got the big hole for the air but also a other hole, if you get the trottle of you can see it...

did you ever check it whit the ecu on the computer at a garage??
And is you're timing correct? the mpi can go up to 3teeds wrong and will drive like it's all normal. i advice to check that to.

 

[Pep0]

It is is pinking then it can do a lot of damage.

If the plugs are so hot they are cooking the plug lead material that is not good either.

Timing is the first thing to check, if it is not out, your plugs are the correct grade, and your petrol is premium pump petrol you may have an engine problem.

Noel

 

[rallycinq]

I kinda assumed that the OP had checked the timing, as thats the easiest one to check.

Cheers

SPD

 

[fingers99]

Does the MPi have a knock sensor?

Cheers

SPD

MPI has a knock sensor. It will retard ignition if it senses knock, but will not advance till just before the point of knock (so using higher octane fuel is pretty much a waste of money).

I can't see it being plugs (if it were, using a colder range of plug -- going up one number on NGKs, for example) would be more effective than playing about with the gap.

I doubt it's pinking.

 

[gp3000000]

Timing was re-set after the HG change I did in June. Timing was checked again when car didn't run properly, and found to be correct. This is when the new Bosch plugs went in.

The leads were replaced also. They weren't burnt/melted then, and neither are the new ones now.

 

[Pep0]

If you can get a endo scope down the plug and there are signs of mice eating the piston, then you have pinking.

When you pulled the plug after 5000 miles

- 1st question what colour was the ceramic insulator and
- second question did it (the insulator) look new?
- 3rd question how much metal did you skim from the head?

Noel

 

[gp3000000]

Ceramic insulator was white/cream - the colour it should be isn't it?
Don't think it looked new. The rest of the plug certainly didn't look new, the metal exposed part was caked in carbon. I scratched some of it off with my fingernail.

No idea how much metal was taken off. I could probably find out if needed.

 

[craigb244]

im surprised if this is pinking! these engines are rather low compression and imho not prone to it.

 

[Pep0]

If there was carbon on the metal it probably was not too hot.

But modern plugs should still look good after 5k.

Can you try & describe the noise cause it is probably not pinking. But it is important not to dismiss that it might be pinking as it will damage.

My sei has so little noise suppression between engine and ears that it growls/roars under acceleration.

Noel