Shad Laws

Hello-

I'm a newbie to the forum... hello, forum! :-)

I just purchased a '93 FD a few days ago. I'm not new to working / building engines by any means at all, but I am completely new to sequential turbocharging control systems.

Today I decided to do a full "look over" of fluids, filters, etc. on the engine. Of notable importance is that I replaced the air cleaner... it appeared to be a foam aftermarket deal and I replaced it with a stock-ish paper one that was much cleaner (and, as I know from previous experience, tends to filter a lot better).

Tonight, I noticed that I had a major loss of boost at high rpm. I do have a boost gauge. Boost kicks right up to where it should be down low, but from ~4500-7000rpm, it slowly dies off and ends up at next to nothing. Yikes.

I suspect that it's somewhere in the control system... the problem is too sudden and too clean/quiet to be a dead turbocharger. I've retraced my steps around the aircleaner, making sure that all the lines are still in place. I also did the best I could to peek around elsewhere looking for stray vacuum lines, and noticed one peculiarity: under the "pressure tank" (the black guy near the alternator) and the intake manifold is a cluster of metal nipples running transversely, facing the driver's side of the car. One of them has no hose! Furthermore, I can't find one nearby as a candidate. Is this a port to atmospheric pressure, or is this a problem?

I started the car in the driveway with the two ~1" hoses on the aircleaner that have brown plastic checkvalves on them removed. Revving it in the driveway, I noted that the hose with the checkvalve closest to the aircleaner was bypassing air like no other. Is this a problem?

Is there something else I could have inadvertently done? The only part of the engine I really stuck my hands into and moved stuff around is around the aircleaner. But, who knows...

Thanks in advance for your help!!!

Take care,

Mr rx-7 tt

iTrader: (5)

Check the vacuum hoses behind the alternator, around the black vacuum box on the intake plentum. Also, check the one way check valves (green) as they go bad and sometimes break.

SleepR1

I don't mean to be rude, but there are a number of existing threads on this particular symptom. Use the search function and type in, "secondary turbo problem", or "boost problems". You'll find a google full of threads explaining what the possible root causes, and how to fix them. There is a also a site that's very helpful. You'll find in one of those threads. As for the uncapped nipple. If you have a manual transmission FD3S, there is an unused nipple, which should be capped off. Local parts stores have small bypass caps to seal offthat open nipple.

FWIW, try this. Accelerate to 4500 rpm WOT, when you see the boost drop after 4500 rpm, lift off of the gas, and allow the gauge to drop to 20 inches Hg vacuum. Once you see 20 inches, immediately get back on the gas WOT. If you have full boost from 4500 rpm to redline, you have a vacuum leak, or are not creating a vacuum for your turbo control actuator/turbo control solenoid to function properly preventing the secondary turbo boost pressure to come online, or your TCA solenoid, TCA, CCA, or CRV or causing problems.

A list of common possible root causes are:

-bad vacuum chamber check valve
-bad connection to the turbo control actuator solenoid
-bad turbo control actuator solenoid (located under the extension manifold, commonly known as the upper intake manifold)
-bad turbo control solenoid (located on the solenoid rack)
-bad turbo turbo control actuator (unlikely, but a possibility)
-vacuum chamber full of oil
-leaking vacuum chamber

injen

i have the same damn prob. he does thats alot of work checking alllll that hose and im not haveing any luck will some one come look at it. j/k

BinaryRotary

[QUOTE][i] As for the uncapped nipple. If you have a manual transmission FD3S, there is an unused nipple, which should be capped off. Local parts stores have small bypass caps to seal offthat open nipple.


I think he is referring to the one at the front of the rack (commonly referred to as the "rat's nest") that is also unused in a manual FD, but it is not capped-off

Shad Laws

Hello-

First off, thanks guys for your responses! I've been busy today tearing apart a 220hp aircooled VW powertrain and selling off the pieces (i.e. selling off one toy to afford the other :-) ), so I haven't gotten a chance to troubleshoot further. Tomorrow, however, is another day...

I tried looking behind the alternator - that's where I found the uncapped metal line. Everything else *looks* okay. I have to go purchase another Mityvac to troubleshoot the check-valves to my liking (I had one, but sold it along with my shop). If they are dead, do I really need Mazda pieces, or will McMaster-Carr do fine?

No, you're not rude... no offense taken. I've been in your spot before on forums, so I understand what you're saying :-).

I tried using the searches and downloading the pdf-copied manuals even before I made my post. I have lots of stuff printed out to go through, too. I was just wondering if my particular case (most notably the air cleaner bit... although perhaps it's all a big coincidence and it has nothing to do with it) would strike a chord, that's all.

It is indeed a manual tranny. Getting a cap is a cinch.

By the time you read this, I'll probably have already done it :-). Thanks for the help! I'll report back here sometime tomorrow after a little more troubleshooting and a lot more reading.

I'll check 'em all :-).

[QUOTE]Originally posted by BinaryRotary

Quote:

[i] As for the uncapped nipple. If you have a manual transmission FD3S, there is an unused nipple, which should be capped off. Local parts stores have small bypass caps to seal offthat open nipple.

I think he is referring to the one at the front of the rack (commonly referred to as the "rat's nest") that is also unused in a manual FD, but it is not capped-off

It's the set of four right underneath what appears to be a small, filtered atmospheric vent.

FWIW, the nipple doesn't have any tell-tale signs on it that anything was covering it at any recent time in the past... it's all evenly-dirty and the inside has a thin layer of oxidation. I dunno if that means that it's been missing its cap for a long time or it never had one, but it didn't just fall off a day or two ago.

Thanks again, guys! Sorry to be such a newbie... <sigh>. I'll report back probably tomorrow night.

Take care,
Shad

Herblenny

iTrader: (13)

shad,

i had many many seq. turbo issues..
finally my car is running like a champ..
anyhow,

to check your one way valves (check valves).. all you have to do is blow them thru each end.. every simple.. if you can't blow thru.. you need to replace them..

Any one way valves should be fine.. I use T2 one way valves BNR supercar gave me..

Most secondary boost problem i have dealt with are from some sort of vacuum issue.. you are probably not building vac or loosing vacuum..

My 2nd turbo problem was one way valves.. I did like 3 vac jobs and it ended up being that.. so, my advice to you is to check all the one way valves..

PHIL

Shad Laws

True, but I'd prefer using a Mityvac. My mouth can do a red and green flag, but not a yellow flag... a slight leak and/or inability to maintain a high differential pressure can't be determined. It's a tool I should get anyway... and it keeps my lips cleaner :-).

Groovy... McMaster-Carr it is :-).

You are absolutely correct about vacuum... I did the test suggested by SleepR1 and, sure enough, if I get the revs high, then drop it into vacuum, then punch it, I get lotsa boost. It's not quite 10psi, but it's close enough to point at the problem (and a heck of a lot more than before!). I ended up having other shtuff to do this evening, but tomorrow afternoon hopefully I'll get a chance to troubleshoot it.

I figure that with a little reading and a little thinking, I can make this into a straightforward procedure... I think too much like a friggin' engineer (oh, wait, crap, I am one... sigh). :-)

G'nite,
Shad