Spark source= pre ignition

Ok guys and gals I need some assistance making sense of this. This week on two separate occasions I have gotten spark source = pre ignition. It starts at 6000 rpm on a wot pull. I haven't seen this before. Mind you in between these pulls I have had wot pulls that don't show it, and this has all been on the same tank of gas. When it has done it, I'm only getting 22-23 degrees of timing but no knock activity. Typically at 6000 I am seeing about 26-26.5 degrees with negative knock retard. I have changed nothing in that area of the tune in quite some time so I'm kinda lost for words. The only thing really different was I enabled flex fuel. However all this has happened on 93. I just switched over to e85 today and it appears to be gone.

Could it all have been bad gas?
Even though some of the time it allowed me full timing?
What causes the car to go into the pre ignition timing mode?

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Originally Posted by rhinogt

Ok guys and gals I need some assistance making sense of this. This week on two separate occasions I have gotten spark source = pre ignition. It starts at 6000 rpm on a wot pull. I haven't seen this before. Mind you in between these pulls I have had wot pulls that don't show it, and this has all been on the same tank of gas. When it has done it, I'm only getting 22-23 degrees of timing but no knock activity. Typically at 6000 I am seeing about 26-26.5 degrees with negative knock retard. I have changed nothing in that area of the tune in quite some time so I'm kinda lost for words. The only thing really different was I enabled flex fuel. However all this has happened on 93. I just switched over to e85 today and it appears to be gone.

Could it all have been bad gas?
Even though some of the time it allowed me full timing?
What causes the car to go into the pre ignition timing mode?

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Pre-ignition spark source is one of the spark timing maps. Like all of the timing maps, if its the lowest at that point, it'll be the limit.
Verify that your preignition timing is above the timing you're running.

Typically stock in the higher RPMs and loads they are limited.
https://i.imgur.com/306bvfK.png

At the points I see it it is about 25-26 degrees in the table so my timing was lower actually

How about borderline vs mbt?

That's just it, the timing I was seeing is below all the tables, borderline, mbt, the preignition, ipc, cylinder pressure, all of them. Normally, at 6000, it uses borderline of mp21,22 and adds timing from the knock sensors to get the actual timing. It's just throwing me off because I don't know why it is using the pre ignition spark source. As in, what parameters tell the computer to use it. I know pre ignition is not good, while not as bad as detonation, it can lead to it. But why the car used it all of the sudden is beyond me.

I wasn't even intending to look at the wot part of my log since I really haven't had to touch that part of the tune in quite a while, I just happened to see it pop up while I was scrolling through the log. And since then I've been scratching my head trying to figure it out.

Could it be that it's now using it since I enabled flex fuel?

If you are getting true Pre-ignition it is bad(unlikely you are). It will not show up on the knock sensor. It's usually caused by a hot spot either carbon build up , lean afr, the plugs are the wrong heat range, coolant temperature tpo high, super high IAT stuff like that. Since it happens before the spark plug fires you don't get the spike in pressure like detonation gives you so there's no engine ringing. Given you turned on flex fuel and that enabled the pre-ignition limit table your problem with running 93 was likely to just be this. Bugasu pointed it out to you. I have read about fuel octane sensors and exhaust gas temperature sensors being utilized to sense pre ignition. Maybe a oxygen sensor is getting a drop in EGTs and that's causing it to go to the pre igntion table? How does the ecu determine pre ignition? Is it just a threshold on any of the numerous temperature sensors?

The term for when an engine is doing both pre ignition and detonation is muddy water.lol

Yea I'm assuming bugasu's table he showed is for a supercharged car based of the load. Do the rest of y'alls look like his as well? Since at 1.0 load it's all 63.5 degrees on his example, and mine is around 26 at 1.0 load maybe I just need to bump it up? Combining the values in that table with the lambda added, it's fairly close to the timing I was seeing.

I know it wasn't IAT's causing it, they were in the 40s and 50s. As far as AFR, I am seeing .82-.84 from the O2s. I doubt I need colder plugs since the car is tune only right now. Carbon build up while possible, is probably unlikely as well since the car has 10k miles. I will look to see if I can log EGTs tomorrow.

I would stay cautious and not start increasing the pre ignition table until you find the source of it using that table. While it's unlikely you actually are getting pre ignition it is still not something you want happening and the ecu has some reason to think is happening. My recommendation is monitor anything and everything to do with tempature and see if that leads you any where. If all temperature is good pull some plugs and make sure they look good. Run something like seafoam thru the engine just to be sure about the carbon build up. After that it would be disassembly time to find sharp edges. In this case though I would say it's okay to increase the pre ignition table.

