Maintenance on my '94 z28 pic heavy

[Mrmaroon]

Here are the .csv and .uni files https://www.mediafire.com/folder/my4dztb7zv1bf/LTXtech

Whats done to the car.

K&N CAI
No A/C (compressor leak)
Skip Shift I unplugged the wires in the PCM
I've changed all the plugs and only the left side wires
180 degree thermostat
manual fan switch
Stock tune
Stock everything
M6

I noticed on record 1170 I got a DTC-29 (AIR I think)
On 1546, 20921, and 22035 I get a data rec error for 1 frame.

[Injuneer]

I'll download the .uni at home tonight. The .csv I can look at here at work.

[Mrmaroon]

I'll download the .uni at home tonight. The .csv I can look at here at work.

Thanks a bunch, don't get fired over it though!


Sent from my iPhone using Tapatalk

[Injuneer]

Do you have your EGR system still in place? There is evidence of fractional degrees of knock retard, and this occurs at the same time the EGR duty cycle goes to 100%. The 100% EGR seems to lag the knock retard by one frame of data. It's almost like you are getting knock retard, and immediately, the PCM opens the EGR to try and cool down the combustion chamber and control it. If EGR led the knock retard, I'd look for a leak in the EGR vacuum system, but that doesn't seem to be the case.

In one case, when you go WOT at rec #5407 there is knock retard as high as 8.6-deg. The left O2 sensor seems to be reading in the mid-800's, while the right side is closer to 900. Recognizing that the stock narrow-band sensors aren't very accurate at anything other than 14.7:1 (450mV) +/- 0.5, always risky to use them for anything serious. The only time the LTFT's are adding fuel are in the high load cells (11, 14, 15). In Cell 15 they are only adding 7.8% extra fuel. But in the low load cells (16, 12, 3, 5) they are pulling a small amount of fuel out (4 to 5% at idle). Might want to check the fuel pressure under max load.

Again at rec #9184 you get a sudden 9.6* of knock retard at WOT. In both cases, the left O2 sensor is reading an average of 40mV below the right side.

In general, the left and right LTFT's seem very close, with the left side maybe 1 or 2 counts less than the right.

That's all I had a chance to look at for now. I'll look at the range difference on the left to right O2 sensors in more detail.

[Injuneer]

PS: They won't fire me..... I told them I was retiring in May, and they asked me to keep working as long as possible. So I'm down to a 3-day week..... Nothing like a 4-day weekend.

[Mrmaroon]

Do you have your EGR system still in place? There is evidence of fractional degrees of knock retard, and this occurs at the same time the EGR duty cycle goes to 100%. The 100% EGR seems to lag the knock retard by one frame of data. It's almost like you are getting knock retard, and immediately, the PCM opens the EGR to try and cool down the combustion chamber and control it. If EGR led the knock retard, I'd look for a leak in the EGR vacuum system, but that doesn't seem to be the case.

The EGR is still hooked up and in stock form.

I don't have a pressure gauge or vacuum gauge, the car has 33k miles. I was going to change the fuel filter but still haven't yet. Maybe that will help the idle some too. I did replace the cracked intake elbow with a new aluminum one.

If you can tell anything about the 02 difference not sure if I should buy a new one or not.

Thanks so much for taking the time to look at this for me. I'm not good enough to see the finer details. I'm not going to turn my car into a drag racer, just trying to get the kinks out before I get it tuned and add some bolt ons. It will be my daily driver hopefully for a long time!

[Injuneer]

Everything looks pretty good, other than what I mentioned above. Still need to look at it some more, including using DataMaster. This is a huge file.

[Mrmaroon]

Everything looks pretty good, other than what I mentioned above. Still need to look at it some more, including using DataMaster. This is a huge file.

Sorry I tried to drive under a lot of different conditions! Thanks again @Injuneer I really appreciate it.

I was doing some investigation tonight on the rough idle. It isn't so bad that you can see the tach needle move. It's intermittent and has no rhythm. I can see the shifter and AIR check valves vibrate when it happens. It does it from a cold start, but gets worse (happens more often same loudness) as it gets warm. If(b=normal sound and B=rough) it happens like this bbbbbBbbbbBBBbbBbBBbbbBbbBBBBbbbBbBBbbbb.

I re-plugged all the spark plug wires at the opti and the plugs. I reconnected the injector plugs. Still the same.

I tried to take a video of it, not sure if it is audible. When I was standing at the exhaust I could hear a few metallic tinks. I've had a problem sometimes with a rotten egg smell. I wonder if my cat is causing it? The car drives great as far as I can tell! It doesn't bog starting in 1st and it seems to run fine when I get on it. I smacked the hell out of the cat a few days ago to see if I could hear rattling and it sounded solid. If you look at the file again maybe there is something that points to a bad cat? (I know @Dan friggin headers lol) I'll try and upload the video soon.

Come to think of it the cat was the first thing that went on my old 3800sII V6 camaro. I actually think I replaced it twice so 3 cats on that one. It was enough to slow me down though.

[Mrmaroon]

Now that I think about it, I did notice a really high pitched noise the last three days or so inside the car. Couldn't tell a location. It kind of sounds like high pitch static or a pressure leak.

I'm going to drop the cat back today if I can and take a look at it. If it seems ok I'll leave it. If not, this is really my friends car and he might punch it out until he can buy a set of headers/ory.


Sent from my iPhone using Tapatalk

[Dan]

Rarely, My exhaust in back will hit the heat shield where it goes over the axle and cause a high pitch scream. The stock catback shouldn't though. Mines 3 inch and was fitted like shit once, then reinstalled a lot better a second time.