So after that interesting little sidebar...

Where are we on generating some waveforms? And fixing the problem?

 

This is exactly what happened in my case. I repaired the insulation and haven't had a problem since.

 

Sorry for the late response. I did try installing the Hantek software on my wife's laptop. It doesn't have a disc reader so I had to download the software off their website again. I ended up having all the same issues I was having on my Surface. Trigger was reversed and when doing the secondary ignition tests I could never get it smooth enough to see anything (trigger wasn't working well, lagging, freezing). Also I tried changing the trigger slope but it didn't have any effect. I was getting so frustrated with it I honestly just had to take a break and move on.

Things I've done since then...

Replaced spark plug wires, spark plugs. No change, I was getting desperate, w/e.

I was never 100% certain I didn't have a vacuum leak somewhere. So I picked up a smoke machine and did a smoke test on the intake manifold. Couldn't see any leaks. After a few minutes a little smoke started coming out of the dip stick tube, I assume by way of the CCV. I don't think that's any cause for concern.

Next I tried swapping my TPS with an old one I had kept from a while back. No change. The miss/roughness is the worst right at 1000-1300rpms. It idles pretty decent at around 600-800rpm and runs fine anywhere after 1300. It's like it's only dependent on that rpm range. It does it hot,cold, in park, in neutral, uphill, downhill. I'm going to check the TPS wiring this afternoon just in case.

Also, I think I mentioned it earlier but I've checked compression like 3 different times since I've had this issue and all cylinders have been between 140 -150psi every time I check.

Seems like it's got to be something to do with the air/fuel mixture right above that idle rpm.

 

Can you post your STFT and LTFT numbers when first started and fully warm? Sticky injectors?
Wrong lifter preload? Are they oiling properly?
Are you able to view all the injectors at once, and duplicate the misfire?
O2 sensor wiring shorting?
You may have posted this stuff but at 73 posts....

 

AH HA! Thanks 97Grand your post got me reading about fuel trim measurements and I started thinking about the O2 sensor (which is the first thing I replaced) and how maybe I could have a small exhaust leak at that joint where the header bolts to the front pipe which could be throwing off the O2 sensor. So I decided to hook up my new smoke tester and find out...



My header is full of dang holes!!!



My header is wrapped in this fiberglass cloth, which I assume is not factory and was done by the PO for some reason. It caused it to rust through in at least 3 places. It also caused me to not be able to see any of the holes without doing that smoke test. I also think maybe it was muffling the sound a little because I couldn't hear the leaks. But I can now that I know they're there lol.

Any of ya'll got a recommendation on a header?

 

Yeah, get a new one! I recommend a junk yard. Yours is steel but the one on mine is cast iron, so, not sure if this is a common problem or not or what to recommend. I have pretty good luck on Ebay for aftermarket stuff.
I could see this happening at a certain RPM range, when the pipes resonate.

 

Given that the exhaust system has positive pressure, I doubt that holes in the exhaust system would have any effect on oxygen sensor performance.

That said, one wonders if a venturi effect might be created near the sensor where ambient air might be brought in through strategically-located holes.

At any rate, oxygen sensor values can be monitored with the Hantek (OH NO! NOT THAT AGAIN!) so that you could objectively look for any anomalies.

New is about 100 bucks. I wouldn't be looking at 20 year old used exhaust pipes.

 

 

Every now and then, when I first start up, the engine runs a little rough. A rev clears it out so I'm like w/e and move along. Once it generated a MIL, and a quick check revealed Engine Misfire Cylinders 1 & 2 (but again clears with a rev so it's not high up on the priority list).

Anyway...

Yesterday, while trying to figure out why your software isn't working right (in the drizzle, BTW), coincidentally the engine was running a tiny bit uneven, and lo and behold cylinders 1 & 2 were only running 35 volts! Wish I took a screenshot, but the roughness disappeared and I couldn't get it to do it again (isn't that always the case?).

Anyway2...

IMO you should go back and check the voltage of cylinder 4. I think normal is about 60-65 volts (on mine anyway). Use the measurement function. Clear the cache on your computer and be patient with the data collection. Perhaps you don't have a software bug, rather you're just clicking on too much stuff and Hantek can't catch up.

 

BTW are using an attenuator? You're set to 20:1 so I assumed you were, but if you're not maybe that's what's screwing everything up (including that although you're on the 20V scale you're actually running a 2.0V scale).

 

Ahh. Hmm. Twirls moustache.

 

Injector #1

Injector #2

Injector #3

Injector #4

Injector #5

Injector #6

Not sure what's up with my current clamp, those values were all over the place. All the waveforms seem pretty much the same though. The voltage was about the same at 35-37V on each cylinder. It would fluctuate maybe 1 or 2V while I was watching.

 

Yes I am using an attenuator. I haven't had as much trouble reading the injector waveforms. Mainly it's just the ignition stuff that has been so difficult.

 

Ok I think you don't have your traces both zeroed out at the 0 line before hooking up the probes, for one thing. Yes that will make them overlap but that's ok. Also it's hard to tell what the divisions are on the scope, I see the vert and horiz hash marks on the axis, but, also there are fainter larger squares in the background I didn't initially see. ? So I am unclear on that. but see nxt post

*I get now. Ch 1 is reading 4 volts/division, you can see when it grounds the injector that the baseline isn't lined up, but you can count a bit over 3 divisions, making the B+ about 12 vdc.
The spike in the voltage is irrelevant because that is simple the voltage spiking going up when the injector is turning off, and as we know when you open the current to an inductor the voltage spikes.

 

Ok, settings and readings aside, what does look odd is that Cyls 2, 4, and 6 are using WAY less current than 1,3, 5...something odd there for sure between the injectors. I would think they are not operating right aka high resistance, unless it's something to do with the scope??