Alex

I've been attempting to diagnose a low secondary boost problem on my 94 R2 and have come to find out that my Chare Relief Valve is switching at 3500rpm instead of the expected 4500rpm.

I've put a vacuum gauge in the line the runs between the solonoid and the CRV and I've put a voltmeter across the terminals of the solonoid then run the car. Both the vacuum and the voltage switch distinctly at the same time, 3500rpm. It does this every time repeatably. I've replaced the solonoid itself but the problem persists.

Putting a vacuum gauge on the Charge Control Valve shows that the vacuum on this circuit is switching right at 4500rpm, as it should. I haven't been able to get a voltmeter on the circuit as it is burried under the manifold.

What could possibly cause the ECU to send a signal at 3500 to the CRV but at 4500 to the CCV?? If there was a problem with the engine speed signal or any other input coming into the ECU, I would think both would be switching at the wrong time.

Please help, this has become very frustrating!

books

iTrader: (8)

just looking at the service manual page F176...states different rpm ranges for test conditions ...manual tranny 4000-5500 rpms... auto tranny 3500-5000 for the CRV... the charge control solenoid is above 5,250 auto and 5,500rpms for manual...I believe you probably can read the resistance of the charge control solenoid by grounding the connector side of pin 4T of the ecu.. should read about 37 ohms with engine cold and about 45 ohms with the engine hot

Alex

When you say ground the connector side, do you mean leave the connector plugged in to the ECU or pull it out? I pulled it out, stuck a pin in the socket of the connector and it measured about 9.1 MOhms. The 4S pin (CCV) also measured 9.1 MOhms. If I measure with the connector in place, will that ground out the ECU and possibly damage it?

By the way I checked the part number on the ECU, it is N3C1, which is correct for my 94 MT, so I don't have the ECU from an automatic by mistake.

books

iTrader: (8)

I have to apologize, I don't know what I was thinking, in order to measure the resistance of the solenoid you need to measure across the solenoid terminals, however you did mange to verify that there was not an open in your wiring from the solenoid to the ecu and yes you did the right thing by by removing the connector from the ecu and measuring at the connector...I assume your solenoid is operating, one way to verify this is to turn the ignition on and ground the connector side of 4T, you will hear it click, I always have ALL the connectors removed from the ecu before I place the ignition switch in the on position...if you want to try this please remove all the ecu connectors, just to be safe...have you checked for any boost leaks? Is this only occuring on the 2ndary? sorry I cannot be of much help...good luck though

Alex

Any more ideas on why the CRV might switch at 3500rpm instead of 4500?

LAracer

Maybe this will help:

http://www.geocities.com/laracers_vr_r1/boost_plots

Keep in mind that nothing seems to happen at the right time on my car since I'm at high altitude. Notice though, that the CRV seems to switch twice - once at 3500 and once at ~5200.

Good luck

Alex

The first part of the CRV trace looks identical on my car, but I don't remember the sudden rise around 5000, but of course a passenger was checking the gauge while I drove. I did confirm though that the voltage switched at 3500rpm, along with the vacuum reading. It doesn't make sense that it could switch twice, where would the signal come from?

LAracer

My understanding (which may be wrong) is that the CRV opens at about 3500 to recirculate pre-spool charge (the air on the compressor-side of the secondary turbo while it is being pre-spooled). Then, once the TCA and CCV have switched (about 4500 for most people, but closer to 5500 for me) the CRV is closed so that secondary charge is not recirculated but sent to the intercooler.

Maybe there is only one electrical signal sent to the CRV solenoid (at 3500); the change in vacuum that the CRV sees at 4500/5500 may act to close it rather than the solenoid. This is speculation, but it would explain why you only measure one signal.

Does it sound like I'm making this up as I go along ?

edit: I just looked at my plots again and realized all this might not make sense since it looks like the CRV closes at 3500. I think the second paragraph may still be accurate though.

Alex

The CRV default is open, it is supposed to close at (I thought) 4500rpm , otherwise all the boost would blow out of it once the CCV opens.
If you follow the vacuum diagram, you'll notice that the CRV gets its pressure signal from the second turbo. Since there is very little pressure in the 2nd turbo until higher rpm, what you may be seeing is the rapidly building pressure rather then an actual step change.

ExpensiveHobby22

You sure you don't have the CRV switched with the ABV? They look the same but have different operating ranges.

Alex

It's not the CRV itself that seems to be the concern, it's the signal going to it that I'm questioning. Swaping the CRV and ABV shouldn't affect the voltage at the solonoid.

ExpensiveHobby22

Ah, I see.

I also just noticed that you are in Royal Oak, MI also. If you want to swing by my place and get readings and stuff from my car you can.

-ray