BLM? What might this indicate

[oehm]

I am chasing down a high Blm problem on my car. I have read through many of the old posts about this, and decided to try blocking off the vacum block, and see what readings I am getting.

Here they are

15" of vacum @ idle w/ Vac block funtional
0" of vacum @ idle w/Vac block blocked off

Int @ 128 w/ vac block blocked off
Int @ 150 w/ Vac block functional

BLM @ 150 w/ vac block blocked off
BLM@ 150 W/ vac block functional

All these readings were taken at idle. I have a new delco PCV valve, and have checked all the vacum lines on the top of the engine. I thought the BLM's should drop below 120 with the vacum block blocked off. Am I missing something? Does this indicate another problem perhaps? Car seems to drive fine under normal driving situations. I have not beat the car since I discovered these high BLM readings. I have a trans plus, and extender chip that I want to install, but should I wait until I get these numbers down?

Any input is appreciated
Ian

 

[MistaScott]

Make sure you reset the ECM between changes. Let the computer learn the new fueling and be sure that the engine is in closed loop idle when you get the readings.

150 with vac block sealed shut means that your problem is not in the vacuum lines. It is likely an exhaust leak or intake gasket/EGR leak. Ignore the INT for now.

Next step is attach MAF to throttle body, then use GM Top Engine Cleaner to rule out exhaust.

Definitely WAIT before making any mods to the car. You don't want to confound the situation.

 

[oehm]

Thanks, I will look into that!!

 

[galoush]

Try another chip . I have one chip thats having the bugs worked out on that shows high blms and my Reds chip is around 128 .

 

[2QWIK4U]

I'm having the exact same problem and have blocked off the vacuum block with almost identical readings.What would putting the MAF at the throttle body tell me?
I've used the GM top engine clean and saw no leaks anywhere.Tried different chips and no luck.I blocked off egr lines and saw no change in the 150 bl#.Anyone with any other ideas?Thanks!!!

 

[turbowidow]

moving the maf to the tb will rule out maf pipe, turbo, and intercooler leaks. keep looking- you have a vac leak somewhere! (took me a month to find mine) ANY gasket, o-ring, or metel to metal surface AFTER the maf could be a source for a leak. you'll find it - happy hunting

 

[oehm]

Well, I found 2 vaccum leaks, and my vaccum at idle is about 19", the INT readings seem to have stabled out a bit, but the BL is still 150. I guess I will keep checking for more leaks.

BTW, what should engine vaccum be at with a stock cam under ideal circumstances? (no vaccum leaks)

 

[MistaScott]

Make sure you have several sets of eyes looking for the exhaust leak, including on the ground at the crossover pipe. I had a huge crack in my header and it was not billowing smoke, it was visible, but barely.

Also, the top engine cleaner will seep out of the intake if there is a gasket leak. Mine leaked at the EGR seal to the intake (not vac line related).

Test the vac system with Mityvac, make sure all lines hold vac.

If it is not exhaust, vac, or intake change o2 and MAF sensors with known good ones.

Recent ECM after any tests/changes and let the ECM relearn.

A 150 leak means it is a big leak -- usually a header cracked pretty good or a hole in a vac line.

If none of this works, let me know.

Scott

 

[oehm]

Just to clear this up, I should be able to take a hand vaccum pump to any vaccum line, pump it several times, and the line should hold vaccum? Are there any vaccum lines that will not hold vaccum?

What about the Solenoid on top of the charcol canister? Should it hold vaccum too?

Thanks for the input guys!!

 

[oehm]

Today, I blocked off the vaccum block again, and double checked the readings. In closed loop, I am still getting blm readings of 150. I installed a new GM Delco purple wire O2 sensor, and sprayed roughly 2 full cans of carb cleaner on any vaccum connection that I could see. I sprayed all the fuel injectors, intake manifold, intake plenum, and throttle body with no changes in idle, or spikes in the O2 readings. I manually inspected all vaccum lines and check valves and they all seem in order. I also attached the MAF directly to the intake, reset the computer, let it run into closed loop and still got BLM's of 150. The MAF reads 5 at idle, and does not stumple when tapping on it. I also visually inspected both headers for cracks, and double checked the crossover pipe..no leaks.

While driving the car today back from the shop I punched the throttle from a dead stop. I experienced no tire spin, and even with a TE 44 and 2800 D5 it took more than 4 seconds for the factroy turbo indicator lights to come on.

I am stumped. Fuel pressure is set at 42 PSI line off, and have tried getting different readings with three different Lubrant Chips (93 oct, 100 oct, 112+ oct)

Any ideas? Could the stock MAF sensor be giving incorrect readings? Is the computer bad? Any input is greatly needed!!

