The car is a 95 M6 with intake, 503 cam, headers, gears etc.

This is the second PCM I tried, bought a used one on here and reflashed it.

I also tried a known stock 95 tune, along with other tunes made by myself and PCMforless.

The problem is when the car is in PE mode the ST BLMs are still working and pulling fuel, they jump around in the 130's. Data master confirms that the PCM is going into PE mode and the BLMs are being locked/ disabled. This seems to happen at about 3800 RPM. LT BLMs go to 128 and dont seem to change but the ST trims keep looking for 14.7.

I am altering the tune using tunercats and loading it using the EEL def file, which is supposed to lock the BLMs

What sensors does the PCM look at while in PE mode? Could one of them be causing this? It seems that when I go WOT it initially locks the BLMs at 128, then within a few seconds the ST trims start jumping up and causing the O2s to read in the .050 to .600mv range.

I need some of the experts here, I am lost.

 

I'd ask TC (tunercat). He's always had good answers for me when I can't figure something out with tune.

 

Funny thing is I did ask them, they were the first ones I contacted. I sent them a copy of my tune and a datamaster log showing the issue. Their response was to check my WOT vs RPM table, which I havent altered in years.

So I got no where with them. The base tune was from PCMforless. I called hoping to speak to Bryan and instead I got some ignorant a$$ telling me that I screwed the tune up by messing with it or there is a driver in the PCM messed up. So, I bought another PCM and same problem.

Fred? ya there? lol...you always seem to have in depth thoughts on wierd issues like this.

I could email some datamaster logs if needed, every one I have shows this issue.

 

I answered your post on the LT1 forum (not a good idea to cross-post). My thought was its slipping in and out of PE mode based on the TP% vs. RPM table... so I guess I'm about as helpful as TC.

 

Sorry for the double post Fred. Just thought it would get more traffic since im LOST on this one.

Anyway, I am not sure why I thought the BLMs were opposite (over 128 is pulling fuel, under 128 is adding). That has been stuck in my head for a while lol.

Plus the datamaster log showed a correlation between the BLMs and the O2 sensors. Such as, as soon as I go WOT, it shows PE mode active and BLMs disabled. The ST and LT BLMs go to 128 and O2's are in the 800's. Then at about 3600-3800 rpm the ST trims start dancing around in the mid 130's to 140's. At the exact time the BLMs go up, the O2's go lean, down into the .600's and below. I am truely boggled at this, especially if BLMs greater than 128 are adding fuel.

I checked my TPS% for WOT vs RPM, it is 60% under 2200rpm, 50% at 2400 rpm and tapers down to 19% at all RPM above 4000.

I understand that if the BLMs are locked, they should be locked. BUT could there be a safety or something that overrides them if it is VERY lean in PE. Like say I add like 15% fuel to the WOT table to see if it satisfies the ST BLMs trying to add it. If you understand what I just tried saying lol.

An no Fred, I havent absolutely verified that it is lean with a wideband. I have been basing this off of the narrow O2 readings. I knwo they arnt very accurate but I also know they should be up near the .850s to .900s when in PE mode, not down in the .200s and such like it is doing.

I really appreciate your feedback.

 

I think i would be looking at somthing else than the pcm or the tune, at wot you should be staying well above 800mv, if they are falling to 200mv like you say than something is causing a very lean condition, the 2 first things i'd check would be a contaminated maf or falling fuel presure at wot under a load.

 

Both the MAF and the fuel pressure seem fine.

The ST BLMs are not staying locked when in PE mode like datamaster says they should be.

There is a direct correlation between the O2's dropping lean and the ST BLMs jumping in the 130s and low 140s. Everytime the BLM jumps up, the O2 mv drops.

 

try raising the baro update rpm to something high, like 6500 rpm. its in the constants table. Guys running boost have issues with this pulling a ton of fuel wen they cross this rpm point. Its supposed to aid in fuel trimming.

Its the only thing i can think of right now that would unlock the blms in PE due to the fuel trims being higher than 128.

Chris

 

Hey thanks Chris, maybe I will give that a shot. I read about that and was considering it but never thought it could affect me since im not boosted. All im looking for is a steady WOT fuel curve to adjust, which the ST blm's are screwing up bad.