Fitted different exhaust and now got problems.

[stove]

Hi folks
I hope somebody can shed some light on this problem . The van is a 2.1 wbx mv with digifant fuel injection.
Have just done away with the catalytic converter by changing everything from the cast knuckle onwards to pipe and silencer from a carb engined van. I welded a boss to take the lambda sensor in a position similar to where it's located on the s/s systems​ . All went well , no leaks so took it for a test drive , after about 3 miles lost power , it wouldn't do more than 20mph foot to the floor . Stopped switched ignition off, started again and full power restored for a short while. Disconnected lambda sensor and then went ok , renewed it with one from Brickwerks
buy still the same.
Any ideas?

[dave lfc]

hi i have had a problem similar to this a couple of times and it was a down to a fuel filter blocked thats located not far back behind the front right wheel and one in the carb.it was proper dirty.worth a look,cheers dave

[Aidan]

so now it starts ok and drives ok for a minute but then black smokes and looses power with the new lambda connected, but runs okay with lambda disconnected ?
when you start from cold, on idle after 15-30 seconds is there a definite change in engine note as ecu switches to lambda monitoring and then starts to alter the fuelling to get optimal exhaust
other than fitting the replacement exhaust and then a new sensor have you done anything else to the van ?

[Aidan]

hi i have had a problem similar to this a couple of times and it was a down to a fuel filter blocked thats located not far back behind the front right wheel and one in the carb.it was proper dirty.worth a look,cheers dave

2.1 MV engine that's fuel injection with DijiFANT not carburettor and different fuel filter and pump set up, the symptoms are those of over fuelling

TO OP
check the small air hose to the fuel regulator from the plenum chamber, the spigot on the plenum can get blocked and without the vacuum connection to the regulator it will run full pressure all the time which will over fuel - I had this on mine (MV engine) and I had to ream the spigot with a small screwdriver and hey presto all was good

TO DAVELFC there should only be one fuel filter on a 1.9 carb set up, the one by the tank outlet, change every 12 months £1-£3, one in the engine bay is a sign it's been messed with by someone who didn't know what they were doing and means another potentially pair of poor joints in the fuel system right next to the hottest thing in the van, a possible recipe for a fire so best to renew the rubber fuel lines and get rid of the filter in the engine bay and fit quality proper fuel pipe hose clamps

[ajsimmo]

To Aidan,
He said the one in the carb, not an extra one...

a fuel filter blocked thats located not far back behind the front right wheel and one in the carb.

[stove]

Thanks for the replys, the van was running well before I changed the exhaust and that's all I have done. The old lambda was difficult to remove from the cat but appart from that the job went well . Just drove it 12 miles with lambda disconected with no problems. On starting up there is no change to engine note with sensor connected or disconnected. Will check pipe to fuel reg when I finish work. Thanks, will keep you posted.

[ajsimmo]

Stove, can you measure the O2 sensor output? If it ran well before the exhaust swap, and it runs ok open loop, it follows that something has changed regarding the probe. Could be the wiring got damaged, or it's corroded and disturbing it was enough to introduce these symptoms. (Eg a corroded earth point could show up as a reduced signal wire voltage, making ECU increase fuelling). Or maybe you used some sealant that's contaminated the probe(s)? Is there any black smoke when it happens? As we don't yet know for sure if it's over- or under-fuelling.
I think it's unlikely to be the fuel pressure regulator, as that would be an unlucky coincidence.

Sent from my B1-830 using Tapatalk

[stove]

Hi folks.
Just tested the lambda sensor output : 0.49 V with just the ignition on , started the engine and it started rising and falling from between 0.3 and 0.9 volts. Removed all the earth's that are close to the coil, none looked bad but cleaned them up anyway. Went for test drive and it just kept going. Hacksawbobs statement in bold red font in the electrical section is now haunting me CHECK YOUR EARTHS. Thanks and respect to everyone who took the time to help me with this problem, also thanks to all the other knowledgeable people on this forum that have helped keep me on the road for the last 9 years of T 25 ownership.