popping?

[shmed]

Ok heres a  stumper lol   the boys car   4.1   pulls great   at first...
what i mean start it up let it  get up to temps  go out make a couple   3-4   wot   blasts   zero knock  800 o2s    18 psi  91 oct chip  TT
ook   go get fuel  drive another  say 5 mins   pull of to the side road  stop..  floor it just as the boost starts  to come on   pop pop pop ok   zero on knock  gauge 
try again   this time stop  an slowly roll into full throttle same thing 1st ok  hits 2nd  starts to come into boost  pop pop pop??  think the wide band was reading 12ish when it happened  zero knock again,
this only seems to happen after its been driving for a little while


he's running 62 62 bb turbo   3 " dp  50  lb ins  hot wired an racetronix  pump   stock convertor can't recall the cam
anyideas

[Forzfed]

Need more info.  But I would start with the coil and change out the spark plugs since they are fairly cheap. 

[Scoobum]

The stock IC may be getting heat soaked after a run. 18 PSI on 91...would be pushing it...at least to me. Popping going INTO boost...is the fuel pressure rising with boost? A PL log would be extremely helpful. As Forzfed says...ohm the coils out...and fresh correct plugs if they aren't already in.

[shmed]

forgot to mention he's running a eastern front mount,
sorry all we have is a scan master an a wideband
ill swap out the coil pack an module i have a brand new new I've been keeping for my car
we  swapped out the plugs new ac 43s  gapped at a tight 30

[earlbrown]

Run a brand new hose from the turbo to the wastegate and zip tie or safety wire the hell out of it.

[Scoobum]

Do like Earl says...and use reinforced vacuum hose. Here's yours truly...being stupid...using regular vacuum hose between the port and the wastegate. The hose collapsed. Plug your ears boys and girls. I never did find the head gaskets...and the boost spiked so high it twisted the drivers side head. And this is the number one reason I use graphite head gaskets. They act like a fuse if something horribly goes wrong. Headgaskets are cheaper than replacing a rotating assembly.



https://www.youtube.com/watch?v=ZHtT8SfMXC4

[earlbrown]

I know for a fact that a leaky wastegate signal can overboost so fast, it can cause popping and backfireing WITHOUT showing on a boost gauge.


That's the first thing to change anytime you're chasing an odd potentially boost related issue.    You just can't tune around a leaky wastegate circuit.

[shmed]

ok  homed the coil pack got 11.6  on the first 2    then no reading on the last four?
so changed coil cack    checked it 11.6 on all 6
went for a ride pop pop pop
so off to the store for some hd hose an gonna try earls idea
fingers crossed

[earlbrown]

Might want to check your meter too.  If you have two pairs of coils reading open, you should have been running on two cylinders.  The car should have sounded like a 2 cylinder riding mower.

[Steve Wood]

Bad module is my guess

Sent from my LG-H810 using Tapatalk

[shmed]

update on popcorn machine...
ok new  module,  coil pack,  msd wires  an plugs.   still popping.
new vac line from turbo to  waste gate actuator,  i  bypassed  the boost solenoid,    still popping.
turned  down the boost as low as the hd  actuator will allow  I'm   hitting about 16-17.   still pop pop pop
tried different maf   ran worse  an still pop
could this be a sign of the flat tappet cam going south?
going to try to install the oem actuator  an lower  the boost even  more hoping its just boost or octane related,  yes i should drain the tank but its almost full
any other ideas 

[Steve Wood]

and the fuel pressure is behaving properly?

[Scoobum]

Still waiting to know if your fuel pressure is rising 1 for 1 with boost. Can you post your SM numbers with the engine warmed up.

[shmed]

yes fuel is running up along with the boost
are there any sm  numbers in particular or you just want a warmed up idle number?

[Scoobum]

Give us da' works...tho I'm curious what the BLM's are. CC's moving around okay?