MX83 MisFire, searching for cause?

[Mr.Matt]

Okay,

1991 Cressida Grande.

Well taken care of, 6th cylinder has started misfiring (the one closest to the firewall).

I replaced all the spark plugs and ignition leads yesterday (and the air filter as I had to take part of the intake parts out anyway) to try to combat this issue.

And it worked fine, but today the problem has returned.

It's running a stock 7M-GE, which is burning off a small bit of oil and water, but no cause for alarm yet (I'm not needing to top it up every day and there's no blue or white smoke coming out of the exhaust).

There was a bit of oil on this specific spark plug when I took out the old one, and it was abnormally tighter than the others (the spark plugs had not been replaced in a while).

Any other info that is needed just ask me, but I am looking for any possible causes/solutions.
And can anyone tell me if this misfire is causing damage to the engine? I do still need to drive the car, so I have just reduced it to a minimum and not driven it hard at all.

Thanks for reading!

[CELICASUPRA7M]

how did you decide no. 6 was missing? by unplugging the lead?
did you have a look at the dizzy cap?
if you know its getting spark, you would assume its a fuel prob (injector) or something worse like head gasket, or broken valve spring (highly unlikely)

[Mr.Matt]

no. 6 was the one that was misfiring in the first place, which is what set off this whole thing.

It had a lot of oil in there so I cleaned it out with de-greaser and then the ignition lead started popping out, which set off the replacement of everything.

I had the cable checked, it is getting electricity (had a mechanic connect one of those strobes that detects it to make sure).

So it's narrowed to essentially fuel injector, or head gasket.

Oil on the plug isn't an issue?

The others had none (or in one or two cases a very small amount).

And assuming it's not the head gasket, is it damaging the engine by running it?

[CELICASUPRA7M]

there would need to be a lot of oil to affect the leads connection.
shouldn't do any damage, but need to sort it asap.

[Mr.Matt]

Okay status update.

Took it back to the mechanic, who found that no. 1 was not receiving any electricity, so we swapped back to the original lead for no. 1.

Which seemed to fix it. The intention being that if the fix seems to last then go get the new lead for no. 1 replaced and be done with it.

Now the old lead is doing the same, considering it has now changed spots, and there is next to no oil at all in no. 1 at all (the plug came out dry as a bone),

I'm guessing now the distributor is on the way out?

Any thoughts?
Thanks for the replies so far.

[allencr]

I'm guessing now the distributor is on the way out?

What's the compression?
#6 is fouled for a reason, quit guessing. Unless you can see a carbon track/crack for #6's post on the dist. cap, the distributor is not affecting #6 any more or less then it is affecting #1 thru #5.

[Mr.Matt]

How do I do a compression test?
(I know what it is supposed to be (9.2), but not sure how to check what it actually is running at.)

And are you sure the distributor cannot be the cause?

#6 went and a symptom was that there was more oil then the others had, but that wasn't a definite cause for the misfire, just an assumed cause as no other evidence was present (and we didn't think to check if the cable was getting any electricity or not).

#1 then decided to go, but #6 was fine, when checked with the mechanics lead tester, we found that the ignition lead for #1 was not getting any electricity (at the time).

Once again not definite, but it was assumed the cable was at fault. Now that swapping cables fixed the issue for a little bit, but the problem with #1 did return. Going to the next component would logically lead to the distributor wouldn't it?

[andrew_mx83]

Where abouts in vic are you mate? I do a fair bit of work on cressidas and 7ms, sounds like either early bhg or oil coming out the rocker covers and pooling up around the plugs.

If u bring it round I can sus it out and do a comp test, I also do reco dizzys for them if that is the problem.

[Mr.Matt]

I'm over in South-Eastern Melbourne.

Living in Brighton East.

I will PM you.

Thanks for the offer btw!