Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Regapped Spark Plugs or clean MAF?

My 4/4 (tuned Ecotec VVTi with MBE ECU) has been getting more and more reluctant to start over the last couple of thousand miles. Nothing too terrible, it runs fine once it's going, but it's worse when it's been sat for a while, sometimes taking a good lot of cranking to fire.

So today I decided it was time to do something. Fuel pump valve letting fuel drain away from the injectors? Knackered spark plugs? Clogged air filter?

I reasoned that the fuel pump was hardly likely to be at fault as the engine's only done 50k miles, so I cleaned and re-oiled the K&N filter, squirted a load of MAF sensor cleaner about the place, and took the spark plugs out for an inspection. Although a lovely light tan, the gaps were a bit big I thought, so I closed them up to a bit over 30 thou (Iridium plugs).

Put everything pack together, and the thing now bursts into life suitably promptly and settles into a very steady idle, most satisfying. Now the only thing nagging me is which bit is likely to have had the most effect? There weren't any misfire or MAF codes stored, and the air filter, although grubby, was not clogged by any stretch of the imagination.

I always squirt MAF sensor cleaner over a clean piece of tissue. That way you can see how much muck comes off Tim, although it's always been spotless. Maybe your checks just disturbed something that was amiss or it was a plug gap issue.

That is why you should always do one thing at a time and check that way you know what has cured the ailment and what has not.

Tim, my money's on the oversize plug gap, straining the coil packs to develop the extra HT volts to jump the gap, this takes extra time to build the charge so can cause the charge to delay and miss a cylinder in random sequence as you crank

Yep, I'm with cooperman. Coil packs age and this might be a sign that yours is getting tired. If it starts to recreate the same symptoms again suspect its on its way out' you might also have loss of power from an inadequate burn if the spark is too small. Incidentally ford revised their iridium plug gaps to 1.2mm which resolved the problem they had with coil packs failing, their original setting was 2.5mm which caused plug failure and then coil pack failure as the gap became so large that the coil was under immense strain, coupled with heat they failed on a regular basis! Hope that helps.

Are you sure that is correct. 1.2mm is a tad under 50 thou and 2.5mm would be a whopping 100 thou or 1/10th of an inch. I can believe a max of 1.2 mm for a standard engine but I would have thought 1.1 mm or 40 thou to be about right. It seems to me that most engine tuners recommend a gap of around 30 to 35 thou for a mildly tuned engine particularly if the cam and or compression have been altered. I am not sure what the pre-set gap is for Iridium plugs recommended for the standard tune Ecotec VVTi .

The iridium plugs I fitted 20k miles ago were gapped to 45 thou, which is standard spec, and they had opened up. I brought them down to around 35 thou, exactly as Peter says the recommended gap for tuned engines.

I'm not worried at all by the condition of my coil packs, they are GM not Ford units and have no history of failure. I'm more concerned by battery voltage, although it's a newish battery I'm not seeing the volts I would like, but the engine spins quite happily and now starts exactly on the 2 seconds cranking that the ECU is set to before it fires.

I'm happy to conclude that the issue was caused simply by the plug gaps wearing a bit wider than the engine liked. I downloaded some run logs from the ECU and there is no data at all that's remotely out of appropriate ranges so I don't think there's any deeper issues of concern.

Ford found that an overly large plug gap eroded/damaged the plug electrodes on iridium plugs, this then increased the gap to a point where it put the coil pack under too great a strain and destroyed them. At dealer level the mechanics started setting the plugs at 1.0mm and this seemed to alleviate the problem to a great extent however ford had instructed them to use copper core plugs while they investigated the problem which was initially of unknown origin and thought to be a Mondeo/Duratec issue and initially spent time investigating the coil packs themselves as the weak point.

It was really the fact that the iridium plugs electrodes were being eroded to nothing very quickly as reported by dealerships that Ford thought it was an issue with plug quality and because dealers were replacing iridium plus at a now suggested 5000 mls it quickly became apparent that knock off plugs from china which certainly weren't iridium were infiltrating the market and the larger gap and increased spark to a small electrode had a predictable outcome. in the end this pointed them to plug gapping rather than coil pack issues.
Personally I set my plug gaps at 33 thou. with iridium plugs (2.0Lt Duratc). I visually checked spark consistency until I was happy as I reduced the gap and I have had no electrode wear at all. If you think you have found a bargain when buying iridium plugs you probably haven't and it may just cost you a coil pack!

If memory serves me well I think most iridium plugs are pre-set at 39thou.

If my memory serves me correctly, the electrode gap for Iridium spark plugs is smaller than for conventional spark plugs...to achieve the same working value. I had Iridium plugs for a while and I am now happily using standard plugs again. Don't get the electrode gap values mixed up.
You can tell very easily if you google a standard type for a Ford plug and look up the Iridium equivalent plug, the electrode gap is different. Just as an ifo, if I go by the values that Ford recommended for my 1.6 Sigma later, they always refer to conventional plugs if I see it correctly.

Yep, if I had a Ford engine I'd be following Ford recommendations and experience. But as I don't, there's not much in the way of parallels to be used. I go by the advice of SBD Motorsport, who are the font of all knowledge when it comes to tuned GM Ecotec engines and MBE systems ECUs.