Falls Flat at zero boost

[vkish]

Help! I've just completed entire rebuild to 1G DSM and while I've got it starting and idling sort of OK, this engine falls flat on it's a$$ when transferring from vacuum to boost. I think I'm missing something obvious that keeps me from progressing. Can anyone tell me what? I've done the diagnostics to the coil and resistor and all seems ok. I'm about to embark on checking the fuel pressure but for some reason, with the dramatic fall off / death I feel this has to be something else. A couple of notes: NO, I don't yet have a data logger. For some reason when we tried to hook one up, it wouldn't read any data. ( We're working on this ). The BOV appears to be leaking at low RPM. Is this normal? ( 1st foray into this kinda stuff. I miss my 1988 Z-28...: ( The timing is set at 5 degrees before TDC with connector grounded out. I'm really looking for some guidence as to where I should be pointing my nose......please?

 

[LaN-]

Help! I've just completed entire rebuild to 1G DSM and while I've got it starting and idling sort of OK, this engine falls flat on it's a$$ when transferring from vacuum to boost. I think I'm missing something obvious that keeps me from progressing. Can anyone tell me what? I've done the diagnostics to the coil and resistor and all seems ok. I'm about to embark on checking the fuel pressure but for some reason, with the dramatic fall off / death I feel this has to be something else. A couple of notes: NO, I don't yet have a data logger. For some reason when we tried to hook one up, it wouldn't read any data. ( We're working on this ). The BOV appears to be leaking at low RPM. Is this normal? ( 1st foray into this kinda stuff. I miss my 1988 Z-28...: ( The timing is set at 5 degrees before TDC with connector grounded out. I'm really looking for some guidence as to where I should be pointing my nose......please?

how do you know the bov is leaking at low rpms? if its a 1g bov do the dodge garage mod (google it).

Make sure your TPS is on tight.

 

[vkish]

I bought an aftermarket / release to atmosphere one and while idling you can feel realeased air onto the back of your hand. Thanx for responding.

 

[viprez586]

uh. you cant vent it to the atmosphere without a proper set up. Reconnect it please. venting your BOV will cause your MAS reading to be off(the ECU calculates the amount of air to be dumped back into the intake).
I've had people ask me if i have an aftermarket BOV and ive done the garage mod. it makes it louder modding your stock bov.
I'd suggest doing some reading up on modifications before you do them. its best to devise a plan. ie going to gm maf so you can vent your bov properly, or a 2g mas. Either one of these you'll need bigger injectors and a way to tune. invest your money into a good logger and a boost leak tester. fix all boost leaks before modding.

 

[schoffs4]

The bov will open at the slightest rev, an then close. It really sounds like you have major boost leak ck that first. Then vent bov back in {RUNS MUCH BETTER}

 

[Epic904]

he does have a maft setup on his car, and if he is using it as a blowthru he should be fine by venting it. you might just want to throw the stock parts on on it one by one to see if it fixes anything. if you upgraded all the parts at once it is going to be kind of hard to pinpoint what part isn't working right.

 

[vkish]

Thanx guys, I'm listening. Sounds like the vent to the air BOV thing isn't a good thing but, before I do any whole sale change backwards I feel I need to check a few things like, fuel pressure ( which is beginning to really get in my knickers ) then, I'll have to fabricate an adaptor of some sort to get my stock BOV back in for the piping has also increased to 2 1/2". What I don't understand about this concept is if I totally disable the BOV ( Remove / plug vacuum line ) it has no effect in regards to the problem. I'm not running it like just, conducted an impromptu test. You're all probably correct in saying that I've done too many mods at once but, I figured what better time than while doing the total engine rebuild after it blew up? ( Valve got pissed at the piston and shot it ! )

Hmmm, thinking and babbling on. While trying to make a template for a fuel pressure system check gauge, I removed the banjo fitting to the fuel filter and low and behold, there was no spray off. No pressure. I don't think this is supposed to be like this and obviously have a problemo somewhere. Maybe the fuel pressure regulator? It did sit empty for 8 months and possibly dried out ? Also, while I accept most all advice I can't help but wonder that even if there is boost leak, wouldn't the placement of the GM MAF very near to the intake inlet sort of minimize that effect in regards to the amount of loss of power for it's reading air flow at the latest point in the game? I'm in no way stating that it's not important rather that in regards to the original problem of this vehicle falling flat on its' face, it's probably not the apparent symptom. Agree?

 

[Defiant]

Fascinating.

Stop venting.

 

[HIGHPSI4]

Acts like a dog when going to boost.....check your knock sensor. If it is new play aroung with how tight it is in the block. If the knock sensor is giving the ECU a crappy reading the timing gets pulled and the unburned fuel gets dumped into the exhaust manifold. You need a logger and an EGT set up. The logger will see knock and the EGT gauge will show you the rising exhast temp.

 

[vkish]

Thanx. OK, I don't think it's a fuel pressure problem after all. After much to-do, I've checked it and the operating pressure is within the defined parameters listed. ( It took me quite a while to get all the pieces in place to make this check even though it's supposed to be easy. Groan ). Now, I'm leaning towards timing. I'll take your advice and examine the knock sensor. Do the diagnostics , etc. Have any idea as to how tight this thing is supposed to be? Even with a torque 'spec.', it'd be kinda' difficult since there's a stupid wire running through it.