Ive checked Mitchell1 and the fuel pressure spec says 50-60 psi at the rail i have 57 psi so we can say fuel pressure is right. I remember something about a carbon canister someone suggested. They said its very common to fail on GMs is there any way to test that? I know the ignition pack is off branded value craft and that may be part of the misfire at idle issue. Should i hold off on that or give it a go?

 

Never checked for intake manifold leak.
Never checked compression and reported values.

Posts four and five above.

LEak down from what pressure?
You don't even know the maximum compression each cylinder is building.

Your long-term trim used to be fine. Now it is whack with the new ECM. You are basically pouring raw gas into the system. The front oxygen sensor sees no oxygen being produced from combustion because it is not combusting in the cylinders it is getting pushed out through the exhaust manifold unburned.

It is then likely getting to the cat where it ignites and backfires or at least burns.

The front 02 see no oxygen and asks for a richer mix in order to create more oxygen. The whole thing spirals out of control because you are getting positive feedback instead of negative feedback.

The only way gas is getting in the cylinders is through the injectors. Have you checked for leaking or stuck open injectors? Don't know if a noid light would help. I think it only verifies the pulses are electrically getting to the injectors, not that they are actually opening or closing.

But I would check for the manifold leak and do the compression check first because those are the two basic tests that will give you an idea very quickly of what the problem is or is not related to.

 

And get those idiotic Bosch plugs out of there and put in the stock NGK plugs.

And read the front 02 with a scan tool and tell us what happens as a function of time with the voltage values. What brand of front 02 do you have

 

No manifold leak

i may have stumbled across something that could be the issue the canister line might be restricted as when i pulled that line while running the car instantly revved up while nothing else could make the car do that not even the throttle itself. The fuel trims dropped but i didnt get to see what they stopped at because i had to leave. I know it created a vacuum leak but i do want to test if the line has restriction of some sort. Im not sure if this really is a canister line or what it is but it runs to the tank with the fuel line. Ill do a little more poking around but i think i may have stumbled upon the issue. The line is connected to the lower part of the manifold and its a fairly thick line if anyone has any info on it id gladly appreciate it.

 

And you still haven't checked the compression to see if this engine is even worth messing with

 

it is because ill rebuild it if it isnt, block isnt cracked heads freshly machined, valve job is done and double checked, only thing left is piston rings if it needs to be done i will do it HOWEVER, that isnt the issue at hand so it will wait. No point in tossing a new motor in if you cant figure out why the old one ran wrong.

 

Now I'm confused. Somewhere above, you said it had leak down issues on number two and number three and that it was the piston rings.

Above, you describe that everything else has been checked and double checked so the only possibility left is the piston rings.

So are you doing this by process of deduction or did you actually hear the leaking air coming out past the rings?

Sounds to me like you're guessing.

Maybe you have incredibly low compression in number two and number three to the point that there is no ignition occurring, fuel is washing the cylinders and getting shoved into the exhaust where it backfires.

I'm not sure why a 10-minute test with a loan a tool that costs nothing is so problematic. It has the potential tell you the basic level of health of your engine but it seems like you just don't want to know. It has the capability of explaining or dispelling possible causes, but you treat it as an afterthought..

And the O2 readings?

 

Its just bickering back and forth at this point im suggestion potential points of interest they dont line up with what you suggest and instead of telling me how to test it you roast me about not knowing what im doing which granted i dont but if you can help with testing procedures of the things i find of interest you can later say i told you so but in the mean time i would simply like help with the path i so choose. With that i ask how to i test for a bad canister? Toss compression aside toss “did you do it right” aside how do i test the things im currently interested in looking at?

 

I'm not trying to roast you.

People come on this forum every day and describe issues with their vehicles.

We do our best to give the most relevant advice based on the answer to questions that we ask you.

Andy is a lifelong mechanic. As in professional.
I am not, but I am an expert in the s series cars.

We try to start with the simple things that can reveal very quickly more information than you may realize about the health of your overall engine.
A redone head placed on a block where there is damage preventing sufficient compression will never run properly. This is why we ask for you to do a compression test at the very beginning. Because it's step one of should I expect this thing to run properly or have I already found a major issue that will affect how it runs?

Likewise, my question about the fuel pressure and the regulator. We've seen that before. The regulators fail and the gas has to go somewhere. Sometimes the return line gets blocked and all the pressure goes to the front of the car.

You established the fuel pressure is in spec. Awesome. (Not sarcastic) because that's the most obvious place to suspect an issue if the car is running rich.

I asked about the O2 sensor because it directly affects air to fuel mix. If the sensor doesn't see a high enough oxygen level, it tells the injectors to stay open longer on each pulse. That keeps going on until it reaches a predefined limit and the PCM throws a code for running rich.

The theme of what I've written above is that we are starting simple with basic evaluations of engine health and obvious potential sources of the problem at hand.

I will be the first one to admit that, when faced with what may be a complicated situation, it's easy to come up with 10 possibilities that could explain what's going on. The key to successful troubleshooting is to step through the most likely causes first, collect information from that testing, and let the results lead you to the next step.

Things get all mentally Tangled if you allow yourself to stray from this path, because you are building assumptions supported by no other hard evidence. I used to do it all the time. Sometimes I still do. And it's just as unhelpful to me as it is to you when we find ourselves in the same situation.

When we make suggestions, they are based on knowledge, previous experience, and the concept of starting simple. The majority of people do what it is that we suggest and report back. Based on what they report, we then suggest what we think is the most logical next step in solving the issue.

This is how we help people put their rides back on the road.

It's clear you have suspicions of certain conditions present or possibly present. There's nothing wrong with that. But it's not going to supersede what we've politely asked you to do FIRST that you simply haven't. You are not letting us help you in the ways we know how. You get frustrated, we get frustrated with you, etc. I think I said I was done with this thread about 15 posts ago because you would not follow the advice being given.

I'm still here because I want your vehicle to run properly. I also want you to understand how we solved the issue. We learn about a situation we've never seen and you sharpen up your troubleshooting skills. It's a win-win, but only if you follow the advice given in the order it is given.

If needed because the troubleshooting effort leads there, we can examine some of the things that you have found, but they are not the primary concern RIGHT NOW until we rule other things out. Otherwise we are chasing who knows what with no strategy and that rarely works.

 

Invest in a vacuum gauge. They can tell you a LOT about the condition of your engine. I have one that's 50+ years old that belonged to my Dad. None of my idiot brothers wanted it or thought it was worth having. Joke's been on them! And you should listen to derf. He KNOWS the S series better than anyone else you're going to talk to. He has studied and worked on these cars for several years. I trust his advice and judgement and feel like I'm speaking to anyone and everyone else who's come to this forum seeking help and advice about the S series cars. He's DA MAN when it comes to S series cars.