86'gn vacuum leak??

[SNAKE250R]

Last summer my 86'gn started a new problem with high bl #'s and eractic o2's.i checked for vacuum leaks with carb cleaner with no luck.i could not get my hands on a smoke machine so i decided to reseal the intake manifold.i just installed a new fel-pro gaskets on manifold and valve covers.i also resealed the plenum,throttle body,valve block and egr while checking vacuum hoses.i also installed new 30lb green stripe injectors while the manifold was off.(factory injectors would not hold pressure)
i just started the car today and thought i had fixed my problem because it now would idle cold unlike before but after it warmed up my scanmaster showed the eractic o2's like before.
Scanmaster readings hot are:
O2'#s 109 - 816
iac #s 26 - 30
af #s 05 - 06
l8 #s 35 - 42
int #s 125 - 136
bl #s 142 - 148
clt 160
ats 97
the car is mostly stock with a lt1 mass + translator,3" exhaust,gutted cat,9" k&n,adjustable gate & feul pressure reg.,hp feul pump + hot wire,poston thumb wheel chip.

 

[turbo nasty]

I would pull the rocker shafts and get a boost leak detector..one like this o r equiv...and use shop air to a few psi over what you normally run.

Intake Leak Pressure Tester

And psi the compressor inlet and spray everything down with soapy water. Best way to find the leaks. You'll probably be surprised at what you find leaking.

 

[SNAKE250R]

Thanks for the quick reply,this weekend i will pull vacuum lines off one at a time and plug them off the manifold and also try to psi the intake with rockers off.
When this all started i remember that i blew the vacuum line off at the map sensor where i teed into for boost gage,do you think that there is something else causeing it to go lean to rich.

 

[turbo nasty]

Leave all the lines hooked up dont plug anything....... you are trying to find leaks.

If you remove/plug/etc the lines then thats not mimicing the engine under boost and will not find the leaks.

Sounds like you replace EVERY single vac line on teh car and ty wrap the connections. After that till due a leak test.

Let the car sit over night some of the lifters will bled down and close the valve so you can do a leak test with eth rockers on but it wont be as good. It will still find leaks if they are decent size

 

[SNAKE250R]

I really appreciate all the help.i'm going to try and make a leak tester out of pvc only because i wont have the new tester for this long weekend.i'll leave the vac lines on but i may pull the rockers anyway only because this is starting to frustrate me.i've read that an exhaust leak can cause this also but am i right that it would have to be prior to the o2 sensor?would a very slight crack in the left header cause this?

 

[robertmee]

What do you mean 'erratic' o2's? Once the car warms up and switches from open loop to closed loop, the o2's will cycle between 100 and 800....If you have a powerlogger, it will look like a sine wave. Each time the O2 value crosses around 400 (I forget the exact #), it increments the # of cross counts on your scan master. This is what causes the cross count to count from 0 to 255 and repeat. So, in essence, for a chip that has closed loop idle (stock, extender, etc.) then the 'erratic' o2 is perfectly normal. If you have a TT chip which keeps idle in open loop all the time, then it is a different story.

The high BLM is most likely a vacuum leak. They can be sneaky to find and carb cleaner will only find leaks around the manifold, intake, injectors unless you are spraying all the vac lines everywhere (messy). I had this problem of higher BLMS and bought a inexpensive vac pump from Advanced. Found vacuum leaks everywhere. The vacuum accumulator ball at the front of the driver's side had a leak. My Vacuum switch on the back of the HVAC control had a leak. Once I corrected these, the BLMs came back down to the low 130's (never achieved the 128 nirvana).

 

[SNAKE250R]

Thanks for the info! I thought that the o2's should be steady in closed loop and i that she was hunting from lean to rich .sounds like i still have a vacuum leak somewere with my high bml's.did you check for leaks by using vac pump on each vac line and see if it would hold vacuum?do you agree with putting compressed air to the turbo inlet to find the leaks?

 

[GNVYUS 1]

Yah, stop using the 02 millivolt readings for anything other than WOT, or when they are dead or lazy telling you the 02 is dead.

Hunting for vacuum leaks on a GN that sees 26-30 IAC counts is a bit tough since it doesn't seem like it's leaking. You can do an actual boost leak test with a compressor but I have a feeling you're not going to hear or see anything special from it.

What's your fuel pressure (line off)?
It can easily be you have the wrong setting in the Translator or base fuel pressure.

