Hi Guys,

Im a total noob with turbo motors and have searched and found a lot of stuff that I dont understand at all...I have an Apexi boost guage that up until now always showed 4 notches of Vacuum reading...suddenly today it only reads two ie half the vacuum that I had up until now at idle!

I have just managed to fix a nightmare of a retractor headlight problem in which I posted all my findings and the solution also...and now this so soon after!

I would really appreciate it if someone could point me to a few places under the hood that a Vacuum Hose could have popped off. I think this will be the problem as the car was fine yesterday and has not been driven hard at all since (very sudden problem) so I dont think that it would be anything too severe.

The car seems to still boost on primary and also secondary..is this possible with the reduced Vacuum reading.

As I said the vac reading seems to be exactly half of what it was up until today so could this narrow down the possible culprits.

Im really sorry for my ignorance in boost/turbo/vacuum issues and I am totally reliant on advice from you knowledgeable guys as I live in Ireland and there is nobody that I can go to with this issue!!

The car is a JDM model and is standard except for HKS Induction, and Zigen exhaust. afaik

Just wanted to take this oppertunity to thank you all for the information that I have put to good use so far in my FD ownership and prior to buying!

 

By 4 notches I mean 20psi vacuum at idle and now today its only 10psi vacuum at idle which is exactly half!

Better way to describe it me thinks!!

 

Double-check your units. I don't think 20 psi of vacuum is physically possible. You're probably talking about 20 inches of mercury (inHg), which is about 10 psi. If you suspect a vacuum leak, try spraying some carb cleaner around the various hoses and vacuum lines in the engine bay: if the carb cleaner gets sucked into the engine, it will cause the RPMs to jump a little.


For reference, my car makes about 9 psi vacuum at idle.

 

You need to be careful that your idle hasn't changed. It doesn't take much to affect the vacuum reading at idle. A drop in idle speed of as little as 200 rpm can drop your vacuum from a "healthy" 18-20 inHg to a "omigosh my engine's blown" 14-12 inHg.

 

Yeah you guys are right it is 20inhg that I was reading until yesterday, and it was rock solid too, never any deviation.

My idle rev is solid also, normally at 650-700rpm!! This hasnt changed.

Is the drop in idle vacuum a symptom of a blown engine?? It certainly doesnt feel like its blown as it still drives very smoothly!!

You have me shitting bricks now Kento!

Where exactly can I get at the hosing attached to the turbos (from engine bay or undernath the car?)
I really need to eliminate a leaky/popped of vacuum hose before I start to panic!!

Can anyone give me a little noob guide to checking the hoses??

 

Sorry, I meant the expressions in jest. I'm just saying that a very small drop in idle can result in a major drop in vacuum that can have people wondering if their engine's blown, when in fact it's simply the idle speed.

An idle speed of "650-700" rpm is a bit low, and it would make the vacuum reading even more sensitive to actual idle speed. It should also be noted that if you had a vacuum leak somewhere in the intake tract, your idle would more likely rise rather than drop.

 

Any chance of that noob guide to checking vacuum hoses??

That is, where they are and how to get at them!!

 

Had a look around the engine bay for leaks earlier...didnt get in at the rats nest but i noticed that the "Y" pipe coupler is a little loose or has a little play wher it attaches to the turbos and where it attaches to the intercooler piping.(I presume there are two clamps on the coupler, one at each end, am I right to presume this??)

Where it attaches to the turbo i couldnt visually check but i definately know that there was play upward and downwards!

Also, where the Y pipe coupler attaches to the intercooler piping I could visually see play and a little gap through which I could see some oil residue (normal amount I reckon, not much)!

Could the above cause the symptoms I have described in my first post??

 

is your gauge electric or a manual one?

Trev

 

Hey supra,

Its a manual!

 

Okay, just checking. I would go ahead and tighten all of your coupler clamps.

Trev

 

It has two electrical wires going into the back of it and the hose also. I dont know how it is wired as it was there when I bought the car but the readings alwasy seemed accurate to me!
The gauge does not light up! So i dont know if wires are for the backlight or something else!

All I know is that it now reads 10-11 hg vacuum at idle and previously it read exactly 20 hg!!!

 

What would you think the wires are for?? And what difference would it have made??

Sorry for stupid Q's!!

 

Can anyone answer the above, i would really appreciate it!

 

Yes. Even if it isn't, you need to have all couplers and clamps tight, regardless.

 

Yeah thanks Kento, would have done the job regardless, but I suppose im just looking for reassurance that this could be the cause of the problem...im a little nervous about it to say the least!!

Could driving it like that have caused any damage??

 

If you go to this website and click on "Download vacuum hose diagram," you will download a schematic of all the vacuum hoses in an FD. (There are 68 altogether; I replaced them all and kept count.) Hopefully that will give you a clue as to the almost limitless possibilities...

 

Thanks for the links they are great!

That is a right bastard of a job...im not bad at doing things for myself but that looks like a bit of a nightmare!!

Any of you guys done this yourselves? And I would be afraid that even after doing all this the problem would still be there (Murphys Law)

By the way I like thr sarchasm, very nice!!

 

In all likelihood, no.

Replacing the vacuum hoses in the rats nest is a tedious and complicated job, especially for a newb who's never been in there and disassembled engine components before. I see too many guys diving in there thinking they've got it handled, then end up mis-connecting one or two hoses when reassembling everything, or not ensuring each hose is tightly connected, or (one of the more common problems with this job) breaking off the plastic nipple on one of the solenoids due to heat and age/hamfisted removal, and not having a replacement on hand, etc.

I strongly recommend that if you do decide to replace the vacuum hoses, that you do a lot of research first, and think the job through before you ever begin to remove anything.

 

Yeah point taken..I read an awful lot of info on it last night and was completely blown away by the complexity of it.

I would also be very worried about breaking nipples in the process as that seems common enough.

I am hoping that I will be able to solve my immediate problem by fixing the Y coupler and maybe 1 other vacuum hose in the rats nest....then as time goes by accumulate the parts and knowledge/skill to attempt the complete overhaul.

But I will do it at some stage, of that I am certain!!