Hi guys. Trying to get some input here. I'm kind of new to tuning but am trying to learn. I have searched and compared files and don't know what I'm doing wrong. I am using Tunercats as my tuner and Tunerpro RT as my datalogger.

First, I have a 78 malibu with a 1994 lt1/4l60e from a trans am. The motor is completely stock. I am running Maf mode. There is no air pump and no cat. Has stock manifolds. Still has Egr. No canister purge. I have removed basic stuff like the air pump and canister purge from the tune and adjusted the speed and such. The car runs excellent. But when I datalog, the car only uses cells 16, 17, and 18. Half hour drive running excellent and only 16, 17, and 18. Since it drives fine, i haven't worried about it. But now I put long tube headers on and removed the Egr, and updated the computer for the lack of egr. It is now running lean and want to do some changes but its kind of hard when the computer is only useing cels 16, 17 , & 18.

Second, I have a 88 RX7 with a 1995 lt1/t56 from a trans am. This motor has an lt4 hot cam. I am runnig MAF mode. There is no air pump, no canister purge, no egr, stock manifolds, dual exhaust w/ dual cats. Same basic stuff removed from the tune, and this one is stuck in cells 16, 17, & 18 as well. This car needs to be tuned for the cam. It appears to be running rich, but is not responding well to changes in Maf tables (blms around 116 and not getting any higher).

I have a feeling I have something set wrong or deleted incorrectly in the tune of both cars. Does anyone know anything common that might cause the computers to stay in cells 16, 17, & 18. Thanks in advance!

 

I have see incorrect disabling of the EGR in a tune cause this problem. I have also heard, but never saw it proved, that messing with the EVAP canister purge causing that problem. To disable EGR correctly set EGR Disable Low RPM Threshold to 0 - EGR disable Hi RPM TH to 0 - EGR Enable Low RPM TH to 0 - and EGR Enable Hi RPM TH to 0 all other EGR settings should be set to stock default values.

 

On the malibu, the EGR was on and functional and the computer was completely stock as far as egr is concerned.

On the rx7, I do not see the specific thresholds you are telling me to change in order to remove the EGR. In the ecm constants table, I see these (description, stock setting, current setting) :
EGR Enable min MAP, 36.2 kpa, 104.1 kpa
EGR Enable min RPM, 900rpm, 100rpm
EGR Enable max RPM, 2100rpm, 200rpm
EGR Enable Cool. temp (Hi Startup MAT), 50degC, 150.50degC
EGR Enable Cool. temp (Lo Startup MAT), 82.25degC, 150.50degC
In the ECM Switch Table I have disabled:
EGR Electrical failure Error 27
EGR Diagnostic Error 32

As far as the canister purge, both cars are set up the same. In the ECM Constants Table, I see this (description, stock setting, current setting) :
Canister Purge enable coolant temp, 59.75degC, 150.50 degC
In the ECM switch table I have disabled:
CCP Electrical failure Error 26.

Have I done these correctly or what should I change these values to to try? On the rx7, I do have a canister that I could hook up and try to put back to the stock settings, just to try if nessecary. Thanks Again

 

I'm having the exact same issue...I'm running the stock tune with all emissions hooked up and everything. I'm just starting to learn the tuning so I haven't messed with anything yet, just did some logging with datamaster and noticed the pcm is only using 16, 17, and 18. My blms are also in the 145 range in 17 and 18 and mid 150's in 16...thats lean right? I do seem to notice the smell of NOx. Any ideas would be really helpful.

 

Is the PCM going into closed loop?

 

Yes, it does go into closed loop.

 

I just got my Malibu out for the spring this weekend and fixed my problem with this. Funny that this thread just got brought up again.

The only thing I did was set the Canister Purge enable coolant temp back to the stock setting of 59.75degC. Even though I have no canister or purge solenoid. Now the car is useing all cells and I can work on my tune.

I hope this helps out.

 

This thread was a huge help. I went back and double-checked, and sure enough I was using a non-factory tune with EGR/CCP improperly disabled.

I switched back to my REAL stock tune, and sure enough, it's going into the other cells now...I'm still running really lean though, with idle being the leanest at around 155, all the other cells are mid 130's to mid 140's, luckily they seem well balanced L to R, but all really high...

Does this mean I have a vacuum leak, or exhaust leak, or do I just need to tune my MAF tables?

 

Thanks for updating the CCP temp setting being the cause.. It verifies what I have heard, but never had a chance to verify...

 

No problem. Thats what these forums are for.

Now, as for my change to long tube headers. The car is running quite lean, and even has a dead spot as soon as you touch the gas. BLMs were 138-155 area. I have richened the MAF tables all by 5% and this definately helped. But there is still a dead spot when you first touch the gas. Almost as if you would need to adjust an accelerator pump. Is there a certain table to be looking at? or should I just continue fine tuning the MAF tables? Is this common for adding long tubes? The O2's are down in the collectors. I don't believe I have an exhaust leak cause right and left BLMs are very similar and richening helped.

Thanks again in advance.

 

Chuck, noticed in you OP you have a hot cam (you should have a signature, that helps). It's critical to get idle perfect to avoid bogs when hitting the throttle. Make sure AFR is good at idle speeds (700-750 M6), blms are not split, IAC is at 30-40, TBS is between .45 and .75 volts. MAP s/b in the low/mid 40's Kpa with that CAM . AFGS 8-10, TB closed timing should be in the low 30's at 400-1200 RPM settings. And tweak the main timing table so as you move from TB closed timing table to main table there is no big difference in the timing transition. Is your TB stock, is MAS stock with a screen ? Any intake air modifications done during the conversion to LT1 ?

 

I guess thats what I get for posting about two different vehicles with the same problem in the same thread, then asking questions about only one of them. My fault.

The malibu is a completely stock LT1 (no hot cam). It has no CCP. For an intake, it has a cone K&N, 3.5 in tube, descreened gm MAF, trickflow intake elbow, and stock TB. Now just recently, it has no EGR, 1 5/8 primary long tube headers, and dual 3in exh (I know its overkill, but its what I have left over from my last engine).

I will check my timing tables to make sure the closed throttle table matches up to main spark tables. I also have a screened stock gm MAF that I can try from my RX7. In fact now that I think about it, the descreened MAF was from the engine I bought for my RX7, and I stole the screened one off this car to make sure the RX7 was running right. I never ran this descreened MAF on this car before I removed my stock exhaust manifolds. Could this be causing my problem? Can descreening a MAF cause incorrect MAF readings, enough to cause a stumble?