I recently bought a 94 firebird. The motor is an LT1 383 stroker with a paxton supercharger. Unfortunately, I don't know a lot of the specs on the engine internals (cam, etc.). It does have 42# injectors although I'm not sure of the brand.

I have FreeScan and TunerCATS and can upload scans/.bins. The motor has about 450 miles on it since a major rebuild and upgrade (cost the previous owner $6500 and did not include the supercharger which was already installed). As far as I know, the computer has not been tuned since the rebuild.

My problem, running FreeScan, the BLMS are constantly at 160 although the car smells rich, there's carbon build up on the rear bumper by the exhaust and i'm getting about 5.5 mpg highway. I've looked pretty thoroughly for vacuum and exhaust leaks and don't believe i have any. Vacuum reads low at idle (10-12 in) at idle I believe because of the large cam (really wish I knew the specs on the cam).

What would cause my problems?

 

If it running in MAF mode or speed density mode? Download the trial version of Data Master and post a datalog for us to look at.

 

Check the injector constant in Tunercats too.

 

Injectors set at 42#
Wil have data master posted today or tomorrow.

,Also, car idles high in closed loop, prefect in open loop. Stays in block 16 most of thetime. Sometimes I get a small backfire through the intake.

 

BLM's at 160 say PCM thinks AFR is lean and it is adding 25% extra fuel . 160 is the stock programmed max and can be set higher to see how really bad things are when looking at problems. "Max BLM " setting in TunerCats constants table. Can you post up a freescan CVS file, like to see what your O2 voltage swing looks like. They should vary between 100 and 900 Mv , I suspect yours are in the lower than 600 Mv range. As said in post #2 download DataMaster for 20 free logs and post one up, it's much more detailed than FreeScan.

 

I'm new and still trying to figure out how to post but I'm pretty sure my 02 sensors look ok. I'm about to a datamaster log and will post that within the hour. If anyone can tell me how, that would be awesome.

 

I have the datamaster (and csv file for datamaster). Anyone up for looking at it? I can email it or post it if someone could let me know how.

 

datamaster> http://www.mediafire.com/?molrg94m7bl71pm
CSV> http://www.mediafire.com/?x21ayz9478f55y5

 

It's idling above spec (950 actual vs 850 programmed), and the IAC motor is closed down all the way (0 counts).

5+ mS pulse widths at idle are very high, driven by the high BLM's and INT's. A 42 #/HR injector should have a very low pulse width at idle.

15+ GPS MAF flow at idle is very high. I'd expect more like 10 GPS. Has the MAF calibration table been altered?

TPS closed throttle voltage is 0.90V... very close to the level that will set a code.

SES light is not functioning (DTC 11)

Codes for auto trans (DTC 82, DTC 84 = shift solenoid circuits)

Left O2 stays very low. But it suddenly starts to move up and down over a somewhat normal range, when the EVAP (CCP) solenoid actuates. Is your EVAP system hooked up? This would appear to confirm the O2 sensors are cabable of reading correctly, but still possibly low. You have to figure what is causing them to be so low when the EVAP system shuts down.

As noted above the 160 BLM's mean its adding 25% more fuel that the PCM would normally supply. And the 180 INT (S Term) is adding another 40% extra, and since they are multipliers in the equation, the PCM is telling the injectors to supply 175% of the normal fuel. Low O2 sensor readings, and the very high MAF reading are causing it to pour fuel in. I saw a 197 INT in there somewhere..... never saw anything that high before.

There's either got to be a huge amount of air getting into the exhaust, or the O2 sensors are reading too low. There are periods during idle where both O2 sensors are reading very lean for a long period of time, and then they will start to rise above 500mV.... but even that is with the huge amount of extra fuel.

As far as the vacuum, the MAP at idle is about 55 kPA. Barometer is 99 kPa, so your vacuum is 44kPa. That is about 13"Hg. Generally, blower cams don't have a lot of overlap. But you do have the blower, and that will affect vacuum, if the blower is contributing even a small amount of boost at idle. On the other hand, if they used a cam with extreme overlap, the amount of air blowing through the overlapped valves at idle would cause the high BLM's. But the high BLM's are present in the high load cells.

When you open the throttle above 50%, you max out the MAP sensor, due to the boost. Not sure how they tune it at that point.

Wild guess here..... are you sure the EGR is closed? If the EGR was open, and with the boost, you might possibly be forcing air from the manifold into the exhaust, which would obviously screw up the O2 readings.

 

Down loaded the .uni , but I need more time to look at the trace. Some questionable things are showing up, I do not have supercharger experience so I'm hesitant to recommend any timing changes. Can you post your tune (.bin file) . I see your idle is set at 850 N and 600 in D , the 600 is low for your cam also the closed TPS Timing is stock and should be upped to at least the low 30's for the 400-1200 RPM ranges in the table. That may improve your MAP of 62 at idle. Also your TPS voltage is a little high (0.9V) however your IAC is almost maxed out trying to let air in at 140, do you have an after market TB, if so are the blade stop and TPS voltage settings set up correctly. You have a constant DTC 11 that says you SES light is missing, do you have it unplugged, also DTC 82 and 84 says you have a couple of transmission solenoid circuits opened, are you a stock 4l60E ??. At record 263 exactly when the 42 second "hot engine" timer hits you are going into closed loop , your O2's are still cold at 0V and start switching a little later, are the heaters working ?. After that It's almost like your PCM is ignoring the O2 feedback, thinks it's in closed loop, or just plain is not adjusting to the O2 feedback. The LT BLM's stay at 160 throughout the trace, and the ST BLM's are changing, but remain high in the 150-160's, like the O2 voltage is being ignored ?? When the O2's do start switching your right O2 is switching low (lean cylinder(s) ??) at 4 - 800 Mv, the left O2 voltage swing looks more normal (100-800 Mv) . Another minor thing, your EGR is enabled and adding timing, do you have EGR in your setup. Again can you post the .bin file, maybe I can see something. You don't have any sort of BLM freeze software installed do you. I'm thinking it may be time to get a clean new code load for your setup.. .

Pic below shows Closed Loop after 42 second timer, however O2's are not switching..also right O2 is lower than normal..
[IMG][/IMG]

 

here is the original read from tunercats
http://www.mediafire.com/?cr3fc3w0txiem8e

 

Anyone take a look at my .bin?

 

Was gone a couple of days, the .bin looks ok, as far a injector flow and cylinder size. Nothing way out that would cause what we are seeing. Any way to try a different code load, nothing obvious on why the PCM is ignoring the O2 feedback and adding 25% ++ extra fuel.

 

But sure what you mean by try a new code load

 

So I found an exhaust leak on the left header. they can't weld it up cause the steering column and other pipes are in the way. I put some jb stick putty on it and relogged the car. Won't be able to post it for a couple days but here's what I've got.

Long term blms were at 160, although they actually dropped at times while on the throttle, even down to 128. it went back to 160 after a second or two. Short terms were split, 190 ish left and mid 130's right.

I can still hear some exhaust leak so the putty maybe wasn't the best idea but it seemed to help.

Any thoughts? Should I keep messing with the putty?