Help!

[Blacken]

My S3 has developed a couple of problems - I'm not very mechanically minded and I don't really know anyone over my way to give me advice.

 

The 2 problems are that

a) my car is difficult to start - the battery does not seem to hold it's charge

b) once started the car idles unevenly and if the revs are increased the exhaust note sounds like a trails bike or a revved moped.

 

Background - 3 year old 125 Sigma Roadsport - 15 months ago upgraded by CC to 150. The car ran really badly in traffic at low revs (kangarooing), CC could not resolve it and said that was how they all ran. At the suggestion of several club members I took it to the 2 Steves for a remap last June. They made it run significantly better. The car has generally run well and done several long trips. In the winter I take the car out if the conditions are ok just to keep things ticking over.

Mileage 11.5 K - car fitted with battery master switch to avoid battery drain (no power in garage).

In April I went up to Wales and then went to the Isle of Wight Blat - no problems. 10 days after the IOW I did a pre MOT check on the car - everything AOK. The next day - the test day the car would not start. I had to reschedule the Test for 05/05/2011.

Managed to get the car running - seemed quite a lot of fuel in the system. A fair amount of dirty vapour came out of the exhaust. I let this burn itself off, took it round the block. It started first time the following day, I took it on a 60 mile round trip to get the MOT - no problems.

 

Due to work pressure I was not able to use the car for a couple of weeks - again it would not start - I got a friend to start the car with a powerpack and had it running up to working temperature but the battery does not seem to be holding it's charge. While running at working temperature it gave a reading of about 13.4 V but it would not restart without the leads. Took another reading with the engine off and it was down to 10.4 V.

More alarming is the noise I am getting if I put my foot on the gas, it sounds like a trials bike or a highly revved moped - I did not dare take it for a spin in case I would inflict damage to the engine/exhaust system.

When it initially fired up there were coughs and splutters and after a while the odd intermittent faint burning smell and the odd small pop from the exhaust. I thought the initial fuel or condensation that was in system would have burned off but the character of the exhaust note did not change.

 

I can imagine the battery might be past it's best even though it is only 3 years old. I have tried my best to keep it running at regular intervals but it has gone for longer periods in the cold months where I have not had a problem with the battery - it would always start first time.

 

The car sounds like it is running unevenly, I don't know if it could be an exhaust related issue. The car was running well in April and it covered about 1,000 miles.

Any advice would be greatly appreciated.

 

[johnv]

my take before someone more knowledgeable arrives ..

I would say that it's not running on all cylinders - the symptoms sound a bit like what happens when you put the plug leads on in the wrong order! Maybe 1 or more cylinders are getting so over fuelled for some reason that they won't fire?

I would be tempted to try a known good battery first, as these modern ECU's seem to misbehave badly with a duff battery.

[myothercarsa2cv]

When you say it sounds like a moped... Does it sound rattly? Have you checked the exhaust connections? Are they loose?

 

Battery is probably on the way out. It's a Banner, right? Bin it 😶‍🌫️

[Nick Chan]

Definitely suspect the battery for starting and possibly for poor running if the Ecu doesn't get adequate voltage. Also the poor running sounds same as my sigma when the barometric pipe from sensor to inlet broke (susceptible to cracks). This is the rubber pipe that goes from the inlet manifold immediately infront of passenger feet to a matchbox sized unit on scuttle behind battery. Maybe lambda sensor as well causing fault as recently happened with another Sigma car. Do a search on techtalk for Sigma and have a look at a thread by me and another by John Hughes

 

Nick

[Jason Plato]

replace the battery

replace the plugs

replace the fuel

[Racing Snake]

Paul give me a call

[Steve Cornford]

Call CC and get them to look at it, as this does not sound right, failing that...

 

When they upgrade a 125 to a 150, they remove the rubber pipe going from the inlet manifold to the MAP unit (the small rectangular box next to the ecu). This leaves the input of the MAP unit open to the atmosphere, but they change the map to suite this configuration.

 

Things to check.

The 150 has a pair of throttle bodies linked in the middle. If these are not "balanced", then you can get similar symptoms.

Under your accelerator peddle there should be a bolt acting as a stop. If this is too low and you you have a heavy right foot, the throttle cable can put a strain on the linage at the throttle body end causing it to go out of adjustment, I believe.

