Plus 2 (S130) - Erratic running when warm

[cjones60]

I have an erratic running problem with my +2 (s130) after it warms up, the car is fine on start-up but after 7-8 miles normal driving and the car is up to temp, if I rev it above 4-5000 rpm it starts running rough, miss-firing and as if it's only running
on a couple of cylinders. If you let the car cool down, it will start again and run
OK until it's warm, then you can rev it harder and replicate the fault (I think the
higher revs brings the problem on rather than the temp as it doesn't overheat)

I have just brought the fault on and took all spark-plugs out and all look fine (Dry - Brown/beige colour) I took the inspection lids off the webers and couldn't see
anything i.e no petrol (but should you see petrol?) again it cools down , starts and idles fine, runs OK until you bring the revs up? could it be fuel starvation?
car is fitted with a facet pump and filter king regulator, the bowl looks full of petrol
but I have no idea of the pressure (I will buy a pressure guage as a starting point)
the car is also fitted with Lucas electronic distributor. The problem on checking the fault is that the car starts and idles fine, I need to take it on a busy main road to bring the problem on so can only check it at quiet times, this may be a slow fix?

Thanks Chris

[Stuart+2]

Chris

Are your spark plug leads in good nick?
I've had very similar problems due to shorting leads.

Cheers

[types26/36]

I agree with Stuart, sounds like something is breaking down.....suppressors, ht cables, coil or electronic ign.
Of course it could be fuel starvation, needle and seat, pump pressure, tank vent etc. and no you will not see the fuel level by taking off the jet covers, if you could replicate the fault, cut the engine dead then remove the top of the carbs you could check if the fuel level is low.

[cjones60]

The HT side looks OK, good condition, Plug leads etc - it will be dark soon, I will see if i can see any stray
sparks, then look at changing out components.

On the fuel side, i followed the previous suggestions (thanks for those) I started the car and let it
idle, then took the top off the front weber and there was fuel in the float chamber (about 1/3rd full)
I then ran the car at high revs and found that it has the problem while the engine is not up to temp,
it sputtered and limped to the side of the road and I removed the same weber top and fuel level
looked similar, i managed to get it back home and dispensed some fuel into a glass so the Electric
facet pump and filter king seems to be OK, the only things i am not certain about is the actual level
of fuel and I only checked the front carb, the other weber is more difficult as it has an elaborate
spring throttle return assy mounted to the top, looks like something Burton would sell, appears to work
fine though as there's no problem with the throttle. I thought I would check the tank venting system next
and started to read the manual, parcel shelf has to come out and rear Screen?
Oh and while I was at the carbs I took the air filter box off (this is standard type but has a K&N at the
end of the flexi up front) some traces of fuel condensation in there but nothing major?

thanks Chris

[cjones60]

Checked out HT side, couldn't detect any shorts anywhere, Car idles fine, took it out revs 4-5000 rpm
fault came on straight away, so it is not engine temp related, seems to die and run on a couple
cylinders, managed to limp it back to my driveway at walking pace ( it's getting worse), this problem
only started yesterday with a few pops in deceleration and and a bit of erratic running at higher revs,
it's now driving at walking pace but i can't determine if it's electrical or fuel related as it recovers
if you park it up for an hour? is there +2 fuel vent problem that could cause this?

I have a receipt from PO who had the car tuned at Northampton Motorsport early this year, they changed
out all ignition (for electronic Lucas) fitted the Facet, re-done the carbs etc their receipt states that
"The fuel pressure was very low" and play in the distributor, Their work and parts would not need re-doing within a year? I am at a loss - Chris

[Stuart+2]

Chris

To cover off the vent issue just leave the cap loose (not clipped down) and go for a run (assuming your tank isn't too full).
Unless someone has covered up both sides of the tank vent outlets or tampered severely with the vents, this shouldn't be the issue.

From the comments above, fuel pressure is a question mark. You can do a rough check by disconnecting a fuel line and covering the end with a finger to gauge the pressure. It would have to be very low to be unable to fill the float bowls. Blocked fuel filter is a possible cause.

If fuel checks out OK then I'd be looking at each electrical component. Is there a strong spark from the coil?

Hang in there

Cheers

[stugilmour]

Chris:

This is a bit of a punt, but are you sure you don't have some moisture/water contaminating the fuel? Can show up as an intermittent problem depending on where the fuel is being picked up from within the tank, as water sits on bottom but gets sloshed to the intake when running but not idling.

Can generally be dissolved back into the fuel with Methyl Hydrate or equivalent. Sold as Gas Line Anti-freeze at the service station (over here anyway). Any of the fuel system cleaning products probably contain a good deal of methyl hydrate as well. It emulsifies with the water and allows it to mix with the petrol and clean up the tank contents. To mix in, pour in several ounces of the stuff and fill tank to mix in with fuel. Can take a couple of "treatments" if you got a dose of bad gas or accumulated condensation from storage.

Perhaps do this one after Stuart's suggestion of running with cap open to eliminate vent blockage.

HTH

[cjones60]

I was thinking it could be the fuel, I may drain the tank and re-fill, the small amount of petrol
i dispensed into a clean glass turned to the colour of lemon juice within a few minutes (this
has lead replacement solution in it as I squirt a capfull in with each tank), I thought this a bit odd
so dispensed some from my lawnmower tank and this does the same thing over a couple of
minutes. I guess I need to check the fuel system, check the LT and HT electrics and I have also ordered
a guage tool to check the compression of each cylinder, I think I need to check the HT stuff today and will have
to take the carbs off to access the distributor, will keep you posted, thanks Chris

[worzel]

Hi

Is the problem "time related" ie does it only occur after using the car for a certain time period rather than the distance covered?

If so do you have an immobiliser fitted- some of these, if wired into the ignition circuit can fail because they're not designed to have current passing continuously thru them. Had the same(similar) problem a few years ago.

Regards

John

[cjones60]

Hi
There's no immobiliser fitted (as far as I know) this morning i have taken the end of the Facet pump
and there is an integral filter, there was very little silt on the filter, refitted and problem still the same,
seems to be high revs rather than time or temp that brings fault on, idles fine for long periods.

I am still thinking fuel delivery, am ordering pressure gauge to monitor fuel up to carbs, i assume
the flow is not restricted - thanks Chris

[cjones60]

I think I have fixed the erratic running on the +2, checked out HT couldn't
find any problems, Back to Fuel starvation and re-visited Brian's suggestion
about taking the top off the carbs, this time when the car started playing up
I killed the ignition (and the electric fuel pump) coasted to the side of the
road and took the tops off both webers fuel levels were really low. The
key to this is killing the igniton/pump as the last time I drove it and the facet
would have re-charged the webers a good bit.

Managed to get it back home and took the Filter King element out, the Facet
pump also has a filter both cleaned but didn't fix it as I dispensed 1 gallon
of fuel with the facet took more than 15 mins, this should pump 20 Gallons/hour
so checked all the fuel line back to the banjo on the tank bottom and this was
full of crud and bits of rust restricting the fuel. cleaned this out and dispensed fuel
into gallon container and put this back in tank, done this 7 or 8 times and it will
fill a gallon container in around 3 -4 minutes, put back together and car runs
great, I will run about in it and after the tank is down a bit , check the banjo
connection again, the tank itself looks in great condition.

Thanks for the help and suggestions

Chris.

[Galwaylotus]

Chris,

Delighted to hear of your success. I'll remember that if my S3 acts up again!