Topic: Bad engine misfire after warm up. (Read 3542 times)

moorej91 · « **on:** 15 January 2008, 18:26:20 »

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 · « **Reply #1 on:** 15 January 2008, 18:27:45 »

Any eml light?

cem_devecioglu · « **Reply #2 on:** 15 January 2008, 18:33:05 »

Seems like a sensor problem but must be verified..

Grumpy · « **Reply #3 on:** 15 January 2008, 19:16:21 »

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 · « **Reply #4 on:** 15 January 2008, 20:06:51 »

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 · « **Reply #5 on:** 16 January 2008, 20:57:34 »

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 · « **Reply #6 on:** 17 January 2008, 17:25:23 »

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 · « **Reply #7 on:** 17 January 2008, 17:29:07 »

has fuel filter been changed lately?

moorej91 · « **Reply #8 on:** 17 January 2008, 17:40:53 »

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 · « **Reply #9 on:** 18 January 2008, 20:33:35 »

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 · « **Reply #10 on:** 18 January 2008, 20:46:42 »

Quote

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 · « **Reply #11 on:** 18 January 2008, 21:30:59 »

Quote

Quote
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 · « **Reply #12 on:** 18 January 2008, 21:46:41 »

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 · « **Reply #13 on:** 18 January 2008, 21:48:30 »

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

Markie · « **Reply #14 on:** 18 January 2008, 23:26:19 »

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...

Marks DTM Calib · « **Reply #15 on:** 19 January 2008, 08:28:43 »

The ideal would be to connect Tech2 up and check the ECU coolant temp reading....

moorej91 · « **Reply #16 on:** 19 January 2008, 09:50:13 »

Thanks again for all your replies. When I was younger I used to work on cars with my dad since I was 5 (now in forties), I was very used to old technology. Fourtunately over recent years I have had reliable cars and not had to do anything to them. The omega seems very complicated and without the right equipment very hard to find the problem.

A very good point from grumpy, he mentioned about sensors and mixture and one thing that did cross my mind is that when I first start the car up there is quite a strong smell like petrol, although this does go. Also my back box on the exhaust has gone (the pipe at the back of the rear silencer has come out) could this also have something to do with it? Saying that the exhaust has been gone for a while and not given me this trouble. Going to have a look at the car now and will get back to you.

Have a nice day!

Markie · « **Reply #17 on:** 19 January 2008, 09:53:39 »

Quote

The ideal would be to connect Tech2 up and check the ECU coolant temp reading....

Aye....you and Jamie dont fancy a haggis fuelled trip to investigate mine in Scotland do you

moorej91 · « **Reply #18 on:** 19 January 2008, 11:45:55 »

Could anyone tell me how much the coolant sensor is and are they simple to fit? Would it be worth changing this anyway? I have someone coming to do a service on monday and change all filters etc,
Just going to check car now.

cem_devecioglu · « **Reply #19 on:** 19 January 2008, 16:09:32 »

Quote

Thanks again for all your replies. When I was younger I used to work on cars with my dad since I was 5 (now in forties), I was very used to old technology. Fourtunately over recent years I have had reliable cars and not had to do anything to them. The omega seems very complicated and without the right equipment very hard to find the problem.

A very good point from grumpy, he mentioned about sensors and mixture and one thing that did cross my mind is that when I first start the car up there is quite a strong smell like petrol, although this does go. Also my back box on the exhaust has gone (the pipe at the back of the rear silencer has come out) could this also have something to do with it? Saying that the exhaust has been gone for a while and not given me this trouble. Going to have a look at the car now and will get back to you.

Have a nice day!

engine problem is not related with exhaust leak..Only will make noise..

CTS is not expensive ..

TheBoy · « **Reply #20 on:** 19 January 2008, 18:03:52 »

Quote

Quote
The ideal would be to connect Tech2 up and check the ECU coolant temp reading....

Aye....you and Jamie dont fancy a haggis fuelled trip to investigate mine in Scotland do you

I'm sure we could meet halfway, ie Lakes, around mid June

Talk_Converter · « **Reply #21 on:** 19 January 2008, 18:18:40 »

Just wondering if this is related to my old Carlton fault, lovely idle but no guts from then on, really lumpy and no speed. Did a full service and checked everything you can think of (ECU, sensors etc.) and found no fault so we removed the lambda sensor and car ran better with the hole unplugged. So we checked the Cat and found it virtually blocked. Temporarily removed Cat and car went like a dream. Might be worth a check if you can't find anything else wrong and need a straw a grab!

moorej91 · « **Reply #22 on:** 19 January 2008, 19:05:02 »

Someone mentioned that you get a smell like rotten eggs if the cat has gone. As I said before there is a smell especially on start up.

How do you check the cat? How do you bypass thecat to check?

Thanks

Talk_Converter · « **Reply #23 on:** 19 January 2008, 19:38:41 »

Usually get that smell when Cat is new, my Cat certainly gave no warning of blockage except for the bad running of the engine. Sometimes it would not be too severe but at others it was really bad, car could not get up steep hills! The Lambda sensor is placed before the Cat so its removal allows some of the exhaust gases to escape through the threaded hole.
Enough to maybe prove if the car is now working better, it will be quite noticeable albeit a little noisy

. If car runs a lot better then suspect blocked Cat. The Lambda sensor may be a bitch to remove, it seems easier to shift if the exhaust is warmed up a little first.

moorej91 · « **Reply #24 on:** 20 January 2008, 20:47:43 »

If the cat was blocked would that not make the engine uneven when cold also?
Have also seen on ebay a tech 2 interface and software. Does anyone know if these could check things like sensors or is it just a code reader or are they the same thing.

http://cgi.ebay.co.uk/Vauxhall-Opel-tech-2-OBD-Diagnostic-CAR-Code-Reader-PC_W0QQitemZ230213857168QQihZ013QQcategoryZ30921QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

dharstay · « **Reply #25 on:** 21 January 2008, 12:44:18 »

these symptoms are identical to mine. i also have checked plug wells etc and paperclip test shows no codes.replaced ht leads as well. going to check coolant temp sensor when rain clears. is there any thing i need to use to clean it up?

moorej91 · « **Reply #26 on:** 28 January 2008, 20:56:06 »

Hi, Thanks for your reply. I took my car into Vauxhall last week and they did a diagnostic check and found no faults. That was £57.50 gone. Because of that they checked the spark plugs. They said there was water by the plugs (not in engine) and they were the wrong plugs. I have had the car for 10 months now and have had no problems with starting or running. They said that is all they could find. They changed the plugs dried up the water and

Success problem solved

Thanks to all and hope this helps others.

Great forum

bertiecbx550 · « **Reply #27 on:** 28 January 2008, 21:50:57 »

i`ve just seen this thread and it sounds like the prob i had with mine if it comes back again try changing the fuel pump/injector relay thats what cured mine...

Guglielmo · « **Reply #28 on:** 03 February 2008, 13:30:29 »

Hi just fixed mine, was the dreaded cam sensor. £10 from ebay and 15 minutes fitting and runs as good as new again.

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Author Topic: Bad engine misfire after warm up. (Read 3542 times)

cem_devecioglu

cem_devecioglu

bertiecbx550