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Not listening to MrMerlin about anything 928 related is just stupid.
The man is an expert.
Anyone who reads his posts, sees his restorations, or has seen him do a tech session can attest to that.
He has factory solutions and better more economical modern day fixes.
He is truly one of the leading 928 authorities-
Not to mention one of the first to always give help and advise on this forum.
Last edited by PC-85-928S; 07-04-2021 at 11:17 AM.
I bet if you put new plugs in the car runs smooth again for a short while. You're issue looks to be cylinder 4 with the plug that doesn't look like the others and the low compression in that cylinder.
I bet if you put new plugs in the car runs smooth again for a short while. You're issue looks to be cylinder 4 with the plug that doesn't look like the others and the low compression in that cylinder.
The plugs aren't fouled or anything. I did a lot of work on it when I got it as it wasn't running properly at all. But I could never get rid of this missfire. So, really, it's been like that from the get go.
At least I know I'm pulling something apart. I'm a bit unhappy about the 150 on cylinder 7 but I'm not sure it's worth pulling the head for. I'll see what the leak down test shows up.
As is traditional, I chucked some oil down cylinder 4 and no difference whatever.
Any thoughts before I order a top end gasket kit?
EDIT:
I don't have a leakdown tester but I've just ordered one so we'll see what the full story is when that shows up.
Good idea to wait for the leakdown tester before ordering the upper gasket set...you might need a complete gasket set.
Euro engines are very sensitive to fuel octane and have a tendency to break piston ring lands, if lower octane fuel is used.
While this may or may not be your issue, it's worth doing the leakdown test, to isolate your problem.
The plugs aren't fouled or anything. I did a lot of work on it when I got it as it wasn't running properly at all. But I could never get rid of this missfire. So, really, it's been like that from the get go.
At least I know I'm pulling something apart. I'm a bit unhappy about the 150 on cylinder 7 but I'm not sure it's worth pulling the head for. I'll see what the leak down test shows up.
The threads on 4 and the tip insukator look very different from all the others like it hasn't bben firing. That's the cylinder to focus your efforts on. If yuu think it's an issue with one port on the fuel distributor you can swap two fuel lines (on CIS cars it doesn't matter which FD port feeds which injector), and see if the bad looking plug changes to a different cylinder, but with the low compression, I don't think that's yiur issue.
It's LH not K-Jet. I'm not sure why the thread is so dry on 4. I don't believe in coincidence but it still might be. The electrodes look the same as all the others (to me).
Greg - my thoughts exactly. Whatever it is, I'm going to fix it but I'd rather have a clear idea. Given the wuffly exhaust note my money is on an exhaust valve but I'm not nearly that stupid
At this point just keep your hope in that the issue lies in the head and not the bottom end.
Do a leak down as recommended above and listen to where the air is hissing out of while the piston is in TDC. Could be the intake or exhaust valves. If it comes out of the dipstick tube I have some bad news....
#4 plug well was filled with water and the white stuff is corrosion.
Low compression in 4 could be a rusty seat or slightly bent valve
Follow my suggestions in post 2 after you determine the leak down results.
I am looking at it as we speak but it's somewhere between inconclusive and not looking good at all (blowing back through the oil filler). I'll be back!
I am looking at it as we speak but it's somewhere between inconclusive and not looking good at all (blowing back through the oil filler). I'll be back!
Oh dear- that does not appear to bode well sad to say if the leakage is via the oil filler. What leak down numbers are you generating?
I couldn't detect any leaks on any cylinder other than 4. That was blowing very gently up the dipstick tube.
So...... ???
EDIT:
There's a distinctly oily smell in the air when testing the 'bad' cylinder. I had a very quick look with an endoscope. It wasn't terribly successful but there appears to be a bit of oil sitting on top of that piston. Not loads but some.
Last edited by thepurpleblob; 07-06-2021 at 02:03 PM.
07-04-2021, 11:13 AM
