MontegoRx

Well, just like the title says, I ran that search on here. I came up with a TON of threads with those words (naturally) and couldn't really figure out my issue. I came across a similar issue, but the thread pretty much died without any conclusive answers. Now that that's out of the way.... here's my mods and question.

Mods: Stock with Koyo Radiator (yeah, not too impressive eh?)

Question: When I pull hard through first gear without redlining... probably about a 5500-6000 shift (I'm scared to redline first cause it ramps up so friggin fast), I shift to second, punch it to the floor and see about 1-2 psi. If I back off and punch it again, the boost will build up fairly normally. At first, I thought my boost line to the gauge was pinched in the pillar, but at 1-2 psi it feels like a Cavalier with 4 bad pistons could pass me. I'm pretty sure a pinched vac line to the gauge wouldn't throw me off that bad mentally, but I pulled it away from the pillar anyways for my mind's sake. Same thing, same numbers, same pecker shrinkage. I made 1-2 psi and felt like I missed 2nd and somehow hit 5th in the bottom left position.

Has anyone came across this problem with the 1-2 shift? Is there something stupid like a vac line that could do this? This problem is freaking me out, and I'm hoping it's something simple. I've made a few 3rd gear passes from about 2500-3000k starts and I swear if it was possible, I'd have an affair with my car's third gear. It's just this stupid 1-2 shift thing that's really getting to me. Anyone have ideas?

dgeesaman

iTrader: (7)

It's a bad check valve going to the vacuum chamber. The turbos need a vacuum source to route the boost properly, and if the valve is bad the act of boosting empties the vacuum.

Start by replacing the black/green check valve in the green lines of this illustration:
http://davidgeesaman.com/rx7/93vacho...sequential.jpg
If you can't get a spare easily, trade it with one of the green/white ones nearby.

Dave

MontegoRx

Well for troubleshooting purposes, would it be safe to pick any of them and try it? Which would be the 'safest' to swap over if I'm assuming I'm replacing it with a failed one for a short run?

Chadwick

iTrader: (12)

Check or replace your turbo control solenoid. It is the one that is mounted to the underside your upper intack manifold.

dgeesaman

iTrader: (7)

The white/green ones feed the emissions systems (EGR, DTC, etc). I think they're all pretty safe to temporarily swap with.

Dave

MontegoRx

That looks to be quite a job to replace, and I can only assume it would be a pretty pricey part. Before I get into that, I think I'll give the check valve a shot, but would you mind giving me some of the reasoning behind condemning that solenoid?

dgeesaman

iTrader: (7)

That solenoid runs about like all the others - $60/ea if new from Mazda.

You do have to remove the UIM to replace the one mounted on the ACV, so it take an hour or so. There is another, equally failure-prone turbo control solenoid in the rats nest rack. That one take a little more time to change since you need (IMO) remove the coils as well.

These two solenoids are the first to go in most cases, and replacing them relieves many hard-to-diagnose general boost problems. If you're fussy, you can tee into the line leading from the solenoid to the actuator and watch with your boost gauge if they are outputting the proper vac/pressure at the proper time.

The reason why I didn't recommend them yet is because your symptoms are classic signs of a bad vacuum check valve, and changing check valves is simpler and faster. I can't guarantee it's issue, but IMO it's more likely than the solenoids.

Dave

MontegoRx

Thanks a ton, I'm gonna go pull the check valve and see what I can find. If I think it might be an issue I'll warm her up and take it for a hot lap before the rain comes.

MontegoRx

well I think I found the right check valve. The one I pulled is working correctly as far as me blowing through it. It makes a strange sound and seems fairly restrictive when blowing through in the correct direction. not sure if that's right.

I also made a full boost run in second gear and saw a beautiful 10 and then 4 to redline on the boost gauge. This thing's really freaking me out since it seemed to running perfectly a couple days back. Not sure what I'm looking for now, but I also have some fluid leaking at the hose connecting to the top of the Y-Pipe. Looks like I'm in for a bit of wrenching, so I'm glad I don't use the 7 as a DD.

MontegoRx

does anyone have any other ideas? I'm trying to get this thing solved before the weather starts getting too bad (even though it's been 60° in Early Feb), and hopefully figure out why the turbos are coughing oil after I figure out why they're not boosting. Since they're making consistent boost in one gear alone, and the problem is only when shifting between gears, I'm still stuck!

dgeesaman

iTrader: (7)

The air flowing thru the y-pipe often carries a bit of oil - so a boost leak there could spray oil mist at the leak. So if this is the case, zip-tie that leaky hose or replace it altogether with better hose (the parts store has basic rubber vacuum hose line that is fine for a repair). This type of intermittent leak could also contribute to your boost problem(s?).

Also, mouth pressure/suction may or may not be enough to find the bad valve. A vacuum pump will test it very nicely, if you can borrow/rent one.

If you get some spare check valves, get 2. Then replace both of the black/green valves shown on that diagram.

Dave

MontegoRx

OK, after working a good bit on the car when I can, I figure I might as well replace the solenoid. Where can I find a new one? Does anyone know a part number?

edit: Oh yeah, I need new check valves too.... any leads on those?

dgeesaman

iTrader: (7)

I would not buy a stock check valve since they are crazy expensive. DaleClark has a source for good check valves.

There are two turbo control solenoids, both of which are important and like to fail. The turbo control solenoid on the ACV is good to do, but if you can get into the rats nest, also replace the turbo control solenoid in there.

Dave

mazda6girl

yeah i already have the manifold, alternator and all the small junk pulled out. I'm not too sure of the history of the car/engine. It came with some good documentation, but i'm the type that would rather replace parts with new/upgraded parts rather than spend nearly as much money to get equipment to test what's in it and then realize it's failed.

Eventually I'll probably get around to testing the racks, and if not, I'll end up selling them on here for the price of shipping, but for now, I figure I might as well just replace what i can with new parts so that when i button it up, I know it's going to run. Dgeesaman, thanks a ton for the info.

edit: forgot I was logged in on my wife's sn

dgeesaman

iTrader: (7)

If you choose to replace solenoids, I would replace both turbo controls, charge control, and charge relief. It'll be 4*$60, but your turbo system will run without major issue for quite some time.

If you also change the hoses and check valves, you'll be in very, very good shape. I'm not cruel enough to jinx you and say you'll be problem free, but you'll be way ahead of the game.

Dave

MontegoRx

For the purposes of saving a little cash, I think I'm just going to swap the two solenoids you mentioned earlier. Just to make sure I'm getting the correct parts, in the file you posted earlier, I'll be getting PN N390-18-741 and N3A1-18-741, correct? I guess I'll try to get in touch with DaleClark and get new check valves also. I have one Green/white broken and a Green/white that I believe is failed. Hopefully I can get the thing running pretty soon.

dgeesaman

iTrader: (7)

Those are the parts.

The check valves are equally important - make sure they're working well too.

Dave