Help Please - 998 Misfire Woes
 

Hi Guys,

Apologies in advance if this post is a bit long, but I want to give all the details so that anyone with any advice for me knows all the relevant info.

The bike is a 2002 998 Bip, DP performance upgrade kit, PC111.

The problem is that when the bike revs to a certain point, the ignition seems to cut completely for a moment, resulting in backfiring, and the motor not revving any further.

The misfire starts at about 5,750 revs, and seems to come down a little to 4,750 as the bike gets fully warmed through (15-20 mins). At lower revs, the motor runs perfectly.

The problem first occurred after giving the bike a good wash and clean. It went away after a few days, so it seems pretty certain to be water ingress somewhere. A couple of weeks later, cleaning again after a very wet ride, and the problem is back, and now it is not going away.

Further info:

• The rev counter instantly falls right down when the misfire ocurrs, well below the drop in revs.
• Other electrical components, headlights, instrument lights are not affected.
• I have isolated the Power Commander and re-connected the original loom to the fuel injectors, but the problem is still there, so it’s not the Power Commander.
• Both cylinders are affected.
• I have removed the plugs, plug leads, coils, disconnected every electrical connector I can see/reach, cleaned all connectors and liberally dosed with water dispersant spray.
• For once, it is not an intermittent fault – eg: I can start the bike in the garage, warm her up, and the symptom is easy to demonstrate revving the bike on the stand.

I am reasonably handy with mechanical tasks (I can strip/reassemble a chassis and remove/replace a motor competently), but I am useless with electrical problems.

The last time I had a misfire type problem, it cost me over £800(!) to find out I had a dodgy Power Commander fitted, so I’m hoping that someone may be able to give me some pointers where to look to try to diagnose the problem.

Any advice or questions to help solve the problems will be gratefully received.

Spin

I guess that you've checked all connections!

Make sure all the earths are clean & corrosion free.

Do the yellow cables from the rectifier get hot?

when did it last have service...blocked fuel filter or dodgy spark plug..Just a thought mate

Had a similar problem with a customers 998. The ECU was returning error on the crank sensor. Replaced that and set the air gap and all was well.
Have you had the ECU interogated for error codes? Worth doing first before you go and start replacing sensors etc.

Thanks Guys for your suggestions:

Chaz – the rectifier cables show no signs of the insulation melting, although the block connector has “darkened” around the terminals, suggesting to me it does get hot.

Daz – Defo not the plugs. I will change the fuel filter (good idea), although the symptoms are not at all fuel starvationy.

Naz - sorry, Nelly – I have a spare 996r ECU (bikes runs R ECU and cams), and will try that. I may see if my local dealers are prepared to read the error codes for me, and let me have the results. How does you go about checking the “air gap” and where is the crank sensor located please?

Any other tips, hints, suggestions are more than welcome.

Spin

I'm Still trying to work out the drop in Tacho reading
Maybe its linked to the Multi-pin connector Just above the battery.
As you can see in the excel doc a lot of signals runs through there.

I'll post the ECU pin-out when I manage to locate it

Fairly certain the Tacho signal comes from Pin 9 of the body connector as its referred to

The feed for the tacho is taken from the crank sensor, via the ECU.

Crank sensor is in the Alternator cover, just forward of the waterpump cover. there's a blanking plug in the forward face of the cover that you remove to check the air gap between the face of the sensor and the idler gear that drives the cam pulleys. Need the hoses out of the way to get at it properly

does look as if it could be crank sensor related and maybe the washing of the bike has coincided with the crank sensor going down or damaged the connections between the crank sensor and the ECU.

Nelly do you have figures (i'll check my manual when I'm at home) for checking the Crank sensor such as Inductance & impeadance.

only figures i have are 680 ohm across 2 of the three pins. That's at the nominal 20 degrees C.
Tbh, that doesn't always prove a fault as the thing can/ could be breaking down under temp.

Just a thought, do you have an alarm fitted? You probabaly don't need one on the Channel Islands.

My 996R had a mystery problem like yours and it turned out to be the alarm at fault. I've seen been told by a Datatool fitter that once the units are a few years old and been subject to V twin vibrations the contacts get a bit iffy and the result in my case was an intermittent misfire/cutting out as you've described but only at certain revs which in ny case was always in between 5 and 6,000 rpm.

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

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.

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.

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

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.:D

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.

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.

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

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

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?

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. ;).

Just wanted to say a big THANK YOU to all of you who gave hints, tips, advice and suggestions to help solve my misfire problem.

The cause was traced to water in the connector for the ignition pick-up sensor, on the advice of Flip998FE of Las Vegas.

It seems that this is quite a common fault, well woth knowing about and protecting yourself against.

Took the bike for a hoon this morning - she just flew!!!

Spin