Thanks
Ian

 

[2QWIK4U]

I feel your pain

 

[oehm]

ttt

 

[turbowidow]

sounds like your having fun . how long ago was your tb done, found my shaft seals were leaking causing my high blm's. have you put a wrench on intake/exhaust bolts to check for tightness? i had a bunch that were loose. have you looked at the egr diaphram, checked egr soleniod/filter? i could not find vac leaks with carb cleaner or propane- best thing for me was a stethascope( cheapy from sears). have you replaced pvc valve and grommet( razor is right-nothing like ac/delco). personally i think you have an exhaust leak( the delay in your spool up) did you get under the car when you did the top engine cleaner? a neat little trick is to pull the crossover pipe, shine a flash light up in the headers and look for any light on the outside of the headers. your gonna have one helluva story about this when your done!
p.s. got the car out today- blm's were 126-136

 

[oehm]

The car came with the throttle body ported already so I have no idea how long ago it was done. How did you narrow your BLM's down to the shaft seals? I checked the intake and exhaust bolts and everything seemed nice and tight. I have a new delco pcv valve. I have had the drivers side header welded and can see/hear no leaks from the exhaust. I will try some top end cleaner this week.

Could a bad MAF be causing this. It reads 5 at idle, but could the calibration be off?

 

[turbowidow]

while under the hood, i could hold the throttle at about 1500-1800 rpm and could hear a "whistle" coming from the tb. i also had a lot of dirt built up around the throttle shaft.
if you suspect the maf, start car and let it come up to temp/closed loop, unplug the maf and watch your blm's. doing this will set the computer in the "limp mode" and your numbers should fall into place, then plug the maf sensor back in and see what happens-car should either stumble and pick back up or die on you. if it dies, try another maf. *note-i'm going on memory with the maf info, you may want to do an archive search on it to make sure of the test procedures AND DON'T DRIVE THE CAR WITH THE MAF UNPLUGGED!!!!!

 

[oehm]

Getting Closer perhaps!!!!

Well, I ran the car up to operating temperature, and unplugged the MAF sensor. The car seemed to idle slightly better and the INT values dropped from 150 to 128. The BLM's stayed at 150 though. Of course it set off a code 34. When I plugged the MAF back in, the car died immediately. Also, when under the hood, if I give the car a slight amount of throttle, I can hear a faint high pitch screech or whistle. It is not the turbo winding up, and it sounds like it is comming from the throotle body/upper plenum area. If I listen close, I can barely hear it from inside the car. I do not hear this noise under normal idle situations. I tried spraying carb cleaner around the throttle body when it was making this noise, but it did not seem to bog down or idle up.


Any more ideas? Does that whistle sound like a vaccum leak, or one severe enough to peg my BLM's?
I think that I am getting closer


As Steve Miller once sang.... "B L M's its driving me mad, its making me crazy"

 

[MistaScott]

Throttle shaft seals or plenum/throttle body gasket could be the whistle. If you do a search there is a discussion about the best place to get new shaft seals.

Also do the top engine cleaner if you haven't already -- it has to be the best overall tool to diagnose BLMs.

 

[MistaScott]

Originally posted by oehm

What about the Solenoid on top of the charcol canister? Should it hold vaccum too?

Thanks for the input guys!!

The canister will hold vac after the check valve, as will the EGR. Since you blocked the vac block and still have 150, you definitely have a problem elsewhere but could still have a vac issue. Try this test again after you find the other leak.

[Also, check valves keep boost pressure from blowing out the canister and EGR solenoids. They cannot be directly responsible for a vac leak or high BLM at idle since they do nothing at idle. If they fail, then you can blow your solenoids which CAN cause a vac leak. Just thought I would toss this in here for all you BLMers.]

 

[oehm]

Getting closer

I think that I may have isolated the problem. I read in another post that somebody used some rubber fuel hose to help detect vaccum leakes. They placed on end of the hose to their ear, and ran the other end of the hose around all areas of potential leaks. I tested this by removing one of the lines that goes to the cruise control. I ran the hose by the vaccum leak to get a sense of what the sound should sound like. I reattached the hose, and began searching. I found two small leaks on top of the vaccum block were the fastening screws hold it down. I also found vaccum leaks at various spots around the vaccum block. I could also hear small amounts of suction noise from both sides of the shaft seals. I also could here small amounts of suction from the front corners of the upper plenum (where it meets the power plate) I sprayed carb cleaner all around these areas in earlier hunts but had no real changes.

Even though the leaks that I have found above are not huge, is that enough to make my BLM's 150?

Also, were would you recomend getting all the new gaskets and seals for the plenum and powerplate? Would it help to use hylomar or another gaskets sealent when reinstalling all of this?
I know I am getting closer, hope this will take car of the problem.

Oh BTW, I have a bad check valve in the fuel pump. I plan on relpacing the pump once it arrives, but could this have any effect on the BLM's? My fuel pressure stays consitant once the vehicle is running, and the fuel pressure regulator is fine.

Thanks again for the input!!!!

 

[2QWIK4U]

I decided to check again today and noticed that it speeds up when spraying carb cleaner around the egr valvegasket area.Anyone know the part # for this gasket?
Also how do you get the harness to reach the MAF when you move it to the throttle body?