My 1989 Mk1 started to misfire yesterday just after I started it up and when revved hard made a knocking sound.
Today I have checked the plugs and leads and all is okay. So swapped over the injectors but the fault still lies with No4 cylinder. Carried out a compression test and No4 and No3 were only 4bar where as No2 was 8bar and No1 was nearly 6bar.
The head gasket was changed 5000 miles ago and there is no loss of water or any signs of the oil emulsifying. I feared a main bearing had gone with the noise I heard but even though it is only firing on 3 cylinders the engine will still rev up to 5000rpm and there is no noise (unless you 'blip' the throttle).
Begining to fear a stuck valve or the head gasket has blown between No4 and No3. Going to get the electrics tested to see if there is a signal going to No4 injector but first got to get new 'O' rings for the injectors as they split when I put the fuel rail back on.
Anyone got any other suggestions as to what could be the problem.
Misfire
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jimi
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Misfire
Sorry to say this but with those reading there's something seriously wrong with your engine.
Did you do the compression check with the throttle wide open ?
Mr T recommends doing the checks with the throttle wide open and cranking over at 250 rpm
Minimum pressure should be 142 psi ( 9.7 bar )
Recommended pressure 179psi (12.3 bar )
pour a small amount of engine oil in each cylinder and repeat the tests, if the readings go up then it's either rings or cylinder wear, if they stay the same then it's either valves or HG
Did you do the compression check with the throttle wide open ?
Mr T recommends doing the checks with the throttle wide open and cranking over at 250 rpm
Minimum pressure should be 142 psi ( 9.7 bar )
Recommended pressure 179psi (12.3 bar )
pour a small amount of engine oil in each cylinder and repeat the tests, if the readings go up then it's either rings or cylinder wear, if they stay the same then it's either valves or HG
Black is not a colour ! .... Its the absence of colour
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Jules65
Topic author
Re: Misfire
It was the head gasket...... again 
£450 and it is done (had blown between cylinders 3 and 4).......... This time by a man who I know and not some back street charlatan like before (who I expect never used new head bolts).
Best thing was there was an oil leak and the water pump bolts were loose too. Was told that one was about to drop into the bottom of cam belt cover and that would have torn through the cam belt..... again.
With luck it will run okay now and the 'hunting' will stop (which I thought was being caused by a leaking radiator).
£450 and it is done (had blown between cylinders 3 and 4).......... This time by a man who I know and not some back street charlatan like before (who I expect never used new head bolts).
Best thing was there was an oil leak and the water pump bolts were loose too. Was told that one was about to drop into the bottom of cam belt cover and that would have torn through the cam belt..... again.
With luck it will run okay now and the 'hunting' will stop (which I thought was being caused by a leaking radiator).
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NDR008
Topic author
Misfire
I wonder if there is another reason, we have quite a few 4A-GEs taking hard abuse on high comp gaskets in Malta and they are fine... Then again they go through a proper full rebuild, so I am thinking maybe there is something causing these frequent hg failures that in our case gets replaced in the rebuild. Hmmmm (thinking hat on).
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billybobbooth
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Re: Misfire
the head gaskets get hotter near no 4 cylinder, its a com prob if a crank will come out the block it will be on no 4 if the hd gasket goes it will normaly be on no4 and guess wht the dizzy goes to oh and guyess where that is near no4 cilynder, your better to have a metal gasket on it stronger than the normal ones, if you ever find on trd mad (not no longer) a carbon head gasket! if you find one use it but if you sell the car take it off. there worth alot of money.NDR008 wrote:I wonder if there is another reason, we have quite a few 4A-GEs taking hard abuse on high comp gaskets in Malta and they are fine... Then again they go through a proper full rebuild, so I am thinking maybe there is something causing these frequent hg failures that in our case gets replaced in the rebuild. Hmmmm (thinking hat on).
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jimi
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Misfire
Distributor is at #1 cylinder end 
Mr T's standard gasket is perfectly good enough for a standard engine in good condition. Certainly not worth spending money on fancy head gaskets unless you intend tuning for high power IMHO
Gaskets tend to go at that end mainly due to corrosion around the waterways, caused by bad maintenance on the cooling system ie not using the correct type of coolant, not changing it often enough or just using water etc. Your dealing with 20 year old engines with average mileages of 100,000 mine is over 110,000 miles, still on the original head gasket and is still going strong and that's not unusual
Best things you can do for these engines is to change the oil, filters and coolant at least once a year for oil and filter and every 2 years for the coolant and keep the cooling system working properly.
Mr T's standard gasket is perfectly good enough for a standard engine in good condition. Certainly not worth spending money on fancy head gaskets unless you intend tuning for high power IMHO
Gaskets tend to go at that end mainly due to corrosion around the waterways, caused by bad maintenance on the cooling system ie not using the correct type of coolant, not changing it often enough or just using water etc. Your dealing with 20 year old engines with average mileages of 100,000 mine is over 110,000 miles, still on the original head gasket and is still going strong and that's not unusual
Best things you can do for these engines is to change the oil, filters and coolant at least once a year for oil and filter and every 2 years for the coolant and keep the cooling system working properly.
Black is not a colour ! .... Its the absence of colour
