Popping off vacuum lines

[Bowtie Mafia]

So my car was working fine Saturday morning, I changed the IAC Saturday afternoon and drove home from a friend's place. On the drive home my car ('87 GN) ran terribly. At 10 psi boost the car starts popping, almost like a backfire and my scan master shows 10 degrees KR. Sometimes it works normally and I can get to 20 psi boost, but the whole car surges before it pops again. I have blown vacuum lines off the vacuum block on the throttle body once and I also blew the hose off the outlet of my intercooler. I am totally at a loss. I don't see any visible connections loose. Any help is appreciated.

 

[Chuck Leeper]

Should you continue w/ the WFO operation, you may blow the FPR hose off, and find yourself changing head gaskets...........If you are lucky.
Lean pop.....
Change out ALL vac hoses, and zip tie them.

 

[Bowtie Mafia]

So a bad vacuum line somewhere would cause those problems?

 

[Bowtie Mafia]

I just replaced the vacuum hoses and the problem is still there.

 

[krom]

Put old IAC back on and see what happens. Check plugs and ohm wires.

 

[Chuck Leeper]

So a bad vacuum line somewhere would cause those problems?

Absolutely. Pop the FPR hose off, and the fuel pressure, will not rise, causing the lean backfire.

Before we make any more SWAGs, I suggest you post up some scan tool readings, fuel pressure, etc. Also post up the modifications that are on the car. You do have such info, right??
If not, STAY off the throttle until you do. Continuing to "lean pop" it, will end up w/ more posts asking about head gaskets, knocking, etc.

 

[highboostgn]

So my car was working fine Saturday morning, I changed the IAC Saturday afternoon and drove home from a friend's place. On the drive home my car ('87 GN) ran terribly. At 10 psi boost the car starts popping, almost like a backfire and my scan master shows 10 degrees KR. Sometimes it works normally and I can get to 20 psi boost, but the whole car surges before it pops again. I have blown vacuum lines off the vacuum block on the throttle body once and I also blew the hose off the outlet of my intercooler. I am totally at a loss. I don't see any visible connections loose. Any help is appreciated.

after seeing 10 degrees of knock at 10psi why in the world would you take it to 20psi??!!

 

[highboostgn]

Here you go. http://www.cometic.com/automotive-gaskets.aspx

 

[Bowtie Mafia]

Is been a consistent problem through two iac sensors. I have asked a knowledgeable friend, he was wondering about my coil pack. I need to go get that tested today

 

[Bowtie Mafia]

Whenever I saw any knock I got off throttle. My casper's knock gauge didn't read any knock and my scan master didn't show any knock, that's the only time I've taken it to 20. The 10 degrees KR was while in park. I'll get mods on soon, sorry

 

[highboostgn]

Whenever I saw any knock I got off throttle. My casper's knock gauge didn't read any knock and my scan master didn't show any knock, that's the only time I've taken it to 20. The 10 degrees KR was while in park. I'll get mods on soon, sorry

10 degrees of knock in park?? Maybe your knock sensor is shot

 

[Bowtie Mafia]

I turned the fuel pursue up to 45 psi with the vacuum off and the problem is still there. Is there a way to test for a bad knock sensor?

 

[Chuck Leeper]

First, check the torque on it...14#/ft is the spec. Too tite, and it can give false knok....