Very rich running!

[Speedy1959]

Hi All,
Yesterday I went out on a decent 105 mile run with a mate..
I originally intended to use the Morgan Carb/Throttle body balancing kit I had recently bought when I got home after a good run.
The first 75 miles or so was excellent with the bike purring away, and I notice its far better low down in the revs since altering the TPS.
However after around 75 miles or so I felt a hickup.. At first I thought I had imagined it..
Then it seemed to get worse and worse in tight corners under a part throttle load..
The symptoms were, if I semi feathered the throttle (like you do in tight bends) it felt hesitant and then would kick in suddenly to being normal and then instantly feel hesitant again.
It felt like an exagerated version of how the bike was before I altered the TPS!!
I was was thinking of various scenarios such as "maybe I didnt tighten the TPS properly and its rotated out of adjustment.
I pulled over and checked that.. It was fine and was positioned where I had left it..
The tickover was steady and fine at the usual 1000 rpm where its always been since I got the bike.
The final 10 miles home were not enjoyable at all.
It actually stalled on a slow bend when I pulled the clutch in to change down gear in order to keep the revs up.
It started OK straight away..
It got quite dodgy around some bends as it ran roughly and then kicked in fully for a second or two.
Hard acceleration seemed fine..
It was the more gentle throttle openings that upset it!

The bikes done about 12,000 miles.
I was thinking the plugs arent old in mileage but they are 15 years old..
When I finally got home I raised the tank to look at the plugs.
I thought I would remove them all and test the resistance to see if 1 or 2 were "different" than the others.
The picture should be worth a thousand words!!



All 4 Plugs were Black and sooty !
Straight away I checked the readings (resistance) of the TPS I had altered last week (I had NOT altered the STPS at that time). It was the same as I had left it and altered correctly as I turned the throttle.

Any ideas?
I strongly suspect its fuel related (obviously)..
Its like the choke is on intermittently when the engine is up to temp.

Question:
What does the STPS do and when does it do it?

S.

[Nic]

Good luck finding the answer mate, I could fix it in a jif if it was an old carby bike, these things with so many sensors, no Idea mate, sounds obvious but have you looked at the air filter. That's all I got, someone here should have a clue, just not me, wishing you good fortune though, it's a PITA.

[Speedy1959]

Hi Nic.
Thanks for your reply..
Air filter looks good.
The problem started 3/4 of the way through a 100 mile rude..
A dirty air filter would not suddenly start giving problems of this nature..
All 4 plugs were black and sooty as though the choke was on (Carbs).
S

[grog]

Speedy, dealer mode test, might throw a code. Happened suddenly, could be a vac hose.

[Hooli]

Aye vacuum hose is a good call, it's 3.2mm if you need to replace it. Don't forget the one to the PAIRs as well. Even if you've removed the PAIRs it'll be there but blocked off. Vacuum leaks don't throw a code either.

The SPS monitors the position of the STVA (secondary throttle valve actuator, the motor in the centre of the throttle bodies), I'd be surprised if that was the issue without a C28/C29 error though & you haven't mentioned the FI light being on so there's no code being thrown up. I've never seen an issue with them reset until the bike is switched off, so an intermittant fault doesn't point to those either.

Roughly speaking, the STVA turns backwards to put the fast idle on when cold & forwards to open the seconardy throttles as you the revs increase. I believe it's around 3.5-4k that this happens. The secondaries serve the same purpose as swirl flaps in cars & allegedly improve combustion at low speeds by increasing swirl in the incoming air so the fuel vapour mixes with the air going into the cylinder better.

It sounds counter intuative but have you cleaned the teabag lately? A loss of fuel pressure means the injectors will dribble not spray. That causes poor fuel/air mixing & bad running, which could explain the black plugs. Also check you haven't kinked/trapped the fuel hose when you've had the tank off.

