Took it for another drive today. kStarted relatively well. Did a 15 mile drive. No codes came up.

Now that I can see misfire info on Torque, I'm thinking it may be messed up. It shows average misfire counts for 10 past drive cycles, and another of misfire counts just for this drive session. I think it shows a lot of misfires in current drive session, compared to the 10 session average. I'm not thinking this tells me anything other than maybe the blue tooth scanner may be flaky.

Car ran fine. No codes showed up. Below is the misfire counts for today.

One question: I am presuming ideally there should be 0 misfires. Is that right? Or is 0 misfires hard to achieve. With the misfires in this report, all show PASS, and I got no code. Report at end of this thread.

I do have a theory on the bad day yesterday: I was running gas with some Chevron Techron Concentrate to clean the injectors. Tank was low. At end of day yesterday I filled the tank. Maybe the ratio on the concentrate was high, and caused misfires. But I am getting misfires today, albeit with no code and seems to run fine.

MID:$a2 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 27Count
PASS
----
MID:$a2 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 110Count
PASS
----
MID:$a3 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 3Count
PASS
----
MID:$a3 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 11Count
PASS
----
MID:$a4 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 14Count
PASS
----
MID:$a4 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 71Count
PASS
----
MID:$a5 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a5 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a6 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 5 Data
Max: 65,535Count Min: 0Count
Test result value: 12Count
PASS
----
MID:$a6 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 5 Data
Max: 65,535Count Min: 0Count
Test result value: 50Count
PASS
----
MID:$a7 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 6 Data
Max: 65,535Count Min: 0Count
Test result value: 5Count
PASS
----
MID:$a7 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 6 Data
Max: 65,535Count Min: 0Count
Test result value: 10Count
PASS
----
MID:$a8 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 7 Data
Max: 65,535Count Min: 0Count
Test result value: 19Count
PASS
----
MID:$a8 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 7 Data
Max: 65,535Count Min: 0Count
Test result value: 31Count
PASS
----
MID:$a9 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 8 Data
Max: 65,535Count Min: 0Count
Test result value: 2Count
PASS
----
MID:$a9 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 8 Data
Max: 65,535Count Min: 0Count
Test result value: 35Count
PASS
----

 

What crank and O2 sensor part numbers did you use?

 

Crankshaft sensor: ACDELCO 12703627
O2 Sensor: GM GENUINE 2131694

 

still seems to me like you're having injector issues. Fuel air compression spark. Its an ls3 crate lets assume it has compression. Its getting air and measuring it properly (certainly vacuum leaks could cause misfires but given your description that doesnt seem to be the case). If your plugs and wires are good, it has spark. That leaves fuel.

Even if you have 1 injector on each bank that's not working correctly, you're gonna have a bad time. It'll throw off all the fuel trims which could cause misfires all over the place.
If you ever plan on letting the car sit for more than a few weeks, use fuel stabilizer. Gasohol (gas with ethanol) isn't friendly to sitting. Coats everything with gunk.

 

Thanks for the input.

I just spoke with the tech support at where I purchased the PCM, TCM, Wiring harness etx, a sponsor here, who has been excellent help. He had also mentioned a couple days ago to use the Chevron Techcron Concentrate to clean the injectors, and he swears by it. At the time of myi last posting that you are replying to, I was at the end of running some through the engine, tank needing refilling. The run through went fine. The recurring issue came back the next morning. Since then I have filled the tank.

So I did a drive yesterday with the full tank, and again today, ~50 miles each. No codes coming up. I was concerned that I was getting misfires according to the scan tool. When I spoke to him today, he indicated that it is normal to have some misfires. If they get to a cound over 300, then you may have problems. In fact the scan tool says PASS on the line it reported the misfires.

So, at this point, I am going to consider it good to go. However, given the recent issues, I won't be convinced until I put several more drives on it.

I appreciate all of the help and guidance here. I"m thinking if the P)300 pops up again, I may pull the injectors and manually clean them.

i'll keep the thread posted if anything changes.

 

Well, &+-$_--5!!!!

So I drove the car 50 miles twice, ran great, no codes. Once late yesterday, and earlier today. Ran great, no codes, and again, the scanner documented misfires in every cylinder, but all said Pass, not, Fail

Then around 6 I backed out to do another drive, and I no more than got out to the street and the P0300 came on again. If I had any hair I would pull it out.

So, tomorrow the injectors are going to get pulled and cleaned.

That's it for now.

 

So at this point, the injectors have been pulled, and pressure cleaning through them. The streams look good.

Put it back together and did 2 test drives today:

Drive 1:

• 30 miles
• Slow traffic to freeway traffic
• All cylinders had misfires, varying count
• Ended with a pending P0300 code

Drive 2

• All cylinders had misfires varying count
• No codes, not even pending

I had a communication with a local tuner. He said "If the cam is a performance cam you will get misfire codes due to the overlap of the cam. We can turn that off if need be."

It's a LS3/430. I don't expect it to be a performance cam. And I've had no issues over 6000 miles over 3 years. At this point, I feel like I need to take it to someone with the expertise and professional scanners. My biggest concern is that it'll go down a dark hole and use up their time, and my wallet.

I will say that it seems that the left bank is getting higher misfire counts than the right bank. I'm thinking about pulling the injectors one more time and running cleaner through them again.

 

Since last post, I decided that it must be either a problem in the PCM or wiring. Given that the car had been in a shop working on the transmission (ruined it...had to go elsewhere to get it rebuilt...a different story), and that they messed with the wiring a lot...I decided they must have screwed up something on that too. I think at one point they even made a change in the programming on the PCM, but maybe not.

