low blms

[pwhite]

when warm my car pegs it blms @ 105 while idle. while driving a steady speed they go from 130's to a steady 105. My fuel pressure is 43 line off, my injectors were pulled and cleaned , I have new plugs and wires , and recently replaced the o,2 sensor.

any ideas


thanks

 

[pwhite]

ttt

 

[2QUIK6]

The BLM will go as low as 90, so it looks like the ecm is still able to control it somewhat. Do you know 100% that the chip you have is matched for those injectors or have you tried other 42.5 chips?
When do the BLMs hit 130?? and then at what point do they go down?
If you had something like a stuck injector they would be low just about everywhere. Do you have a scan tool that lets you see all of the BLM cells since there are 16 of them, you may be seeing the jump from 130 to 105 when it jumps from one cell to the other.

 

[MistaScott]

MAF is a suspect here as well. What chip are you running?

Check t6p.com in the library -- Razor runs through a list of possiblities, most of which you have covered.

105 and 150 are the usual default pegs, but some ECMs do hit 90/160 or thereabouts. If the number is pegging at any extreme you have something going on.

 

[pwhite]

I have tried all three of my chips a 20* for 42.5 and a 23* for 42.5s . I even put the stocker in with the same results. if i punch it it hits 120 to130 but as soon as I go back to part throttle it slowly goes back to 105. How do I check for a bad maf. is there any way other than switch to a known good? thanks

 

[pwhite]

how do i check for a bad maf ? I taped the hell out of it and no change in idle. I have no known good maf to chang eto . does anyone know how to check a bad one.

 

[MistaScott]

You can check voltage to the MAF as a crude test, but you need an oscilliscope to get the square wave frequency. Best bet is to track down a good MAF, or even buy one you can return after testing.

http://www.wellsmfgcorp.com/counterpoints/Counterpoint3_2.pdf

and

http://www.t6p.com/forums/showthread.php?t=1127

 

[pwhite]

where is the best place to try the old buy and return the maf trick. autozone? oreilly?

 

[TT/Ameasap]

What about a vacuum leak or header leak? That would richen the motor up.

 

[pwhite]

I am pretty sure that would lean a motor and peg the blms at the other extreem 150

 

[MistaScott]

That is mostly correct: exhaust leak is going to richen things up in the motor but the BLM will stay pegged at the upper limit.

As for a good MAF, try Advance Auto or Napa. Make sure it is the correct MAF with the angled connector plug. They will take it back in any case, even if you break it because half the time the remans come back from CARDONE with the screens falling out anyway.

 

[Warped]

Cam sensor position?

This probably isn't it but it happened to me. I had a no start condition and swapped cam sensor caps to see if that would fix it. Turned out to be the injector fuse but I just left the spare sensor cap on. Now I had a low blm problem with the same numbers you are talking about. I posted the problem and checked all the usually suggested items. This went on for weeks. Later I remembered switching that cap and that I had read some racers will bump the cam sensor position to richen up the motor. I didn't think that was the problem but I changed the cap back anyway and sure enough the blms came back up. I had set the sensor with the original cap using Casper's tool so it was dead on. I wouldn't think there would be that much production tolerance in a sensor cap but in this case there was. Something else to check.

 

[quickbrick]

napa and autozone make crappy replacements, ive been through several new ones that didnt work right. i went to oriellys and got a gm reproduction and havnt had a prob since.

 

[quickbrick]

Originally posted by MistaScott
That is mostly correct: exhaust leak is going to richen things up in the motor but the BLM will stay pegged at the upper limit.

As for a good MAF, try Advance Auto or Napa. Make sure it is the correct MAF with the angled connector plug. They will take it back in any case, even if you break it because half the time the remans come back from CARDONE with the screens falling out anyway.

yes i had a screen fly out and get wedged in the intake, i thought i blew my engine. it wont happen again though, its in for good