Bison
Active Member
- Posts
- 119
- Location
- Newport, South Wales
Hi all
Just thought I would give you the answer to my marathon problem.
Problem - P38 Misfires on Petrol but runs perfectly on LPG. 4.lire Auto
The bottom line was cylinder 4 was sucking in air because the lower inlet manifold gasket had gone.
Things that confused the issue were!
The cat on the problem side had collapsed. Resulting in the readings of the Lambda sensor to be stuck at a given reading. Check your cats to see if they are glowing red. If they are they are knackered.
Opposite Lambda sensor giving a closed loop reading all the time. The heater element in the sensor was not working apparently.
My solution
I had the cats cut out. You didn't need the cats if you run on LPG
Replaced both Lambda sensors. It makes sense to change Lambda sensors in pairs apparently! They wear!
Changed the Inlet Manifold Gaskets upper and lower. The lower gasket was the problem gasket!
Incidentally, I changed the axillary drive belt seeing as I had it off during the dismantling stage. Saved a job for the near future!!
Now that all the sensors were working properly and the cylinders not sucking in air! I had the fuel petrol/LPG remapped.
As of today it works fine. A bit throatier because the cats are no longer fitted.
This is summary of the huge thread I started a couple of months ago. Hope it helps.
Lotofnames had virtually the same symptoms. It transpired that he was sucking in air from a spark plug. So I am guessing that the sucking in unwanted air is the clue to this problem!
Just thought I would give you the answer to my marathon problem.
Problem - P38 Misfires on Petrol but runs perfectly on LPG. 4.lire Auto
The bottom line was cylinder 4 was sucking in air because the lower inlet manifold gasket had gone.
Things that confused the issue were!
The cat on the problem side had collapsed. Resulting in the readings of the Lambda sensor to be stuck at a given reading. Check your cats to see if they are glowing red. If they are they are knackered.
Opposite Lambda sensor giving a closed loop reading all the time. The heater element in the sensor was not working apparently.
My solution
I had the cats cut out. You didn't need the cats if you run on LPG
Replaced both Lambda sensors. It makes sense to change Lambda sensors in pairs apparently! They wear!
Changed the Inlet Manifold Gaskets upper and lower. The lower gasket was the problem gasket!
Incidentally, I changed the axillary drive belt seeing as I had it off during the dismantling stage. Saved a job for the near future!!
Now that all the sensors were working properly and the cylinders not sucking in air! I had the fuel petrol/LPG remapped.
As of today it works fine. A bit throatier because the cats are no longer fitted.
This is summary of the huge thread I started a couple of months ago. Hope it helps.
Lotofnames had virtually the same symptoms. It transpired that he was sucking in air from a spark plug. So I am guessing that the sucking in unwanted air is the clue to this problem!
