No boost

[Nefarious21]

Could a cracked manifold cause no boost? My boost gauge goes from about 25ish in.Hg at idle and jumps as soon as the throttle is pushed down, when enough throttle is given the gauge will hit 6-7ish in.Hg and will slowly start to gain vacuum the higher the rpms go. It never reaches boost at all and is extremely slow especially at higher rpms, anything past 4k. wot is out of the question because it will bog like crazy. The waste gate actuator is new, everything else is stock other than replaced vacuum lines as far as i know. I traded a crx for this msp so i have no knowledge of prior conditions of the car. I am going to take it to the Mazda dealer so my friend can do a boost leak test using a smoke machine.

 

[Spiced MSP]

welcome to the forum. It will definitely affect your boost. Let us know what you find. What mods does the car have?

 

[tweety2300]

It should still build boost with a cracked manifold. Sounds like the hit or cold pipe popped off. Or the waste gate is toast

 

[CHIQLES]

check to see if the wga isnt stuck or come off...you can take the air line off and get a bicycle pump or what ever you have handy to pump pressure into the wga and see if it moves freely it should move foward under pressure and jump back without..
good luck

 

[Nefarious21]

All it has is a turbo timer, boost gauge, deleted cat and second O2 sensor, and the wga has been replaced because we thought that might have been the problem. I ran the car without the vacuum line on the actuator for a while with the same results. When I replaced the actuator i moved the waste gate arm around to make sure it wasn't stuck, it moved freely. I guess it could not be closing all the way, i'll have to take the whole thing out and check. My friend is going to weld the cracks on the exhaust manifold so I will have it apart and check out the waste gate.
All the pipes are where they should be.
What about the bypass valve?

 

[CHIQLES]

yes that could cause the problem as well if its bypassing air under pressure pluss you would get super rich..

 

[CHIQLES]

keep us posted on what you find when you take it apart..

 

[tweety2300]

Unless you bake it it will just crack around the welds

 

[Nefarious21]

Unless you bake it it will just crack around the welds

Yeah my friend has been welding exhaust manifolds for a while and has learned a few things, he said since it is turbo all the heat will eventually cause it to crack again, but i am only looking for a temp fixed until i save up enough money to buy a replacement.

I'll tear it apart as soon as i get my eclipse running which should be soon. I'll let you guys know what i find. If you got any other ideas throw them out there. I have some ic piping, fmic, and bov i have laying around so i am going to through that in there and see what happens.

 

[Nefarious21]

Finally an update on this thing. When i pulled the manifold off, the cracks went almost all the way around and even cracked into the o2 sensor hole!. I bought another manifold and it hits BOOST!!! But it seems kinda sluggish, maybe it's just me but something doesn't feel right. I'll keep digging

 

[tweety2300]

Reset the ecu

 

[Nefarious21]

Reset the ecu

I already did, I am going to check the spark plugs, what gap are you guys running?

 

[tweety2300]

.28-.32 is about right iirc

 

[jim9]

40-44 for NGk if you have, does it hit full boost after new manifold?

 

[Nefarious21]

Alright thanks guys, i'll check the gaps right now.

40-44 for NGk if you have, does it hit full boost after new manifold?

Yes it does

 

[Nefarious21]

Got NGKs and now I am getting the power I was expecting out of this car
It had champions gapped at .5 something almost .6!!