350patriot

Hey fellows

i recently got ahold of some tuning software that i can tune and datalog the pcm on my 94z. before i did any major changes to the tune i done some datalogging and found that the blms were around 138-142 on the left side and around 154-158 on the right side. because of seeing this lean reading, i searched and found an exhaust leak on the passenger side header gasket and replaced both sides earl's header seal gaskets. I started up the car again and done some more logging and found that the blms never changed even after disconnecting the battery and reseting the pcm. i swapped out the 02s and placed each one on the other side and the reading was still the same, so i added alittle fuel to the tune and still nothing changed.

I'm also noticing that the car is running very rich in closed loop and throws raw gas out the exhaust and even smokes heavily when you give it more throttle. when i reset the blms and onplug the 02s to keep the car in open loop, i notice that i have a little knock retard at idle but exhaust at idle smells alot cleaner, and it still smokes alittle on heavy throttle in open loop, but it is nowhere near as bad as when the 02's are connected.

originally i was thinking that the o2's may be fouled, but after getting the same reading even after swaping them to the other sides and constently seeing the voltage change on them it makes me wonder if there is something else wrong.

my current mods on the car are; bored to 355ci, cc502 cam with 1.6 roller rockers, long tube headers with full exhaust, k&n cold air intake and f.a.s.t 36lb injectors along with an upgraded walbro fuel pump.

the injector flow rate table has been changed to 36lbs and the cylinder volume table has been bumped up to 726.22 ml for the slight increase in cubic inches.

Is there anything else i can do or check on the car or in the pcm tune that might help this rich mixture?

any help will be appreciated.

Thanks

bobdec

What are you using to datalog, if .uni .xdl .csv can you post a log up on a file sharing site. Or e-mail it to datalogs@comcast.net and I'll take a look. If the readings above are LT BLM's (used for fueling calculation) then the PCM is adding 9-9.6% fuel and the results of that correction (actual engine burn) will be the ST readings, how do the ST BLM's look, are they better than the LT's . Adding that much fuel would be a major vacuum leak, a plug not firing (raw fuel reads as super lean). Saw one thread with plug wires 6 & 8 swapped causing the same conditions. An injector not working, very low fuel pressure.

350patriot

the log file is an xdl from the tunerpro rt software. the ST fuel trims stay around 128 and look much better than the LT fuel trims. I'll email you a log file that I did of the car a couple days ago.

bobdec

Here is a link to your log for other readers to view.. https://www.dropbox.com/s/bvl37a7xai9em2b/3.28.2013.xdl

Everything looks good.. AFGS around 7, IAC 30, TPS voltage .55, ST BLM's 128+/-, Spark 29*, MAP 41 Kpa, RPM 750. The LT BLM's in BLm cell 16 (idle) are bad and rock solid at 152/136. That says the PCM is correcting, adding 8-9% fuel at idle and your end burn is actually good. What I did see is when you tapped the throttle three times during the log you correctly went to BLM cell 18 (TPS not = 0 and speed = 0), at that time your LT BLMs went to 132/129 that says at off idle more air flow the lean readings get better.

What we have to do is determine if you are really running rich, the ST BLMs are saying no, but your observations, smell and gas out the exhaust say yes. Unfortunately if and injector is not opening, or a plug not firing. The PCM will add fuel to correct a lean O2 reading. But usually does not effect both banks the same. Are you sure it's fuel out the exhaust, not water mixed w/fumes. Do you have an IR thermometer to test the header primaries for a cold or hot cylinder.

Two other questions.. 1- What TB are you running if other than stock. And 2- What do the LT BLM's look like in BLM Cells other than 16 (when driving), thinking this may be a low air flow fueling thing that gets better with more air.

350patriot

the blms seem to stay closer to 128 while driving, maybe some fluctuation here and there, and I also have the stock throttle body on the car. it seems to smell really rich at idle and also throws out a greyish colored smoke when when you go heavy on the throttle.

at first I thought the smoke was actually oil burning since it is not truly a dark black color, but when I pulled the spark plugs, they seem to have a black color and not the whitish carbon color you get from when oil gets in the cylinders. also when I reset the blms and unplug the o2 sensor I notice there is a lot less smoke when there is heavy throttle.

the smoking seems to occur close to or around PE mode engagement, but I was really stumped by this because PE mode was already leaned out some from a mail order tuner before I ever got the tuning software.

the spark plugs were copper ngk's gapped at .050, is it possible that the gap is off on top of a possible vacuum leak maybe?

bobdec

A minor vacuum leak, will get better off idle as vacuum drops and the small leak becomes an insignificant percentage of un-metered air in the intake. Is your PVC system still stock ? Connections between MAF and TB good ? A bad injector, non firing plug, valve train problem usually shows lean at all BLM cells.

350patriot

the pcv system is still stock, but i'll have to check for maybe a possible vacuum leak around the intake area. I don't notice any misfires from the engine, but the spark plugs from all the cylinders have a dark color. What would be the best way to check to see if all the cylinders were firing right?

Kevin Blown 95 TA

A couple other tuning parameters to consider if and only if it is mechanically sound (no leaks, no ign probs):
* this applies to off-center blms at idle only - your turn on times might be slightly off
* minimum pulse width is too high
* sometimes TB opening can affect split blms

Other things to check is your rocker adjustment & make sure you got a healthy temp sensor. Also possible leaky injector

dmaderaitt

check out the MAF and the IAT, both were bad on mine, and the O2 on the drivers side was reading bad an caused the same problem you described

350patriot

Update.

Well guys, i may be finally getting to the bottom of this. I have been checking all the sensors, rocker adjustments, compression and fuel/ignition components for the past week. when it came to the plug wires at first i did a visual inspection, and did notice that one had a slight cut on it, possible arching and making a weak spark. after seeing this i decided to pull all the wires and check the resistance with a multimeter on each one. I came to found out that some of wires had a short in them as they wouldn't produce a resistance reading until i would bend them a certain way.

This problem really had me stumped as the car itself seemed to run really good and not miss, but just run super rich. i have had problems before with plug wires before, but i could always tell a difference because there would be a slight miss and the throttle response would be sluggish. the plug wires themselves are msd 8.5mm superconductors and do not have alot of miles on them, but i guess the extra heat from the longtube headers really took a toll on them.

regardless though, I want to thank everyone that responded to my post and gave me ideas on things to look for and check.

dmaderaitt

Awesome, something for me to keep in mind on mine.

bobdec

Appreciate the fix feedback.