Flyin_Z28

Hi guys. I am starting to suspect that I may have a small vacuum leak due to rich readings at idle. So far I have modified the MAF table where the car seems to idle and its boundaries. I have pulled 10% away from the stock calibration table in the corresponding frequencies and I am still getting rich LT blms. I have not touched the VE tables from stock yet.

There are no visible vacuum leaks even when testing with propane enrichment in the most obvious areas but no success in finding any leaks. Brand new opti and spark has been verified at all cylinders. I have pulled plugs and the car is indeed running rich since the plugs are black soot vs. tan brown.

Datamasterloghttp://www.mediafire.com/download/n3..._Baseline4.uni

There is a very weird duration in the log between record 2259 (617 secs) and 2306 (626 secs). The injector pulsewidth drops to 0.0 then comes back on at a lean condition. I took the car for a short cruise to get an idea of how the readings looked under load vs. at idle to help track down if a vacuum leak.
Please have a look at my datalog and help point out some areas which might stand out.

Thanks for the help in advance guys.

Injuneer

Link keeps trying to download .exe files, not your .uni file.

Flyin_Z28

Sorry about that. Try this link instead.http://www.mediafire.com/download/n3..._Baseline4.uni

bobdec

Just a quick observation.. 2259 is DFCO Deceleration Fuel Cut off (TPS= 0% MAP=18 Kpa). The log looks like you not tuned for your injectors/mods looks rich across all conditions idle and running. PCM is pulling 10-15% across the board, not just at idle. LT BLM's are hitting 108 (lowest displayed, but may be lower). PCM is working like heck to lean out O2's reading rich conditions, ST trims show PCM is correcting, but it can only do so much and it's not winning. At idle BLM cell 16 RPM 750, AFGS 8.34, MAP low 40's, idle timing low 30's looks like OK readings with decent size cam and opened up intake/heads. IAC, TPS voltage look good. Usually a vac leak would show lean mix w/PCM adding fuel. Yours is pulling fuel.. Can you verify tune, injector settings, engine displacement are set up OK. Fred has more experience on modded setups, he may see something I missed..

Flyin_Z28

bobdec,

Thanks for the feedback about the DFCO.

I can verify the tune with Tunercat and TunerPro. The cylinder volume is currently set to 788.97 ml/cyl. Try setting at 784.53 but defaults back to 788. Only a 1% difference off actual. The injectors are set as per Racetronix offsets and injector flow rates, 42lb/hr.

Kevin Blown 95 TA

Flow rate is dependent also on fuel pressure so keep that in mind. If your fuel pressure is where you want it, then raise your injector constant and see where that gets you (You probably should put your MAF table back to stock first)

Flyin_Z28

Thanks, I have the stock fuel pressure regulator although I have not verified the actual pressure.

Flyin_Z28

Hey all, I put the MAF table back to stock settings and have increased the fuel injector rate up to 46.5 lb/hr in order to see if it makes any difference. Here is an updated datamaster log.

http://www.mediafire.com/download/u0..._Baseline6.uni
It seems like it is having to make slightly less fuel corrections but still very rich LT conditions.

I have also attached a pic of one of the spark plugs.
http://www.mediafire.com/view/rxs5x7...amaster_Files#

I always like to check plugs to make sure that the O2 sensors are not bad causing false rich readings. I did pull the O2 sensors the other day and they seem to be fine and not sooted or plugged up. These were new when I put the 383 in a couple of years ago.

Should I increase the fuel injector rate another 10% in order to try and see if that makes any difference?

Injuneer

Still can't download, and it's still trying to download an .exe file. This is a second window that pops up after clicking "download" on the main screen. My virus software wouldn't accept the download from the second window.

Injuneer

OK.... tried a different PC and browser, downloaded both files.

I don't see anything other than the O2 sensors hanging at rich levels for an extended period of time. They're supposed to be cycling rich/lean multiple times per second, but they are hanging at 800-900mV's for extended periods of time, driving the LTFT's down.

I would verify fuel pressure before doing anything else. And check the plugs. If you are getting a false rich from the sensors, you aren't going to see sooted plugs or O2 sensors. If it's really running as rich as the O2 sensors indicate, the plugs should be showing it.

If it was a false rich, and was actually running lean as a result of the very low LTFT's, I would expect some knock retard, but there is no evidence of it in the first file. On the other hand, the driving wasn't very aggressive, and the coolant temp wasn't very high, so maybe you just didn't push it hard enough for the KR to show up.

With stock BLM limits, the LTFT's can't go below 108 (-15.6%). Once they reach that value, the STFT's have to try and correct the rich condition. At the end of the last data log (all idle/Cell 16) the STFT's on the left banks are also below 128, indicating even the 108 BLM isn't curing the problem.

bobdec

Baseline6.uni is little better, ST's are showing close to 128 near the end of log, but LT's show PCM is still pulling fuel, LT's at 108/110. By the way in TunerCat-Constants-Fuel Parameters there's a setting called 'Minimum BLM' stock setting is 108, you can temporary lower it too see how low the LT BLMs are actually going. Won't help your problem but it will show how bad things really are. At this point pulling 15% is a lot and I would be real Leary of telling anyone to tune that much out of MAF or injectors without a wideband to make sure you don't hurt the engine. The O2's look like they are switching OK, but you can't rule then out and risk damage on what they are telling the PCM. Have you pulled plugs on both banks to see if conditions are the same on each side. PCM gets confused if one or more valves/cyls are doing strange things. Your plug looks like the engine is rich and as Fred said there's no knock, assume you have not tuned it out.. As far as cylinder displacement, I have never really understood it's use in MAF fueling as PCM calculates fueling based on Air Flow. However in SD mode it's a different story.

Flyin_Z28

Fred,

Thanks for the feedback. Do you know of any other free FTP/share sites which you you would recommend for future?

I am going to pick up a fuel pressure gauge and take some readings this weekend.

I have pulled plugs and they all seem to be very close to the same. These were pulled right after shutting down and idle run.

Bobdec,

The stock knock settings are in place and have not been modified.

Here is the actual .bin file if you guys wouldn't mind taking a look.
http://www.mediafire.com/download/yx...jectors_v6.bin

GaryDoug

I have had no issues downloading any of these files and viewing them in Datamaster. I am using Firefox release 21.0. Sometimes I have noticed Firefox get a bit weird and need restarting though.

bobdec

Interestingly you're tune is supposed to be on the lean side. The O2 rich/lean voltage thresholds (where the PCM basis BLM at 128) are set about 8% lean (407 Mv) at low AFGS and move towards 5% lean (425 Mv) at higher air flow. Your tuned for your mods. The one thing that stands out is your injector offsets at 13.2 volts are about 2X stock. Stock is 366 usec (.366 Ms) and your set at 763 usec (.763 Ms). I have read some forum posts that Racetrack supplied offset and flow numbers can't be trusted. One post says a 30% reduction in offsets was needed to get BLM's in line. Something to research as the offset is added to the injector PW and will throw BLM's out. Sorry that's about all I could see, nothing else stands out as being out of wack.....

Flyin_Z28

Thanks Bob for doing some digging into my tune, very much appreciated. I will track down the offsets and see if there is any history on the injectors.

BTW, I can't seem to find the Rich/Lean O2 threshold table. Where is that located in Tunercat?