Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Help Please - 998 Misfire Woes

[spinoli1]

Skidlids – thanks for the multi-pin connector legend. That could be useful for so many things.

Nelly/Skidlids – do you have the correct figures for the air gap clearance on the crank sensor? I reckon I can check this bit myself. For electrical stuff, I’m afraid that I will need to draft in a grown-up. The only uses I have for electrical terminology are, for example:

- Volt do I do with this bit?
- Amp pretty confused now.
- Ohm my God it’s on fire!

BDG – The bike does not, and has never had an alarm fitted (thank God) – one of the advantages of Jersey, though it is changing fast, and we’ll need them soon.

I will not be able to put any of your advice and suggestions to use until the weekend, but I am very grateful indeed for your suggestions, and I am optimistic that I can sort this soon with your help.

Cheers,

Spin

[skidlids]

Had a look in my mauals last night, my 998 Testastretta manual only seems to cover the engine and the 998RS one doesn't have much on the electrics.
I can unplug the sensor on one of my 998s and get a resistance reading and if I borrow a meter from work I can measure its inductance, but not a lot of good to you unless you can do the same.

[nelly]

Air gap is spec'd at 0.65 - 0.7mm. It's adjusted with shims under the sensor body. You should be OK at about 0.6 - 0.8 though.
If that hasn't been touched, i'd be erring on the side of the sensor breaking down tbh.

[BDG]

If it's not the alarm, then i'd blame Nelly for being a useless good for nothing layabout living in England instead of Jersey

[Ray]

Had a similar problem on me 998, split second cut of the spark/tacho, only happened on track as far as I can recall and much higher up the rev range.
I used to think it was me bouncing the motor off the rev limiter as I made up for my lack of talent on the corners.

It used to happen very occasionally but sometimes when it did it would happen a few times in a day. Used to think it was linked to low voltage as the tacho could be made to go to zero by putting the battery under load with the lights on full beam.

It doesn't happen often enough to warrent too much worry and the problem seems to have gone away after a new battery was fitted and some partially fried wires near the rectifier were replaced.

If it was still doing it, or doing it regular I'd start looking at the crank sensor, or getting someone else to.



Ray.

[centurysup]

Originally Posted by Ray

the tacho could be made to go to zero by putting the battery under load with the lights on full beam.

Had a similar experience with my 998 about a year ago. Tacho would occasionally drop to zero, or "flutter" wildly, with the problem appearing more frequently when lights were on. When I put it in to get fixed, two problems were discovered.

1. I had a slight misfire - didn't even feel it - that was due to some faulty alarm-related wiring.

2. The tacho problem was traced to the ECU. Fortunately, I still had the original ECU (it had been replaced as part of an engine upgrade) and when this was put back in it sorted the problem.

[spinoli1]

Thanks for all of your advice guys.

I will be applying your suggestions to the problem tomorrow, and I will let you know how I get on.

Spin

[spinoli1]

Quick update:

- PC111 eliminated as possible cause (for the second time).
- Different ECU tried - nope.
- Removed, cleaned etc ECU ground plate, and earth - nope.
- ECU plugs closely examined, cleaned, sprayed etc - nope.

I did find that the lower plug that connects to the ECU is cracked, and the securing bar fractured (bar now repaired) - I'm going to try to get a replacement plug/loom section. Any suggestions?

Tomorrow I will have a go at measuring the air gap on the ignition sensor pick-up (does look quite tricky to do, and I would prefer not to drain the coolant system if possible).

Thanks for listening,

Spin

[MARTIN H]

Crank sensor or wiring to it would be my guess, does the missfire only happen when the bike is warm? If so it may be worth getting hold of a can of freezer spray and cooling the crank sensor (with the bike warm and running) to see if the missfire stops or changes in anyway. Had an 3 litre Alfa years back that went through quite a few crank sensors and the freezer spray worked in diagnosing the problem. Worth a try anyway?

[spinoli1]

Thanks Martin - cool tip (groan). Well worth knowing.

I have just found a lot of water in the block connector for the ignition pick-up sensor - which seems pretty suspicious to me.

Once that is all dried out, I'll try the bike again with all my digits crossed.

BTW - That, there, what you're doing with that Multistrada in that picture - that's not natural, that's not. Stop it immediately. .