Oil fouled spark plugs, high RPM stumbling problem
04-30-12, 06:37 PM
#1
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Oil fouled spark plugs, high RPM stumbling problem
Hey everyone, been having some issues with my 79, posted mostly in the 1st gen forum about this. A little back story is that I have been chasing a 5000rpm+ stumble/miss. I know this is not fuel related since it happens at any throttle position or engine load. Early this spring, I did get the problem fixed by changing the spark plugs out for new NGK BR7ET, stock plug for the 79 12A. However, after driving a short time, the problem has reappeared.
A short time after I got the car last august, I noticed that the engine would burn some oil, especially after sitting for a couple days. The smoke plume was similar to that seen after fogging the engine for winter storage or something of that effect. I didn't think much of this as I don't have to worry about emission/smog testing where I live and it didn't seem to burn any oil in normal driving. After a while, and during test drives to find the cause of the stumbling issues, I started noticing a large plume of blue/white smoke out the back of the car while the engine would wind down from 7000rpm. Again I didn't think much of this at the time.
My finding this past weekend have put the potential oil problems at the top of my list of causes of the stumble. I found that if I shut the engine off shortly after running up to 7000rpm the spark plugs would be black and had a bit of oil residue on them. This leads me to my question, is it possible that the oil control rings or other seals within the engine are leaking by bad enough that the spark plugs are fouling in high RPM and causing them not to fire? With my knowledge of engines, it seems pretty logical to me that this is my problem. Am I way off base here?
I have eliminated everything else I feel by rebuilding the carb, removing all emission equipment and the rats nest, converted to electronic dizzy with brand new coils, known good plug wires, new cap and rotor, and what were new plugs. I have checked every electrical system related to the engine and everything is working as it should. I have litterally checked every possible external engine system for the cause and I have yet to find anything that would cause this stumbling to reappear, besides the fouled spark plugs. Thanks for any help.
A short time after I got the car last august, I noticed that the engine would burn some oil, especially after sitting for a couple days. The smoke plume was similar to that seen after fogging the engine for winter storage or something of that effect. I didn't think much of this as I don't have to worry about emission/smog testing where I live and it didn't seem to burn any oil in normal driving. After a while, and during test drives to find the cause of the stumbling issues, I started noticing a large plume of blue/white smoke out the back of the car while the engine would wind down from 7000rpm. Again I didn't think much of this at the time.
My finding this past weekend have put the potential oil problems at the top of my list of causes of the stumble. I found that if I shut the engine off shortly after running up to 7000rpm the spark plugs would be black and had a bit of oil residue on them. This leads me to my question, is it possible that the oil control rings or other seals within the engine are leaking by bad enough that the spark plugs are fouling in high RPM and causing them not to fire? With my knowledge of engines, it seems pretty logical to me that this is my problem. Am I way off base here?
I have eliminated everything else I feel by rebuilding the carb, removing all emission equipment and the rats nest, converted to electronic dizzy with brand new coils, known good plug wires, new cap and rotor, and what were new plugs. I have checked every electrical system related to the engine and everything is working as it should. I have litterally checked every possible external engine system for the cause and I have yet to find anything that would cause this stumbling to reappear, besides the fouled spark plugs. Thanks for any help.
05-03-12, 04:52 PM
#2
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Am I just asking a dumb question here or does nobody know the answer? I figured somebody may be able to give a bit of insight into the oil problem as this is not something I have experienced before.
05-07-12, 06:51 PM
#3
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Im interested as well. Just had my 94 13b rebuilt with single turbo and am having a similar problem. Only driven the car 3 times since getting it back, including when I picked it up from the shop.
Now it has developed a consistent stumble at 6000rpm. My first thought was the spark plugs has I dont think they were changed after break in. But then over the weekend I found that my HKS foam intake filter had some how caught fire and melted out a nice chunk from the bottom of the filter. Just out of sight till I removed the filter.
After inspection of the turbo and hard pipes it does not seem that any burnt foam pieces made it to the engine itself.
So back to the thought of bad plugs and the two issues being a coincidence.
Having the guys from the shop come by first to get their thoughts.
Also, my tuner is having me run a gas/oil premix. 1oz per gallon along with my factory oil injection system. Maybe too much oil?
Now it has developed a consistent stumble at 6000rpm. My first thought was the spark plugs has I dont think they were changed after break in. But then over the weekend I found that my HKS foam intake filter had some how caught fire and melted out a nice chunk from the bottom of the filter. Just out of sight till I removed the filter.
After inspection of the turbo and hard pipes it does not seem that any burnt foam pieces made it to the engine itself.
So back to the thought of bad plugs and the two issues being a coincidence.
Having the guys from the shop come by first to get their thoughts.
Also, my tuner is having me run a gas/oil premix. 1oz per gallon along with my factory oil injection system. Maybe too much oil?
05-18-12, 05:42 PM
#4
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The oil consumption problems were in fact causing the problems I was seeing. I put some Lucas oil stabilizer in the engine with the first oil change of the season and the oil consumption virtually disappeared along with the spark plug fouling and stumbling issues.
IIRC 1 oz per gallon is the standard mix you want to use if you are only premixing and not using the original oil injection. Sounds like too much oil to me with both together, but I am far from an expert on what you should do for a fresh rebuild.
IIRC 1 oz per gallon is the standard mix you want to use if you are only premixing and not using the original oil injection. Sounds like too much oil to me with both together, but I am far from an expert on what you should do for a fresh rebuild.
05-19-12, 06:42 AM
#5
Original Gangster/Rotary!
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Carbonfiber, that may very well be too much premix, esp if the duty cycle on the OMP has been turned up.
Try backing it off to 1/2 an oz per gallon along with the OMP.... what apex seals are you running? I'm guessing RA
Try backing it off to 1/2 an oz per gallon along with the OMP.... what apex seals are you running? I'm guessing RA
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