Boost issue that goes away when restarted

Oct 24, 2018
44
36
18
North East
Just bought an FD and it has in intermittent boost issue, when driving it would struggle to build speed and splutter, when in neutral it won't rev past 4k.

If I turn it off and restart it would quite often clear the issue and appear to drive fine although I've never driven an FD before so can't compare it.

I've read into it and quite often the "rats nest" is mentioned so thought I'd look into this so I've removed the top intake and given all the vac pipes a once over and nothing seems to be amis, I have the later series engine so has the "black box".

Any ideas what the issue could be? Anything else I can look at?

Thanks all.

Here's the car, it's a 96 NZ import.

IMG_20190314_170622.jpg
 

jdmr_neil

Well-known member
Jan 12, 2018
1,234
726
123
Northumberland
Sounds like a check valve is fucked. Either the pressure or vac tank isn't holding and leaking past the check. New viton ones are cheap to replace.
 
Oct 24, 2018
44
36
18
North East
Splutter and not going above 4K sounds like limp mode
Even if it clears itself when restating and could be fine for a good while? The engine has had a rebuild be Rxmotors less than 1k miles ago, I've not even given it the beans yet. What thing's could cause it to go into limp?
 

Jit

Moderator
Jan 7, 2018
480
276
73
London
You can take apart the box and replace solenoids individually. Youll first need to pull the fault codes off the ECU to identify which solenoid it is. A new Mazda black box is no guarantee of success; some have spent enough time on the shelf that the solenoids are stuck
 

Greg87

Member
Feb 7, 2018
52
18
18
31
Stubbington
Your issues sound like what I previously had.

It started every now and then, and a quick restart sorted it, but it eventually got worse and would take a few times to get it running properly.

In the end, it turned out to be the black solenoid box.
Had a working second hand one fitted by reworx and it sorted the issue out.
 
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Oct 24, 2018
44
36
18
North East
Your issues sound like what I previously had.

It started every now and then, and a quick restart sorted it, but it eventually got worse and would take a few times to get it running properly.

In the end, it turned out to be the black solenoid box.
Had a working second hand one fitted by reworx and it sorted the issue out.
Good to know, I think I am gunna put it all back together as vac pipes look fine, do some fault codes and see what I get and look to replacing either the whole black box unit or possibly a solenoid(s) and go from there.

Cheers