Hi,

Need some help if anyone knows right off-hand. I just installed a clean, low mileage JDM engine in a 1993 Automatic RX-7.

The car idles perfect, no vibrations, runs smooth, BUT the boost pattern is 10-5-5. It drops off at transition when the secondary starts to spool up. Runs solid when boosting also.

Hearing no noises.

Stock JDM motor with stock USDM auto computer.

Any help would be great. I believe it is going to be something pretty simple.

Thanks,
Tim

 

try this
http://www.fd3s.net/boost_problems.html

 

Anything that branches to/from the pressure tank. Make sure that check valve flows toward the tank.

Also make sure the two lines from the turbo control solenoids aren't crossed.

It might be worth doing the koko test on that link to see if the CCA and TCA are working normally.

Dave

 

OK,

Here we go. I replaced the rubber hoses connecting the turbo Y-Pipe and intercooler with new silicone hoses. The old ones were hard and I was not sure they were sealing or leaking. With this said, the below statements are identical as before changing the hoses.

Now, I started the boost test referred to by BillM's link.

1. This ECU is not displaying any codes, but the other ECU turns the light on and throws the missing component codes (No EGR, AWS, Relief 2). But otherwise, the engine runs fine.

2. Engine at operating temperature and the double throttle vacuum line is not sucking.

3. Engine vacuum at idle is at 14 on my gage, (gage not very accurate).

4. Checked no load operation of turbos by briefly accelerating engine WOT in neutral. Supposed to get +4 PSI but only can obtain +0 psi. The precontrol rod does not move.

Stopped here and did not do the KOKO because I need another set of eyes.

Does anyone know what would prevent my turbo from boosting +4 psi at WOT no load? Could it be the ECU and the missing USDM components on the JDM motor?

When I let the throttle off, you can see the intercooler accordian hoses expanding. When I run the car, I am getting 10 psi of boost starting at 2500rpm.

 

Make sure your pre-control and wastegate solenoid electrical plugs aren't swapped. Mine were and I had the same boost pattern.

 

I get a weird boost pattern in first and second gear... 10-8-5 but every other gear is fine, 10-8-10...

 

make sure the line running from your wg actuator to the solenoid is not cracked or loose...this will cause the WG actuator to bleed pressure on the opposite side causing it to open way faster

 

Actually that will cause too much boost since it won't keep enough pressure in the wastegate actuator to open it.

Dave

 

I'll check, but I never had them off. The engine arrived as pulled from the JDM car and I installed it the same way.

Tim

 

OK,

Started to troubleshoot a bit today. Found the following:

The electronics to the wastegate and precontrol actuators are working correctly. I verified that the wiring is on the correct solenoids. I also verified the correct Ohms for the solenoids. I checked voltage while running in Neutral WOT. The Wastegate turns on at about 3k and up. The Pre-control turns on during transition, then off after 4.5k RPM.

I manually checked each of the control rods. The wastegate and precontrol rods move when I add pressure to the air line.

I checked the pressure tank. I pulled off the hose after about 4 minutes and pressure blowing out was heard.

Charge Control valve working properly when WOT. Can visually see it opening about 4.5k RPM.

I think that is all I checked. Any comments on why my boost is at 0psi WOT in neutral?????

Tim

 

Try this link, it does an excellent job of explaining and troubleshooting the twin turbo system.

http://www.autosportracetech.com/RX-7/rx7stuff.htm

 

me also but i believe thats because my secondary turbo is going bad, steve kan even said so.. first and second gear dont want to go full boost most of the time but it works sometimes.. every other gear is fine

 

OK,

I have reviewed this information. Nowhere does it show anything about the pressure at WOT in neutral. The other website I looked at stated that you need to have 4psi boost. Again, when running the car, the boost is normal on the primary turbo up to transition. Everything else seems to be normal, then it drops off to 5psi at transition.

Anyone else have any ideas?

Tim

 

You might wanna just try switching the pre-control and wastegate solenoids anyway... I thought mine were fine as well before.. Everything checked out, as well as the factory dots matching eachother!! But I switched them, and it fixed my 10-5-5 pattern...

 

They are working electronically as described in the threads posted above and the factory shop manual. Also, the wiring is color coded correctly for each one. It is highly unlikely that this is the problem, but will switch them for peace of mind.

