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Discussion Starter · #1 ·
I swapped cams cams to the Stage1X and added SLP headers in early August. About a week later(Aug 11), I went to pass a car on the highway and I got a horrible misfire and the SES light started flashing on the dash. I limped to a shop and scanned. Misfire cylinder 1. Check the wire. Fine. Pull the plug and it's smashed. Regapped it and went on my way. It has always nagged me, what caused that?

Last week (Wed), I was coming off of a stop light (not very hard as there was a car infront of me) and I got the same misfire with a rattling noise whenever I'd give it a little gas. Got to a gas station where I could pull off the road and hooked up my LS1M. Random misfire multiple cylinders. By this time the rattling noise was gone. I cleared the code and headed home with the misfire still. It tripped a misfire code again and it was cylinder #1. I took it to a machine shop the next day. The plug was smashed and looking through a boroscope the shop said that the piston looks like it had been "sandblasted with really coarse sand". I told them to replace the plug and I'll figure out what I wanted to do. I drove it home and around a little bit that night, never giving it much throttle. On the way to work the next morning (Thurs) the misfire came back. I scan and this time it's #6. I pull the plug and it's smashed. I regap it and put it back in and have been running ok since. I haven't given it much throttle since because it would probably do it again.

I'm sure that #1 is done since I've smashed the plug twice and the piston looks "sandblasted". Now I've smashed #6 so it is probably gone. All the scans I've run show that I'm running a little rich with my WOT O2's starting at 960 at the beginning of the run then going down to 915 by the end of the run. LTFT is at -14.1. I have around less that 1.5°KR through 1st and around 3° through 2nd with a spike up to 8° at the 2-3 shift which I assume is false. Here is a link from a run that was done the week before last.

http://mywebpages.comcast.net/Justin0247/joe9-23.html

Anyone see anything in this scan that might suggest what is causing my engine to explode cylinder by cylinder? Or any other thoughts? I really need to figure this out before I put a new engine in and pop that one too.
 

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Not that this is really a fix but i would think running that size of pulley and haveing a cam that you would want some colder plugs in there. Like AL 104s (2 stages colder) or AL 103s (3 stages colder).
 

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Discussion Starter · #3 ·
The TR6 is 2 ranges colder than stock, I believe. Do you think I need even colder?
 

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Joe,

I don't see anything wrong with your O2's but I see what looks like constant KR. Continual and repeated KR will damage pistons. Most people don't understand this. It is true that KR is the retarding of timing that the PCM does to stop detonations. People understand this and assume that KR is protecting them. The subtle point that most people miss though, is that the PCM does not predict the future. It pulls the timing back (KR) only in response to "heard" detonations. If you get some real KR, you can be certain that your motor had some detonation for a short instant before the PCM pulled timing.

If you've been experiencing KR continuously for a long time then it is possible that all your pistons are stressed and any of them can go at any time. The event(s) that stressed them could have happened months ago. You need to find the cause of KR and deal with it. Taking what's happening into consideration, I would NOT assume that ANY part of your KR is false. If this was my car, I'd look to replace all six pistons, or the shortblock. I'm sorry, I know that this is not what you want to hear, but....

This is one of the reasons why once we start modding these motors and adding boost we also need to keep an eye on KR.

John
 

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Discussion Starter · #5 ·
johnt said:
I'm sorry, I know that this is not what you want to hear, but....


John

I know that this is the case. I'm sure fragged piston has damaged the head and valves as well as the cylinder walls and I've already talked multiple times with the great people (Ed) of Morad Parts Company (free plug) about getting a lower mileage long block. I'm just trying to figure out what went wrong so I don't blow the next engine up as I did this one.
 

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Like I said, the event(s) are long gone. If you're not the original owner, it could have even been caused by the previous owner. The only clue we have is that you have KR. You need to concentrate on eliminating that.

John
 

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swinginbeef said:
The TR6 is 2 ranges colder than stock, I believe. Do you think I need even colder?
I wasnt sure if they are 1 or 2 stages colder. If they are 2 then you can always try a colder plug. im tempted to try the race plugs (4 stages colder).

Like John said, the cause is KR.
 

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when you say the plugs are smashed i take it you meen that the gap has closed up and there was no real damage to the plug and you were able to regap it and reuse the plug, if so your getting some hard detonation, before i went for a new engine i would try new plugs and drop back to the 3.4 pulley. the sandblasted look through the bore scope may just be some carbon shook loose from the piston, from your mods and the scan the 3.25 should be ok but something is causing detonation, maybe hot spots from carbon build up
 

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Discussion Starter · #9 ·
I guess that depends on what you mean by "no real damage". The plug was smashed down and to the side of the electrode and it has visible gashes in it. I did straighten it back out and regap it and it's been running for a couple weeks now. Though the car is running ok right now, not good but ok, and I know that there will be a rebuild in my future, I'm assembling parts now and will get the rebuild going before too long. I have dropped back to a 3.4 for now to try and keep it running untill rebuild time which I believe is a couple weeks away.
 

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Smashed Plugs

I had the same thing happen last week. Started with cylinder one. Cylinder one plug actually had broken the porcelain, but the electrode contained it. Correlates with a fuel fill. Replaced the plug. I got out the Tech 2 and looked for KR. None detected. About 3 WOT runs into second gear over about 100 miles, cylinder three was acting up. Cylinder three plug had a battered electrode. I suspect heavy detonation based on dyno plugs I have seen in the past. Maybe left bank knock sensor is insensitive and/or I got some bad fuel. I have 103s, rockers, exhaust, intake, 160, 3.0 pulley and the car has run great in this config for about 5000 hard miles - including hot summer days with 5-7 degrees of KR. Ambient was 52 F when cylinder three went. After cylinder 3 plug was smashed, a slight knock developed - sounds like a rod bearing. :(
 

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Discussion Starter · #11 ·
When I replaced my engine, cylinder 6 looked ok, I didn't look very hard. THat was the cylinder that had a plug smash once. Cylinder 1 on the other hand, had a chunk along the edge that was better than 3 inches long (about 1/4 of the edge) and about a half inch wide that was broken off. I could hardly believe that it still ran at all. You should probably find a boroscope and look at your cylinders and see what you've got. The sound you heard could have be a chunk of piston rattling around in the cylinder before it breaks up enough to be sucked out the exhaust valve.
 

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sounds like a piston to me...

1 question nobody else addressed was... why are your LTFT values so horribly bad???? those should be with-in +/- 3 maybe 4.... -14.1 im sure if you tunned that down w/ a mini-afc 2.0 you should be able to elimiate knock for sure....

good luck with your piston!
 

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the same thing has just happenned to me last week. I had a bad misfire after a quick WOT. Cyl#3 plug had a smashed tip and once I replaced all seem fine. I dont hear any rattling noises or anything that can be interpretaded as a loose chunck of metal inside this cylinder or something. Still, this got me worry and I'm asuming the worst. Need to get a borescope and face my biggest fear.
 
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