With MAF #1--BLMS=112/115, MAF unplugged--BLMS=135/138 at idle??
05-06-2006, 11:32 PM
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With MAF #1--BLMS=112/115, MAF unplugged--BLMS=135/138 at idle?? Still trying to get the LT1 running right since the engine swap. Put a stock 95 F-body LT1 into an 86 T/A with a 700r4. !VATS, !AIR, !CCP, !EGR. Been fixing it but still finding new problems. So far I have had a bad MAP and bad O2's but have replaced them. Fuel pressure is good but slightly high. 39 PSI at idle, 47 psi at simulated full throttle. Compression is good.
Anyway, with MAF #1 plugged in, I'm seeing 112/115 blms at cell 16 at idle after letting it idle for a while. All other cells while driving are low, Cell 17 hits 108/108.
I dont know if it would do any good to unplug the MAF but i figured i'd try it. BLMS hit 135/138 with MAF unplugged in Cell 16 at idle after a while. So, next i tried a friend's MAF from his 95 T/A but his MAF is de-screened. BLMS dropped to 108/109 quickly once it hit closed loop. I reset the battery each time before I changed the MAF conditions. I have knock retard in every condition when i stomp on the accelerator quickly at idle say to at least 3500 rpm. No noticable pinging/detonation, the replacement MAP got rid of that.
I think I could be looking at a bad MAF and something else perhaps? Possibly a combination of things being wrong. I think i may have an exhaust leak at the header that came back from the dead. One thing I am going to try is running a scan on the other car to see how the MAF's effect the BLMS on that car. Any suggestions/help would be great.
Anyway, with MAF #1 plugged in, I'm seeing 112/115 blms at cell 16 at idle after letting it idle for a while. All other cells while driving are low, Cell 17 hits 108/108.
I dont know if it would do any good to unplug the MAF but i figured i'd try it. BLMS hit 135/138 with MAF unplugged in Cell 16 at idle after a while. So, next i tried a friend's MAF from his 95 T/A but his MAF is de-screened. BLMS dropped to 108/109 quickly once it hit closed loop. I reset the battery each time before I changed the MAF conditions. I have knock retard in every condition when i stomp on the accelerator quickly at idle say to at least 3500 rpm. No noticable pinging/detonation, the replacement MAP got rid of that.
I think I could be looking at a bad MAF and something else perhaps? Possibly a combination of things being wrong. I think i may have an exhaust leak at the header that came back from the dead. One thing I am going to try is running a scan on the other car to see how the MAF's effect the BLMS on that car. Any suggestions/help would be great.
Last edited by Firebat; 05-06-2006 at 11:40 PM.
05-07-2006, 06:23 PM
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Yoy don't have a bad MAF....
You need a tune to scale the MAF table to the engine combo....Or have the guy change your injector contant. If your want the NON-maf numbers to be say in the 128ish area your going to have to add some ve. in the ve table...I can't remember if the timing goes into a different table or a subtractor program takes out timing in a MAF failure mode.....(been playing with HP tuners to much lately a can't remember all the tables in lt1 edit). But, I do believe some of the difference in blm's is also caused by timing taking a dump at idle and driving while in "SD." You could also drop fuel pressure to help raise your Blm's but, I can't garantee your fueling numbers will be good at WOT....Get it tuned with No exhaust leaks prior to the OXY sensors (no sensor failures of any kind), and you'll be good to go....
You need a tune to scale the MAF table to the engine combo....Or have the guy change your injector contant. If your want the NON-maf numbers to be say in the 128ish area your going to have to add some ve. in the ve table...I can't remember if the timing goes into a different table or a subtractor program takes out timing in a MAF failure mode.....(been playing with HP tuners to much lately a can't remember all the tables in lt1 edit). But, I do believe some of the difference in blm's is also caused by timing taking a dump at idle and driving while in "SD." You could also drop fuel pressure to help raise your Blm's but, I can't garantee your fueling numbers will be good at WOT....Get it tuned with No exhaust leaks prior to the OXY sensors (no sensor failures of any kind), and you'll be good to go....
05-09-2006, 09:29 PM
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this is stock engine with shorty headers that was email-tuned by madz28.com. The tune might explain why BLMs were high with MAF unplugged, maybe?
I question the MAF because some people say they cause lower blms as they age and if you unplug the MAF it should be the same blms as with the MAF. It doesn't make sense to me why its a 20-25% change in the blms with the MAF unplugged. Exhaust leaks cause an increase in BLMs and i see an increase only with the MAF unplugged.
O2's change voltage all over the place. Its just funny right before it hits closed loop with MAF, the O2's read 950ish mV and with MAF unplugged right before it goes into closed loop the O2's read 50ish mV. I dont know if those numbers mean anything though.
Really i wouldn't even care about the BLMs so much, its the spark retard thats bothering me. And since I've replaced the MAP(not MAF) the engine seems to be running good but i see max retard being pulled while driving 20mph so thats not good.
I'll try running a stock tune with MAF again and then stock tune with MAF with injector constant increased, and a stock tune with MAF unplugged. And see if I have an exhaust leak or not.
I wouldn't mind dropping the fuel pressure but i dont think there is a way to do that with the stock regulator.
Another thing that is going on is that i'm hearing a louder ticking noise from the driver's side valve cover. Its not much louder though then the other side. I don't know, I might be paranoid.
A few questions:
Can valves that are not adjusted right cause lower blms like 108/108 or spark knock? I have never touched the valves and this engine was stock but you never know.
I question the MAF because some people say they cause lower blms as they age and if you unplug the MAF it should be the same blms as with the MAF. It doesn't make sense to me why its a 20-25% change in the blms with the MAF unplugged. Exhaust leaks cause an increase in BLMs and i see an increase only with the MAF unplugged.
O2's change voltage all over the place. Its just funny right before it hits closed loop with MAF, the O2's read 950ish mV and with MAF unplugged right before it goes into closed loop the O2's read 50ish mV. I dont know if those numbers mean anything though.
Really i wouldn't even care about the BLMs so much, its the spark retard thats bothering me. And since I've replaced the MAP(not MAF) the engine seems to be running good but i see max retard being pulled while driving 20mph so thats not good.
I'll try running a stock tune with MAF again and then stock tune with MAF with injector constant increased, and a stock tune with MAF unplugged. And see if I have an exhaust leak or not.
I wouldn't mind dropping the fuel pressure but i dont think there is a way to do that with the stock regulator.
Another thing that is going on is that i'm hearing a louder ticking noise from the driver's side valve cover. Its not much louder though then the other side. I don't know, I might be paranoid.
A few questions:
Can valves that are not adjusted right cause lower blms like 108/108 or spark knock? I have never touched the valves and this engine was stock but you never know.
Last edited by Firebat; 05-09-2006 at 09:41 PM.
