Rough/jerky running, related to exhaust leak?

I've had my 155 2.0 TS for a month now, and for the past 3 weeks there has been a problem with quite rough idle running *when cold* and there has also been jerking while driving and lacking in power (also when cold). Now I know that there is an exhaust leak and I know, based on the sound, that it's somewhere near the engine even though I haven't seen it. The sound from the exhaust leak has been becoming gradually worse quite fast during the last 3 weeks and so have the rough running issues together with poor gas mileage.

Now my stupid question is that can these two things be related or am I facing two different problems?

Also, sometimes when cold, the engine shakes so much when idle that the entire car vibrates, but the rpm are always at a steady ~1000. The last time when I drove the temp outside was +7 degrees celsius and for the first 500 meters or so the car ran very jerkily, it felt like two cylinders were out. It had never been this bad before. Then suddenly things picked up and it felt like the car got a massive boost to its power. The fuel injection warning light hasn't turned on so no problem there.

It could be more than one problem but the only way you're going to find out is by fixing the exhaust.

I'd guess you have a split at or near the flexi-pipe. That will fool your lambada sensor into thinking there's more oxygen in the exhaust gas than there really is, so it'll be running weak.. making it misfire when cold.


Ralf S.

Coincidence, my front pipe cracked the other day and started blowing badly. The leak was before the lambda and I could tell the difference straight away, car was lumpy at low revs, down on power and generally running badly.
Seemed to be running rich to me though :/
.... lambda detects higher oxygen level, thinks it needs more carbons and tells the ECU to richen the mixture?

Replaced the pipe today and the car is much smoother to drive and much zippier about 3-4k rpm.
If you've a leak before your lambda probe then it will definitely cause running problems.

Well I patched up the holes today, it was definitely leaking quite bad before the lambda probe. Remains to be seen if it fixes the jerky/poor running... Oh and would the front pipe-section from a 156 TS fit as a replacement into the 155? They are much easier to come by

Here's a (bad) picture of the leaks that I fixed today:

see that alloy cover over the zorst, remove it saves the sump from being destroyed on a speed bump

EA isn't half joking about the alloy brace, remove it!!

Well, the new front exhaust has been ordered and should arrive within 1-2 weeks. My temporary fix was a failure and now the exhaust is leaking worse than ever before it seems. The car has also been VERY thirsty for gasoline, while driving short distances in the city I'm looking at ~17MPG (14l/100km) .

Now my question is can this still be explained by the exhaust leak before the lambda probe OR is the lambda probe dead? The car passed the MOT 1 month ago with flying colours, before the exhaust began to leak.

Is there an easy way to find out by yourself if the lambda probe is dead? Oh and the fuel injection warning light is not lit.

Wait until you fit the exhaust m8
Once you fit it you can then start checking any other probs (if there are any!)

btw from your first post about poor running and missing when cold might be worth checking down in the plugwells to make sure they're not full of oil or water.... especially cylinders 1 and 2.
Also , what mileage is on the car - the plugs are only good for 70k miles or there-abouts.
Worn plugs can cause problems on cold startup but not as extreme as you describe.

just a thought but i had bother with my plug leads after bieng a bit forceful ham fisted so i am! gave similar probs but like mo4 said not that major. i,d say if you just bought her do yourself a mini service eg plugs leads oil and filter little thing and all that!