Another idea is check the resistance of the oil temp sensor, I've had one go bad & show about 10x the correct reading. No code thrown as the ECU still saw the sensor attached, but the bike thought it was running at about -30c & doing 25mpg as it was enriching so much for the temp it saw. Approx readings are on a graph in the workshop manual.

Other thoughts. Check the earth lead where it fits above the gearbox is clean & tight, along with the small earth connector under the RH side panel. Either, particularly the former, could cause a poor spark and hence crap running.

Oh & finally, the big grey connector under the LH side panel can trap water & cause issues as every injection related wire goes through it. Worth a quick check the ECU plug is dry too. There's a drain hole at the front left corner of the ECU tray, they can get blocked so water sits around the ECU. The waterproof ECU plug isn't, it's just moisture resistant.

Oh one last one. Check the clutch switch isn't stuck on, that affects the fuelling & ignition maps. Just re-read & noticed you said it started as you pulled the clutch in.

Good luck.

[Hooli]

Of course, having said that.

Can you trigger the problem by using exactly the right amount of throttle? Both TPS I've had go bad had a very small range where they didn't work properly, about the amount of throttle used in normal crusing. Winding on more or less throttle would cure it everytime. I could even put the right amount of throttle on & trigger rough running on the overrun from high revs.

Both times the sensor worked when tested on a non-running bike, it must have been the vibrations of a running engine that causing the fault. They are only a resistive track on a little circuit board after all so won't last forever.

[KiwiCol]

I'm gonna watch this thread with interest, I wanna know what caused it too.  Plugs being black = rich mixture, too much fuel or too little air.

I'm going for those Vac hoses myself.

[Speedy1959]

Blime Hooli that's one hell of a comprehensive answer!!
No FI light and I'm not aware of any codes, though to be honest I didn't think to look at the display.
I assume a code would only display for a few seconds when the ignition is switched on ?
I am at work just now but when I get home I shall systematically look at all your suggestions. 

I REALLY do appreciate you going to the trouble of posting such a comprehensive response to my problem.
I shall keep you all posted as I hopefully find what the problem is.
S.

[Hooli]

If you didn't get a FI light then there's no codes, that displays to say an error has been detected which is the point it has a code.

Hope it all helps. The vacuum pipes are a good place to start, the t-pieces can snap as well as the hoses too. I got 3mm ones & they fitted fine when I last sorted mine.

I was stood in a server room waiting for tapes to unload, so seemed rude not to give you a decent reply.

[Will14]

@Speedy1959 out of interest when you checked and adjusted the TPS & STPS where did you take the readings from, the big grey multiplug on the LHS or each sensors own plug? The reason I ask the night before last I checked mine at the grey multiplug and also at each sensors plug, after balancing the Throttle Bodies

Now I have been messing around a bit lately trying to get my bike to run smoother at idle altering the TPS & STPS, so knew the readings would be out of spec however there was a big difference in readings from each plug, as shown below

TPS
Grey multiplug 995 Ohms
TPS Sensor plug 1100 Ohms
Left this as it was

STPS
Grey multi plug 700 Ohms
STPS Sensor plug 750 Ohms
Adjusted up to 800 Oms at sensor plug

I haven't been out on the bike since doing this, although my cold start functioned before it would start when cold at 2000 RPM then gradually drop to idle, since making these most recent adjustments she starts and runs at 1500 RPM then drops to a steady idle which I think is what the manual states it should do

The bloody bitch still seems lumpy at idle to me though with a bit of a chuffing sound coming from the end cans, and I'm starting to loose patience with her now  if anyone has any ideas

The point of this is that readings at the two different plugs can vary quite a lot, this is probably not the cause of your current problem but possibly worth rechecking? I also had a similar occasional symptom to you when powering on the throttle there was a sudden loss almost like the kill switch had been flicked on and off then power kicked back in - not nice on a bend as you say! Will see how she behaves tomorrow evening when I go for my Friday night run

Cheers

Pete

[Speedy1959]

Hi Will14,

I did adjust at the grey plug with the allowance for the differences as shown in your readings..
For 250 - 300 miles it was the best its ever been !!
I honestly dont think my problem is because I took readings from the large grey plug..
My TPS at the Grey plug was something like 1365 (approx 1465 at the sensor plug), so however you measured it was a fair bit out!
The very lowest I could rotate the sensor to showed 1065 at the Large grey Plug (approx 1165 at the sensor plug, which is a lot nearer).

