NeoSNK

I used datamaster and pcmcomm.
Knock count 1738
fuel trim cell 16
L term counts 156 160
S term counts 132 147
Airflow 5(idle) to 26(at 3000 rpm) gm sec
O2's are cycling
The car kind of bogs from 1500-2000 rpm. But it idles fine and WOT is fine. I thought it was a bad o2 sensor but they both cycle, one is brand new. Any ideas?

Injuneer

Limited value in that data. Its idling, and adding just about the maximum amount of extra fuel the system is capable of adding. The key is the 156/160 long terms. For some reason the PCM is forced to add 25% extra fuel to get wht it "thinks" is the correct A/F ratio. The fact that you are only seeing 5 GPS air flow at ilde may be a key to the problem.... looks a shade low. Low readings on the MAF will force the LT corrections up.

But there's not much to be learned from a single frame of data. The knock count is a continuously incrementing field, so a single value means nothing. Its how fast its changing that may be important. Ditto on the short term fuel corrections.... they are moving as fast as the O2 sensor readings, changing close to 10 times per second. A single data point shows nothing.

Run a continuous log in DataMaster.... cold start, through warmup, some "normal" driving trying to get it to operate in as many of the long term fuel correction cells as possible, than a WOT pull in at least one gear.

NeoSNK

Ok, I'll do that.

TobyZ28

Clean the maf sensor (electrical cleaner/ cutips etc) and compare maf results at idle.

Be sure your before and after comparisons are done with the engine warmed up both times.

Dave89IROC

I agree on the low MAF readings, clean it, clear everythig, and then see what happens

NeoSNK

Ok, I'll try that. I checked the air filter and its nice and clean.

NeoSNK

Ok, I cleaned the maf. I think it helped the maf readings but I still have the bog. I emailed the file injuneer. Hopefully we can figure this out.

Injuneer

Got it.... I'll try and look at it tomorrow.

Injuneer

A lot of screwy stuff in that log... repeated check-sum errors on the data, lots of codes that show up all of a sudden then disappear, data that makes no sense at all (like DataMaster is not reading the data correctly). Appears to be a communications error, but might also indicate a PCM problem.

Do you have the EGR system disabled? The knock shows up every time one data frame before the EGR system is activated.

The long terms are max'd out on the right side all the time, every cell. But the right side runs a bit richer at WOT, compared to the left side. May be a flase lean. Then, at WOT the pulse widths drop all of a sudden, and the O2 sensors indicate very lean readings. Hard to tell if this is real data, or part of the communications error. There's a spike of 13.3deg knock retard that is an obvious data error.

I'll post some more info, but the above is a general over view of the problem that may be a communications problem.

NeoSNK

Hmm, yes the egr is disabled. I'm running regular(87) gas too. The 02 sensor on the left side is a brand new ac delco and the right side was changed at the dealer about 4 yrs ago.

NeoSNK

Should I quit running regular gas? I thought it would just adjust the timing to make up for it.

Injuneer

You are running low-octane horse pi$$, and you have knock retard and you're wondering why? Doesn't explain the problem with the long terms, but it sure would explain a "bog".

You also indicate on your website that the car is "stock".... but apparently it isn't if you deleted the EGR. EGR helps prevent detonation (KNOCK) when lugging the engine, so between the low octane and no EGR you've set yourself up for nothing but problems. What other change are there that you aren't telling us about? It really helps to know up front what the EXACT details of the car are, so that the abnormalities in the data log can be accounted for. It just makes it harder to help when you don't give people all the info up front.

Sweetred95ta

Regular 87 octane!! Whoever told you the timing would correct itself for 87 octane is a damn fool.

NeoSNK

The egr went bad so I just plugged it. I didn't think it was that big of a deal. I have no performance mods or anything. The only other thing than normal maintenance was the tb bypass mod. So I would consider it stock. I thought egr was only used at highway speeds.

NeoSNK

I filled it up with 94. It seems better but theres still a little vibration around around 1700 rpm. The knock count dropped from 1600 down to 1200. The S term fuel counts were going in the red. I don't remember the number. But I could log another run if you wouldn't mind looking at it. Would a new egr take care of this? I never changed it because you have to pull the intake. The funny thing is, it's been disabled for years and I've been running regular gas for about a year and a half. This problem didn't show up till this summer. I noticed the exhaust didn't sound the same and it has this funny bog. I figured it was an 02 sensor going bad again.