MIsfire - Done the normal replacements, still struggling some. Any Ideas?

[3706mht]

Morning all. Had a misfire for the last few weeks. Car is a 94 1.0 Base model, all standard, no mods. Car starts a treat, runs but power low and running rough. This is what I've done today:

1. Changed plugs for nice fresh NGK's .... 1 & 2 were a nice colour, 3 & 4 were quite dark and a bit oily.

2. HT leads were changed with decent ones ... no significant improvement. I guess those were maybe 3-4 years old

3. Distributor cap was changed for a Lucas one.... it was very worn and the metal electrodes white and quite a bit of dust in there

4. Rotor Arm was changed with a Lucas one ... was also very rough at the end.

5. Distributor Cap gasket seemed to have disappeared .... not sure about that. Heat? Anyway that's changed.

As I say, it starts a treat, it's running but I'm not sure it's running hugely better after changing those parts. All the parts freed up and changed nicely. I ran the car between each plug, lead and component change. So I'm confident the bits done are done right as it were.

Would be grateful if anyone has any steer what might be looking at next. Replacement distributor? Throttle body fix has been done in the dim past but wondering if that could be a factor? Anyway any ideas would be very welcome and appreciated.

All the best

 

[bubba]

Morning all. Had a misfire for the last few weeks. Car is a 94 1.0 Base model, all standard, no mods. Car starts a treat, runs but power low and running rough. This is what I've done today:

1. Changed plugs for nice fresh NGK's .... 1 & 2 were a nice colour, 3 & 4 were quite dark and a bit oily.

2. HT leads were changed with decent ones ... no significant improvement. I guess those were maybe 3-4 years old

3. Distributor cap was changed for a Lucas one.... it was very worn and the metal electrodes white and quite a bit of dust in there

4. Rotor Arm was changed with a Lucas one ... was also very rough at the end.

5. Distributor Cap gasket seemed to have disappeared .... not sure about that. Heat? Anyway that's changed.

As I say, it starts a treat, it's running but I'm not sure it's running hugely better after changing those parts. All the parts freed up and changed nicely. I ran the car between each plug, lead and component change. So I'm confident the bits done are done right as it were.

Would be grateful if anyone has any steer what might be looking at next. Replacement distributor? Throttle body fix has been done in the dim past but wondering if that could be a factor? Anyway any ideas would be very welcome and appreciated.

All the best

Have you done a compression test on each cylinder, Could be piston compression ring or even a valve not seating or burned, sounds like you've covered most of the easy stuff..
Remove all leads from spark plugs remove one spark plug at a time and turn over engine and with a tester see what each cylinder putting out.
Make sure you put the spark plug back in before moving to next cylinder.
You may find one of those cylinders the reading will be low, could even be a head gasket gone leaking between a cylinder.
Easy on a car where the spark plugs don't sit so deep in the head.

 

[3706mht]

Have you done a compression test on each cylinder, Could be piston compression ring or even a valve not seating or burned, sounds like you've covered most of the easy stuff..
Remove all leads from spark plugs remove one spark plug at a time and turn over engine and with a tester see what each cylinder putting out.
Make sure you put the spark plug back in before moving to next cylinder.
You may find one of those cylinders the reading will be low, could even be a head gasket gone leaking between a cylinder.
Easy on a car where the spark plugs don't sit so deep in the head.

Good call Bubba .... no I didn't.

We have just removed the injectors and No.3 seems off. We just going to swap 3 and 4 and see what happens.

But no I didn't think to test compression. We not loosing a drop of water to fingers crossed not head gasket. We are dropping some oil . I think that's from the sump plug .... hope it is.

But thanks for the direction on that. Will definitely be testing that.

 

[bubba]

As for the head gasket if it was gone just check the expansion tank (Radiator) see if there is any oil in there floating on top of water, I doubt its a head gasket But I've had them no over heating or loss of water but the gasket was blown accross the cylinder.
It's likely to be a valve or compression ring but yes if all else fails do a compression test.

 

[3706mht]

As for the head gasket if it was gone just check the expansion tank (Radiator) see if there is any oil in there floating on top of water, I doubt its a head gasket But I've had them no over heating or loss of water but the gasket was blown accross the cylinder.
It's likely to be a valve or compression ring but yes if all else fails do a compression test.

No the water in the rad and header is unusually clean and anti freeze coloured .... amazingly so, no discolouration as all. Odd in a car this age.

Finger crossed it's an injector but otherwise we start looking at that later today.

 

[3706mht]

Update - we checked the compression and good news, it's solid and consistent.

The No.3 plug I mentioned was a bit dark and oily. We ordered and fitted a replacement injector and indeed the misfire has gone! Good news but now we have mad idle variation and hunting. And so I guess it's throttle body time.

I think I did the rebuild on this a few years back so this time it's going to be a new one. Hopefully this brings things back to where they have always been. Mind you, MPG has not been as good as remember it and for some years now thinking on. So maybe it's been going a good while longer than I thought.

It appears that the plugs, leads, rotor and cap although old and looking very worn, were in fact all OK.

Will report back with results on the Throttle Body.

 

[bubba]

Well glad you got yours sorted.. Yes Throttle body sounds the point.. Haha I had a missfire the otherday turned out after checking the spark plug was the problem!
A garage which used to service this car stated spark plugs had been changed they were never touched!! Naughty naughty garage.
I won't be naming names but when I see the original owner I shall be advising them change the garage or get someone In the know to check their work...
Anyway good you got things sorted throttle body I know you got to go through a set up procedure not sure if this is after cleaning?
Me I've never had to do that, but no doubt one day I will get one!