The econoseal connector on the Lambda probe, have you gone over any harsh speed bumps recently. Check that the connector is tight.

 

Check the plug leads are on tight.

You have to undo three bolts + a plastic clip that retains the accelerator cable in order to remove the plastic cover over the plug leads. Be careful when you replace the bolts, as I think some were supplied too long, and when you tighten them, they pull the brass nut out of the camshaft cover. SHould have one or two washers under them to stop this happening. It might just be one lead that is loose. ps dont check with the engine running

 

Has your battery got a date label on it? If so what is the date?

Have you checked the acid level in the battery?

Are the sides of the battery bulging?

 

Hope this helps, otherwise Blatmail me as I also have a 125 that has been upgraded to a 150, and we can compare notes.

 

Edited by - Steve Cornford on 10 Jun 2011 23:05:07

[Blacken]

Sorry I could not respond earlier but Blatchat was unavailable to my computer last night.

Tomorrow is the first day off I've had in 2 1/2 weeks so I will have a look and try and make sense of it.

I don't want to move it in it's current state because of the alarming noise coming from the exhaust.

To be honest, in retrospect, the 150 upgrade was probably the worst £3,000.00 I ever spent with all the knock on problems it has caused and I was rather disappointed by the lack of support from the installer.

[Bio]

Hi Paul

If the battery is faulty and not holding charge there may not be enough voltage to operate the car electronics properly once started.

Try a new battery first.

 

John

[jeffi]

In my opinion the SV150 is a wonderful performance engine when tickerty-boo but is a very sensitive soul and susceptible to any degradation of the battery (or non-charging alternator), Earth connections (loom and under dash), TPS track, idle setting or sub-loom, spark plugs, Lambda sensor, air-flow/throttle body balance, MAP sensor (even if ECU version doesn't require it to be piped to the manifold), HT stuff, filthy or faulty injectors (pretty much anything!). The earlier ECU map versions used the pipe connected to the MAP sensor and the later versions have it disconnected. My build required three ECUs before I found one that fired normally and didn't sound like a can of ball bearings being shaken due to totally wrong map for the Sigma causing mis-firing of injectors with loads bangs, pops and rattles! And then when it had the right ECU, it was very jerky on light throttle (in traffic) until the air-flow and TPS were balanced again. I then had a later jerky fault when the TPS went faulty. Now it's bedded in its great and quiet, but I'm expecting issues in a year or so when any of the sensors age and go out of trim.

 

 

[Blacken]

What battery would you recommend? 🤔

 

A lot of people seem to have an aversion to the Banner.

 

As I have mentioned I use the Battery Master switch whenever the car is not in use. I also don't use the lights unless the conditions demand it and I don't have any in-car media other than the occasional use of a Satnav. (I checked my diary and it was actually only 8 days between the IOW and my having to cancel the MOT test.)

 

If a battery is better quality and less problematic then I would probably go for it.

[Bio]

I would just use another Banner, If you use other types you will need to modify the retaining strap or battery tray.

 

John

[Stationary M25 Traveller]

Paul - the one I told you about doesn't need wiring mods. It is half the thickness of the Banner, so you just fit a spacer block to fill half of the clamp. Also less than half the price

[Martin J]

The banner on my sigma lasted 3.5 yrs, I belive they have a 3 year warranty.

I didn't bother with a conditioner for the first year & a half & that I think that shortend it's life as it went flat a couple of times.

I allways keep it hooked up to one now.

[Blacken]

Unfortunately, I don't have power in the garage - so it is remove the battery for a charge or persistant usage of the car.

 

Rained all day - put paid to any investigation - too dark in garage even with headtorch. Still, it was nice to see Stoner overtake Lorenzo in the championship *thumbup*and well done Jenson! *thumbup*

 

Is the RMD25 are superior battery to the banner?

 

 

[Stationary M25 Traveller]

It does the job well, is sealed, so no topping up needed, is half the size, half the weight and half the price. Works for me ! Don't know if it lasts longer when car not driven, as I always plug it in to an Optimate when in the garage.

[Blacken]

Gave the Banner the works this week - electrolyte top up plus a charge up within 18 hours it has gone from 13.14V to 10.71V.

The funeral will be held on Friday - no flowers please. 😬

 

As soon as my Racing Battery arrives I will proceed to test the car for the other issues in case the rough engine/ exhaust problems are all ECU derived matters.