Help with 04 pointy front cylinder failure

Hi all.
For the second time this year I have had to let my bike to rest in the garage and add it to the list of repairs.

Over the past few months Ive noticed my bike Misfiring occasionally in the front cylinder, more frequently in wet weather. Foolishly i made the assumption it was a defect in with the HT lead or coil pack. But apparently i was wrong.

On a regular 25 miles trip to work, the front cylinder cut Stopped Firing completely. I pulled over and noticed on idle it would occasionally fire, creating back pressure great enough to lift the throttle bottle bodies for a split second.
Honestly i don't Know how to describe the noise other than a spitting noise.

What I have checked and found nothing,

Coil Packs
Spark Plugs
Air box
Crankcase Breather Pipe
Run Self Diagnostics fitted to bike
Compression tested - 220 psi in front cylinder, 215 psi rear cylinder.
Valve Clearance Checked - front cylinder only
Timing chain Checked - front cylinder only

Whilst creating this thread cracked on with a little more work and have now removed the tank, airbox and throttle boddies. after removing the throttle bodies i noticed alot of black deposites on the underside of the front throttle body's lower butterfly. next i checked down the intake manifold for the front cylinder and noticed alot of liquid sitting ontop of my valves with a very stong smell of petrol. so here is what ive checked since then.

fuel injectors checked
TPS Sensor

if anyone else can offer an help here or even refer me to another thread with similar issues i would be really thankful as im very quickly running out of ideas.

Cheers guys.

[Sid Squid]

When you say 'checked', what do you mean? Have the parts you mention been replaced or tested? Has all the relevant wiring been buzzed and checked good?
If the engine is backfiring - that is, you say; 'enough to lift the TBs' - from that it would appear to be firing/still burning while the inlet valve is open, this could be problems with; timing, coil/HT lead/cap/plug, or slow burn from a weak mixture.

The coils and injectors can be swapped from cylinder to cylinder, do those one at a time does the fault move from front to rear? If yes, the problem should be apparent, if no, borrow a known good ECU and try again. (Clearly you may already have done this.)

By checked i mean i have checked the tolerances of the valve clearance and that the cam shafts are installed into the timing chain correctly.
The Air Filter has been checked for blockages
sparks plugs electrode gap checked and adjusted. (will buy new ones when able to get to halfords)
When i ran the self diagnostics, returned code C-00 (meaning no fault)
Crankcase breather pipe checked for blockages.

Ive never Really worked within this part of the electrical system but from what i can tell, all relevant wiring has been checked and is ok.

I Have an old ECU from a 55 sv650 that i crashed a few years back but couldnt even get the bike to run on that so i assume that my spare ecu is damaged already. According to the haynes manual to check the ECU for defects it must be taken to Suzuki, So plan on taking it to my local suzuki dealer to get checked.

After reading your reply i have swapped the injectors over and the fault didnt move to the rear cylinder but the bikes does run a lot better with the swap but doesn't stop the problem completely.

[yorkie_chris]

Hey up pal, I've seen it before on pointies where the coils break down. Can you swap one or check for a spark the old fashioned way?

[Sid Squid]

This is true, not all coil failures will show a fault code. I suspect the self check system - useful as it is - is not as absolute as we might desire it to be.

Originally Posted by yorkie_chris

Hey up pal, I've seen it before on pointies where the coils break down. Can you swap one or check for a spark the old fashioned way?

Yup mine did that. Fixed with a new coil pack.

As above have you checked for a spark?

My front coil pack died and didnt give any codes, I had to remove the pack in plug it into the rear pack connectors to check if it was dead.

[timwilky]

I think you need to approach this methodically.

Your description points to an electrical rather than mechanical failure so analyse the components and function of the ignition system.

Firstly, consumables are such because they are designed with a target life, treat them as having a life, they are no different to humans. We have infant mortality, sudden unexpected middle age death followed by old age. So manufacturing fault, accidental damage and simply worn out.

Spark plugs do fail under the recommended replacement threshold. Coil packs surprisingly do fail. So I would investigate these first. Change the plugs or even swap them front to back, any change? no, swap coil packs, any change. (no move the coil pack feeds, I recall the SV uses a lost spark so it should still fire the fueled cylinder).

good luck

[yorkie_chris]

Originally Posted by Sid Squid

This is true, not all coil failures will show a fault code. I suspect the self check system - useful as it is - is not as absolute as we might desire it to be.

I reckon a self check would have to be really really fooking clever... like checking for the proper back voltage and stuff when the field collapses in the coil.

Just resistance doesn't work, half of the coils I've replaced have still shown resistances in spec.

On the other hand the "ow-ye-fockin-bastid" test seems fairly reliable.

[timwilky]

Originally Posted by yorkie_chris

On the other hand the "ow-ye-fockin-bastid" test seems fairly reliable.

Only those who have conducted that particular test will understand Chris.