I Give Up!!!

[cmokem]

Started the Gn the other day and noticed the BLM's at idle were 148-150...after the car ran for a while they came back down a bit. Drivability and wot looks great..O2's look good at cruise but here is the catch. after a short cruise blms are 141, After idling for a while the blms creep back up..it seems the hotter the engine compartment gets the higher the blms. If I shut down the car for a bit and then restart it the BLM's are at 148 for several minutes and then work down to 142. I have checked the lines for a leak but found none. Vaccuum is 16.5-17 in park. Any suggestions are welcomed

TIA
Bob

 

[Red Regal T]

cracked header

 

[Carolinaturbot6]

For the archives...

"There is nothing wrong with your chip or fuel delivery system, even in normal driving, when your BLM (Block Learn Mode) numbers are anywhere between 110 & 145. The car will still be running stoichiometrically correct no matter what the BLM numbers show, as long as they are between 110-145. Numbers below 128 show that the computer is taking away fuel & numbers above 128 show that the computer is adding fuel. In either case,the car is not running rich or lean! The BLM numbers basically show what fuel corrections the computer is making in order to keep fuel delivery stoichiometrically correct. BLM numbers will vary with types of gasoline, weather, & at idle when you turn on the a/c!
Now if your scan tool shows BLM numbers always way below 128 or way above 128, it shows that some fuel correction is necessary. Often this can be adjusted with the fuel pressure regulator. But still, the computer is working (only "harder") to keep the fuel mixture stoichiometrically correct. If BLM numbers are always below 110 or always above 145, that's when you start looking for a fueling problem!"

 

[cmokem]

Thanks for the reply guys...
John my header was fixed about 2 years ago but I will look again

Carolina.. the car runs great at cruise 128-138 blms...but I never seen it as high as 150 at idle warmed up...fuel pressure is 45 with 009 injectors. I was thinking maybe the maf sensor (3 1/2 may be bad but not sure how to check them.


Thanks Again for your replys

Bob

 

[blackbuick87]

I think you are worrying about nothing. If the car is around 128 at cruise and you are not fouling plugs/blowing black smoke dont worry about it

 

[terryk]

I kinda agree that if the car's otherwise running well, don't get hung up on it, but........I can't stand that approach either. It's either right or wrong. Slammed BLM's are wrong.

I had the same problem and it was a cracked header and leaking crossover joints. The BLM's at idle would hit 150. I fixed the leaks and now it idles at 132. Close enough for government work.

Look for exhaust leaks before the O2. A long hose and an ear is all you need. Air is dropping the O2 reading and forcing the ECM to increase the fuel.

Terry

 

[cmokem]

Thanks for the replys once again. I will put the car on jackstands this weekend and check the connections of the exhaust system. In most cases is it just a matter of tightening these connections up or is there a part that needs replacement (Donut)?

TIA
Bob

 

[terryk]

It depends on the leak (see, I'm an expert now).

Get a long piece of vacuum hose, stick one end firmly in your ear and go hunting.

1. Start with the seal between the header and the heads and start working outward. Check every weld all the way around.

2. Check any line on the tubes that look like a seam exists.

3. Check the seal between the up pipe and turbo and downpipe and turbo.

4. Check the crossover at every seam and coupling.

5. Check every turn and bend closely.

When you find a leak, you'll know it......

All welds are suspect. All seams are suspect. All gaskets are suspect.

Use some white nail polish to mark EVERY crack and leak. You might get luck and only need to replace seals and gaskets. Otherwise it's a trip to the welder.

When you think you've found a leak, rev the engine. It will be very loud at the leak.

 

[cmokem]

Great info Terry...thanks

I gave the car the once over and didnt find any major leaks in the exhaust system. I did however found that the drivers xover pipe was a bit loose where it joins at the header. After tightening I started the car and let it run...BLMs were at 142 which was better..went for a drive and had normal (128-136) blms throughout the drive ...came home shut it down and let it cool for 10 minutes...fired it back up and the blms are at 151 for several minutes before coming down to 142.....maybe its really nothing

thanks for the help

Bob

 

[SITHV6]

a neat tool to have...

I've always had in my trunk a doctors stephescope with a metal brakeline at the end of it. It not only keeps a hand free but the metal end lets you get to the cracks while the headers are awfully hot. (besides, it was always fun putting it on as i look over a friends driverside header. I looked like a "GN Doctor!" lol) Oh and ANY leak you find with it is Unmistakeable.

 

[TurboJim]

Could be a failing O2 sensor

 

[cmokem]

Jim..I replaced the o2 sensor yesterday as PM,,,,still no luck...but thanks for the suggestion

Bob

 

[cmokem]

Well guys looks like I fixed the problem...problem is that I did a "shotgun approach" and changed 3 things...I pulled the check valve off the pcv line and just ran the pcv, I changed back to my original KN filter that I had I in the fall....and I changed the vac block on top of the TB. LAst year I went to vac brakes and had to bolt on the vac block with the xtra nipple...I think the latter is the problem....BLMs went from 142 to 118. Whoa!!!! turn the FP and the Tranlator down to the default position. Tomorrow i'll start re-installing the air filter and check valve to double check.

Thanks to all that helped me with this post

Bob