Ok. I'll look into it. I've got time to search since I'll have to burn through this tank of e85 first anyway.

If it's bumping into the preignition limit on ethanol you can safely raise the preignition tables. The proper way to do it is to use the alcohol preignition adder table but it hasn't been defined in the software yet. Just be sure your timing advance while using gasoline isn't high enough to actually cause issues that would be normally limited by the preignition table.

If your curious about what mine looks like. I have a GT so its naturally aspirated.

Attachment 56051

A lot of studies I've read say the only worry about ethanol and pre-ignition would be the AFR being incorrect. They used glow plugs to simulate hot spots and cause artificial pre-ignition.
93 its a different story.
So if you have Flex fuel enabled and are running 93 and your AFR is bouncing around a little to much(bad gas) the ECU could kick in the pre-ignition timing source.

Im thinking it has less to do with some temperature sensor could be tripping the pre-ignition timing source.

It looks like you can log EGT for every cylinder so I would definitely check it out.

Again very unlikely you have true pre-ignition. Most pre-ignition that's caused by a hot spot happens at the bottom of the stroke and the engine is just compressing extremely hot gases which the piston soaks up and you get a hole in the piston very quickly. This is also why EGT will decrease rather than increase. Another thing that happens is if a spark plug is not tightened properly it doesn't disperse heat as effectively and can cause pre-ignition.

Thanks for the help guys!

Murfie, it looks like our lambda adder tables are the same but my pre ignition table timing is lower in the wot range. I haven't messed with it so I assumed it was the stock value but I originally started with a tuned file from my previous tuner. It must have be altered a little by said tuner. I log some more and report back.

Thanks for the help guys!

Murfie, it looks like our lambda adder tables are the same but my pre ignition table timing is lower in the wot range. I haven't messed with it so I assumed it was the stock value but I originally started with a tuned file from my previous tuner. It must have be altered a little by said tuner. I log some more and report back.

Yes that is stock untouched values in mine.

Ok did some pulls on the way to work. Good news, all 3 pulls were staying on borderline throughout the pull. However the knock sensors weren't adding a whole lot of timing that I would expect from e85. I am going to fatten her up some and see if that helps.

Since I really cant troubleshoot the pre ignition issue right now until I switch back to 93, Im going to make the best of this tank of e85 and see what the car likes.

Well, after adjusting the WOT lambda, the car added back timing, right up to the MBt values. That's the good news. The bad news is I forgot I reduced the WOT MbT values a while back so the car wouldn't push itself too hard down the road. Turns out I need to add some back, based off of what I've read about coyotes and e85.

How much richer did you make it? Does e85 need different WOT Lambda settings to make power?

Well I initially tried the lambda that pre populated when I activated flex fuel. Today I just matched my e85 lambda to my 93 lambda.
.84 up to 3000
.83 3000 to 5000
.82 5000 and up

I'm still playing with it though so my final numbers may differ.
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Just a quick update,

It appears your nailed it on the head murfie. After I looked at my logs with a different monitor where I could see the lambdas' lines better, they were fluctuating during the pulls that went into preignition. There were a couple spots it dipped down to .76 lambda. These were quick dips that only lasted a count or two each, but they do coincide with the preignition on the logs. I am back on good 93 and the car is happy again. I am going to assume my wife filled the car up with craptastic gas while I was gone on my trip two weeks ago. Now I just am waiting until this 93 burns up so I can get back on the corn!

[QUOTE=murfie;414424A lot of studies I've read say the only worry about ethanol and pre-ignition would be the AFR being incorrect. They used glow plugs to simulate hot spots and cause artificial pre-ignition.
93 its a different story.
So if you have Flex fuel enabled and are running 93 and your AFR is bouncing around a little to much(bad gas) the ECU could kick in the pre-ignition timing source.

Im thinking it has less to do with some temperature sensor could be tripping the pre-ignition timing source.

It looks like you can log EGT for every cylinder so I would definitely check it out.

Again very unlikely you have true pre-ignition. Most pre-ignition that's caused by a hot spot happens at the bottom of the stroke and the engine is just compressing extremely hot gases which the piston soaks up and you get a hole in the piston very quickly. This is also why EGT will decrease rather than increase. Another thing that happens is if a spark plug is not tightened properly it doesn't disperse heat as effectively and can cause pre-ignition.[/QUOTE]