Misfire is back

Post by **GreenyUK** » Wed Jan 29, 2014 2:33 pm

Hi all. So I'm away from home visiting family and my car has started misfiring again badly.
Put you foot on the go pedal and it sounds like a car that runs on 3 cyclinders ad it spits and bangs! Think I also saw abit of Smoke maybe? Steam? In the rear view.

Since this was doing the same thing last time when the engine check light was on, which was egr valve which I took off and cleaned. The car was fine even though the light with the same egr code kept coming on!??

Now the car is playing up again.
I've also got a crack and a hole in my exhaust down pipe before and after the sensor which is causing it to run rich could this be the issue? Are the Ecu's that sensitive?

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Jan 29, 2014 2:40 pm

Is it fine when cold but plays up when it's warmed up?

If so, then yes I'd say this could be caused by the downpipe hole before the 02 sensor.

When the sensor is cold, the ECU ignores it. When it's warm, it uses the O2 sensor to adjust mixture and a downpipe hole before the sensor would screw up emission readings for the sensor. How big is the hole?

jozefsan · Post by **jozefsan** » Wed Jan 29, 2014 2:56 pm

wurlycorner wrote:Is it fine when cold but plays up when it's warmed up?

If so, then yes I'd say this could be caused by the downpipe hole before the 02 sensor.

When the sensor is cold, the ECU ignores it. When it's warm, it uses the O2 sensor to adjust mixture and a downpipe hole before the sensor would screw up emission readings for the sensor. How big is the hole?

prelude use heated o2 sensor so sensor is always in temperature for correct reading
full open TB, engine use ecu map for a/f and not o2

if he have hole in exhaust it will cause problem with a/f as hole push fumes out but suck air in as well

Post by **GreenyUK** » Wed Jan 29, 2014 3:39 pm

Well was going to su I think it's probably when it's warm but it's benign doing it all day to day an I've been doing lots of visting so never really been cold.

Although it seems if it's heated won't e that :/
Well it's lots of small holes it's basically cracking so if left will snap clean in due time.

I've just done another paper clip tea and still getting the code 12. When I cleaned te egr it was just the valve I did not drill through all the plugs on the manifold to clean those.
I've never know an egr to cause so much trouble though. It's like half and engine when it happens. However if I gently touch the accelerator and accelerate at the slowest possible speed it tends not to happen, well not as much for sure.

Got me stumped. Have a 170miles trip on Saturday :/

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Jan 29, 2014 3:51 pm

jozefsan wrote:prelude use heated o2 sensor so sensor is always in temperature for correct reading

Interesting, yep just checked manual and you're correct - my error, hadn't noticed the lude has a heated sensor.
It's still correct that the mixture is (also) adjusted by the coolant temperature sensor though, until the engine gets up to temp then the coolant temperature sensor has nothing to do with mixture adjustment.

Either way, we both agree a hole prior to O2 sensor could affect mixture and cause misfire!

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Jan 29, 2014 3:53 pm

Which bit of the downpipe has holes?
Is it a plain tubular bit? If so, you could try covering it in exhaust putty or covering with gungum tape as a temporary fix to take that out of the equation and cover you until you get the new downpipe.

bb1boy · Post by **bb1boy** » Wed Jan 29, 2014 4:05 pm

Wrap it up in RedBull cans

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Wed Jan 29, 2014 4:22 pm

You may joke - I have had to do a split baked bean can/jubilee clips repair job on a snapped exhaust before now...

Think I ran it like that for a couple of months while Citroen had a Citroen only part manufactured to order and shipped out

bb1boy · Post by **bb1boy** » Wed Jan 29, 2014 4:25 pm

^^ brilliant

Post by **GreenyUK** » Wed Jan 29, 2014 4:30 pm

Yes I could try and block it up for now. I've used that exhaust bandage in the past, could use some of that for now as it's quite long?
What you think?

Yes could look at the can idea, think it's close to fleck bit though so might not seal that well.