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[john1dart]

Gents
I've just spent the last day and a half changing the rocker gaskets and trying to cure a misfire.
Jobs done:-
New plugs and leads
Oil and filter change
All new gaskets
New fuel filter

The Vent housing was clogged solid as was the breather bridge post throttle breather, well this was solid to be exact, and took some clearing. The leads and plugs were drowning in oil so these definately needed changing. Don't worry the new ones have gone on in the correct firing order.
Although its running better than it was, there is still a misfire. If i've missed some crud in the breather bridge post throttle breather, and its not quite clear, could this cause the lack of power and the misfire.
The sypmtoms of the engine running are:-
On idle (800rpm) every 30 seconds or so the engine revs itself to about 1200 rpm and drops again.
Driving with the revs fairly high, I don't get the misfire or it running lumpy, but there is definately not the right amount of power there for a 2.5.
If I'm doing 30 in 4th and floor it, the misfire is there and the car starts chugging away.
Basically if the revs are fairly high, the engine sounds ok but definately a lack of power.

Any ideas fellas???

[sounds2k]

possibly DIS pack ... it's not unheard of for HT leads swimming in oil to cause DIS pack damage ...

[Admin]

Hang on... "on idle 800rpm"  

Idle should be 500rpm with air con off or 600-650rpm with air con on.

Did you clean the idle control valve?

Did it ilde at this level before you did the work?

[john1dart]

laidback
It did idle at this before the work yes. Idle control valve cleaning??? would this cause it to run rough or misfire??

[john1dart]

i don't know if this will help diagnose the problem but when i rev the engine, there is a hesitation and what sounds like a quick blip of vaccuum from it sounds like the breather bridge.

oh well going to clean the breather bridge again..

[Auto Addict]

laidback
It did idle at this before the work yes. Idle control valve cleaning??? would this cause it to run rough or misfire??

The ICV, unless cleaned properly will cause the eratic idling.

[Markie]

agreed, sounds like a breathing issue, only after this would i look to dispack, however its doubtful with the other symptoms that this is dis related. Lots of carb cleaner required  

[Admin]

Clean and lubricate the idle control valve... then see how things are...
Simple things first!

[Mike Collins]

Is it worth blanking off the EGR? that was one of the things that stabilised my idle.

[john1dart]

agreed, sounds like a breathing issue, only after this would i look to dispack, however its doubtful with the other symptoms that this is dis related. Lots of carb cleaner required  

now on my 3rd can and god knows how many soaks in hot hot water. i'll fit it back to the motor 2 morrow. got brassed off with it. got some beers and watching the darts. hope that cures it.  

[john1dart]

Clean and lubricate the idle control valve... then see how things are...
Simple things first!

is the ICV at the top of the right hand bank as you look at the car from the front?

[john1dart]

agreed, sounds like a breathing issue, only after this would i look to dispack, however its doubtful with the other symptoms that this is dis related. Lots of carb cleaner required  

now on my 3rd can and god knows how many soaks in hot hot water. i'll fit it back to the motor 2 morrow. got brassed off with it. got some beers and watching the darts. hope that cures it.  

3rd can of carb cleaner by the way. 6th can of beer.

[Admin]

Clean and lubricate the idle control valve... then see how things are...
Simple things first!

is the ICV at the top of the right hand bank as you look at the car from the front?

Yes, it is attached to the right side of the plenum. Electrical connector at the back and rubber pipe on the front.

When replacing, make sure there is a tight fit to the plenum.

[john1dart]

Clean and lubricate the idle control valve... then see how things are...
Simple things first!

is the ICV at the top of the right hand bank as you look at the car from the front?

Yes, it is attached to the right side of the plenum. Electrical connector at the back and rubber pipe on the front.

When replacing, make sure there is a tight fit to the plenum.

cheers laidback. i'll try it in the morning

[Markjay]

1. I don't think that blocked breathers will cause a misfire as such.

2. The breather box is venting into the front of the intake plenum, if it is not tightly sealed then you could have a vacuum leak into the intake which will cause erratic idle.

3. If you had gunk from the breather box drop into the intake manifold on regular basis you could have a problem with blocked injector(s). I would try some fuel system cleaner such as Redex or Forte, though you may need to have the injectors cleaned professionally since these fuel additive have limited efficiency.

4. Do not overlook the obvious - have you changed the air and fuel filters?

5. As said above, ICV is also a very good candidate, followed by DIS pack.

6. And I suggest that you don't drive the car, misfires can kill the cats...




Hope this helps...