Misfiring 190 - please help

[big col]

I have a 190 2.0L 1989 Carburetor. (102.924)

History of the car:
Had for 3 years and serviced myself regularly. Never has idled well, always a little lumpy. Have replace HT leads, dizzy cap and rotor arm and sparkplugs (replaced regularly).
It seems to use a little oil and water (coolant). The carb has been dismantled, cleaned and gaskets changed (by me so not professional). I don't think there are any air leaks in the vacuum system.
It has never idled at the correct speeds ... it takes a few seconds, after starting, to get to fast idle speed, then drops below 650rpm before the car reaches optimum operating temperature. After that it normally idles at about 750 but varies from 650 to 900 when fully warm.
It occasionally runs on after turning the ignition off but not for very long and not very often.
I get ‘mayonnaise’ in some of the hoses at the top of the engine.

Over the last few months I can here a tapping sound in time with the engine revs. It sounded like it was more during warm up and then went off, now it is intermittent but happening when warm and when warming up.
Recently it has been using more water I think and the idle speed (when warm) has dropped to about 600 and it feels like it is going to stall (but doesn't).
I measured the HT leads going to the spark plugs and found that the plug at the back of the engine was not firing all the time.
I remove the spark plugs and they looked like this (Left is back of the engine moving right to the front of the engine) (at other spark plug changes they have all looked good):

New plugs have been put in.
The coolant looked mainly like rust although it was changed (I think) 3 years ago. I have flushed and replaced this. I have not seen oil in the coolant.
Before the plugs were replaced (at the same time as the idle low idle started), the car is producing white? smoke, more when the car is idling at low speeds. This continues after the spark plugs have been replaced.

As you can see the plugs indicate a problem. Is it definitely valve seals or could it be something else? I have never got to the bottom of the lumpy idle either if anyone has any ideas.

Thanks for any help

Colin

 

[mattkh]

Hi
What a good idea to put up the pictures.
The cylinder numbers go 1 2 3 4 from the radiator backwards.
The state of the plug from cyl 4 agrees with the HT lead being faulty. How did you suspect the lead 4?
What is the mileage?
Did new plugs and new leads not cure the idle?
Please put up a picture of the engine.

 

[jibcl500]

I would also do a compression test, lack of compression can seem like a misfire.
jib

 

[big col]

update...

New plugs have improved but nut cured it. The HT lead was replaced 3 years ago, I have not changed it recently (but I have a spare so will try it).

I think the car has done 115k, I have done about 25k of those.

I used a multimeter that measures each HT lead pulses, and could see that No 4 was not always measuring logical numbers.

Thanks so far...

Col

 

[wireman]

Coolant looking rusty is often a sign of exhaust gasses entering the coolant in excesive quantities, perhaps the head gasket is dying or worse the head is cracked.
The redish residue is what is left of the antifreeze after it has chemicaly reacted with the hot gas.

Check the compressions of each cylinder both dry and with oil injected into each cylinder.
Low pressure with oil sugests bad valve seating or cylinder head gasket.

Your multimeter (if its the ordinary dvm kind) will love being used on the running HT leads, dont trust any measurement that you now make with it. Use a neon timing lamp in line with the plug or hold a neon screwdriver against the lead as and indicator that there is some spark voltage present.

To spark in atomospheric pressure takes about 1-2Kv, to spark at 150 psi takes 20 or more Kv, your detector probably is not able to detect the lower voltage pulses from a possibly duff cylinder.

Resistive ht lead has around 10,000 ohms per foot. Do not worry about lost energy in the lead resistance, the ignition system was designed to use these cables and works better with resistive cable than it would with the wire stuff that boy racer magazines recomend. Yes more energy gets to the plug but over a much longer time period with the wire stuff, the carbonised string leads shorten the time constant of the coils HT winding giving a short fast and hotter spark.

As for your plugs:- no1 OK, no2 a bit rich, no3 OK, no4 scrap.

White exhaust smoke is probably condensed water, thats ok in a cold exhaust since about half of the exhaust gas is water anyway. If the white smoke persists with a thorougly warmed up car then one has to speculate where the water is from, head gasket?

 

[big col]

Now even worse...

Hi Wireman and everyone

Much worse today. I lost a couple of litres of coolant on the way to work (25min drive). Was worse when warm and loads and loads of white smoke. Feels like it is now running on only 2 cyl too.

I feel the must me a head gasket, so will fix this tomorrow.

Any hints etc for this? I have the Haynes manual but it can be a bit basic sometimes. I have not done any engine work before ... but can't afford a pro and I would like the experience of fixing it.

Is there anything else I should do at the same time at the head is off?

And lastly, if the head is cracked or warped, can I tell this with a flat steel ruler or something, or do I need to take it somewhere?

Thanks again....

Colin

 

[big col]

And here was the problem ...

 

[brandwooddixon]

I was going to say that the head gasket is leaking, but as you've found a crack it obviously is.

For reference to others I've always found that if your careful in removing the head then inspection of the gasket is a pretty good indicator of where the problem is.

I've also found that it's best to get get the head skimmed and fit an appropriately thicker gasket, if needed. Quite often any defect in the cylinder head can be too minor to spot by using a straight edge and yet shows up immediately once the head skimming starts!

 

[big col]

Head's been skimmed

And was warped slightly too. Looks brand new now ...