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[moorej91]

Have had a few problems with my car which with the help of the forum have been sorting them out, now I have another one. Over the last couple of days my car has started to run really rough. It starts fine from cold but seems that as soon as it starts to get warm it misfires and does not run on all cylinders. When hard on accelerator the car will only do about 10 miles an hour if that. Is there a common fault that I should check? Any other ideas would be appreciated.

Thanks

[alexandjen]

Any eml light?

[cem_devecioglu]

Seems like a sensor problem but must be verified..

[Grumpy]

1)Check your EML light works, if ok, action a Paperclip Test iaw
   the following link. Your 2.0L will probably give 4 digit codes and
   is actioned with ignition on but engine NOT running. This will tell
   which sensor, if any, the ECU is concerned about.

http://www.omegaowners.com/forum/YaBB.pl?num=1189022687

2)Check your coolant level. If losing coolant check that your HBV is
   not spraying water over your Dispack. Check that water is not
   leaking  from your scuttle area on to the Dispack. The Dispack
   is mounted centrally on the back of your cylinder head.

3)Check the connection to your Coolant Temp Sensor on the back of
   the Cylinder Head, near your Dispack. Clean up the connector
   and reseat. If possible, do a continuity check between the cable
   connector and the ECU.

4)Remove the black 'ECOTEC' strip from the top of your cam cover
   and check for oil in the spark plug wells beneath the strip.

The fact that you are running fine when cold would seem to indicate
that a sensor is breaking down when hot, the ECU is receiving a
false Engine Temp, or water or oil is interfering with your ignition
system when enough of the wet stuff has doused your components.

I would have said to change the fuel filter, due to inability of
engine to accelerate, but if, as you say, the engine is fine when
cold, then I would tend to discount this possible fault.

[moorej91]

Thanks for your replies. When I had my last problem, I had the cam sensor changed along with the cam belt and pulleys. All seemed to be running fine until recently. As I said the car starts first time and idles fine, after about 2 to 3 miles is when the problem starts. It is like the engine wants to rev but cant, the engine will not rev even under no load. No eml light and no coolant loss. Will do paperclip test and getback.

Thanks

[Guglielmo]

I am trying to find out a very similar problem. With mine if I turn the ignition key off and on again it will start and run for a while as if its cleared something. Does yours do that? If I get it fixed I'll let you know what it was.

[moorej91]

Checked paperclip test again, but no fault showing. Still got problems. Have found that car always starts first time and runs for about 4 mins then problem starts. It seems as soon as engine gets to running temperature a sensor kicks and the the engine starts to run rough. It will not pick up even under no load. While the engine is stil warm always has this problem even if you turn engine off and restart. If left to cool no problems. Grumpy says it could be coolant sensor that goes to ecu. Anyone tell me where it is. Would anyone be able to find this fault on a diagnostic check?

Thanks

[TheBoy]

has fuel filter been changed lately?

[moorej91]

Fuel filter never been changed by myself have had car for about 9 months. As I have not needed it before can you tell me where the filter is? Also would this affect the running when cold or hot?

[moorej91]

Have just changed the fuel filter (thanks to maintenance guide which was spot on). It seemed to be better but still got problem. I think I was hoping it would be a cheap quick fix. Going to check the oil in the spark plugs wells tomorrow. Still would like to know which is the coolant temp sensor that goes to the ecu, can anyone tell me?

Thanks

[Andy B]

Have just changed the fuel filter (thanks to maintenance guide which was spot on). It seemed to be better but still got problem. I think I was hoping it would be a cheap quick fix. Going to check the oil in the spark plugs wells tomorrow. Still would like to know which is the coolant temp sensor that goes to the ecu, can anyone tell me?

Thanks

I don't know the 4 pot engine, but it'll be the sensor with two connectors on top. The single connector sensor is for the dash temp gauge.

[Marks DTM Calib]

Have just changed the fuel filter (thanks to maintenance guide which was spot on). It seemed to be better but still got problem. I think I was hoping it would be a cheap quick fix. Going to check the oil in the spark plugs wells tomorrow. Still would like to know which is the coolant temp sensor that goes to the ecu, can anyone tell me?

Thanks

I don't know the 4 pot engine, but it'll be the sensor with two connectors on top. The single connector sensor is for the dash temp gauge.

Yup....back of engine below DIS pack its screwed into a coolant block.

[Grumpy]

As 'Andy B' said, it's the sensor with 2 leads, not 1.
You'll find it mounted on the back of your Cylinder Head,
low down in between the Dis Module, (the black lump with
your 4 ignition leads coming out of it), and the EGR valve,
(a big valve with various pipes connected to it, on the passenger
side of your Dis Module.)

It may just need corrosion cleaning off the connections, if your
scuttle has been leaking rainwater over it.

I once had an Alfa33 that used to overheat. What I tracked it
down to was corroded terminals on the fan switch that was
failing to signal the fan to run.

If a false cold signal is being sent to your ECU, when the engine
has warmed up, it will over fuel and give too rich a mixture to
combust properly, leaving you coughing and spluttering and
going nowhere fast. I'm not too sure of the next bit, maybe
a Tech 2 expert would care to comment. But if the combustion
was incomplete, this would leave too much oxygen entering
the Cat, (because it wasn't being burnt), which would be sensed by
the Oxygen sensor. The ECU would interpret this, incorrectly, as
a weak mixture and enrich the fuel to compensate, thus compounding
the problem. I know this is working a**e about face in relation
to how the Oxygen sensor and the ECU normally interact, but this
is the sort of thing that happens when things go wrong.

Just a theory, happy to hear other comments on this musing out loud.

I've found that 90% of mechanical faults turn out to be electrical
in nature.  

[Grumpy]

I see Marks DTM Calib beat me to it whilst I was scribbling
my mini-novel reply.  

[Markie]

interesting thread. Ive long given up trying to solve my misfire when engine warm on the estate...

No coolant loss, no oil in plug wells, no fault codes or eml, new leads, plugs, fuel filter, dis pack and so on. Car runs fine for about 30 minutes then its edgy and lumpy..

Guess i too am checking my coolant temp sensor...