 

[Morden]

How would you know what setting in the translator to use?
Also how can you tell what maf is on the car?
I have been chasing high Blm mine is around 143 some
Times 137.
Thanks

 

[SNAKE250R]

thanks for all the help.i will get my translator settings,base fuel and line off fuel pressure settings.i guess this is how you learn,but i'm not haveing any fun learning yet. thanks guys

 

[robertmee]

Thanks for the info! I thought that the o2's should be steady in closed loop and i that she was hunting from lean to rich .sounds like i still have a vacuum leak somewere with my high bml's.did you check for leaks by using vac pump on each vac line and see if it would hold vacuum?do you agree with putting compressed air to the turbo inlet to find the leaks?

Yep, I pulled each line off the manifold and started there. If the line held pressure with a vac pump then I went on to the next one. The ones with just a couple of things on them (fuel reg, PCV) are easy to check. The one with the HVAC, cruise and vac accumulator are more problematic. Best thing there is to start at the end and work your way back to the manifold. Check the acc ball, then the cruise, then the check valve, then the hvac lines, etc.

On the HVAC lines, depending on where you have the slider switch on your HVAC control that will direct the vac to different dampers under the dash for air routing. Best to check all those too as you don't want a leak to your defrost damper affecting performance. Just remember, as you pump these they will take a few pumps before you see any pressure as the damper has to move into position before raising vacuum.

 

[SNAKE250R]

I did some vac pump checking today and found the egr soleniod wont hold any vacuum.the egr valve will hold.my translator settings are base #5,wot #0,on on on off.feul pressure is at 28 and 35 with line off.i plugged the egr line but the blm # stayed at 144.i've got to do more checking this week with a new soleniod.

 

[Toady]

I went through this a few weeks ago and also found the EGR solenoid not holding vacuum. Since my chip doesn't use EGR, I blocked off the line.

That first check valve was also bad - which is prob. what blew out the solenoid, and if the 3-way valve hadn't held the HVAC might have blown out, too - so as long as you're this far into it, I'd suggest testing all the check valves as well. nos4gn/highway stars has them if you find a bad one.

 

[SNAKE250R]

i'm going to call today on a new egr soleniod and check valves from gm dealer.i've read other posts on the egr solenoid that you have to take the filter apart and put your finger over something to check it?should it hold vacuum without doing this?

 

[Razor]

I did some vac pump checking today and found the egr soleniod wont hold any vacuum.the egr valve will hold.my translator settings are base #5,wot #0,on on on off.feul pressure is at 28 and 35 with line off.i plugged the egr line but the blm # stayed at 144.i've got to do more checking this week with a new soleniod.

You just answered your own question. High blm means its adding fuel.

Your fuel pressure is too low for any aftermarket chip. You need to increase fuel pressure as its too lean. Typically most aftermarket chips call for 43-45 PSI line off. You have 35. Meaning your chasing your tail thinking its a vacuum leak.

 

[SNAKE250R]

thanks for the info!i can't remember when i was tuning the car why i set the fuel pressure where it is,maybe it was my thinking that the lower the pressure the leaner the mixture?i have read some posts recently about adjusting fuel pressure to adjust blm #'s to a certain point.i will adjust the fuel pressure regulator tonight and re-check my blm's.i still question my egr solenoid,should my egr solenoid hold vacuum with a hand pump?

 

[SNAKE250R]

i appreciate all the help! thanks guy's! i will keep every one updated.

 

[Razor]

thanks for the info!i can't remember when i was tuning the car why i set the fuel pressure where it is,maybe it was my thinking that the lower the pressure the leaner the mixture?i have read some posts recently about adjusting fuel pressure to adjust blm #'s to a certain point.i will adjust the fuel pressure regulator tonight and re-check my blm's.i still question my egr solenoid,should my egr solenoid hold vacuum with a hand pump?

What usually happens is the check valve by the regulator goes bad allowing boost to hit the solenoid and thats what kills it. There are two ports on the front and one under the cover with a foam filter on it. You need to plug the hose to the solenoid and see if the problem goes away.

Same the check valve on the hose going to the cannister goes bad allows boost to mess up the solenoid on top of it.

 

[SNAKE250R]

i'll check both check valves tonight along with egr solenoid.i'll raise my fuel pressure and see if blm's drop.

 

[SNAKE250R]

I found that the check valve to the egr solenoid was bad as well as the solenoid.i plugged the egr vacuum line and raised my fuel pressure to 43 with line off and 37 line on.i watched the blm's drop from 144 to 130 then came back to 144.i shut the car off,unplugged the ecm and restarted the car and the blm's stayed at 128 - 130 sometimes dropping to 122.the car runs good but surges a little at idle.i'm going to replace the egr soleniod and check valve.
My new scanmaster readings hot at idle are: (egr plugged)
af #05
l8 #33-38
int #128
blm #128-130
ats #88
tps #.44
iac #20-23
i dont think you could own a grandnational without a scan tool,this forum,and a little know how! Thanks guys!