98 Suburban 7.4

[Spareparts]

I'll give it a try. It feels pretty good everyplace else except the idle up to about 1K RPM.
I will not be able to post a log till tomorrow after work.

[SiriusC1024]

That's no problem. Take your time.

[Spareparts]

The last tune made a nice difference. It is certainly feeling like it smoothed out and seems to be heading in the right direction still a little rough but better for sure.
Also, i think after doing more reading i have been using "write entire" every time and should have been using "write calibration". So i may have been making things harder but im not sure.

SiriusFinallog3.hpl

[SiriusC1024]

Correct do a write config.

[gtstorey]

Correct do a write config.

Write Calibration? Just so he's clear.

[SiriusC1024]

Haha yeah that's it thanks. Write config is from something else.

[Spareparts]

Thanks man! I'll get this loaded and post a log and how its doing tomorrow after work.

[Spareparts]

I dunno man. Sometimes it feels great other times rough. Seems like when it first starts it feels great but as soon as the o2 sensor trims start is when it gets rougher.
The warmer it gets the better it feels except at idle. When the idle was lower it felt better at idle.
Was watching the misfire's and it seems kinda odd how it switches between #7 and #8 the most. I wonder if something is up with the ignition but it is all new.
Anyway here is a log from today.

SiriusLog4.hpl

[SiriusC1024]

Idle can be a real bitch sometimes. When you say it feels great sometimes and rough others is that just the idle or where?

[Spareparts]

Mostly under 1K but it is slightly felt up to maybe 1.5k (ish)

[Spareparts]

Hard to describe. I can say for sure it is running way way better than it did when we first started.
Above about 12/15 hundred rpm it feels smooth as glass and can accelerate great! Below that it is still a little rough. When the idle was lower it was not as noticeable. With the higher idle it sometimes feels like a dead misfire but not always.

[SiriusC1024]

Here's the tune with the idle settings back down. I see you have disabled EGR. I zeroed out the EGR spark table.

I have no idea why it's misfiring. Trims are good and minimal KR. IAC isn't all over the place. Spark is stable. What also isn't making sense is that it gets worse with higher idle. Rough idles usually improve with RPM increase. Is the EGR valve stuck open slightly or are there any vacuum leaks? Bad ignition I doubt. That would show everywhere and probably get worse with higher RPM's and loads.

I'm not trying to ditch out or anything, but I honestly don't know what I can do in the tune. I'll keep researching what adjustments could be made.

[Spareparts]

My mistake!.
I was playing around trying to learn some simple things and i never intended to load that tune i changed the EGR on. Im not sure how i got it mixed up and loaded it.
Anyway, I don't think my egr is bad but i guess it's possible. Im going to dig into this engine and figure it out.
I did not get a log today. Dang laptop battery was dead. Gimme a few days and ill see what i can find.

[SiriusC1024]

Ok might try re-enabling it and the EGR spark, too. See if anything changes.

[SiriusC1024]

Let's do a little experiment. I adjusted a bunch of idle settings. Tail end of Log 4 where it's idling gave me some ideas.

[Hondaeater]

When the EGR spark table is disabled did the misfires get worse? You would want to watch the manifold vacuum in the scanner starting with the lower RPM and increase it my 25 RPM increments slowly allowing time for everything to settle. You want to watch the manifold vacuum fuel injector MS and timing while it is enabled in your tune file to help determine if that's the source of your misfires.

The EGR valve should not operate at idle speed for engine stability in STOCK form. Rraising the idle RPM for your can and torque loss, you're probably entering the light throttle/ low load area. Remove and block it off is your best option. Because you have a cam and lower than factory vacuum the EGR valve is diluting what little bit of airflow comes in even more! You might increase the amount of spark. Is your EGR valve electronic or mechanical/vacuum? It's been a minute since working on that model.

[Hondaeater]

Wow I need to do more proofreading. Use the green button special functions in your scanner and set for a lower RPM and increase it slowly 25 RPM at a time. Watch those channels I mentioned.

[SiriusC1024]

I wasn't going to come out and say it because you never know when an EPA troll might be lurking, but yeah...wink wink nod nod.

[Spareparts]

Well yeah this is for off road only
DUDE! that made a big difference in it. It is smoother for sure and i would say the best so far but right at idle i can still feel a misfire.
Watching misfire counts it looks like cylinder #7 has a problem at idle. Since the EGR is disabled i will block it off at the intake. That should eliminate any question of leaking or not.
I have done compression test and it is good. I did a injector bleed down test and it passed. Spec is ? 4 lbs. Mine are all within 2lbs.

SiriusLog5a.hpl

[SiriusC1024]

Good. I'll keep trying at it. It's reassuring that the idle is responding to changes the way they should. Was getting a little annoyed lol. Does your ECU support STIT (short term idle trim) and LTIT? If so load this tune. Add those channels to the scanner. BRAF and Adaptive Idle are a lot better but still needs work. In this tune Adaptive Idle is disabled, so we're going to be focusing on BRAF. That way the adaptives won't be doing so much compensation. All you have to do idle for 5 min from a cold start.

In the meantime you do your thing. Shouldn't feel a dead miss type misfire from any cam. I was dealing with EGR issues on another guy's 7400 vortec. His was working as it should, but whenever EGR was active B1 and B2 had a 5-6% differential in fuel trims. Similar behavior on the logs here, but it's everywhere. Decreases with RPM perhaps because more air for the same EGR "stuck open" position. That's what made me ask about it. Plus bad EGR makes a rough idle where there's a definite miss.