I did some searching on here on people who seem to have a problem with their computer maxing out the lower end of the BLM range. As kind of a background, my car has an SCREENED mass air flow as well as the other mods listed in my signature. Oxygen sensors are month old Delco sensors and plugs were changed at the same time with properly gapped NGK TR55s. I also have an Actron handheld scanner so I really don't have scanning software available to me because I don't have a cable (but I do have a laptop). Before tuning, the best my car ran with the headers was right around 14.2@97mph, which is really slow for the mods that it had. Knock retard before tuning was around 7-8 degrees at WOT. Gas mileage seems to be *decent* with about 24-25ish highway and 12-13 in the city.

As a part of trying to figure out what is going on with my car, I started by doing some things that people have said to check out. Since I have had my OBDI conversion, if I use 93 octane gas, then I have absolutly no knock retard. Being up in Oklahoma for school, the highest octane I have available to me is 91 octane, which I must say is very bad gas. Today I ran my car to see what kind of KR that I am seeing at WOT and it usualy is around 6 degrees, then lowers down to about 3 after a few seconds.

I then tried disconnecting my MAF, as suggested by someone in another thread. I have to say the car seemed to run great! I had much more throttle responce and BLMs, while slightly spit at usualy 4 points, stayed in the low 120s at idle and high 1-teens at throttle. The car also seemed a LOT more peppier and at WOT there was zero knock retard.

My question being, would this point towards a failing MAF? Are the effects that I am seeing just tempoary and I will actually see results similar to what I had before I unplugged it? Anything in particular that would cause the slighty spilt BLMs? I apologize for the long post but I am just trying to give a good background. Let me know if there is any other info I can provide for you to help out.

 

4 points is really not split. Split is when you have a large gap like more than 10.

And yes it could be the MAF if the problem goes away when you disconnect it. Try to find another MAF you can swap in to test and see if it runs better.

 

I went for another ride today to go to a gas station that sells 93 and noticed that the BLMs once again creeped back down to about 108-111 again with slight throttle. However, once I did get a fresh tank of gas, the BLMs crept back up to about the high 1-teen range. I plugged my MAF back in and once again the BLMs went back to 108.

Another wierd thing I also noticed was with the MAF unplugged, I would still get about 6 degrees of KR even with the 93 octane, but once I plugged in the MAF I got none.

 

Just so happens that I have an extra MAF. I swapped it in and the same readings came as with the other MAF. At idle, it was *slightly* spit at 108 and 111. I suppose the next thing I should check is my fuel? Maybe I have a leaky injector or a bad FPR?

 

I guess easy stuff first... check fuel pressure to see if it is correct. Did you get a new tune? Is it programmed for the correct size fuel injector?
A severe exhaust leak before the 02 could cause the 02 sensors to think it is running lean and the computer will richen it up.
Ignition miss maybe but, you would probably feel that in driving it.

 

I dont know what the problem is exactly but that descreened MAF isnt helping. A tune would raise the BLMs back up if you mention the problem if your order one.

 

2nd sentence in original post:

 

You are correct in that an exhaust leak before the O2 would cause it to think I was running lean, however, the computer is correcting a situation in the other direction. It thinks I am running very rich and is subtracting fuel to compensate for the overly richness.

I might try taking it up to a dealership today and see if I can get them to check the fuel pressure.

 

UGGGG! Spend the 30 dollars on the gauge and screw it on. You will save money and have a tool to show for it

 

I have one at home, but I am up at school and I don't think the 7 hour drive back home is worth it haha.

 

I'd spend $30 on a second fuel pressure gauge vs going to the "steeler" any day!

Ken R.

 

Haha I read that as descreened! Most people dont post their MAF is screened.

 

Could be burst knock retard kicking in since you said it goes away when MAF disconnected, try zeroing out the burst knock table if you have tuning software, burst knock retard is overkill anyway. Also, I think RedRyder really meant his MAF is descreened, he hasn't clarified that.....but why would he bother mentioning that it's screened when that's how they come? When my MAF was descreened it caused burst retard to kick in. Also, descreening it would lower BLM's because it's seeing more airflow and adding more fuel as a consequence, then the O2's see the extra fuel and the BLM's drop.

 

I really don't have any tuning software available to me only because I don't have a cable. I do have a laptop but no cable. My MAF is in fact screened and I put that because a lot of the threads about this problem had people with descreened MAFs and I just wanted to clairify that, but it seemed to cause a little bit more confusion than I intended.

 

I checked my fuel pressure today and at idle it was at 54 psi which I know is way too much. I pulled off the vaccum line and it jumped to 64 psi. My FPR is adjustable though I have never touched it since I got the car. Is the high pressure a good reason for my low BLMs? What should it be at, like 42-44 psi? Thanks!