Boost issue that goes away when restarted

[Efini_Dave]

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.

 

[jdmr_neil]

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.

 

[Efini_Dave]

Are these Vinton check valves readily available anywhere? Do I need to get a certain size?

 

[Jit]

Splutter and not going above 4K sounds like limp mode

 

[Efini_Dave]

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?

 

[Efini_Dave]

Also worth mentioning is when it's doing the issue I can apply the throttle ever so slightly and can slowly gain speed/revs

 

[Jit]

Limp mode generally means solenoid failed. Most likely within that black box

 

[Efini_Dave]

Seems like all I can buy is the entire black box and not the individual solenoids for it, and not cheap either.

 

[Jit]

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]

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.

 

[Efini_Dave]

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

 

[Efini_Dave]

Ok so I've just put my car back together and taken it for a spin, it pulled fantastic, but then after a while I started it's issue again, spluttering and not wanting to go above 4k, if I switch off and restart it quite often clears the problem however it doesn't pull anywhere near as good as before it gets fully up to temperature.

So assuming it works great when cold/warm could this be a solenoid issue? Breaking down when it gets hot.

All vac pipes look fine and I've replaced a few, going to change the easy check valves first and report back although surely a check valve would be fine hot or cold?

Anyway any pointers or advice please let me know.

Thanks.

 

[Jit]

Solenoid

 

[Adam]

If you start then rev it and key off and back on again before it shuts off it ignores limp mode. Works every time.

 

[Efini_Dave]

Took it for another spin today, everytime I drive it I get a new experience, pushed it abit further this time.

Pulled amazingly well then noticed after it got fully up to temperature a slightly different sound to it and the hks blow off makes a slightly different noise, none of the spluttering just slow to build boost on the primary turbo however come the second turbo and it's pulling how it should be again.

Have a friend at mazda so making enquiries about new solenoids and I might have a crack at renewing 1 or more of the solenoids within the blackbox. Awaiting on some new check valves to arrive too.

So it's something controlling the primary turbo that's giving me issues but seemingly only when hot.

 

[Adam]

Stock ecu? Pull the codes. Jump a couple of pins in the diagnostic box uner the bonnet and read count the flashes. Can’t remember the exact sequence. I think I used an led at the box to read the codes. Been a while.
I had the same issue as you only spooling the first turbo a quarter of the time. Mine was the charge control solenoid.
You can get the black box on rhdjapan for a few hundred quid. Or go non sequential for free.
If you are sticking with the twins I would replace them with Mac valves.

 

[jdmr_neil]

Davey where abouts NE are you, i don't mind having a look for you as many of us have played with twins (ahem) a few times

 

[Efini_Dave]

Yeh stock ECU, I'll have a read up on pulling codes and see what I get.

I wanna keep it sequential twins, I've only owned the car a few week so never got a proper feel of it yet.

Yeh seen the black box on rhd

Mac valves?

 

[Efini_Dave]

Davey where abouts NE are you, i don't mind having a look for you as many of us have played with twins (ahem) a few times

I am located near Darlington.

 

[Adam]

Mac valves are just solenoids. They are cheap and robust. Would be quite involved to do, there are write ups on t’internet somewhere. I would just go non sequential for now and save the pennies for a single turbo and save yourself the headache.