So anyway, I had pulled the injectors and cleaned them. I videoed the spray, and Gary confirmed the spray looked good.

I took it for a 50 mile test drive. The Torque app indicated I still had misfires in all cylinders, but nearing home, it had not set a P0300. I turned down a street just made for putting your foot into it. After I let off the pedal, I looked down and had an Engine light again. Pulled over, read fault codes, and I had P0300 and again the P0606.

At this point I'm ready to get past all this. I called Gary and said I think I should change the PCM AND the harness. He said he thinks someone has messed in the PCM (which I think may be the case). This because of the P0606. He said that they typically see a P0606 if someone has changed some things in the PCM. I asked if he knew at what point they would see the P0606. He said right after getting into it, WOT. That's exactly what happened to me. So I sent the PCM and TCM in and they tested it and said they didn't think anything was wrong with it. But I just purchased a different one with a new software/tune loaded anyway.

Long story short, still get P0300, but no P0606, even after multiple episodes of "get into it".

So I talked to Gary again, and he said there's only one thing left that would possibly cause this. (By the way , the car is running better than ever). Anyway, asked me to take a look at the tensioner. He gave me info on how an alignment marking should be centered between two tabs on the tensioner. Mine was flat against one of the tabs. He said that was not a good thing, that varying things with the engine could cause that tab to slap, and that could cause misfires. He said the belt may be stretched.

My belt is a 76" one. I had an extra new one which I put on, and it raised the marker up away from the tab, but didn't center it. So I went to auto parts store and was going to get a 75" and a 75 1/2" belt. The didn't have the 75 1/2" one. So I came home with the 75. It won't go on, too tight. So I have them bringing in a 75 1/2" belt.

Now, wouldn't it be crazy if this actually fixes the problem?

<sigh></sigh>

 

Getting the belt correct (new belt) did not help. I decided to swap the coil between the cylinder with the highest count of misfires with the one with the least (which is pretty consistent). The misfires did not follow, so it isn't the coils.

 

The saga continues.

@bobcratch I too am feeling that maybe it's fuel related.

This week I noticed that my fuel pressure was at 84#. Should be around 52#. So, I replaced the regulator/filter. Of course, no help from that. Still every cylinder getting misfires. Also, I tested a coil. Cylinder 3 has been the usual worst count on misfires, and Cylinder 4 the lowest count. So I swapped the coils to see if the count changed. It did not.

Below is the misfire tracking from today's 48 mile test:I don't recall for sure if I mentioned earlier that I went through a process to clean the injectors. I can't say it helped. The counts seem to be growing in numbers. One thing that stands out is that the left bank (odd numbered cylinders) is pretty much always worse than the right bank. Interestingly cylinder 7 was the worst today, at 202. But that is also on the left bank.

I had decided I'd pull the injectors and take them to a good shop that cleans and analyzes them. However, I found they want $60/injector to do that. I can purchase brand new AC/Delco injectors from RockAuto for $45 each.

So I'm thinking now I'll order 1 new injector and see if it brings the count down on the cylinder that has the most miscounts. I am sitting here thinking I may get a reply that the others misfiring would ultimately affect cylinder 3 (the usual bad guy).

Should anyone think I'm wasting my time buying just one, let me know.

Hoping the end of this thread is coming soon, and that some day it will help out someone else.

 

I did the "change one fuel injector" technique and the "change one coil pack" technique . . . no help. But the "change one whole PCM" technique DID work though it helps that I have a stack of them here ready to go, for cheap. No HP Tuners credits or EFI Live money required and junk yard PCM devices are never more than $37 around here and sometimes as little as $16.

Rick

 

@B52bombardier1, Sure would be nice if I could have the same results as you.

The change of the belt and getting the adjustment mark on the tensioner set between the tabs did not stop the problem.

So at this point I was thinking: the left bank is considerably worse than the right side. Given it was my first attempt at cleaning the injectors, I thought maybe I didn't do it good enough. I purchased 4 new AC/Delco injectors, and put them on the left bank. I figured if that improves the left bank, then I'd get them for the right bank as well.

Hrumph! Not only did it not get better...it got worse (based on 1 test drive of ~40 miles. So here's the misfire count for that drive (resulting in a Pending P0300):I have an appointment with a shop (whose owners and a tech own old cars...not sure if they are LS or not) to figure it out. I'll be telling them of what I have tried so far:

• Replaced Plugs and Wires
• Replaced O2 sensors
• Replaced the belt (Centered to the tabs)
• Replaced the Crankshaft Sensor
• Swapped the coil from 3 with the one on 4 to test coils
• Replaced the PCM and TCM, with fresh tune from PSI
• Took to a shop to relearn crank position relearn procedure. No options existed to do it, and Gary at PSI indicated not necessary on a build car
• Cleaned the injectors, then replaced some
  • Ultimately decided maybe my clean of the injectors wasn't good enough. Given that the left bank was worse than the right bank, I purchased 4 new AC/Delco injectors, and replaced all on the left bank. Tested worse than the old ones.

 

This thread is such a collection of sadness and futility that I honestly don't remember if anyone asked the obvious question - are the left/ right o2 sensors swapped?

 

LOL, Definitely seems futility is the word of the day.

Yes, O2 sensors are the second item of things tried in the post above.

Appreciate the suggestion though.

 

you replaced them, yes. My question is - are the left and right banks swapped? can you check your long term fuel trims with torque? if they are maxed out in one direction or the other that could indicate that the o2 sensors are swapped bank to bank