My thoughts are that there has to be a leak in boost pressure from the turbo to the intake to only give me the 0psi boost reading that I am currently getting. With the air cleaner off, there is a large woosh volume of air that appears to be pretty high pressure leaving the Blow off valves when this happens.

Tim

 

I was just recently experiencing the exact same problem as you are in my '93 automatic FD..I was getting a 10-5-5 boost pattern..So I decided to change out the stock cat with 121k miles on it because I thought it was clogged..Now i'm boosting 10-4-10..I've been following this thread intently for some tips since you were having the same problem as me..There is my input,although it isn't much and i'm still having problems..

 

I know the catalytic converter is good. The precat was removed and the JDM downpipe was used. The cat looked very new (later found out they were replaced under warranty), so I believe it is fine. I did, however, install a generic cheapo muffler. It is clamped on, so I am going to remove it and see if that makes a difference.

I am going to try that and also try to get a better pressure reading coming off of the turbo instead of at the intake to see if there is a difference in reading.

Thanks,
Tim

 

Today I checked the following:

Turbo Control Actuator: Checked the actuator mechanically and it moves freely when pressure added to backside or vacuum added to front side.

Removed intake to turbo pipes: Turbos appear to be very clean. Both turbos spin when throttle is pressed (second starts to spin at 3.5k for transition).

Removed intake. At WOT, still getting 0psi without turbos hooked to the intake. Turbo pressure coming through the intercooler is strong. Put my gage hose inside the hose going to the intake, put my hand over it and revved the throttle, pressure readings around 4-5psi before it blew my hand off the hose.

Still at 0 psi WOT in neutral.

Left air filter and air intake hoses off of car.

Took car for a drive, first few runs at 10-5-5
Switched Pre-control and Wastegate solenoids. Now this is where I am unsure. I drove it one pass and not at WOT, but I thought I did see 7psi above 4500rpm. I turned around and next pass was 10-5-5 again. I went to switch them back and the one pressure hose to the pressure tank was blown off. I left wiring backwards, installed pressure hose and went for another pass. 10-5-5 again. Switched the wires and again the pass was 10-5-5 Not sure if I was seeing the wrong RPM's or not.

Decided to let the car cool down since it is a hot day.

While driving home, noticed a noise just before the turbo kicks in at 2500rpm. That noise sounds like one of the actuators moving, then boost kicks in immediately going up to 10 psi for the first turbo. I thought this was a bit unusual.


New questions: (remember, this is an automatic, not 5 speed)

Should there be an increasing and steady throttle response from a rolling start until the turbo boost starts kicking in? Mine seems to be at 2500rpm and BAM it is there all at once.

The boost pressure seems like the turbo wastegate opens up at transition and the boost is limited to 5psi from that point on. If I remove the wastegate solenoid, what damage could I do on a WOT pass????

Tim

 

I decided to change out the ECU and at the same time, changed out the wastegate and turbo precontrol solenoids with another used set.

After changing these out, took the car for a run.

First time I did a boost run, it went to 10 psi, then down to about 5, then back up above 7psi and pulled hard without full throttle.

Thought it was going to be right. Did the boost test in 2nd gear (auto on hold) and boost went up to a solid 10, then back to 5 again.

Then I decided to do a boost test in Drive. This time focused on the tach and the boost separately. Each run started boost at 2500 rpm with boost climbing quickly to a solid 10 psi. At exactly 4250rpm each time, boost dropped off quickly to 3psi, then climbed back to 5psi by 4500rpm and all the way to redline, it stayed around 5 psi.

I thought it was occurring at the beginning of the prespool process, but now am convinced it is dropping off at the end of the prespool process when the boost is combined.

Not sure why it boosted above 5 after this on the first try.

Any comments, questions, etc would be appreciated.

Tim

 

Tim: a couple questions

- did you manage to run a KOKO test yet? Since you're not getting boost in neutral you'll have to get out on the road for a moment first to charge the pneumatic tanks.

- were these solenoids from the transplant engine? In other words, is this something that just started to go wrong, or is it possible these solenoids and stuff had a problem all along that you're now trying to weed out?

I'm thinking it may be worthwhile to see if big things like the TCA are operating. The KOKO is one method, but another is to tee your boost gauge into each line running to the TCA to observe the results. Steve Wynveen wrote a nice sequence about this that's still on fd3s.net.

