I recently had trouble starting my 1970 KE17 / 3K engine which after much trying would only fire on three cylinders. After replacing both the coil and distributor cap which I found had a crack, that problem was solved. The car then went to a paintshop where it sat for three months being worked on. On return, I now have another engine problem which I just can't work out. The car starts beautifully, idles like a dream and is a pleasure to drive. About 5-10 minutes into the drive when the engine has reached normal operating temperature, it starts to idle a bit rough and gets progressively worse to the point where I have to keep one foot on the accelerator and the other on the brake if I want to keep it running (its an automatic). Take the foot off the accelerator and the engine will stop and not start again until it has completely cooled down. I have replaced the carby (stock standard) with a refurbished one, no luck. I have also replaced the fuel pump with a new one, no luck. Someone suggested head gasket failure to me, but the car has none of the symptoms, no moisture out of the exhaust, no loss of coolant, no emulsion smear from water in the oil or oil in the radiator. I just don't understand what else can possibly be wrong. Any takers?

Have you done a compression test?

Have you done a compression test?

No, not yet, because as long as the engine is cold, it runs perfectly...

Yeah but things expand when it gets hot.

Yeah but things expand when it gets hot.

What do you suggest might be expanding...because as I said, there are no water leaks, and incidentally no visible oil leaks either?

check the plug leads, they can break down when the engine gets warm.

They should read 20.000 ohm's per 300mm (using a ohm's meter)

Edited November 2, 201213 yr by TRD ke70

Just had a similar issue on my 4k. Turned out to be a vacuum leak on inlet gaskets.

 

To test, get a can of startgas and spray around inlet manifold flanges while its ideling,

 

If revs increase when youre spraying, youve probably got a leak.

Check for rotten vacuum hoses and ptc valve as well

Just had a similar issue on my 4k. Turned out to be a vacuum leak on inlet gaskets.

 

To test, get a can of startgas and spray around inlet manifold flanges while its ideling,

 

If revs increase when youre spraying, youve probably got a leak.

Check for rotten vacuum hoses and ptc valve as well

 

The start gas is definitely something I'm going to try :-) But forgive my ignorance, ptc valve, what is it? I only have one vacuum hose which goes from the carby to the distributor, and that one seems to be ok.

Sorry, my mistake, meant pcv - positive crankcase ventilation valve. Oneway valve between valve cover and plate under carb...

 

ke1#

might not have them tho.

Edited November 2, 201213 yr by tojo2

Vaccum leak, check the Carby base gasket & inlet manifold gasket.

Richen the idle mixture and see if that helps. Its got a fair chance to be an inlet leak that leans it out, maybe the horrible twin inlet gaskets.

I have had the radio Suppressor on the coil fail before and I had the same problem that you are describing. Disconnected it and had no more dramas.

check the plug leads, they can break down when the engine gets warm.

They should read 20.000 ohm's per 300mm (using a ohm's meter)

I replaced the leads together with coil and distributor cap.

 

Just had a similar issue on my 4k. Turned out to be a vacuum leak on inlet gaskets.

 

To test, get a can of startgas and spray around inlet manifold flanges while its ideling,

 

If revs increase when youre spraying, youve probably got a leak.

Check for rotten vacuum hoses and ptc valve as well

Tried that today, unfortunately no luck. I couldn't detect any change in idle when spraying the stuff over the manifold and around the carby, only of course when some got sucked into the air intake. So there doesn't appear to be an intake manifold leak where it bolts on.

 

Vaccum leak, check the Carby base gasket & inlet manifold gasket.

Replaced carby base gaskets above and below the insulator, no luck.

 

I have had the radio Suppressor on the coil fail before and I had the same problem that you are describing. Disconnected it and had no more dramas.

My coil is a brand new one and it doesn't have a supressor, so that's out too.

 

Richen the idle mixture and see if that helps. Its got a fair chance to be an inlet leak that leans it out, maybe the horrible twin inlet gaskets.

Now here's something interesting: with the choke on just a little and revving from about 2500 upwards, engine runs perfectly. Take the choke off and drop the revs, it dies. I have then tried yet another carby from an engine I salvaged some 17 years ago still running at the time and sitting in my shed since. With that one, regardless how tight you set the mixture screw, it runs terribly rich, but - it even idles if you can call it that, very very rough but refuses to give up. Move the choke even just a touch, the engine revvs up to about 2500 to 3000 and runs perfectly well, just too rich. And its not the idle screws, I set them at reasonable speed before the engine was hot enough to start its evil game.

 

I am at my wits' end.