Just finished working on a friends rx-7, it has the strangest boost problem.

You get no boost until 4500rpm, and then it kicks in strong and boosts to up to 14 psi.

I have checked the CCV and it passes the KOKO test, i.e. it pulls in when you switch the ignition on.

I checked to see if the wastegate control and turbo precontrol solenoids had been swapped, even swapped the electrical connections and that made no difference.

Both these solenoids are working fine, they hold pressure/vacuum until 12v is applied.

I looked under the car, the rods for the turbo control and turbo pre-control actuators are attached, they can be moved by use of a screwdriver as a lever.

I know there are a million boost threads, and believe me I have searched and tried what tests I have read about.

Anyone got any ideas of the next things to test?

Richard

 

well it is some sort of wastegate problem. Something is happening somewhere with the wastegate since that would control and create the problem you are having, but I could be wrong whoe knows. Did you check all of your vacuum lines to see if something was accidentaly switched or something is being crimped or isn't conected? I would say to look for that or possible leaks. That's where the problem would be I would think.

 

so he put a large single in... ?

Maybe the primary is shot and when it goes to the secondary (at 4500 rpm) it gets boost again.
But hopefully not.

 

that could be it too, but its a vacuum problem now that I think about it. I had the same problem when I first got my car 2 years ago. I took it to the shop and had them do silicone vacuum job and it worked just fine after that. So that's what its gotta be.

 

14 psi?! what mods are we talking about on the car?

-bill

 

Thanks guys,

My feeling is that it is a vacuum, or tubing problem somewhere.

The car has only just recently come back from the shop, where it had a 'full' service which took a month !!

It came back sick as a dog, the coupler from the y-pipe was loose and it was losing all boost. Last night I noticed the check valve to the MAP sensor was on the wrong way round, I tested it, found it working and put it back the right way, but it made no difference to the general running of the car.

The 'shop' have also been into the rats nest, because plenty of the original black pipes have been replaced with blue silicone, so it may well be that one has split or one of the solenoids isn't working any more.

I guess the next job is to remove the UIM and go through everything with a fine tooth comb, just hoped I could avoid that experience.

Mods, I haven't a clue, it looks like a basic induction kit upgrade and a back box, but other than that we don't know as it was an import from Japan.

I am convinced it has an inlet manifold leak too, it idles at 1200rpm (much higher than mine), and when restarted the idle will hunt for 20 seconds or so.

Thanks for your help, I have a feeling this is going to take some finding.

Cheers,

Richard

 

heh it might be a bad a non-seq coversion but nothing double clutching can't fix

 

I had a similar problem with my car. How ever it was the opposite of what u are haveing to deal with. Well my car would get boost of the primary and loost all bost at the transition. Upon trouble shooting with a friend it was found out to be a bad silionoid. He was able to switch it from no boost from the primary turbo and only boost under the secondary at the 4500 transition point. I do not know what silionoid it is, because after i was told what the problem was we opted to go non seq on my car. I dont know if this will help but i hope it does.

 

There is another mode of the CCV. The line that goes from the back half of the Y-pipe, through the LIM, to the CCV solinoid. Then the solinoid connects back through the rats nest to through the LIM to the CCV. The KOKO only tests the operation of the CCV under stored vacuum. Tee the boost gauge into the line on the CCV from the LIM. That is the return line from the CCV solinoid. Start the car and see. If it has vacuum there is a problem it should be about 0. The CCV hooks to the solinoid on one side and the primary boost on the other. It opens when it sees equal pressure/vacuum on each side. So if someone hooked the connections up wrong it will open when the car is running, but not off.

 

So, would that mean I would see it pull in when the ignition is turned on, and then see it move when the engine is started?

Presumably it should only move when you hit 4500rpm?

Just a note to anyone who has responded, thanks guys your help is appreciated.

Richard

 

I agree, I had this same exact problem on my old car and it started after I picked it up from the shop that did a vacuum hose job. I never figured it out though because the car got stolen before it got fixed. IMO, it is a misplaced vacuum hose. Good luck.

-Kevin

 

I have a couple things you could try... These are what Damian has had me do when I've had no primary but full secondary.

#1) Take a length of wire or large-ish zip-tie and hard-wire the CCV actuator in the pulled in (CCV shut) position. Take the car out and go wot from 1500-4000 rpm in 2nd or 3rd and see what you get for boost. Do not take the car over 4500 since the secondary boost will have nowhere to go with the CCV wired shut.

If you get proper boost, it is likely something with the CCV lines or solenoid, or your vaccuum tank/lines/check valve. The boost is being generated, however since the CCV is open it escapes back toward the secondary and out the CRV. In my case I found a nipple on the CCV solenoid that was broken off causing the CCV to be open all the time. I fixed that and was back to full boost.

#2) With the car on and idling look at the TCA arm from under the car. You should be able to jack the passenger side up and see it near the bottom of the Turbos. If it is pulled in then it is seeing vacuum when it shouldn't and the TCV will be open, allowing excess exhaust to get to the secondary, which creates boost which is promptly vented out the open CRV under 4500 rpm. If you turn the car off and remove the hose from the vac chamber then the TCA arm will move back out.

This was what my car was doing last night. The primary was only seeing minimal exhaust until the transition because my TC Solenoid was stuck open, so the TCV was nearly wide open. Since the secondary had less restriction it was producing tons of boost and venting it out the crv making a fair amount of noise (I have the crv vented to the bay). I was only producing a max of 1-1.5 psi of boost at the manifold until 4500 rpm at which point I was getting full boost.

Someone correct me if I've said something wrong here.

Thanks to Damian for helping me figure this all out.

 

Thanks GooRoo,

Those sound like excellent diagnostic methods.

Next time I have another go at sorting this out, I will try both of these and see what happens.

It seems very logical that the problem is one of the following:

1). CCV is opening before 4500 rpm, even though it shouldn't

2). TCA is opening, and venting the boost

3). The primary turbo is goosed, but I doubt that and hope for my friends sake that it isn't.

Unfortunately all of this has reinforced my distrust of 'shops' when it comes to these cars and will keep on looking after my car by myself.

Thanks,

Richard

 

Yep. I know how that goes.... When I first got the car 2.5 years ago I took it to a dealer to get a coolant line replaced. $1500 later I had the car back, and it now had boost problems and of course still had a coolant leak. Never again unless it's a RX7 specialty shop. Of course I'm spoiled since Damian and a whole host of other knowledgable FD people are 20 minutes or less away.

I'll be interested to see what you find out.

 

just a brief add...

if you are getting reasonably sustained 14 psi boost after crossover your primary turbo is of course working. the motor won't do 14 sustained psi after 4500 on one turbo. a wastegate/actuation system problem relating to the primary turbo. you probably already know that. do post what you find when it gets fixed.

howard coleman