UPDATE SO FAR:

Last night I needed to collect "modded" PAIR valve covers from a mate (My cars clutch has gone) so I went on my bike and did a 15 mile round trip..
Initially I thought "oooh its allright now"..
But the chugging started once fully warmed up.. NOT as bad as when I did a long run on Wednesday but its there..
Because I am looking for it, its more noticeable..
When I got home I did several things..
1. I removed and cleaned the camshaft senser (as to Barmys Howto).. A small amount of crap but Im not sure it was the problem.. We shall see.

2. I pulled all the vacuum hoses off the Throttle Bodies and pulled the vacuum hose off the electrical connector thats between the coils.. I plugged the 4 ends that would go onto the throttle bodies and blew / sucked the remaining electrical connector end.. All the vacuum hoses seem fine with no detectable leaks..
By the way what is that electrical connector that the vacuum hose goes to (Number 13 in attached photo).. Can I remove the hose from it and plug the hose ??

3. I also checked the 2 Earth connections that Hooli reffered to earlier in this post.. They seemed fine.

4. Once again I removed the plugs.. They were still dark in colour but starting to change much paler at the tips (I hadnt cleaned them after last time when they were dark and sooty !! (My Bad).
This time I measured the resistances which I noted changed as the plugs cooled down after my 15 mile trip.
Readings below:
Plug 1 = 6.8k oHms but fluctuated wildly and was hard to make a contact with.. It could be 12k oHms one minute then drop to 6.8!
Plug 2 = 3.92k oHms
Plug 3 = This was similar to Plug 1 but with multiple attempts to get a reading it eventually showed around 5k oHms.. Again fluctuating wildly!
Plug 4 = 3.82k oHms
On Saturday I intend to replace all 4 plugs as there is obviously a discrepancy between the plugs!

I wont get chance to ride till Saturday when I go for new Plugs.. Talking of which the manual suggests replacing plugs every 7,500 miles!
My bikes done around 12,000 ish miles..

I shall keep you posted as and when there are new developments
P.S Can anyone tell me what the electrcal connector is the fits to the frame between the coils.. Vacuum hos (13) in photo fits to it.
S.

[Speedy1959]

Here is the photo Re Vacuum hose (number 13)

[Hooli]

That's the MAP (manifold absolute pleasure) sensor. It's used at low revs/throttle to measure the intake vacuum to calculate the fuelling at higher revs the ECU just uses the throttle position to calculate airflow.

It's the same part as the atmospheric pressure sensor on the RH side of the aurbox  you could swap them if you suspect a fault, but I don't think I've heard of one failing yet.

The bike will run with it unplugged as that's how you balance the throttles. It'll put the FI light on doing so, but it'll run ok mine always loses a few revs and isn't quite as smooth like that.

The bike won't run at low revs if you disconnect it from the vacuum pipes and leave it plugged in. That's because the ECU will see normal atmospheric pressure and assume the engine isn't pulling any air in so doesn't need any fuel.

[grog]

I dont know on 14, will have a think about it. Cars with faulty MAP sensor always run very rich. Was quite common 20 yrs back, people used to push down on accelerator when starting, often caused a backfire, this went up vac line to sensor, popped its diaphragm.

[Hooli]

Well like I said grog, there's a 'spare' on the bike you can swap it with to see if things change & the bike will run with it disconnected.

Your backfire comment makes sense, I've not seen it but then I don't do such stuff for a living.