Dave

 

Dave,

I was just reading a post that you were answering about 2 years back and it referenced tee-ing into some items.

As far as the motor, it is a totally stock JDM 1992 motor from an auto tranny car. The turbos look clean as new. Rubber hoses and wiring harness soft. When I removed the spark plugs, there was NO dirt on the threads. My guess is that this motor was about 15k miles motor tops.

No modifications that I can see other than the JDM stock downpipe instead of precat. Transplanted into my car using the JDM harness. I have some spare parts (78K miles auto car I used to have) around that I have been swapping out. Already changed both the Air Bypass Valve and Charge Relief Valve with no different results.
Already changed both Wastegate and Turbo Precontrol solenoids with no apparent change in results.
I hooked wires up to both these solenoids along with a volt meter and during a KOKO, both solenoids fire. Assuming that I would have pressure and vacuum, the rods should be moving, but I cannot check by myself. I know the pressure chamber is holding pressure because I hear it hiss out when I pull the hose off.

I will try again tomorrow afternoon or Monday afternoon to see what else I can find with your comments above.

Also, mechanically, using pressure and vacuum, all the actuators are working/moving when vacuum/pressure is applied.

Tim

 

New problems,

I tried to check boost of secondary turbo by teeing into the nipple coming up off of the secondary to the Y-Pipe. First try was showing a bit of boost, then nothing. I cannot determine if the blow-off is opening up or not.

But now, there is major hesitation when I get above 0 psi boost. I can get to 10psi, but it is MAJOR bucking and hesitation as it quickly goes up. The bucking starts at any boost pressure. Runs OK, feels hesitant under light throttle.

Also, after running it lightly with no boost, I parked it and popped the hood. The under hood temp is about 10,000 degrees and the fans are not running. After shutting off the engine, there was bubbling noises and a big throw up going to the overflow that I heard. After cooling down about a hour or so, I opened the radiator cap (not the ast) and it is about 1" down. But this is always the way it is when I check. As I open the cap, there is a big suction and the level is always down about 1 inch. I add about 2 oz of water to top it off.

Any thoughts?

I am now thinking of tearing down the intake and the water pump and start from there by replacing the check valves and checking all solenoids. I am also planning on replacing the gasket for the water pump housing to the engine since I could see a tiny bit of wetness at the gasket, but no visible leaking.

I am also going to replace the thermostat since I think it might be sticking, but the temperature gage has not moved above 1/2 way EVER.

Tim

 

Update:

Took the upper intake manifold off. Found the Double Throttle solenoid nipple broken off. Also, the front white (automatic) check valve located in a clip at the rat's nest front was also bad. Replaced them and some new hoses where I can see they are loose. Funny thing is that I have a spare rat's nest and the same nippple and check valve are bad on it also. All other check valves appear to be working for now. The rest of the solenoids look good also.

I am going to replace the thermostat since I had to remove the antifreeze and am going to replace the gaskets for the water pump and housing. Also found the one nipple going into the AST broke off when I bumped it. Probably cracked causing the boiling over sounds that I heard in the last post.

As far as the no boost at WOT in neutral, I am removing the runners from the turbo and checking as much as I can from there to the intake for boost leaks.

Tim

 

If you have the manifold off and you have access to a vacuum pump, I'd consider testing the solenoids. Between two rats nests, you can easily find enough that test good.

Of course if it's a stock rats nest with original hoses I can appreciate leaving it alone for now. To do this "right" IMHO can be a big tedious job.

Dave

 

Update 2,

Dave, I think I am going to leave it go right now because the hoses are relatively soft and flexible considering, but they don't like to seal back up when they are removed.

I also finally found the nipple on the front Vacuum reservoir broke off also. I believe this is the root of all my problems. I thought I had a spare, but don't so I took a metal nipple from an intake, heated with a torch and melted it through the original plastic nipple opening. I then took JB Weld and welded it in place. I cocked it slightly at an angle to alleviate the stress that the original one was put under. It appears the hose is pulling on this nipple from original design. Vacuum tested this morning and holding at 20mm/Hg.

Now just waiting for my new gaskets to arrrive today to reassemble and test.

Crossing my fingers that this is all of the problems.

Tim