Finally took the viper for drive the other day. New plugs, wires, fuel pump and few other things. Seemed to run fine for the most part. After driving for about 30 minutes it started to seem to not have full power from all 10. Pulled a few plugs and one was clearly different than the others. All of them don’t look the best to me but especially the darker one. I did a compression test and it was about 175. Did a leak down test and it is clearly not as good as the other cylinders. From the sound of the air it seemed like it was only passing through the piston rings out the oil cap/valve cover. Anyway just wondering if you guys had any tips or tricks if all the plugs had issues or just the one. They have about only 50 miles on them. Still learning this car and it has a lot of aftermarket stuff so trying to figure it out as I go. Sure was nice to finally take it on the road after a few months of working on it!
Those leakdown tests are pretty accurate. Sounds like major surgery is the only option but if you wanna do it on the cheap you could replace just the rings on the suspect cylinder. Personally I go big or stay home. I'd pull the motor and redo the whole thing.
My plugs always look too lean to me - like the white one, but I come from the old carburetor days. I would be more concerned about consistency across the plugs. JMO the white one looks too white but the other three don't look white enough. Definitely get more opinions. I'm not a pro.
Not seeing any metal but I would say your detonating... sound like marbles in a can at times?
Either way reduce the timing in the tune and get some better gas. Are you sure it doesn’t have a race gas tune?
This. Looks really lean to me. What plug are you running? All in all, I'd just check the tune and not over think things. Compression is fine. Leakdown is leakdown. If I recall from my auto engineering days, about 18% leakdown is normal. Not sure what percentage you are at.
no I totally agree. The plugs seem super lean which is what I was hoping some one could tell me. I have no idea what this car is tuned at. I'm finding some evidence that this car had nitrous on it at some point. It has MSD boxes on it. (no idea what they are doing).
It does idle at around 450rpm. Should a handheld tuner get me in the right direction or do I need to take it somewhere to find out the current tune?
Also I haven't noticed pre-detonation before on this car.
tanish color should be normal. Does the compression test go up if oil added to the cylinder? Should check the compression across all cylinders. If cylinder wall has issues, new rings would be of no help. If compression was down to 100 on one cylinder and 160-180 on all cylinders, then would worry about the bottom end. If they are all similar, probably just fine for now.
so you bring up a good point and this is my struggle. all cylinders were about 175 psi on a compression check.
On the cylinder with the weird spark plug I decided to do a leak down and its losing about 25% (other cylinders about 5-10% loss)...sounded like it was coming out the valve cover oil cap area. not intake, not exhaust, not coolant. which makes me think rings or cylinder.
So is it possible to pass a compression test but fail a leak down test and it be rings? I would think if rings are the problem that it would also have low compression.
I didn't add oil. Will try that (if it helps with leak down). Based on above sounds like I need to check for a lean issue as well.
It is possible those plugs could be fairly new and the brownish one is evidence of different fueling/oil consumption/not torqued.
The real story is going to be deep down into the plug that can only be seen by cutting the threads away, or looking through an illuminated jewelers lens; that's your WOT or heavy load fuel mixture evidence. If the plugs are new, modern unleaded fuel with detergents is usually dark gray on the porcelain, black soot may gather around the ground ring if they are a step or two colder. If the brown one does not have soot on the rim like the others, then it's running leaner/hotter than the rest.
looking at the picture again looks like the main difference in the "bad" leak test cylinder is the porcelain is brown vs all the others being white. Also the tip arm looks more solid white than the rest. not burning correctly? which leads me to rings which leads me to too much oil in the cylinder past the rings...
I would say it is probably just fine as is for a while, unless looking for excuse to do a build. It is probably not really putting much oil in to the cylinder, but blows exhaust and fuel in to the oil to where shorter oil changes intervals should be used. PCV system might be pulling extra oil up in to the intake. But the ignition/fueling might be a bit of an issue worth working on. %25 leak down is not that good, but not trashed either.
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