Poor running after cat replacement

Macca5001

I have just replaced the cat on my 2.2 2001 vectra. I also did a oil and filter change.
The reason for cat replacement was due to the flexi had split.
Since I have replaced it the car runs lumpy when cruising at certain speeds like 30 mph in 3 rd gear.
Before that it was fault less
Has anybody have any ideas.

Matt

Any EML on the dash? Has the O2 sensors been connected correctly?

Macca5001

No lights on dash. I'll recheck connections tomorrow. The fuel consumption has dropped from 33 to 23.

Matt

Which cat was replaced? The main cat?

Macca5001

The oil I put in was 10 40w. Which is what the shop said for that engine but I'm sure It was 5w 30 last time.

I know years ago when I worked for Vauxhall everything but turbos had 10 w 40. So I can't see that being the problem

Macca5001

The main and pre are all one unit.

Matt

Macca5001 said:
The oil I put in was 10 40w. Which is what the shop said for that engine but I'm sure It was 5w 30 last time.

I know years ago when I worked for Vauxhall everything but turbos had 10 w 40. So I can't see that being the problem

Yeah, 10W40 is what you should be running on these engines.

Macca5001

I have a suspicion it may be the front sensor. Maybe it has been damaged when replacing cat. Went for a drive in car and eml light came on.

Code was something about bank 1 heater in sufficient.
Think I'll try a sensor on it.

z22_cariad

acca5001 said:
The main and pre are all one unit.

Pre cat Is in downpipe above the flexi. Main cat underneath is it not ???

Macca5001

Yeah that's right but the pre and main are both in the same section of exhaust.

evocarlos

Macca5001 said:
Yeah that's right but the pre and main are both in the same section of exhaust.

yeah they are
but most downpipes now have the pre cat removed as it can cause the manifold to crack

Macca5001

Oh right this one still has it in. The way it's running is making me think it's a broken wire. One min it's okay next it runs rough.

MikeS

you know if it is front lambda

start up from cold and give it a few mins and gently rev engine between 1000 - 3000 and you should have a light electric misfire, keep it revving it as the fuelling should be all over the place

otherwise just disconnect front lambda and it will use reference voltage of .45 and see how it runs

Macca5001

MikeS said:
you know if it is front lambda

start up from cold and give it a few mins and gently rev engine between 1000 - 3000 and you should have a light electric misfire, keep it revving it as the fuelling should be all over the place

otherwise just disconnect front lambda and it will use reference voltage of .45 and see how it runs

Thanks for reply tried what you said and it's defo front sensor. Plugged in and checked what front sensor was doing and it was all over. Disconnected it and it held a solid 0.45.
Must be because it was disturbed when fitting to new cat.